Energy Research at Stanford Universitygcep.stanford.edu/pdfs/energy_at_stanford_2004.pdfIntroduction In 1982, the Institute for Energy Studies published the original Energy Research

Energy Research at Stanford University

Contributed Abstracts 2004

Introduction In 1982, the Institute for Energy Studies published the original Energy Research at Stanford University report to improve the flow of information about the range of energy research projects at Stanford. Today, the University continues to broaden its commitment to energy research as this important topic is being investigated by a growing number of departments and interdisciplinary programs. In 2003, following the lead of the Institute for Energy Studies, the Global Climate and Energy Project (GCEP) started a new online version of Energy Research at Stanford University. Now, this updated 2004 report, which is available through the GCEP website at http://gcep.stanford.edu, continues to list abstracts from investigators conducting research in the energy arena at the University. About a third of the projects listed are sponsored by GCEP, while the others are sponsored by outside organizations. The abstracts have been categorized into the following areas of energy resources, systems, and uses:

• Advanced Coal Use

• Advanced Materials

• Advanced Transportation

• Climatic Impacts of Energy Use

• CO2 Capture and Storage

• Combustion Science

• Energy and Human Welfare

• Energy Policy and Economics

• Hydrocarbon Reservoirs

• Hydrogen

• Renewable Energy

As many research efforts are interdisciplinary, each abstract is listed in one main category with a notation in the Table of Contents if it fits under another area as well. Also, an index of researchers and the corresponding page number of their abstracts is provided at the end of the report. We would like to thank those who contributed abstracts for sharing their knowledge with the research community. The GCEP staff looks forward to compiling updated editions of Energy Research at Stanford University in the coming years. We hope this continuous flow of information will help facilitate the discussion and research of our energy future. For more information: http://gcep.stanford.edu Email: [email protected]

Table of Contents

Advanced Coal Use 7

See Mitchell Abstract, P. 50

Advanced Materials 8

Cho, KJ. “Hierarchical Multi-Scale Modeling of Nano-Materials Engineering for Hydrogen Technology”

9

Nilsson, A. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis”

12

See Bent Abstract, P. 81 See Brongersma Abstract, P. 83 See Peumans Abstract, P. 90

Advanced Transportation 14

See Edwards Abstract, P. 38

Climatic Impacts of Energy Use 15

Schneider, Stephen H. “What is ‘Dangerous’ Climate Change?”

16

See Victor Abstract, P. 56 See Weyant Abstract, P. 59

CO2 Capture and Storage 20

Harris, Jerry M. “Monitoring of CO2 Sequestration in Geological Formations”

21

Orr, Franklin M. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Pollard, D.D. and A. Aydin. “Structural Heterogeneities and Paleo-Fluid Flow in an Analogue Sandstone Reservoir”

26

Zoback, Mark. “Assessing Seal Capacity of Exploited Oil and Gas Reservoirs, Aquifers and Coal Beds for Potential Use in CO2 Sequestration”

28

Combustion Science 30

Bowman, Craig T. “Controlled Combustion—An Approach for Reducing Irreversibilities in Energy Conversion”

31

Edwards, C.F. “Development of Low-Irreversibility Engines”

36

Edwards, C.F. “Homogeneous Charge Compression Ignition via Exhaust Reinduction Using Variable Valve Actuation”

38

Edwards, C.F. and C.T. Bowman. “Measurement of Species, Temperature, and Velocity in a Compact, Swirling Combustor for Validation of High-Fidelity CFD Simulations”

40

Edwards, C.F. and C.T. Bowman. “Mesoscale Burner Arrays for Gas Turbine Reheat Applications”

42

Gerdes, J. Christian and C.F. Edwards. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines”

44

Golden, David M. and C.T. Bowman. “Process Informatics—A New Paradigm for Building Complex Reaction Models”

46

Hanson, Ronald K. “Smart Sensors for Combustion Control”

48

Mitchell, R. E. “Characterization of Coal-Char and Biomass-Char Reactivities to Oxygen at High Temperatures and High Pressures”

50

Energy and Human Welfare 52

Arrow, Kenneth and Lawrence Goulder. “Research Initiative on the Environment, the Economy, and Sustainable Welfare”

53

See Victor Abstract, P. 56

Energy Policy and Economics 55

Victor, David G. “The Program on Energy and Sustainable Development”

56

Weyant, John P. and Hillard G. Huntington. “The Energy Modeling Forum”

59

Wolak, Frank A. “Energy Market Design, Performance Measurement and Monitoring”

62

See Arrow/Goulder Abstract, P. 53 See Schneider Abstract, P. 16

Hydrocarbon Reservoirs 64

Mavko, Gary. “CO2 Sequestration in Coal Seams”

65

Mavko, Gary. “Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization”

67

Nur, Amos. “Computational Rock Physics”

69

Nur, Amos. “Lithology and Fluid Detection in Hydrocarbon Reservoirs”

71

Nur, Amos. “Rock Physics of Methane Hydrate Reservoirs”

73

Hydrogen 75

Goodson, Kenneth E. and John K. Eaton. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76

Jacobson, Mark Z. “Effects of a Hydrogen Economy”

78

See Cho Abstract, P. 9 See Nilsson Abstract, P. 12

Renewable Energy 80

Bent, Stacey F. “Hot Wire Chemical Vapor Deposition of Photovoltaic Polymer- based Films”

81

Brongersma, Mark and Shanhui Fan. “Plasmonic Contacts for Energy Efficient Solar Cells and Light Sources”

83

Horne, Roland N. “Properties of Steam/Water Flow in Geothermal Rock”

84

Jacobson, Mark Z. “Mapping U.S. Wind Resources”

86

McGehee, Michael D. “Nanostructured Photovoltaic Cells”

88

Peumans, Peter. “Organic Optoelectronics for Renewable Energy”

90

Somerville, Chris. “Genetic Modification of Plant Cell Walls for Enhance Biomass Production and Utilization”

93

Walbot, Virginia. “Impact of UV-B Radiation on Corn (Zea mays L.)”

95

See Mitchell Abstract, P. 50

Renewable Energy (cont.)

See Nilsson Abstract, P. 12

Index by Researcher 97

Advanced Coal Use

See Mitchell, R. E. “Characterization of Coal-Char and Biomass-Char Reactivities to Oxygen at high Temperatures and high Pressures” . . . . . . . . . . . . . . . . . . .

50

Energy Research at Stanford 2004

7

Advanced Materials

Cho, KJ. “Hierarchical Multi-Scale Modeling of Nano-Materials Engineering for Hydrogen Generation and Hydrogen Storage” . . . . . . . . . . . . . . . . . . . . . . . . . . Nilsson, A. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis” . . . . . . . . . . . .

9 12

See also: Bent, Stacey F. “Hot Wire Chemical Vapor Deposition of Polymer-based Films” . . . Brongersma, Mark and Shanhui Fan. “Plasmonic Contacts for Energy Efficient Solar Cells and Light Sources” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Peumans, Peter. “Organic Optoelectronics for Renewable Energy . . . . . . . . . . . . . . .

83 85 90



Hierarchical Multi-Scale Modeling of Nano-Materials Engineering for Hydrogen Technology

Investigators: KJ Cho, Assistant Professor of Mechanical Engineering Description: We propose to develop novel nanomaterials for hydrogen energy technology applications. We plan to work closely with experimental groups to study nanomaterials for hydrogen generation and storage. As we develop a rational conceptual framework for nanomaterial design, we also plan to proceed to apply the nanomaterials for efficient hydrogen engines and fuel cell devices. For these research purposes, we plan to develop hierarchical multi-scale modeling tools to investigate and design materials from atomistic and quantum mechanical understanding of the energy conversion processes. Specifically, we will focus on controlling the atomic structure of nanomaterials with corresponding mechanical and chemical properties for hydrogen technology. As a non-toxic and non-pollutant future energy source, hydrogen technology − hydrogen generation, hydrogen storage, and energy conversion − has been studied. Significant portions of hydrogen technology, especially hydrogen generation and hydrogen storage, are operated by catalytic reactions; adsorption, diffusion, reaction and desorption processes at atomic scales. To develop practical technologies for hydrogen generation and storage, it is crucial to develop a detailed understanding on the atomic scale mechanisms involved in these processes. A fundamental mechanistic understanding will facilitate the design and development of new materials for hydrogen technology. Nanomaterials provide a unique opportunity for hydrogen technology due to their strong coupling among structure and electro-chemical properties. By controlling nanomaterial structures, it will be possible to tailor-design materials with specific properties required for hydrogen technology applications. Currently, we are investigating to control the chemical and mechanical properties of nano structured materials, particularly, composed of metal alloys or carbon materials, to improve the efficiency of current technologies. Our studies are based on different scales of simulation techniques to increase the efficiency of the computations; atomistic simulation and quantum mechanical simulation, including Tight-Binding, Density Functional Theory, and Quantum Monte Carlo simulations. The hierarchies of the simulation methods are summarized in Fig. 1. We will further develop and apply the multi-scale modeling tools to the nanomaterials engineering problems.

Figure 1. Hierarchical Multi-scale Modeling

Hydrogen Generation Currently, hydrogen fuel has been generated mostly from organic materials, such as, methane or methanol. However, due to the production of carbon dioxide during the hydrogen generation and the limited fossil fuel resources, the organic materials have to be replaced eventually by non-



hydrocarbon source materials. Generation of hydrogen from water provides an opportunity to develop a clean energy source without generating CO2 by converting water into hydrogen and oxygen using the energy of sunlights. As initial progresses, photosynthetic water splitting (Fig. 2) on metal catalyst and, more recently, III-IV semi-conducting catalyst have been demonstrated. [1] We have studied the adsorptions and diffusion of molecules on metal or semi-conducting materials surfaces, and we plan to extend the study to understand the role of catalyst and the fundamental mechanism of the photosynthetic reaction at an electronic level. Based on the understanding of the catalytic reactions, we will explore the development of possible nanostructured materials that can maximize the energy efficiency of hydrogen generation. Once we find the optimized nano structures, our collaborators will examine the nano structures experimentally. Current nanotechnology can handle atom-by-atom movement within nano scales. Based on our previous studies of self-assembly to fabricate metal or semi-conducting nano structures, we will investigate possible mass fabrication paths. For this project, we have ongoing discussion with Prof. Anders Nilsson on photo-catalytic splitting of water molecules on designed metal nanostructures. Hydrogen Storage Due to the high risk of high-pressure gaseous hydrogen and the high cost of liquid hydrogen storages, new types of hydrogen storage methods have been searched. One of the most attractive candidates is solid material with high hydrogen storage capacity such as metal hydrides or carbon nanomaterials. [2] It was shown that some metal hydrides could store hydrogen even more than liquid hydrogen in volume storage capacity. During the recent development of metal hydride, metal alloys with two or even more than two metal elements have been investigated. Generally, the metal alloys are composed of two parts; the catalyst to decompose hydrogen molecules to hydrogen atoms, and the actual storage medium for atomic hydrogen. Possible issues on the metal alloys are the kinetics of hydrogen decomposition and hydrogen atom diffusion. Thus, the sizes of metal alloys need to be smaller than several tens of micro meters. Due to the small sizes of metal hydride, the distribution of each metal element and the structure of the metal cluster can influence the properties of metal clusters significantly. We plan to investigate nano metal clusters, which can maximize the storage capacity without possible degradation during the hydrogen storing and extracting. Our study will cover the catalytic hydrogen molecule decomposition as well as the storage capacity of candidate metal alloys. Since metal hydrides have heavy weights, carbon materials in graphitic structures have been studied. Due to their lightweight and potential high mass % capacity of hydrogen storage, they became one of the promising materials for the storage. We have studied the chemical reactivity of nano carbon materials, including carbon fullerenes and carbon nanotubes. We have developed an accurate model to predict the strength of hydrogen chemisorption on carbon nano structures. We have shown that the hydrogen chemisorption can be controlled by the local curvature of carbon nano structures. Based on the results, we will study the possible carbon structures that can

Figure 2. Hydrogen generation and hydrogen storage (metal hydride)



maximize the storage capacity and the rates of hydrogen adsorption and hydrogen desorption. Our study will also include doped carbon materials. Energy Conversion in Hydrogen Consumption The nanomaterials to be developed for the hydrogen generation and storage would have a direct relevance to fuel cell and hydrogen engine applications. We envision that our research will evolve toward these directions as we gain more understanding on the hydrogen science in nanomaterials. We expect to develop collaborations with Profs. Chris Edwards and Fritz Prinz on these research areas. Concluding Remarks We believe that the hydrogen energy technology will provide an excellent opportunity to bridge the Energy Initiative to the Advanced Materials Initiative through the nanomaterial development. From materials viewpoint, developing nanomaterials capable of converting energies among different forms are major challenges requiring detailed understanding of atomic and electronic properties as well as advanced fabrication and characterization equipments. We are very hopeful that Stanford will emerge as the leading institution to develop a new energy technology based on nanomaterials engineering. References 1. O. Khaselev, and J.A. Turner, “A monolithic Photovoltaic-Photoelectrochemical Device for

Hydrogen Production via Water Splitting,” Science 280, 425 (1998) 2. H. Smithson, C.A. Marianetti, D. Morgan, A. Van der Ven, A. Predith, and G. Ceder, “First

Principles Study of the Stability and Electronic Structure of Metal Hydrides,” Physical Review B 66, 144107 (2002).

Related Publications • S. Park, D. Srivastava, K. Cho, “Generalized Chemical Reactivity of Curved Surfaces:

Carbon Nanotubes,” Nano Lett. v.3, no.9, p.1273-1277 (2003).

• M.I. Larsson, B. Lee, R. Sabirynov, K. Cho, W. Nix, and B.M. Clemens, "Kinetic Monte Carlo Simulations of Strain-induced Nanopatterning on Hexagonal Surfaces," Material Research Society Proceedings 731 W.3.14 (2002)

• S. Park, D. Srivastava, and K. Cho, "Local Reactivity of Fullerenes and nano Device Design," Nanotechnology 12 (3) 245 (2001).

• S. Han, K. Cho, and J, Ihm, "Ab-initio study on the molecular recognition by metalloporphyrins: CO interaction with iron porphyrin," Physical Review E 59, 2218(1999).

• K. Cho, E. Kaxiras, and J.D. Joannopoulos, "Theory of adsorption and desorption of H2 molecules on the Si (111)-(7x7) surface," Physical Review Letters 79, 5078 (1997).

• M.I. Larsson, R.F. Sabiryanov, K. Cho, B.M. Clemens, “Nanopatterning of periodically strained surfaces: Predictive kinetic Monte Carlo simulation study,” JOURNAL OF APPLIED PHYSICS, v.94, no.5, p.3470-3484 (2003).



Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis

Investigators: A. Nilsson, Associate Professor; H. Ogasawara, Research Associate; T. Schiros, Graduate Student; L.-A. Näslund, Graduate Student; K. Andersson, Graduate Student; L.G.M. Pettersson, Professor, Stockholm University. Sponsors: U.S. Department of Energy, National Science Foundation, Energy Committee of the Swedish Research Council and Swedish Strategic Research Foundation. Description: Our research focuses on obtaining a deep understanding of chemical bonding, charge transfer and interfacial reactions in catalytic processes and hydrogen-bonded networks of importance to energy processes. Synchrotron based, core-level spectroscopies are employed to probe model systems and provide element-specific, polarization sensitive information about the geometric and electronic structure, molecular orientation, chemical shifts and bonding information around a given atomic site. Our studies address fundamental questions in electrochemistry (fuel cells), photocatalysis (hydrogen production), and catalysis (ammonia synthesis). In recent investigations we revealed the structure of water on the surface of platinum (111) to be that of “flat ice” and established the H-down bonding mode of adsorbed water as shown on the right. These findings contribute to a more detailed understanding of photodissociation, electrical potentials of metals, water at electrode surfaces, corrosion and the catalytic reactions of hydrogen fuel cells. The results challenge current models and are further illuminating with respect to our current research concerning the photocatalytic decomposition of water into hydrogen and oxygen. Phys. Rev. Lett. 89, 276102 (2002) In photocatalysis the energy of sunlight is captured, converted and then stored in a H2 chemical bond for future use as a fuel. However the realization of photocatalytic water-splitting as an industrially viable option for hydrogen production will require a strong scientific effort to find suitable materials that can effectively absorb sunlight and create charge separation at different electrodes and a deep understanding of interfacial processes involving water. In the latter case the process is currently limited by the efficiency of the charge transfer processes that drive the reaction at the solid-liquid interface. We aim to build a molecular level picture of these elusive processes via spectroscopic probing and density functional theory calculations of model systems. In particular, we address the initial charge transfer and consequent bond and surface structure transformations, proton transfer in the liquid, the structure of water at the interface, the structure of active sites, reaction mechanisms and intermediates, and poisoning at the interface. This information



will allow for determination of favorable and unfavorable changes in free energy, rate limiting steps, and pathways for redistribution and recombination among reactants. From this basis, we can derive chemical trends and predict the catalytic properties of different materials with respect to their ability to decompose water into hydrogen and oxygen. In the future, fundamental information relating structure and charge transfer to the kinetics of catalysis can be applied to other systems. Our research in catalysis has elucidated how nature has developed sophisticated electrochemical processes to produce needed energy and materials. This is particularly evident in the electron and proton transfer involved in the redox steps of many enzymatic processes involving reduction and oxidation of nitrogen and methane. We are currently investigating N2 activation through a comparison of adsorption and reactions on active sites on metal surfaces and Fe-S clusters similar to the active center in the enzyme nitrogenase. We aim to apply this knowledge to control reactivity for ammonia synthesis using nanoscale molecular clusters anchored on surfaces. We are also studying dissociation of nitrogen on stepped Ru surfaces as the rate limiting step in the Haber-Bosch process for ammonia production (which currently accounts for half the energy consumed in agriculture). Information related to how metal coordinated N2 and O2 can hydrogen bond to water or protonated water will help us to determine under which structural conditions proton transfer is possible. New pathways open as research related to the photocatalytic decomposition of water for hydrogen production identifies materials which can create charge separation at different local electrodes. We envision that further modification of such materials could potentially provide electrochemical catalysts for a number of chemical processes. Status: Collaboration within Stanford University with Prof. Hari Manoharan and Prof. Kyeongjae Cho is being established. A new soft x-ray endstation capable of kinetic and spectroscopic studies of surfaces and solid-liquid interfaces under ultra-high vacuum and ambient conditions is in preparation for February beamtime during which we will further investigate N2 dissociation on steps and water dissociation on Pt(111). Publications: H. Ogasawara, B. Brena, D. Nordlund, M. Nyberg, A. Pelmenschikov, L. G. M. Pettersson and A. Nilsson, “Structure and bonding of water on Pt(111)”, Phys. Rev. Lett. 89 (2002) 276102. S. Myeni, Y. Lou, L.-A. Naslund, M. Cavalleri, L. Ojamae, H. Ogasawara, A. Pelmenschikov, Ph. Wernet, P. Vaterlein, C. Heske, Z. Hussain. L.G.M. Pettersson, and A. Nilsson. “Spectroscopic Evidence of Unique Hydrogen Bonding Structures in Liquid water.” J.Phys.: Condens. Matter 14 (2002) L213-219.

A. Nilsson. ”Applications of Core Level Spectroscopy to Adsorbates” J. Electron Spectr. 126 (2002) 3. Contact: [email protected]



Advanced Transportation

See Edwards, C.F. “Homogeneous Charge Compression Ignition via Exhaust Reinduction Using Variable Valve Actuation” . . . . . . . . . . . . . . . . . . . . . . . . .

38

Climatic Impacts of Energy Use

Schneider, Stephen H. “What is ‘Dangerous’ Climate Change?” . . . . . . . . . . . . . . . .

16

See also: Victor, David G. “The Program on Energy and Sustainable Development” . . . . . . . . Weyant, John P. and Hillard G. Huntington. “The Energy Modeling Forum” . . . . . . .

56 59



What Is “Dangerous” Climate Change?

Investigator: Stephen H. Schneider, Professor, Department of Biological Sciences; Senior Fellow, Stanford Institute for International Studies; Professor by courtesy, Department of Civil and Environmental Engineering; Co-Director, Center for Environmental Science and Policy; Co-Director, Interdisciplinary Program in Environment and Resources Sponsors: Partial support from the Winslow Foundation and the U.S. Department of Energy Description: In 2001, the Intergovernmental Panel on Climate Change (IPCC) released its Third Assessment Report (TAR), which stated that the authors expected that the climate would warm between 1.4ْ to 5.8ْC by 2100. Based on these temperature forecasts, the IPCC has produced a list of likely effects of climate change, some of which are positive (e.g., longer high-latitude growing seasons), but most of which are negative, including more frequent heat waves (and less frequent cold spells); more intense storms (hurricanes, tropical cyclones, etc.), and a surge in weather-related damage; increased intensity of floods and droughts; warmer surface temperatures, especially at higher latitudes; more rapid spread of disease; loss of farming productivity, mostly at lower latitudes; rising sea levels, which could inundate coastal areas and small island nations; and species extinction and loss of biodiversity. The IPCC also suggested that climate change could trigger “surprises”: rapid, non-linear responses of the climate system to anthropogenic forcing, thought to occur when environmental thresholds are crossed and new (and not always beneficial) equilibriums are reached. These surprises could include collapse of the “conveyor belt” circulation in the North Atlantic Ocean or rapid deglaciation of polar ice sheets and would likely qualify as what the 1992 United Nations Framework Convention on Climate Change called “dangerous anthropogenic interference with the climate system”. Unfortunately, climate change assessments rarely consider low-probability, but high-consequence extreme events like surprises. Thus, decision-makers reading the “standard” literature will rarely appreciate the full range of possible climate change outcomes, and might be more willing to risk adapting to prospective changes rather than attempting to avoid them through abatement than they would be otherwise. We advocate an inclusion of abrupt events in scientific climate assessments is advocated, so that scientists can aid policymakers in defining “dangerous,” particularly by outlining the elements of risk, which is classically defined as probability x consequence, and suggesting policy measures that may be effective in reducing the chances of dangerous climate change occurring. Ultimately, what constitutes “dangerous” climate change must be decided by value judgments of policymakers, based on what risks they are willing to face and what risks must be avoided (and hopefully based on sound scientific information). One study we have done this year (Mastandrea & Schneider, 2004 – listed in “Selected Publications”) attempts to show what constitutes “dangerous anthropogenic interference” (DAI) – which we suggest defining in terms of the accumulation of various impacts of



climate change – and shows how climate policy measures can significantly reduce the chances of it occurring. We choose a median threshold for dangerous climate change (DAI[50%]) of 2.85°C of additional warming (as the IPCC projects that after “a few degrees”, many serious climate change impacts could be anticipated), and then calculate additional threshold values above and below the median (from 10% to 90%), to account for a range of climate sensitivities. The use the figure below to illustrate that whatever the threshold temperature for DAI, climate policy controls significantly reduce the probability of DAI occurring. For example, if DAI occurs at 1.925°C (DAI[25%]), meaning climate impacts sensitivity is high, then there is about an 85% chance that it will occur by 2050 in the absence of policy, and a less than 20% chance it will occur if the strongest policy (carbon tax of $400/ton) is implemented. If we inspect the median threshold for DAI (the thicker black line in the figure), we see that a carbon tax by 2050 of $150-$200/ton will reduce the probability of DAI to nearly zero, from 45% without policy.

Our research indicates first, that abrupt changes are possible when certain thresholds are exceeded, and second, that including abrupt changes in integrated assessment models – common policy analysis tools which couple models of the climate system and the economic system and balance costs and benefits of climate change mitigation to determine an “optimal” policy – like the one discussed above could significantly alter the definition of what is “optimal”. Policy is also highly important in inducing more research into the development of “clean” (non-CO2-emitting) technologies. There is overwhelming evidence that energy policies are of critical importance to the development of alternative technologies and are more effective in spurring technological advancement than subsidies. “Optimal” policies will rely not only on climate sensitivity and the degree of climate damages, but on the discount rate. Discounting is a method of aggregating costs and benefits over a long time horizon by summing net costs (or benefits), which have been multiplied by a discount rate typically greater than zero, across future time periods. If the discount rate equals zero, then each time period is valued equally (case of infinite patience). If the discount rate is infinite, then only the current period is valued (case of extreme myopia). The discount rate chosen in assessment models is critical, since



abatement costs will be typically incurred in the relatively near term, but the brunt of climate damages will be realized primarily in the long term. Thus, if the future is sufficiently discounted, present abatement costs, by construction, will outweigh discounted future climate damages. In our recent research, we have found that incorporating large, non-linear damages (like “surprises”) into our modeling considerably increases present “optimal” carbon taxes, using conventional discounting with pure rate of time preferences (a factor proportional to the discount rate) of 1.5% to 3.0%. In the figure below, also from Mastandrea & Schneider (2004), we show how the probability of DAI changes with the pure rate of time preference. As shown for the median threshold case, the probability of DAI rises from near zero with a 0% PRTP (implying high carbon taxes) to 30% with a 3% PRTP (implying low carbon taxes).

Other recent research has centered on equity issues in climate change (and especially abrupt climate change), particularly on the uneven distribution of effects climate change promises to bring and the injustice inherent in the policymaking process itself. We have also spent considerable time on our climate change website, where we present facts on climate science, impacts, and policy; maintain an up-to-date climate news section; and discuss various problems related to and solutions for getting messages on climate change out to policymakers and the public (including a very tongue-in-cheek section called “Mediarology”). In summary, my group’s work has focused on climate science and impacts (including equity impacts), climate policy, and the crossroads between them. We attempt to express uncertainties in climate science and impacts estimation quantitatively as probability functions, though we do not assign high confidence to such probability distributions; much more research is needed in this area. We believe approaching climate change probabilistically gives the best chances of assuring that scientists’ and decision-makers’ respective areas of expertise are applied credibly to the policy process. Status: A multitude of projects continue in the areas of subjective probabilities, “dangerous” climate change, surprises, evidence of anthropogenic climate change affecting plant and animal communities (known as fingerprinting studies), using



integrated assessment models to find “optimal” abatement (and other) policy solutions, and other topics. Selected Publications: Mastrandrea, M.D. and S.H. Schneider, 2004: “Probabilistic Integrated Assessment of ‘Dangerous’ Climate Change”, Science 304: 571-573. Root, T.L., J.T. Price, K.R. Hall, S.H. Schneider, C. Rosenzweig, and J. A. Pounds, 2003: “'Fingerprints of Global Warming on Animals and Plants,” Nature 421:57-60. Schneider, S.H., 2003: “Imaginable Surprise", Chapter 54 in Potter, T.D. (ed.), Handbook of Weather, Climate, and Water (Hoboken, NJ: John Wiley and Sons), 947-954. Schneider, S.H., 2004: “Abrupt Non-Linear Climate Change, Irreversibility and Surprise,” Journal of Global Environmental Change, in press. Schneider, S.H. and J. Lane, 2004: Dangers and thresholds in climate change and the implications for justice, Chapter 2 in Adger, N. et al. (eds.), Justice in Adaptation to Climate Change (Cambridge, MA: MIT Press), in press.

Contact: [email protected] Website: http://stephenschneider.stanford.edu



CO2 Capture and Storage

Harris, Jerry M. “Monitoring of CO2 Sequestration in Geological Formations” . . . . . Orr, Franklin M. “High Resolution Prediction of Gas Injection Process

Performance for Heterogeneous Reservoirs” . . . . . . . . . . . . . . . . . . . . . . . . . . Pollard, D.D. “Structural Heterogeneities and Paleo-Fluid Flow in an Analogue

Sandstone Reservoir” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zoback, Mark. “Assessing Seal Capacity of Exploited Oil and Gas Reservoirs,

Aquifers and Coal Beds for Potential Use in CO2 Sequestration” . . . . . . . . . .

21 24 26 28



Subsurface Monitoring for Geologic Sequestration Investigator: Jerry M. Harris, Professor, Department of Geophysics Sponsor: Global Climate and Energy Project Description: The objective of this project is to develop strategies for subsurface monitoring of injected CO2. Geophysics offers a variety of methods that operate over a wide range of geological environments, scales, and reservoir depths. The focus of our research is to develop cost-effective time-lapse imaging methods that can provide quasi-continuous monitoring and adapt to changing reservoir conditions. An important principle we follow is that the monitoring effort must decrease with time, and eventually stop when safe containment is no longer an issue (Figure 1). The challenge of the subsurface imaging is to follow the CO2 while simultaneously monitoring a steadily growing reservoir volume. Though not yet specified, a thorough description and numerical simulation of subsurface flow and monitoring capability will likely be an important and required part of the safety case when a site is presented for licensing.

This project is conveniently divided into three phases, each having several tasks: (1) Quantitative assessment of the geophysical options; (2) Numerical models to simulate selected monitoring strategies that include survey design, subsurface imaging, and dynamic leakage assessment; and (3) Tests with field data. During the first phase of the project, we developed first-order models that describe the changes in the bulk rock-fluid properties with injected CO2. We then incorporated those models into a variety of geophysical monitoring methods, e.g., seismic, electrical, magnetic, electromagnetic, gravity, and surface deformation [Wynn, D., 2003]. The major conclusion of this initial study was that seismic methods provide the most effective means, technically speaking, for subsurface monitoring for most geological storage scenarios. However, seismic imaging, as we perform it for petroleum reservoirs, is probably too expensive for continuous or repeated long-term use. We have proposed using adaptive seismic monitoring methods. Essentially, our monitoring strategy trades spatial resolution for temporal resolution. The conventional imaging approach for petroleum recovery (Figure 2) is to produce a sequence of high-resolution reservoir snapshots, perhaps years apart as reservoir development progresses. Changes are detected by differencing the snapshots. Our new approach (also Figure 2) is designed specifically for CO2 disposal monitoring, where high spatial resolution may not be as important. We produce a sequence of difference images ∆mi, each taken perhaps

Figure 1. Before the injection begins, a relatively high cost and detailed subsurface image is needed to characterize the storage site. During injection, the cost of monitoring may vary because of dynamic injection conditions. In the closure phase, the cost is very low and eventually goes to zero.



months or even weeks apart. We record a sequence of time-lapse data sets, each with reduced spatial resolution and/or coverage. The data sequence is processed to explicitly include a time-varying reservoir model [Day-Lewis, 2003]. Moreover, we incorporate new survey geometries, acquisition schemes, and processing methods that together reduce costs and provide quasi-real-time monitoring capability. An example is the cross-linear array (Figure 3a) where sources and detectors are distributed along three linear arrays, two along the surface and one along the injection borehole. The 3-axis arrays provide reduced spatial resolution, but at greatly reduced acquisition and processing costs. Both sources and receivers are permanently embedded to maximize survey repeatability and reduce deployment costs. Additional surface lines (Figure 3b) may be added or different sections of the emplaced arrays may be activated at different times to track the CO2 or to target specific zones or problem areas. Status: We are now in Phase 2 of the project. The adaptive seismic subsurface imaging is being studied. We are developing tools for optimum survey design specially for lower-cost monitoring. Numerical simulation is used to study time-lapse tomography and dynamic leakage assessment. Moreover, the monitoring project is leveraged by other research activities on coal bed methane, multi-scale numerical simulation, and seismic attenuation. Publications: Wynn, D., (2003), Survey of geophysical monitoring methods for monitoring CO2 sequestration in aquifers, Department of Geophysics, Stanford University, 2003.

Figure 2. The conventional time-lapse imaging approach is to produce a sequence of snapshots, mi, each taken perhaps years apart, e.g., m0 and m1 in the upper figure. Our new approach is to produce a larger sequence of lower resolution difference images, ∆mi.

m0 ∆m1 ∆m2 ∆m3

m0 m1

Conventional Approach

New Approach

Figure 3. (a) 3D cross-linear arrays. Both in-plane and out-of-plane imaging are possible with this configuration. (b) More surface arrays are activated or added as the CO2 spreads.

(a) (b)



Day-Lewis, F, J.M. Harris,and S. Gorelick, (2003), Time-lapse inversion of crosswell radar data, Geophysics, Vol. 67, no. 6, November-December; p. 1740-1752, 2003. Harris, J.M., Akintunde, O.M., Mukerji, T. and Urban, J (2004). A feasibility study for CO2 monitoring in coal, Expanded Abstracts, 2004 AAPG Meeting, Dallas. Akintunde, O.M., Harris, J.M. and Quan, Y (2004). Crosswell seismic monitoring of coal bed methane production: A case study from the Powder River Basin of Wyoming (US), Expanded Abstracts, 74th International Exposition and Annual Meeting of the Society of Exploration Geophysicists, paper TL4.2, Denver.



High Resolution Prediction of Gas InjectionProcess Performance for Heterogeneous Reservoirs

Investigators: Franklin M. Orr, Jr., Professor, Margot Gerritsen, Assistant Professor, KristianJessen, Acting Assistant Professor, Yildiray Cinar, Postdoctoral Fellow, Bradley Mallison,Carolyn Seto, Sebastian Matringe, Sharoh Marquez, Nitin Srivastava, Jichun Zhu, graduatestudents, Petroleum Engineering Department

Sponsors: U.S. Department of Energy, SUPRI-C Gas Injection Industrial Affiliates Program

Description: High pressure gas can displace oil and gas relatively efficiently in subsurfacegeologic formations if displacement conditions are selected appropriately. Our fundamentalobjective is to understand the physical mechanisms that control displacement performance ingas injection processes and use that understanding to develop efficient and accuratecomputational tools for prediction of project performance at field scale.

Previous research on the interplay of viscous fingering, gravity segregation and permeabilityheterogeneity indicates that in many reservoir settings, the flow is dominated by theheterogeneity of the reservoir rocks. Thus any simulation tool that we use for field-scalepredictions must be able to handle high resolution representations of the heterogeneouspermeability field if it is to represent the flow realistically.

In addition, gas injection processes are fundamentally compositional. It is the interaction ofphase behavior and flow that controls local displacement efficiency in high pressure gas drives.Compositional simulation is appropriate for such flow systems. Unfortunately, conventionalcompositional finite difference simulators are too computationally intense for high resolution 3Dcomputations to be practical, and computations with coarser grids are generally badly affected bynumerical dispersion.

We are developing the streamline compositional simulation approach for gas injectionprocesses. Streamline methods decompose the problem into a 3D pressure solve used todetermine the streamlines and a set of 1D computations along those streamlines that represent thephysics and chemistry of the displacement. The streamline methods are fast if the flow isdominated by heterogeneity as the positions of the streamlines change slowly in time allowingfor larger timesteps relative to the FD approach. In addition, streamline methods are naturalcandidates for parallel computations and adaptive mesh refinement on the pressure grid as wellas the streamline grid.

Permeability field and well locations in 3D example calculation.



We are investigating ways to assess the limitations of streamline methods (they do notrepresent flow across streamlines, for example). Finally, we are investigating experimentallyhow low interfacial tensions that arise in some high pressure gas drives influence flow behavior.

Saturation distribution after 2500 days of injection by: a) SL simulation and b) FD simulation.Speedup ~ 1600 times.

Status: A three-dimensional streamline compositional simulator has been developed. It allowsassessment of the performance of gas displacement processes using an analytical solution formulticomponent displacement along a streamline in combination with high resolutionrepresentation of heterogeneities in the calculation of streamline locations. The resultingpredictions of process performance are more accurate than conventional finite differencecompositional simulations and can be obtained with orders of magnitude less computation time.Investigation of efficient methods for inclusion of gravity, capillary phenomena, streamlineupdating, and numerical solution for the 1D flow problem are underway.

Publications:

Mallison, B., Gerritsen, M., Jessen, K. and Orr, F.M. Jr.: “High Order Upwind Schemes forTwo-Phase, Multicomponent Flow”, SPE 79691, SPE Reservoir Simulation Symposium,Houston, TX, February 3-5, 2003.

Seto, C.J, Jessen, K. and Orr, F.M. Jr.: “Compositional Streamline Simulation of Field ScaleCondensate Vaporization by Gas Injection”, SPE 79690, SPE Reservoir SimulationSymposium, Houston, TX, February 3-5, 2003.

Jessen, K and Orr, F.M. Jr., “Compositional Streamline Simulation”, SPE 77379, SPE AnnualTechnical Conference and Exhibition, San Antonio, Texas, September 29 – October 2, 2002.

Zhu, J., Jessen, K., Kovscek, A.R and Franklin M. Orr, Jr., “Recovery of Coalbed Methane byGas Injection,” SPE 75255, 2002 SPE/DOE Improved Oil Recovery Conference, Tulsa, OK,April 13-17, 2002.

Jessen, K., Stenby, E.H. and Orr, F.M. Jr. "Interplay of Phase Behavior and NumericalDispersion in Finite Difference Compositional Simulation", SPE 75134, 2002 SPE/DOEImproved Oil Recovery Conference, Tulsa, OK, April 13-17, 2002.

Jessen, K., Sam-Olibale, L., Kovscek, A, Orr, F.M. Jr.: "Increasing CO2 storage in OilRecovery", First National Conference on Carbon Sequestration, sponsored by the NationalEnergy Technology Laboratory, Washington, DC, May 14-17, 2001.

Jessen, K., Wang, Y., Ermakov, P., Zhu, J. and Orr, F.M., Jr.: "Fast, Approximate Solutions for1D Multicomponent Gas Injection Problems," SPE 56608/SPE74700, SPEJ, December 2001.

log(K)Sgas

a) b)



Structural Heterogeneities and Paleo-Fluid Flow in an Analogue Sandstone Reservoir

Investigators: D. D. Pollard and A. Aydin Department of Geological and Environmental Sciences Sponsor: US Department of Energy Grant: DE-FG03-94ER14462 Description: This integrated project is designed to develop conceptual and mechanical models for the evolution of structural heterogeneities in sandstone and to assess their effects on fluid flow in an analog groundwater and hydrocarbon reservoir. Such structural discontinuities include joints, sheared joints, deformation bands of shear and compaction types, and slip surfaces. They typically occur isolated in sets, or compose fault zones that evolve over time with increasing complexity. These structures can substantially impede or enhance fluid flow through an otherwise porous and permeable rock. At Valley of Fire State Park, Nevada, we study their distribution within the Jurassic Aztec Sandstone and measure their geometric and hydraulic properties to serve as input parameters for numerical fluid flow and mechanical models. The petrographic and compositional analysis of diagenetic zones and field maps of their patterns (Eichhubl et al., 2004) revealed that the rock attained its red color by hematite coating of the grains during or immediately following the deposition. The white, yellow, and orange alteration bands are related to goethite and are associated with the bleaching and partial iron remobilization first by reducing hydrocarbon-related brines under deep burial conditions and second by meteoric fluids under vadose conditions. The earlier paleo-fluid flow is correlated with the emplacement of Cretaceous Sevier thrusts; the later is largely synchronous with Tertiary strike-slip faulting.

Structural field investigations and numerical modeling address the processes of deformation band formation. We currently focus on compactive deformation bands (Sternlof et al., 2004, figure 1-left) that exhibit predominantly band-normal compaction. Based on measurements of band width variations with band length, bands’ porosity reduction, and boundary element modeling of band propagation, we find that compactive deformation bands can be modeled as brittle “anti-cracks”. Grain rearrangement and porosity reduction in the wake of a propagating tip and secondary clay mineral infiltration resulted in the relatively impermeable feature. The anti-crack model predicts systematic patterns of elastic interaction among adjacent deformation bands that are consistent with patterns in outcrop.



The process of fault development by shearing of joint zones in sandstone is well displayed in Valley of Fire (Myers and Aydin, 2004; Flodin and Aydin, 2004). For example, the photograph in figure 2 (on the left side) shows a left-lateral strike-slip fault offsetting the boundary between the red and white sandstones by 22 meters. We map, analyze, and measure the petrophysical properties of the fundamental elements making up such fault zones with increasing complexity. We develop an improved upscaling methodology using numerical fluid flow models and the geometry and permeability of the component structures of the faults (Flodin et al., 2004, Jourde et al., 2002). Subsequently, upscaled fault permeabilities for sections of faults with various slip values are used to establish a slip-permeability transformer (Flodin et al., 2001). This relationship can then be used to represent similar faults in petroleum reservoirs and aquifers. Future efforts will be directed to stochastic/mechanical characterizations of such a fault system to facilitate a better interface with reservoir

simulators. Selected Publications: Eichhubl, P., Taylor, W. L., Pollard, D. D., and Aydin, A., 2004, Paleo-fluid flow and deformation in the Aztec Sandstone at the Valley Of Fire Nevada-Evidence for the coupling of hydrogeological, diagenetic, and tectonic processes. Geological Society of America Bulletin, v. 116, p. 1120-1136.

Flodin, E. A. and Aydin, A., 2004, Evolution of a strike-slip fault network, Valley of Fire, southern Nevada. Geological Society of America Bulletin, v. 116, no. 1/2, p. 42-59, DOI 10.1130/B25282.1.

Flodin, E., Aydin, A., Durlofsky, L. J., and Yeten, B., 2001, Representation of Fault Zone Permeability in Reservoir

low Models, SPE paper# 71617, p. 1-10. F Flodin, E. A., Durlofsky, L. J. and Aydin, A., 2004, Upscaled models of flow and transport in faulted sandstone: Boundary condition effects and explicit fracture modeling. Petroleum Geoscience, v. 10, n. 2, p. 173-181. Jourde, H., Flodin, E., Aydin, A., Durlofsky, L., and Wen, X. H., 2002, Computing Permeability of Fault zones in Aeolian Sandstone From Outcrop Measurements. American Association of Petroleum Geologists Bulletin, v. 86, No. 7, p. 1187-1200. Myers, R., and Aydin, A., 2004, The evolution of faults formed by shearing across joint zones in sandstone. Journal

f Structural Geology, v.26, no.5, p.947-966. o Sternlof, K., Chapin, J., Pollard, D.D. and Durlofsky, L.J. 2004, Effective permeability in sandstone containing deformation band arrays: American Association of Petroleum Geologists Bulletin, v. 88.

Contact: [email protected], [email protected]; http://pangea.stanford.edu/geomech/



mailto:[email protected]

http://pangea.stanford.edu/geomech/

Assessing Seal Capacity of Exploited Oil and Gas Reservoirs, Aquifers and Coal Beds for Potential Use in CO2 Sequestration

Investigator: Mark Zoback, Professor, Department of Geophysics Sponsor: Global Climate and Energy Program Description: In this study we will investigate the seal capacity of exploited oil and gas reservoirs, deep aquifers and coal beds in order to assess their potential utilization for CO2 sequestration. Excess pressures at the top of the formation used for sequestration arise from the buoyancy of the CO2 column with respect to the water or oil originally in the reservoir. The excess pressure has the potential to hydraulically fracture the cap rock (allowing leakage to occur), or to activate reservoir-bounding faults, as in the case shown below on the left, which resulted in leakage of natural gas from reservoirs at depth. This concept, which we refer to as dynamic seal capacity, has been applied in a number of oil and gas fields around the world. An important outstanding question is how such processes may influence CO2 sequestration. Fault maps of two oil fields in the northern North Sea. In both cases, the faults in field were active during opening of the North Atlantic, more than 140 million years ago. However, because they have rotated to lower dip over geologic time, the faults in the oil field shown on the left are critically stressed in the current, compressive stress field and are thus prone to reactivation and leakage (as indicated by the red color). Those in the field on the right have not rotated over time and are much effective as seals (corresponding to the green and blue colors). These theoretical predictions have been borne out through direct measurements made in the oil wells in these fields.



Another process to be investigated is whether there has been production induced faulting in oil and gas reservoirs that may have dramatically changed the seal capacity of faults present in the reservoir. This has been documented in a variety of oil and gas fields around the world. If such faulting has been induced by the production of hydrocarbons, reservoirs which had been well sealed in the past might not be sufficiently well sealed to sequester hydrocarbons in the future. Status: The research to be carried out can be summarized as follows:

⋅ Investigate the Dynamic Capacity Process (and Other Seal Integrity Questions) in the Context of CO2 Sequestration

⋅ Develop Screening Criteria for Assessment of Seal Capacity in Depleted Oil and Gas Fields in Different Geologic Environments

⋅ Develop Systematic Work Flows to Apply These Criteria ⋅ Test the Work Flow by Investigating Oil and Gas Fields in Different Parts of

the World that Might be Candidate Sites for CO2 Sequestration Projects ⋅ Assess Applicability of the Work Flow to Deep Aquifers ⋅ Investigate Applicability to CO2 Sequestration Associated with coal bed

methane production



Combustion Science

Bowman, Craig T. “Controlled Combustion—An Approach for Reducing Irreversibilities in Energy Conversion” . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Edwards, C.F. “Development of Low-Irreversibility Engines” . . . . . . . . . . . . . . . . . . Edwards, C.F. “Homogeneous Charge Compression Ignition via Exhaust

Reinduction Using Variable Valve Actuation” . . . . . . . . . . . . . . . . . . . . . . . . . Edwards, C.F. and C.T. Bowman. “Measurement of Species, Temperature, and

Velocity in a Compact, Swirling Combustor for Validation of High-Fidelity CFD Simulations” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Edwards, C.F. and C.T. Bowman. “Mesoscale Burner Arrays for Gas Turbine Reheat Applications” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gerdes, J. Christian and C.F. Edwards. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines” . . . . . . . . . . . . . . . . . . Golden, David M. and C.T. Bowman. “Process Informatics—A New Paradigm for Building Complex Reaction Models” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hanson, Ronald K. “Smart Sensors for Combustion Control” . . . . . . . . . . . . . . . . . . . Mitchell, R. E. “Characterization of Coal-Char and Biomass-Char Reactivities to Oxygen at High Temperatures and High Pressures” . . . . . . . . . . . . . . . . . . . . .

31 36 38 40 42 44 46 48 50



Controlled Combustion—An Approach for Reducing Irreversibilities in Energy Conversion

Investigators: Craig T. Bowman, Professor, Department of Mechanical Engineering; Neelabh Arora, Kevin Walters, Graduate Research Assistants Sponsor: Global Climate and Energy Project Introduction: Energy specific CO2 emissions from combustion devices can be reduced by improvements in energy conversion efficiencies. In conventional combustion devices, the chemical conversion of fuel and air into products occurs rapidly in an unrestrained and highly irreversible process (flame), with work extraction after the completion of combustion. This does not have to be the case. Conversion of fuel and air into products can be accomplished in a more reversible manner if the process is restrained so that work is extracted during the conversion process. An example of work extraction during fuel conversion is the fuel cell. What has not been previously recognized is that the fuel cell is not the only device that has this potential. Using high air preheat and dilute reactants, the chemical conversion process can be slowed to the point where mechanical energy extraction can be used to reduce the irreversibility of the energy conversion process and thereby increase efficiency. One example of controlled combustion is the well-known "flameless" oxidation process1 in which exhaust heat recovery and exhaust gas recirculation are employed to cause combustion to occur in a more homogeneous fashion. An important additional benefit of this concept is that by controlling the peak temperature of the products, NOx emissions can be reduced by orders of magnitude over conventional combustion processes.

In the present project, this concept is being extended to include diluents such as

nitrogen and carbon dioxide that could be produced in separation processes and delivered to the combustion system. Carbon dioxide is particularly interesting in that it can have both a thermal and chemical effect on the combustion reaction. The primary objective of the project is to develop and validate detailed models of the combustion chemistry for use in modeling low-irreversibility combustion engine concepts.

Background: Figure 1 shows the regimes of combustion processes in terms of the oxygen content of the oxidizer and the preheat temperature. The controlled combustion regime lies outside the regimes of conventional combustion processes as a result of the very low O2 levels and high preheat temperatures, and the chemical processes in the controlled combustion regime are poorly understood at the fundamental level needed for design optimization, especially for high-pressure combustion systems, such as gas turbines and diesel engines.



Figure 1: Regimes of combustion.

The regime of controlled combustion is being investigated experimentally in a high-pressure flow reactor facility, Fig. 2, in which important parameters, such as preheat and dilution can be independently controlled.

Figure 2: High-Pressure Flow Reactor (HPFR)

Figure 3 is a schematic layout of the reactor and the sampling instrumentation.

Figure 3: HPFR and sampling instrumentation.



The spatial evolution of the chemical reaction is monitored by sampling for key reactant, intermediate and product species using an extractive sampling probe coupled to on-line analyzers and temperature measured by a thermocouple probe. Detailed modeling of the profile data will yield chemical models for use in the design of controlled combustion systems and particularly for use in modeling low-irreversibility combustion engines, another project being carried out under the Global Climate and Energy Project2. The starting reaction mechanism is the Gas Research Institute mechanism, GRI-Mech 3.0, for natural gas combustion3. The fuels being used in the study include methane, ethane and methane-ethane mixtures (to simulate natural gas). The HPFR operates in the pressure range of 1-50 bar. Studies to date have been conducted at atmospheric pressure.

Results

Figure 4 show comparisons of calculated profiles of temperature, fuel, CO and CO2 for methane and ethane at the nominal operating condition of the HPFR, which is in the controlled combustion regime shown in Fig. 1.

Figure 4: Temperature and species profiles for CH4 and C2H6 for an

initial mixture temperature of 900°C.



As expected, significant differences in fuel reactivity are observed at this operating condition.

Figure 5 shows initial comparisons of calculated and measured temperature profiles at

atmospheric pressure for CH4 and C2H6. Good agreement between the model predictions and the experimental data is found.

Figure 5: Comparison of calculated and measured temperature profiles for CH4 and C2H6 at atmospheric pressure.

Progress: The majority of energy forecasts for the 21st century4, 5 indicate increased use of fossil fuels to meet global energy demands, particularly in the transportation sector, with a corresponding increase in carbon emissions. Even the most optimistic forecasts4 show significant dependence on fossil fuels for the first half of the century, with a leveling off of carbon emissions by mid century, but at levels that are higher than today. Hence, there can be a beneficial impact on carbon emissions by improvements in the energy conversion efficiencies of combustion-based power systems utilizing fossil fuels. Combining these higher efficiency systems with carbon capture could provide significant benefits in terms of reducing greenhouse gas emissions. The GCEP low-irreversibility combustion engine initiative, of which this project is a part, is investigating this novel approach to reducing irreversibilities through controlled heat release. Given the fundamental nature of this exploratory research effort, it is not possible to estimate the potential for reductions in emissions of greenhouse gases that result from energy use at this time. Future Plans: Over the next year, experiments and modeling in CH4-C2H6 systems will continue. Following completion of the atmospheric-pressure study, higher pressures will be investigated, starting initially at a pressure of 2 bar and then increasing pressure. References

1. Tsuji, H. (ed), High Temperature Air Combustion: From Energy Conservation to Pollution Reduction, CRC Press, 2002.

2. Edwards, C. F., Low Irreversibility Combustion Engines, GCEP Advanced Combustion Project.



3. Smith, G. P., Golden, D.M., Frenklach, M. Moriarty, M.W., Eiteneer, B.,Goldenberg,M., Bowman, C. T., Hanson, R.K., Song, S., Gardiner, W.C., Lissianski, V.V., and Qin, Z. http://www.me.berkeley.edu/gri_mech/

4. Global Energy Perspectives, Cambridge University Press, 1998. 5. IEA Energy Outlook 2003, U.S. Department of Energy, 2003.

Contact: [email protected]



Development of Low-Irreversibility Engines

Investigators: C. F. Edwards, Associate Professor, Mechanical Engineering Department; M. N. Svrcek, K.-Y. Teh, Graduate Researchers Sponsor: Global Climate and Energy Project, Stanford University Description: Internal combustion engines suffer from a significant loss of efficiency due to the irreversibility inherent in unrestrained combustion. Consider, for example, the gas turbine engine. As illustrated in the block diagram to the left, atmospheric air is compressed to a high pressure, fuel is injected, and a flame transforms the reactants to products in a process with no work and essentially no heat extraction (adiabatic combustion). The result of this traditional form of combustion is a high temperature gas that is then expanded through a turbine to develop work. The Brayton model, shown on the Mollier diagram of the next page (states 1-2-3-4), is an idealization of this process. The difficulty with this approach is the entropy generation that occurs between states 2 and 3. This entropy generation leads to a loss of potential work of an amount i. This is the irreversibility of the conventional gas turbine (Brayton) cycle.

WoutWcC

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Until recently it was not realized that it is possible to reduce this irreversibility. This can be accomplished by modifying the component configuration as shown in the schematic to the right. The essential aspect of the configuration is that the combustion process is no longer conducted in isolation, but is instead combined with the work extraction process. In this way, a portion of the chemical bond energy that would have been transformed into sensible energy (i.e., would lead to a high temperature) is transformed directly into expansion work in the turbine. The result of this transfer of energy is a lower peak temperature and concomitant lower entropy generation. A secondary but important side benefit is a potentially significant reduction in NOx emissions. A depiction of this reduced entropy (low-irreversibility) approach is shown by states 1-2-3’-4’ on the Mollier diagram. This diagram shows the reduced irreversibility (and therefore increased work) that is possible from implementing a set of processes with a 50% reduction in entropy generation. In this cycle, some sensible energy increase (and temperature rise) is still necessary to insure that the combustion reaction goes to completion.



Studies to date have shown that a carefully designed work extraction process, implemented by intelligent control strategies, may permit significant improvements in the efficiency of the simple cycle gas turbine engines.

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Status: Current efforts are focused on combined thermodynamic and chemical kinetic analyses of model low-irreversibility combustion processes, as well as the design of a facility to conduct proof-of-concept testing. Contact: [email protected]




Homogeneous Charge Compression Ignition via Exhaust Reinduction Using Variable Valve Actuation

Investigators: C. F. Edwards, Associate Professor, Mechanical Engineering Department; J. C. Gerdes, Assistant Professor, Mechanical Engineering Department; N. B. Kaahaaina, Research Engineer; P. A. Caton, G. Shaver, Graduate Researchers Sponsor: Department of Energy, Office of Transportation Technologies Description: Homogeneous Charge Compression Ignition (HCCI) is an alternative method of conducting the combustion process in piston engines. It is achieved by generating a high sensible energy mixture which is capable of autoigniting homogeneously upon compression. The unique aspect of our work on HCCI is that it is achieved by using fully flexible (computer controlled) valving to reinduct the exhaust from the previous cycle in order to obtain the high sensible energy mixture. Accomplished in this way, HCCI based on reinduction can be accomplished at a sufficiently low compression ratio that it can be incorporated with conventional spark ignition (SI) engine operation in a multi-combustion-mode, gasoline fueled engine. By allowing the control system to choose the optimum mode for combustion, a vehicle which meets consumer demands for both power and efficiency can be developed.

A key feature of HCCI combustion is that it produces very low NO emissions. This is due to the fact that, although the sensible energy of the mixture is high (due to use of the hot exhaust gas), the chemical energy of the charge is relatively low (due to the dilution effect). The result is that although HCCI starts from a higher temperature than SI combustion, its peak temperature is actually lower, dramatically reducing NO. In fact, as shown by the figure, NO values in the



single-digit range (less than 10 ppm) can be obtained using HCCI. This is sufficiently low to meet SULEV emissions standards without the use of NO aftertreatment. An additional benefit of achieving HCCI using variable valve actuation is that the engine can be operated without throttling. As such, pumping losses—normally a serious loss a light load in SI engines—can be essentially eliminated. Status: This work is continuing under a DOE university consortium for HCCI. Current efforts are focused on expanding the dynamic range of HCCI, reducing the peak pressure and rate or pressure rise during combustion, and defining approaches to control of HCCI. These are key requirements for developing a quiet, wide dynamic range, multi-combustion mode engine. Publications: N. B. Kaahaaina, A. J. Simon, P. A. Caton, and C. F. Edwards, "Use of Dynamic Valving to Achieve Residual-Affected Combustion," SAE Technical Paper 2001-01-0549, in press for the SAE Journal of Engines, 2002. Caton, P. A., Simon, A. J., Gerdes, J. C., Edwards, C. F., “Residual-Effected Homogeneous Charge Compression Ignition at Low Compression Ratio Using Exhaust Reinduction,” in press International Journal of Engine Research, 2002. Contact: [email protected]




Measurement of Species, Temperature, and Velocity in a Compact, Swirling Combustor for Validation of High-Fidelity CFD Simulations

Investigators: C. F. Edwards, Associate Professor, Mechanical Engineering Department; C. T. Bowman, Professor, Mechanical Engineering Department; E. Tribbett, C. M. Sipperley, Graduate Researchers Sponsor: NASA, Ultra Efficient Engine Technologies (UEET) Program Description: High-fidelity approaches to computational fluid dynamics like large-eddy simulation (LES) require experimental data for validation and testing. A key requirement of experiments used to provide such testing is that they must be both realistic and provide well-defined, well-controlled boundary conditions. This is particularly challenging for gas turbine combustion since control of acoustics, the ability to provide a stable but lifted flame, and the need to provide high-intensity combustion all lead to significant experimental trade-offs. An experiment has been developed to provide the data needed to challenge this type of simulation for gas turbine engines. It can be operated with either liquid or gaseous fuels and has both physical and optical access for use of laser-based or conventional measurement methods. Data are obtained for temperature, velocity statistics, and stable species (HC, CO, CO2, O2, NO). Velocity field data are also obtained under cold-flow (non-reacting) conditions.

Mean Temperature

Mean Species Concentration A key feature of the experiment is that the inflow to the combustor is a swirling channel flow with sufficient development length to provide fully developed turbulence. The swirl imparted to



the flow is achieved by use of thin, helical-blade swirlers designed to prevent separation and therefore the introduction of anomalous turbulence structure. Another key feature is the use of coannular swirl to provide a lift-but-stable flame configuration. The first feature is necessary for simulations that require full-field inflow boundary conditions. The second is required to provide a significant challenge to chemistry/turbulence models near the point of flame stabilization. Status: Work has been completed on a gaseous fueled test case. Our efforts are now focused on a liquid-fueled case which uses a lean, direct-injection (LDI) inflow geometry. Publications: Final Report Experiments in Fluids paper Contact: [email protected]




Mesoscale Burner Arrays for Gas Turbine Reheat Applications

Investigators: C. F. Edwards, Associate Professor, Mechanical Engineering Department; C. T. Bowman, Professor, Mechanical Engineering Department; S. Lee, K.-Y. Teh, Graduate Researchers Sponsor: NASA, Ultra Efficient Engine Technologies (UEET) Program Description: Use of a reheat cycle with high pressure ratio can significantly improve the specific power and efficiency of gas turbine engines for flight applications. The key to developing such engines is the ability to provide compact (in the axial direction) but distributed (in the transverse direction) combustion either between the high- and low-pressure turbine stages or even within the turbine stators passages. Achieving these requirements necessitates the use of a distributed approach to combustion. Mesoscale burner arrays have been developed to meet this requirement. Here the combustion is distributed such that diffusion is fast, but not dominant, and inertia is important, but not controlling. The result of operating with combustion in this regime is that compact, stable flames can be formed which are suitable for use with reheat cycles, but which also produce near-premixed (lower limit) levels of nitric oxide (NO).

Center post Quarl 5m

Swirler Inlet layer

Fuel layer A key feature of the mesoarray is that it is fabricated from silicon nitride. This material has excellent high-temperature capabilities and can be gel-casted using mutlt-mold shape deposition manufacturing into parts with complex internal manifolds. These internal manifolds are needed both to provide fuel distribution within the array and for thermal management. Status: Sixteen-element (4x4) arrays have been fabricated and tested using gaseous fuels. These arrays have shown that near-premixed NO levels can be achieved. Current work is focused on fabrication of a one-hundred element (10x10), multilayer array for gaseous fuels. Work has also begun on analysis and design of an array for liquid fuel testing.



10x10 Multilayer Array in Development Publications: Final Report WSSCI Paper Contact: [email protected]




Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines

Investigators: J. Christian Gerdes, Assistant Professor, Mechanical Engineering Depart-ment; Christopher F. Edwards, Associate Professor, Mechanical Engineering Department; Gre-gory M. Shaver, Matthew J. Rolle, Patrick A. Caton, Hanho Song, Graduate Researchers; NaluB. Kaahaaina, Research Engineer

Sponsor: Robert Bosch Corporation

Description: Homogeneous charge compression ignition holds great promise as a means toreduce NOx emissions and increase efficiency in internal combustion engines. There are severalmethods used to initiate HCCI, such as heating or pre-compressing the intake air, trappingexhaust gases from the previous cycle by closing the exhaust valve early, modulating intake andexhaust flows using variable valve actuation (VVA) to re-induct residual exhaust gas from theprevious cycle or some combination of these. Our approach is to use VVA to re-induct exhaustgas.

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misfires

Figure 1: Application of control in experiment - left: step change in desired in-cylinder peakpressure, right: cyclic dispersion reduction

Residual-affected HCCI combustion exhibits some fundamental control challenges concern-ing cycle-to-cycle coupling and combustion phasing. Unlike spark ignition (SI) or diesel engines,where the combustion is initiated via spark and fuel injection, respectively, HCCI has no specificevent that initiates combustion. Therefore, ensuring that combustion occurs with acceptabletiming, or at all, is more complicated than in the case of either SI or diesel combustion. Com-bustion timing in HCCI is dominated by chemical kinetics, which depend on the in-cylinderconcentrations of reactants and products and their temperature. In addition, residual-affectedHCCI exhibits strong cycle-to-cycle coupling through the residual gas temperature. Work output

1



is dependent on both the combustion phasing and the elevated in-cylinder pressure generatedfrom the combustion event. Thus, to control HCCI with VVA it is essential to understandhow the valves influence mass flows and combustion timing and how previous combustion cyclesinfluence the temperature of the reinducted products.

Although HCCI represents a complex physical process, the aspects most relevant for control- in-cylinder pressure evolution, combustion phasing and work output - can be captured withsimple physics-based models. These system models have VVA controllable parameters (residualmass fraction and effective compression ratio) as inputs, and relevant measurable parameters(peak pressure and phasing) as outputs. A control strategy that decouples phasing from peak in-cylinder pressure can then be formulated. This approach, as shown in Figure 1, has been shownto increase system stability, decrease the likelihood of misfire and allow accurate steady-stateand transient control of the engine.

Status:Current research efforts include experimental verification of techniques for the simultaneous

control of combustion timing and load. This control framework will be investigated for useduring SI to HCCI mode transitions.

Publications:Gregory M. Shaver, Matthew Roelle, J. Christian Gerdes, Patrick A. Caton and Christopher

F. Edwards, Multi-cycle Modeling of HCCI Engines Utilizing Variable Valve Actuation, Toappear in the ASME Journal of Dynamic Systems, Measurement and Control

Gregory M. Shaver and J. Christian Gerdes, Cycle-to-Cycle Control of HCCI Engines throughVariable Valve Actuation, In review: IEEE Transactions on Control Systems Technology

Gregory M. Shaver, J. Christian Gerdes, Parag Jain, Patrick A. Caton and ChristopherF. Edwards, Modeling for Control of HCCI Engines, Proceedings of the American ControlConference, pp. 749–754, 2003

Gregory M. Shaver and J. Christian Gerdes, Cycle-to-Cycle Control of HCCI Engines, Pro-ceedings of the 2003 ASME International Mechanical Engineering Congress and Exposition,IMECE2003-41966

Gregory M. Shaver, Matthew Roelle and J. Christian Gerdes, Multi-Cycle Modeling of HCCIEngines, Proceeding of the 1st IFAC Symposium on Advances in Automotive Control, 2004

Gregory M. Shaver, J. Christian Gerdes and Matthew Roelle, Physics-Based Closed-LoopControl of Phasing, Peak Pressure and Work Output in HCCI Engines Utilizing Variable ValveActuation, Proceedings of the American Control Conference, pp. 150–155, 2004

Gregory M. Shaver, Aleksandar Kojic, J. Christian Gerdes, Jean-Pierre Hathout, and JasimAhmed, Contraction and Sum of Squares Analysis of HCCI Engines, To appear in the proceed-ings of the 2004 IFAC Symposium on Nonlinear Control Systems

Matthew J. Roelle, Gregory M. Shaver, and J. Christian Gerdes, Tackling the Transition: AMulti-Mode Combustion Model of SI and HCCI for Mode Transition Control, To appear in theproceedings of the 2004 ASME International Mechanical Engineering Congress and Exposition


2



PROCESS INFORMATICS—A NEW PARADIGM FOR BUILDING COMPLEX CHEMICAL REACTION MODELS

Investigators: David M. Golden, Consulting Professor, and Craig T. Bowman, Professor, Department of Mechanical Engineering

Sponsor: Global Climate and Energy Program, Stanford University

Scope of Process Informatics: Process Informatics is a data-centric approach to developing predictive models for complex chemical reaction systems. It deals with all aspects of integration of pertinent data of complex systems (industrial processes and natural phenomena) whose complexity originates from chemical reaction networks. The primary goal of process informatics will be information gathering, validation, and transformation into useable form. The latter will include development of predictive (numerical/computer) models with quantified degrees of reliability. While such a scope may be applicable to any process, the immediate focus of Process Informatics will be on chemically-based processes.

Motivation: Chemical reaction models will never be complete. A problem is that the data on which models are based are scattered over different sources and are not properly evaluated. Most importantly, these data cannot be applied directly to practical problems—they have to be “transformed” into useful models. Such models, however, cannot be created by simple “compilation” of the data. Chemical reaction model building is a time-consuming activity that requires expert knowledge. The goal is to convert such model building into science, automate the methodology, and make the results available in a prompt and convenient form for the user.

Immediate needs for predictive reaction models presently exist in combustion engineering, the petrochemical industry, atmospheric chemistry, materials processing, biological systems and pharmaceuticals. As computers become more powerful and more readily accessible to industry, the industrial interest in process simulation is continuously growing.

Vision of Process Informatics: The Process Informatics infrastructure will have two principal components: a Database and a collection of Tools.

The Process Informatics Database will represent the most currently complete set of knowledge available in a given field. In the field of combustion, it will contain experimental data, on both combustion systems and on elementary reactions, molecular properties determined from quantum chemical calculations, reaction rates obtained from reaction-rate theories, and similar information. The Process Informatics Tools will be of two general kinds, those enabling the collection, transfer, organization, display, and mining of the data —i.e., computer science tools, and those enabling processing and analysis of the data along with assembly of the data into models—i.e., scientific and numerical tools.

The two principal customers of the Process Informatics System are the data provider and the model user. During the development stage, there will also be a model builder, whose role will eventually be automated—and providing the means for this automation will be a prime objective.

A Data Provider (Experimenter, Theorist) makes a request to deposit new observations or new computational results. The protocol assures completeness of the data submission. The deposited data are immediately analyzed for consistency with the database and the results are reported both to the data provider and to the scientific council (see below). Upon approval of the council, the database is modified. In other words, the database will be fluid and will be continuously modified and these modifications will be documented.

A Model User (design engineer, CFD researcher) requests a kinetic model (or a simulation with such a model) and specifies the conditions of interests, the desired level of accuracy, and the mathematic form of the model (detailed, reduced, parameterized, etc). The system checks for the existence of such a model, if none is available one is generated.



Another user might be a project manager (a member of the Scientific Counsel, or a researcher) who

wants to know whether a proposed experiment/calculation will improve the current database, and by how much. Various scenarios with the envisioned experiment or calculation can be evaluate. A similar question can be posed differently: what needs to be done to improve the predictability of a given model? Repeat old experiments? Under what conditions? New experiments? Which ones? New Calculations? What level of local error must be maintained to accomplish the stated goal?

The goal is not merely a collection of tools, but a shift in the paradigm of the scientific process: building targeted knowledge by the entire community and providing the wealth of information in its entirety to every user. To attain the vision described above will require the following: a) creation of enabling software infrastructure; b) development and implementation of scientific methods taking the full advantage of the approach; and c) establishment of a new paradigm of scientific collaboration for data collection, evaluation, and utilization.

Road to Process Informatics: Development of the above vision requires a concrete system. Reaction chemistry of combustion will serve as the initial system. Nearly all of the energy currently used in the industrialized world comes from burning fossil fuels and chemistry is the essence of combustion systems, from internal combustion engines to gas turbines. Knowledge of the chemical mechanism is at the center of device design to limit combustion-generated environmental pollution. Societal demands for cleaner and more efficient combustion are rapidly bringing the chemical aspects of combustion processes to the forefront.

A first effort at developing the new paradigm for dynamic models of complex chemical systems has been demonstrated with a quantitative chemical model for natural gas combustion, “GRI-Mech. http://www.me.berkeley.edu/gri_mech/

Organizational Structure: The success of the undertaking will also depend on organization and management. Based on the experience gained from the GRI-Mech project, the following organization is envisaged: To initiate the project, several working teams will be created, organized by subject and each containing representatives of different disciplines as necessary. An underlying goal will be a periodic release of “the best current model” via a dedicated web site. Leaders of all teams will form a management team, with a rotationally assigned leader. The entire team will meet periodically, probably coinciding with or as a part of a professional and contractual meeting

Scientific Council: The concept of the Scientific Council is an important component of the proposal. Its mission is “quality control” of the knowledge buildup in the scientific community, with combustion chemistry as the initial focus. The Council membership will begin with a few experts, with the intent of encompassing and engaging the entire community in time.

In many ways the Scientific Council is similar to a Data Evaluation Panel, an established practice today for database quality control. The difference—and hence the novelty underlying the shift in the scientific paradigm—is that the Council activity will be based on the analysis of the entire knowledge available in the field. It will be the goal of Process Informatics to develop tools and infrastructure to enable such operation of the Scientific Council.

Team: As this document is prepared, interest has been expressed in Process Informatics from the several organizations in the United States and abroad. Status: The GRI-Mech project is complete. This new project will begin with GCEP funding.

Contact: <[email protected]>



http://www.me.berkeley.edu/gri_mech/

mailto:<[email protected]>

Smart Sensors for Combustion Control

Investigators: Ronald K. Hanson, Woodard Professor, Department of Mechanical Engineering; Jay B. Jeffries, Senior Research Engineer; Daniel W. Mattison, Lin Ma, Jonathan Liu, Xin Zhou, Adam Klingbeil, and Gregory Rieker, Graduate Research Students Sponsors: Global Climate and Energy Project, Stanford University; Air Force Office of Scientific Research; Office of Naval Research; General Electric; and Zolo Technologies Description: Control of combustion using feedback from advanced fast-response sensors has the potential to minimize the environmental impact of energy conversion; for example, real-time control of combustor temperature can minimize emissions of combustion pollutants (such as NO, CO, and unburned hydrocarbons) while simultaneously maintaining combustion efficiency. These sensors thus offer great promise for monitoring and control of combustion and energy conversion technologies of the future. The laser-based sensors under development at Stanford are non-intrusive, in situ devices, which remotely interrogate the reactive gas/liquid stream and avoid the problems of the wall-mounted or extractive sampling sensors used today. These sensors, based on spectrally resolved absorption spectroscopy, target specific chemical constituents and thus enable novel new control strategies for modern energy conversion technologies, for applications ranging from transportation engines to large-scale stationary power plants. Such sensors offer the possibility for real-time measurements of multiple combustor variables, such as: gas temperature, combustion products (H2O and/or CO2), unburned hydrocarbons (UHC), reactive radical species (e.g., OH) and critical pollutants (e.g. CO and NO). Specific sensor and control strategies are under investigation for eventual use in closed loop control to maximize combustion efficiency and/or minimize key emissions (e.g. UHC, CO, and NO).

We have pioneered the development of sensors based on non-intrusive optical absorption exploiting the inexpensive semiconductor laser technology developed for the telecommunications industry. Figure 1 illustrates the sensor concept used for

Air + C H2 4N Shroud2

CO2 nmλ=1997

T, H2O nmλ=1343

T, H2O nmλ=1392

FiberCombiner

FiberPitch

Grating

1.5 cm

1.34 um1.39 um 1.8 um 2.0 um

T, H2O nmλ=1799 Burner

Free space laser light

Optical fiber

Flame

Figure 1. Compact, wavelength-multiplexed, diode-laser sensor for gas temperature and combustion products.



measurements of gas temperature and concentrations of combustion product (water vapor and carbon dioxide) in a laboratory-scale combustor. Light from a suite of diode lasers is combined in an optical fiber and pitched across the flame, dispersed, and directed to individual sensors for optical absorption measurements. Such sensors were recently combined with control algorithms to reduce the CO and unburned hydrocarbon (UHC) emissions from a laboratory-scale combustor by more than an order of magnitude. Using control strategies that capitalized on the rapid time response capabilities of tunable diode-laser sensors, we achieved combustion control times of less than 100 milliseconds, which is dramatically shorter than achieved with any previous control system. The same strategy was recently applied to an industrial-scale incinerator at the Naval Air Warfare Center in China Lake, CA with a similar reduction in CO and UHC emissions. This pioneering and highly successful demonstration of closed-loop control illustrates the potential of diode-laser absorption sensors for application to the advanced energy conversion systems of the future.

These compact and rugged sensors are suitable for harsh environmental applications; for example, fiber coupling of the light enables in-cylinder measurements in piston engines and combustor exit monitoring in gas turbines. The uniquely-fast time response enables these sensors to identify acoustic fluctuations in the gas temperature or to measure in-cylinder property variations with time (crank angle) during an individual engine cycle. Status: This work continues on a variety of fronts. Fundamental sensor development for air-breathing aero-engines is sponsored by AFOSR and General Electric. Integration of new temperature sensor strategies with combustion control in a swirl-stabilized, liquid-fueled combustor is supported by ONR. GCEP sponsors the development of new sensors for emissions monitoring and control applications. Our collaboration with Zolo Technologies provides access for state-of-the-art electro-optical components to enable compact packaging of laser-based sensors. Publications: 1. M.G. Allen, E.R. Furlong, and R.K. Hanson, “Tunable Diode Laser Sensing and

Combustion Control,” in Applied Combustion Diagnostics, ed. K. Kohse-Hoeinghaus and J. B. Jeffries, Francis and Taylor, New York, (2002), pp. 98-127.

2. J. Wang, M. Maiorov, J. Jeffries, D. Z. Garbuzuov, J. Connolly, and R. K. Hanson, "Remote Sensing of CO in Vehicle Exhausts using 2.3 µm Diode Lasers," Measurement Science and Technology 11, 1576-1584 (2000).

3. D.W. Mattison, C.M. Brophy, S.T. Sanders, L. Ma, L., K.M. Hinckley, J.B. Jeffries, and R.K. Hanson, "Pulse Detonation Engine Characterization and Control Using Tunable Diode-Laser Sensors," Journal of Propulsion and Power, 19, 568-572 (2003).

4. J.T.C. Liu, J.B. Jeffries, and R.K. Hanson, “Wavelength Modulation Absorption Spectroscopy with 2f Detection using Multiplexed Diode Lasers for Rapid Temperature Measurements in Gaseous Flows,” Applied Physics B, 78, 503-511 (2004).

Contact: http://navier.stanford.edu/hanson



Characterization of Coal-Char and Biomass-Char Reactivities to Oxygenat High Temperatures and High Pressures

Investigators: R. E. Mitchell, Associate Professor, Mechanical Engineering Department; P. A.Campbell and L. Ma, Graduate Researchers

Sponsor: The Global Climate & Energy Project

Description: There is considerable concern regarding the potential global environmental impactof fossil fuels used for power generation. By increasing the fraction of renewable energy in thenational energy supply, some of the impact can be mitigated. Co-firing biomass with coal intraditional coal-fired boilers or using biomass as a reburn fuel in advanced coal-fired boilerconfigurations represent two options for combined renewable and fossil energy utilization.Gasification of the biomass offers additional options. For example, gasification products can beupgraded, through synthesis, to methanol and even hydrogen, or the products can be burnedexternally in a boiler for producing hot water or in a gas turbine for generating electricity. Thehot gas from the gas turbine can be used to raise steam to be utilized in a steam turbine toenhance overall efficiency (i.e., an integrated gasification combined cycle (IGCC) scheme can beused). Other proposed, but not yet demonstrated, options involve combusting the gasificationproducts with coal in either co-fire or reburn boiler configurations.

The physical characteristics and chemical composition of the biomass influences how it can bestbe utilized. Upon rapid heating, some biofuels have high gas yields, rendering them suitable forgasification and reburn applications. Other biofuels have high char yields, and are better-suitedfor co-firing in direct combustion configurations. With the proper choices of biomass, coal,boiler design, and boiler operation, reductions in pollutant and net greenhouse gas emissions canbe realized. Identifying the proper choices requires that we gain a better understanding of thebehaviors of coals and biomass of various origins when exposed to specified conditions oftemperature, pressure, and gas composition. Understanding how the properties of the coals andbiomass influence their conversion rates to gaseous products is a necessity. Identifying optimumboiler configurations and operating conditions requires that we develop models capable ofpredicting accurately boiler performance and pollutant emissions. This requires anunderstanding of processes that control the physical transformations that fuel particles undergowhen exposed to hot, oxidizing environments and the chemical reactions responsible forconversion of the solid material to gaseous species and ash.

In this project, research activities are aimed at providing the information needed to characterizethe fundamental chemical and physical processes controlling coal and biomass conversion togaseous species in the type environments likely to be established in advanced biomass-firedgasifiers and coal-fired and biomass-fired boilers and furnaces. This requires examining theconversion process in high-temperature, high-pressure environments. The research effort willresult in a biomass-char gasification and combustion model applicable to advanced systems.

In our efforts to date, a laminar flow reactor is used to simulate the high-temperatureenvironments coal and biomass particles are exposed to during devolatilization and combustionin real devices. Partially reacted char samples are extracted from the flow reactor at selectedresidence times and subjected to a variety of tests to determine their physical and chemicalproperties.



As an example of recent results, a scanningelectron micrograph of almond shell charparticles extracted from the flow reactor 33 msafter injection into a hot gas containing 8 mol-% oxygen at 1243 K is shown on the right.The almond shell biomass has undergoneextensive mass loss during devolatilization at ahigh heating rate, rendering high-ash charparticles at over 92% conversion, by weight.

Particle size distributions, apparent densities,specific surface areas, and conversion rates in6 mol-% oxygen at temperatures from 623 Kto 873 K have been measured and used todetermine intrinsic reactivities to oxygen.

Scanning electron micrograph of the char ofalmond shell particles at 92% conversion

The figure on the right shows a plot ofreactivity versus conversion for the partiallyreacted almond shell char exposed to 6 mol-%oxygen at 623 K. The line representscalculations made using the following reactionmechanism involving the adsorption of O2 atfree carbon sites (Cf) and the desorption of COand CO2 from sites with adsorbed oxygenatoms (C(O)):

2 Cf + O2 2 C(O)

Cf + C(O) + O2 CO2 + C(O) + Cf

Cf + C(O) + O2 CO + C(O) + C(O)

C(O) CO + Cf

Measured and calculated reactivities duringoxidation in 6 mol-% O2 at 623 K

The excellent agreement between measured and calculated reactivity throughout char conversionserves to validate the chemical sub-model. Predicted mass loss rates at gas temperatures as highas 1300 K agree with measurements obtained in the laminar flow reactor, suggesting that thekinetic parameters used to describe the rate coefficients are reasonable.

Status: In this project, the type study undertaken with the almond shell biomass is beingundertaken with other biomass materials to provide data for analysis in our quest to understandhow biomass properties influence char conversion rates and the physical changes particlesundergo during the char conversion process. Data to characterize the impact of pressure on coaland biomass char conversion rates also need to be obtained as well as data on how pressureimpacts initial char-particle morphology. The data will permit the development and validation ofthe physical and chemical sub-models used in comprehensive models for coal-fired and biomass-fired process units. The comprehensive models can be used to investigate potential designstrategies and can help define optimum operating conditions that benefit coal and biomassconversion processes.




Energy and Human Welfare

Arrow, Kenneth and Lawrence Goulder. “Research Initiative on the Environment, the Economy, and Sustainable Welfare” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53

See also: Victor, David G. “The Program on Energy and Sustainable Development” . . . . . . . .

56



Research Initiative on the Environment, the Economy, and Sustainable Welfare

Principal Investigators: Kenneth Arrow and Lawrence Goulder Summary: Economics professors and IIS senior fellows Kenneth Arrow and Lawrence Goulder are coordinating a three-year Research Initiative on the Economy, the Environment and Sustainable Welfare, stemming from a 3-year, $1.5 million grant from the William and Flora Hewlett Foundation. Now beginning its second year, the Initiative involves 16 faculty or senior researchers from Stanford and elsewhere and consists of several projects to improve the management of natural resources so as to insure the quality of life of future generations.

The Initiative taps the expertise of economists, legal scholars, political scientists,

biologists, and engineers. It aims to incorporate relevant legal, political, ecological and technological information within an economics-based framework for identifying and evaluating policies to safeguard human well-being over the long term.

The Initiative has three main components. The first seeks to develop better

measures of whether particular nations are following economic paths that are “sustainable,” that is, which allow future generations to continue to enjoy the same quality of life as current generations. This work has both theoretical and empirical aspects. On the theoretical side, this work aims at expanding earlier measures of sustainability to incorporate uncertainty, technological change, and population growth in a consistent fashion. On the empirical side, a key issue is the extent to which potential substitutes are available for critical natural resources or for the various services that they provide.

The other two components of the Initiative focus on specific natural systems or

resources and on policies to improve their management. The second component concentrates on sustaining the climate system. It examines both domestic and international policies to slow the rate of accumulation of greenhouse gases in the atmosphere. A distinguishing feature of this work is the attempt to incorporate political constraints in the economic analysis of climate policy. Domestic policies under investigation include various emissions permits schemes, subsidies to research and development in low-carbon technologies, and policies targeted to the electricity and transport sectors. International policies under investigation include the Clean Development Mechanism, an important element of the Kyoto Protocol and international discussions, as well as new contracting mechanisms to reduce the risks that developing countries might otherwise face in engaging in international climate-change efforts.

The third component investigates the management of water resources. It includes

the evaluation of water projects in developing countries, with attention to the competing needs of upstream and downstream users of water, as well as the competition between the needs to preserve water to maintain ecosystem services and the current demands for water by humans. It also includes an exploration of the potential for developing water markets in developing countries to improve the allocation of water among competing



users. A third line of work in this component explores the feasibility in various countries of utilizing natural watersheds to provide water filtration and other important services. In the U.S., some water-management districts have enjoyed considerable savings by utilizing nature’s water-filtration services rather than depending on man-made water-treatment plants. Research under this component aims to assess the potential for similar cost-savings in other countries.

The Initiative is producing scholarly papers for academic journals as well as less technical reports oriented to a broader audience. It includes several workshops and conferences involving researchers from the academic community as well as individuals from business, government, and environmental organizations. Principal Investigators: Kenneth J. Arrow, Stanford University Lawrence H. Goulder, Stanford University Co-Investigators: Geir Asheim, University of Oslo Edward Barbier, University of Wyoming Antonio Bento, University of California at Santa Barbara Lans Bovenberg, Tilburg University, The Netherlands Gretchen Daily, Stanford University Partha Dasgupta, Cambridge University Karl-Goran Maler, Beijer Institute for Ecological Economics Urvashi Narain, Resources for the Future, Washington, DC Ian W. H. Parry, Resources for the Future, Washington, DC Sandra Postel, Global Water Policy Project, Amherst, Mass. Stephen Schneider, Stanford University Barton Thompson, Stanford University David Victor, Stanford University Roberton C. Williams III, University of Texas at Austin Postdoc: John Farrow, Stanford University Ph.D. Students: Daniel Barreto, Stanford University Derek Gurney, Stanford University Emeric Henry, Stanford University Mark Jacobsen, Stanford University Xiaoying Xie, Stanford University Undergraduates: Ben Abadi, Stanford University Wendy Sheu, Stanford University



Energy Policy

Victor, David G. “The Program on Energy and Sustainable Development”. . . . . . . . . Weyant, John P. and Hillard G. Huntington. “The Energy Modeling Forum” . . . . . . . Wolak, Frank A. “Energy Market Design, Performance Measurement and Monitoring” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

56 59 62

See also: Arrow, Kenneth and Lawrence Goulder. “Research Initiative on the Environment, the Economy, and Sustainable Welfare” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Schneider, Stephen H. “What is ‘Dangerous’ Climate Change?” . . . . . . . . . . . . . . . . .

53 16



The Program on Energy and Sustainable Development

Investigators David G. Victor, Director; Mark Hayes, Hisham Zerriffi, Erik Woodhouse, Nadejda Victor, Chi Zhang, Research Fellows; Becca Elias, Josh House, Research Associates Research Overview The Program on Energy and Sustainable Development is a research program with a core staff of 15 at Stanford and nearly four dozen partners overseas – mainly in key developing countries. Established with core funding from EPRI, the program examines the political, economic and institutional aspects of energy services worldwide. The program began in 2001 expanding with additional core funding from BP in 2003 and presently works on four topics: Electric Power Markets This research platform examines the interaction of the political, legal and economic forces that affect how countries restructure their electricity systems away from SOE-domination and toward greater use of markets to allocate resources. The Program is sponsoring a comparison of the political economy of power market restructuring in five major developing countries: Brazil, China, India, Mexico and South Africa. PESD held its first conference on the Political Economy of Power Market Reform at IIS on 19-20 February 2003. Close to ninety of the top minds in the field attended. In addition, the Program is conducting a joint study on the role of Independent Power Producers (IPPs) in the restructuring of power markets with the Bechtel Initiative for Global Growth and Change (BIGGC). The Program is also participating in in-depth studies on power market reform in China and India. In China the Program is sponsoring studies on scenarios for power market reform in Shanghai and Guangdong provinces. In India the Program is working with the India Institute of Management in Ahmedabad (IIM-A) on a USAID-funded study that examines the impact of market restructuring on the efficiency and dispatch of power plants in the states of Andhra Pradesh and Gujarat. The Program's newest research in this area will investigate how institutional structures affect the development and deployment of distributed generation technologies. The Program is also supporting a new project that will investigate the impact of a federal regulatory structure on private participation in infrastructure. Geopolitics of Gas By most estimates, global consumption of natural gas--a cleaner-burning alternative to coal and oil--will double by 2030. In the electric power sector, technological advances in turbine technologies have already made modular gas-fired power generation facilities the preferred choice for new investments.



But in the areas of highest-expected demand--North America, Europe, China, and South and East Asia--the projected consumption of gas is expected to far outstrip indigenous supplies. Delivering gas from the world's major reserves in areas like Russia and Iran to the future demand centers will require a major expansion of inter-regional, cross-border gas transport infrastructures. To investigate the implications of this shift, PESD is sponsoring a joint project with the James A. Baker III Institute for Public Policy of Rice University on the Geopolitics of Natural Gas. The study will utilize historical case studies as well as advanced economic modeling to examine the interplay between economic and political factors in the development of natural gas resources; our aim is to shed light on the political challenges that may accompany a shift to a gas-fed world. Our newest research on gas will focus on the gasification of the world's two largest countries, China and India. Energy and Development Industrialization brings a well-known shift from traditional energy sources--such as wood and crop residues--to more modern fuels and technologies. For households at the lowest income levels, rising welfare is both a cause and consequence of a shift in fuels and technologies. The Program on Energy and Sustainable Development is sponsoring research on the factors that explain when and how this "energy transition" occurs and its consequences for human welfare. How strong is the influence of income in driving the transition? What is the role of policies and programs in promoting the shift? The Program's niche is the development and application of sophisticated quantitative economic and engineering models. These models are being developed in tandem with field research, based principally in South Africa, India and China. Our aim is to allow policy makers to better predict energy--and in particular electricity--demand patterns, and in doing so maximize the efficiency of, and access to, modern energy systems. The Program's newest research in this area will investigate how institutional structures affect the development and deployment of distributed generation technologies. DG offers the potential to significantly improve the delivery of energy services in many of the world's poorest countries. Climate Change Whether or not Russia ratifies the Kyoto Protocol, the real question for serious climate policy is the period beyond 2012 when the Protocol's commitments expire. Should governments craft new agreements using the Kyoto framework, but with more stringent targets? Are new institutions and frameworks needed? The Program on Energy and Sustainable Development's newest area of work will contribute to this discussion in several ways. We are focusing on issues surrounding engagement of developing countries in the international effort to tame carbon--with attention to the special types of international commitments and activities that may be needed to attract these nations. We are also examining how the various emission trading systems that are presently taking form--such as in Europe, in some U.S. states, and



private schemes--could evolve into a more integrated global trading system. The centerpiece of our efforts will be a book laying out an effective international architectures for tackling the climate problem. Contact: http://pesd.stanford.edu



The ENERGY MODELING FORUM (EMF)

Investigators: John P. Weyant, Director, Energy Modeling Forum and Professor, Management Science and Engineering and Co-Investigator, Hillard G. Huntington, Energy Modeling Forum

Sponsors: The U.S. Department of Energy, The U.S. Environmental Protection Agency, National Renewable Energy Laboratory, and EMF affiliate’s program members Description: The Energy Modeling Forum (EMF) was established in 1976 to provide a structured framework within which energy experts from government, industry, universities, and other research organizations could meet to study important energy and environmental issues of common interest. Each study is conducted by an ad hoc working group, which compares the results from numerous models to help understand how these models differ from each other and how they collectively can be used to improve decisions. In the process, the forum provides an interesting and productive approach for identifying future research needs that will address policymaking and corporate strategies.

Each study focuses upon a specific study. In an issues-oriented process, each working group first identifies the questions of paramount concern to policymakers and decision makers. The group decides which issues can be best addressed with available energy and environmental policy models. In a decentralized approach, each model proprietor simulates his own model according to key assumptions and standards agreed upon by the larger working group. The Forum staff provides an integrating role in comparing the results and focusing the group’s discussion on the critical issues. Each study produces a short summary document for policymakers and corporate decision makers as well as a technical volume with supporting papers by participating experts. The EMF has completed major studies on a wide range of energy and environmental problems. Final reports for EMF 19 on “Alternative Technology Strategies for Climate Change Policy” and EMF 20 on “Natural Gas, Fuel Diversity and North American Energy Markets” were published during 2004. In addition, EMF 21 on “Multi-Gas Mitigation and Climate Change.” entered the publication process. Finally two new studies EMF 22 on “Long Run Climate Policy Scenarios and Scenarios in Transition," and EMF 23 on "World Natural Gas Markets and Trade" were initiated. EMF continues to run a yearly multidisciplinary workshop featuring many of the leading experts on climate change adaptation, mitigation and modeling. The EMF 20 study on “Natural Gas, Fuel Diversity and North American Energy Markets” addresses whether the nation can rely upon natural gas as a potential bridge fuel to a more environmentally friendly future. Working with the National Renewable Energy Laboratory and Stanford’s Program on Energy Sustainability and Development, the EMF has organized a set of working groups to evaluate a range of available and cost-effective technologies and options that use gas. These prospects would allow non-carbon energy sources to be developed over the next several decades. A much greater reliance upon natural gas would be possible if technology could find new ways to discover gas



resources cheaply. On the other hand, increasing reliance upon natural gas could force higher prices that would make natural gas less desirable, if gas supplies were more limited. Through model comparison and supporting analysis, the EMF 20 group explored these issues. The EMF 21 study on “Multi-Gas Mitigation and Climate Change” seeks to evaluate the effects of including mitigation of non-CO2 GHGs and terrestrial sequestration into climate change targets. The Non-CO2 GHG Network, organized by the IEA Greenhouse Gas R&D Programme, the US Environmental Protection Agency, and the European Commission Environment Directorate-General, is also coordinating the study with EMF. The study includes over 20 modeling and analysis teams from 11 countries and the modeling work for it was concluded in early 2004. In the last few years, much advancement have been made in climate policy analyses with the incorporation of non-CO2 GHGs (methane, nitrous oxide, HFCs, PFCs, and SF6) into economic models. The objectives of this new study group are to: • Conduct a new comprehensive, multi-gas policy assessment to improve the

understanding of the effects of including non-CO2 GHGs and terrestrial sequestration into short- and long-term mitigation policies. The study will answer the question: How important are non-CO2 GHGs and terrestrial sequestration in climate policies?

• Advance the state-of-the-art in integrated assessment/climate economic modeling. • Strengthen collaboration between non-CO2 GHG and terrestrial sequestration experts

and modeling teams. • Publish the results as a special issue of The Energy Journal.

This study has brought together the traditional EMF climate economic modelers with experts on non-CO2 GHGs and terrestrial sequestration to foster better cross-discipline understanding and improve the overall analysis of climate change mitigation. In addition, the non-CO2 GHG and terrestrial sequestration experts have developed new data specifically for the study in collaboration with the modelers. This data has allowed the development of global and tropical forest carbon sequestration supply curves. The EMF 22 study will consider new climate policy stabilization and transition scenarios, as well as pushing the state-of-the-art in modeling black carbon and land use forward. About twenty modeling teams from all regions of the world have expressed interest in participating in this study. The EMF 23 study on "World Natural Gas Markets and Trade" addresses the pending international competition for natural gas resources and its competitive future against other energy sources. A key world energy transition over the next several decades will be the extent to which natural gas can replace coal in the electric power sector as nations seek to improve the environment. The EMF is currently organizing a set of working



group meetings to evaluate a range of available and cost-effective technologies and options that produce, transport and use natural gas. These prospects would allow non-carbon energy sources to be developed over the next several decades. A much greater reliance upon natural gas would be possible if technology could find new ways to discover gas resources cheaply. On the other hand, increasing reliance upon natural gas could force higher prices that would make natural gas less desirable, if gas supplies were more limited. Through model comparison and supporting analysis, the EMF 23 group will explore these issues. The EMF has also sponsored yearly two-week summer workshops on integrated assessment of climate change for ten years. The goal is to improve the representation of climate impacts within the integrated assessment modeling frameworks. These workshops bring together researchers working on climate chance impacts with those working on integrated assessments and modeling of climate change. The workshops are funded by the U.S. Department of Energy, U.S. Environmental Protection Agency, U.S. National Oceanographic and Atmospheric Administration, U.S. National Science Foundation, National Institute of Environmental Studies of Japan, the Australian Bureau of Agricultural and Resource Economics, Electric Power Research Institute and ExxonMobil Research and Engineering. These “Snowmass” workshops have been extraordinarily successful in increasing the level of interactions between the integrated assessment modeling teams, between that group and the climate impacts community and even, in some cases, among key researchers in the climate impacts community. These workshops will continue for at least another few years. Publications: E. Farrow, “Energy Modeling Forum Conference: Retail Participation in Competitive Power Markets,” in Electricity Pricing in Transition, 2002. H. Huntington, “Market Based U.S. Electricity Prices: A Multi-Model Evaluation,” in Electricity Pricing in Transition, 2002. J. Weyant, editor, on “The Costs of the Kyoto Protocol: A Multi-Model Evaluation,” Special Issue of The Energy Journal, 1999. J. Weyant, editor, "EMF 19: Alternative Technology Strategies for Climate Change Policy," Special Issue of Energy Economics, 2004. Contact: [email protected] Website: http://www.stanford.edu/group/EMF



Energy Market Design, Performance Measurement and Monitoring

Investigator: Frank A. Wolak, Professor, Economics Department

Sponsor: National Science Foundation

Description: In spite of the California electricity crisis, three years of unusually high prices in theUS natural gas industry, two electricity crises in the New Zealand electricity market in three years,and several other episodes of aberrant market outcomes in energy industries in other countries, theprocess of worldwide energy industry restructuring continues. One lesson that has emerged fromthese events is that the unique features of the structure of production and regulatory oversight inelectricity and natural gas industries make them susceptible to the exercise of unilateral marketpower. This fact makes successful restructuring in electricity and natural gas industries extremelychallenging. The only thing regulators can be sure of is that the initial market design will containflaws that must be corrected, and if they are not corrected significant consumer harm can occur ina very short time. Consequently, particularly for these two industries, there is a need for consistentmeasures of market performance that can be compared across regions and over time to detect marketdesign flaws and determine the appropriate regulatory intervention or market rule change.

This research devises and implement techniques for measuring market performance inelectricity, natural gas and petroleum industries. This research has four lines of inquiry measuringperformance in wholesale electricity markets. I plan to apply the methodologies for measuringmarket performance in the electricity supply industry presented in Borenstein, Bushnell and Wolak(2002) and Wolak (2003b) to provide a comprehensive diagnosis of the causes and solution to theCalifornia electricity crisis. The second project will adapt these two methodologies for measuringmarket-wide and firm-level market power (or market inefficiencies) to wholesale electricity marketsthat use locational marginal pricing (LMP) procedures to price electricity. The third topic is howto value the net benefits of transmission network upgrades in a wholesale market regime.Transmission network expansions have the potential to increase the competitiveness of a wholesaleelectricity market because they can increase the number of independent suppliers able to competewith each local supplier, a source of benefits to transmission upgrades that did not exist in the formervertically-integrated regime. The power outage in the eastern U.S. on August 14 and 15, 2003,suggests that an internally consistent methodology for valuing transmission upgrades in a wholesalemarket regime is far overdue. The fourth line of inquiry will study the extent integration of financialmarkets for electricity with the real-time market for electrical energy. In all U.S. wholesale markets,electricity is traded in a number of financial markets in advance of delivery. There are a numberof arbitrage relationships that should hold between these markets if energy traders are risk-neutral,and a different set of relationships that should hold if energy traders are risk-averse. This researchwill derive these relationships and examine their empirical relevance.

In all countries around the world, the natural gas industry is increasingly integrated with theelectricity supply industry because combined cycle-natural gas-fired facilities are the least cost wayto meet an increase in electricity demand in virtually countries with a natural gas deliveryinfrastructure that do not have significant unexploited hydroelectric resources. Most all of the morethan 100,000 MW of new generation capacity constructed in the U.S. over the past four years isnatural gas-fired. This enormous increase in the demand for natural gas has put substantial stress



on the North American natural infrastructure. Prices in the U.S. natural gas industry for the pastthree years have averaged almost double their average values during the decade of the 1990s. Tounderstand this sequence of events, my proposed research will construct a measure of natural gasmarket performance similar to the measures of electricity market performance described above andapply it to the U.S. natural gas industry using data collected by the Federal Energy RegulatoryCommission (FERC).

The final project analyzes the performance of the California gasoline market. For the pastyear, retail gasoline prices in California have averaged close to two dollars per gallon, and slightlyhigher in large metropolitan areas. More important, these prices are 30 cents per gallon higher thanaverage retail prices in the rest of the United States. Two major factors blamed for higher gasolineprices in California are: (1) higher production costs to meet California’s stringent environmentalstandards, and (2) a less competitive refining and retailing sector which leads to higher marginsabove the variable cost of production earned by both gasoline refiners and wholesalers. Thisresearch will quantify the relative contribution of each of these and other possible explanations forhigher gasoline prices in California.

Status: This work continues research previously funded by the National Science Foundation andthe Energy Foundation.

Publications (available at http://www.stanford.edu/~wolak):

Borenstein, Severin, Bushnell, James and Wolak, Frank A. (2002) “Measuring Market Inefficiencies inCalifornia's Restructured Wholesale Electricity Market,” American Economic Review, December,1367-1405.

Wolak, Frank A. (1999) “Market Design and Price Behavior in Restructured Electricity Markets: AnInternational Comparison, in Competition Policy in the Asia Pacific Region, EASE Volume 8,Takatoshi Ito and Anne Krueger (editors) University of Chicago Press, 79-134.

Wolak, Frank A. (2000) “An Empirical Analysis of the Impact of Hedge Contracts on Bidding Behavior ina Competitive Electricity Market,” International Economic Journal, Summer, 1-40.

Wolak, Frank A. (2003a) “Identification and Estimation of Cost Functions Using Observed Bid Data: AnApplication to Electricity,” Advances in Econometrics: Theory and Applications, Eighth WorldCongress, Volume II, Mathias Detwatripont, Lars Peter Hansen, and Stephen J. Turnovsky (editors),Cambridge University Press, 133-169.

Wolak, Frank A. (2003b) “Measuring Unilateral Market Power in Wholesale Electricity Markets: TheCalifornia Market 1998 to 2000,” American Economic Review, May 2003, 425-430.

Wolak, Frank A. (2003c) “Diagnosing the California Electricity Crisis,” The Electricity Journal,August/September, 11-37.




Hydrocarbon Reservoirs

Mavko, Gary. “CO2 Sequestration in Coal Seams”. . . . . . . . . . . . . . . . . . . . . . . . . . . . Mavko, Gary. “Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nur, Amos. “Computational Rock Physics” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nur, Amos. “Lithology and Fluid Detection in Hydrocarbon Reservoirs” . . . . . . . . . . Nur, Amos. “Rock Physics of Methane Hydrate Reservoirs” . . . . . . . . . . . . . . . . . . .

65 67 69 71 73



CO2 Sequestration in Coal Seams

Investigators: Gary Mavko, Professor; Manika Prasad, Research Associate; Tapan Mukerji,Research Associate; Anyela Morcote-Rios, Graduate Student, Geophysics Department.

Sponsors: The Stanford Rock Physics Consortium.

Description: We initiate an extensive rock physics investigation of various coals. The mainmotivation behind this study is to compile a list of seismic attributes of coal that can be used formeasuring, monitoring, and verifying the efficiency and risks of carbon sequestration in the sub-surface. Coal seams have a large potential for CO2 storage. In turn, CO2 sequestration in coalseams can enhance methane production. However, since their geophysical properties are notfully understood, indirect monitoring of sequestration success remains a challenge. The mainobjective of this work is to create a rock-physics database and relevant models of seismicsignatures of coals of different ages, geologic basins, and ranks. Several samples of natural coalwill be tested in the laboratory to obtain the dependence of their P- and S-wave velocity anddensity on porosity, maturation, and other key properties.

A special focus of the research will be on changes in rock physics properties of coal during gas(methane and CO2) sorption and desorption. We will study the relations between seismicattributes and conventional coal petrographic and proximate analyses. We will also developtheoretical models defining seismic velocity-to-physical property transforms in coals. Theultimate goal is to provide key diagnostic technologies for quantitatively interpreting seismicdata and linking them with geologic models to estimate risk and efficiency of carbonsequestration in coals.

The non-destructive technique of acoustic imaging has proved to be a powerful tool in mappingmacro- and microstructure of cleat systems in terms of elastic impedance at a cm-scaleresolution. The opaque nature of the kerogen and the associated pyrite makes opticalcharacterization rather challenging thus making other non-destructive methods necessary.

Figure 1 shows acoustic sounding of a coal sample along with an optical line trace of its mainfeatures; the C-scans (Figure 1a) are surface images showing cleats and dull and bright coalbands. The B-scan (Figure 1b) is a zero-offset reflection profile that shows reflections frominterfaces with an impedance change and cleats. Figure 1c is a reconstruction of a 30 x 30 x 8mm volume of the sample created from 40 B-scan images. The dull and bright coal bands withdifferent impedance imaged in the C-scans (Figure 1a) are seen to dip in the B-scans (Figure 1b)and in the reconstructed volume image (Figure 1c). Figure 1c also maps numerous cleats that cutacross the dipping layers. “Ground truth” for the scans is seen from the line trace of the featuresmade after cutting the sample to expose the sides (Figure 1d).

Status: This work continues, sponsored by the Stanford Rock Physics Project.



Publications:

Prasad, M., Mapping impedance microstructure in rocks with acoustic microscopy, The LeadingEdge, 20, 172-179, 2001.


Figure 1. Low-frequency (25 MHz) scans (a-c) and a line trace image of optical features (d)of a coal sample. C-scans of top and bottom faces (a), a representative B-scan (b), and a 3-Dimage (c) made from consecutive B-scans show the internal structure of the coal. Thereconstructed top surface in (c) correlates well with the C-scan image above it and with theoptical line traces in upper part of (d). The cleats, dull and bright coal bands, and theiralignment at depth can be traced in both B- and C-scan images as well as in thereconstruction volume image. The optical line traces in (d) were made after cutting the sidesof the coal sample. They show ground truth for the scans and for the 3-D reconstruction.



Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization

Investigators: Gary Mavko, Professor, Dept. of Geophysics, Stanford Rock Physics Lab; Tapan Mukerji, Research Associate; Diana Sava, Ezequiel Gonzalez, Juan Florez, Graduate Students; Per Avseth, Senior Geophysicist, Norsk-Hydro, Norway, Geophysics Department. Sponsors: Stanford Rock Physics Project; U.S. Dept. of Energy, Norsk-Hydro, PDVSA

Figure 1: An example of seismic reservoir characterization.Isoprobability surfaces resulting from a statistical rock physicsanalysis of near and far-offset seismic impedances. The surfacesindicate zones of high probability of oil sands and shales.

Description: Stanford Rock Physics Lab continues its pioneering research in applied statistical rock physics for reservoir characterization. The goal is to quantify and reduce uncertainties in reservoir exploration and management by integrating fundamental concepts and models of rock physics, statistical pattern recognition, and information theory, with seismic inversions and geostatistics. Rock physics allows us to establish the links between seismic response and

reservoir properties, and to extend the training data by Monte Carlo simulations. Prior geologic information can help to constrain the various possible interpretation models and help reduce the uncertainty. Seismic imaging brings an indirect, but nevertheless spatially exhaustive, information about reservoir properties that are not available from pinpoint well data alone. Classification and estimation methods based on computational statistical techniques such as non-parametric Bayesian classification,

bootstrap, and neural networks help to quantitatively measure the interpretation uncertainty and the mis-classification risk. Geostatistical stochastic simulations incorporate spatial correlation and small-scale variability. Figure 1 shows a North Sea example of Bayesian classification guided by rock physics modeling. Combining deterministic physical models with statistical techniques helps us to develop new methods for interpretation and estimation of reservoir rock properties from seismic data. These formulations identify not only the most likely interpretation but also the uncertainty of the interpretation, and serve as a guide for quantitative decision analysis. Subsurface property estimation from remote geophysical measurements is always subject to uncertainty because of many inevitable difficulties and ambiguities in data acquisition, processing, and interpretation. Even with perfect data, interpretation is uncertain because of intrinsic natural variability. It is therefore necessary to express quantitatively the information content, and uncertainty in rock property estimation from seismic data. Geologic information can provide very useful constraints to reduce the uncertainty of interpretation. One of the focus areas of our research has been to reconcile and integrate qualitative geologic descriptions with mathematical rock physics models. An example of this is shown in Figure 2 from a fractured reservoir characterization study. Outcrop and well log studies showed that the limestone reservoir had three different depositional facies: sub-tidal,

1



shoal margin, and shoal, with different probabilities of occurrence as shown in Figure 2. The shoal environment had a fracture occurrence of only about 16%. Well logs indicated that the shoal facies had distinctly lower velocities and impedances. This combined to give a robust prior constraint on fracture occurrence. This simple prior probability helps to constrain more complicated interpretations based on P-wave seismic anisotropy. Diana Sava at the Stanford Rock Physics Project has developed innovative Bayesian methods for fracture prediction from seismic data by combining geologic information with rock physics models of fractured porous media. One of our projects involves applying these methods to characterize basement fractures in offshore India.

We are also working on applying the methods of statistical rock physics to analyze converted wave (P-to-S) seismic attributes. Ezequiel Gonzalez is developing practical methods for exploiting P-to-S AVO behavior. By combining near and far offsets it may be possible to distinguish fizz water from commercial gas concentrations. Statistical rock physics analyses shows the promise of P-to-S impedances to increase dramatically the probabilities of seismically discriminating high and low gas saturations.

Figure 2: Depositional environments and fracture distribution.

Status: The work continues sponsored by Stanford Rock Physics Project. Some of the

emerging research areas in applied statistical rock physics include: strategies to better understand, quantify, and integrate qualitative, 'fuzzy' geologic information in terms of probabilities for seismic interpretation of reservoir properties and a better understanding of the physics behind attributes based on mode conversions and wave attenuation. Publications Avseth, P., Mukerji, T., Jorstad, A., Mavko, G. and Veggeland, T., 2001, Seismic reservoir

mapping from 3-D AVO in a North Sea turbidite system: Geophysics, 66, 1157-1176 Gonzalez, E., Mukerji, T., and Mavko, G., 2003, Near and far offset P-to-S elastic impedance for

discriminating fizz water from commercial gas, The Leading Edge, 22, 1012-1015. Mukerji, T., Jorstad, A., Avseth, P., Mavko, G. and Granli, J. R., 2001, Mapping lithofacies and

pore-fluid probabilities in a North Sea reservoir: Seismic inversions and statistical rock physics: Geophysics, 66, 988-1001

Sava, D., Mukerji, T., Florez, J. and Mavko, G., 2001, Rock physics analysis and fracture modeling of the San Andres reservoir, 71st Ann. Mtg: SEG., 1748-1751.

Sava, D., Florez, J., and Mavko, G., 2002, Seismic fracture characterization using statistical rock physics, James Lime Reservoir, Neuville Field, 72st Ann. Mtg: SEG., 1889-1892.




Computational Rock Physics

Investigators: Amos Nur, Professor; Youngseuk Keehm, Research Associate; Tapan Mukerji,Research Associate; Manika Prasad, Research Associate; Ayako Kameda, Graduate Student;Ezequiel Gonzalez, Graduate Student, Geophysics Department.

Sponsors: The U.S. Department of Energy; Shell Exploration and Production; ApacheCorporation; Rock Solid Images.

Description: Earth sciences is undergoinga gradual but massive shift fromdescription of the earth and earth systems,toward process modeling, simulation, andprocess visualization. This undertaking ischallenging because the underlyingphysical and chemical processes are oftennonlinear and coupled. In addition, manyprocesses occur in strongly heterogeneoussystems. An example is two-phase fluidflow in rocks, which is a nonlinear,coupled and time-dependent problem andoccurs in complex porous media. Tounderstand and simulate these complexprocesses, the knowledge of underlyingpore-scale processes is essential. Thisresearch project focuses on buildingphysical property simulators in realisticpore microstructures. These pore-scalesimulators, such as fluid flow, elastic, electrical and NMR property simulators, are modules of acomputational rock physics framework (Figure 1), which is a new paradigm of quantitativemodels for coupled, nonlinear, transient and complex behavior of earth systems. Thiscomputational environment can significantly complement the physical laboratory, with severaldistinct advantages: (1) rigorous prediction of the physical properties; (2) interrelations amongthe different rock properties in a given pore geometry; and (3) simulation of dynamic problemswith coupled and nonlinear physical processes.

A rigorous pore-scale simulator requires three important traits: reliability, efficiency, and abilityto handle complex micro-geometry. We have implemented single-phase and two-phase flowsimulators using the Lattice-Boltzmann (LB) algorithm, since it handles very complex poregeometries without idealization of the pore space. Parallel single-phase and two-phase flowsimulators have been also implemented for fast and accurate calculation of fluid flow propertiesof rocks. Finite-element method (FEM) is used for elastic and electrical property simulators, anda random-walk technique is used for NMR simulation.

Digital PoreGeometry

f(minerals, fluids, t)

Numerical Simulation Techniques(Lattice-Boltzmann, FEM, Parallelization)

ElasticProperties

NMRProperties

FluidProperties

ElectricalProperties

Simulation of nonlinear and coupledprocesses

Figure 1. Computational rock physics framework



Permeability estimation from thin sections consists of two components – stochastic 3D porousmedia reconstruction, and flow simulation using the LB method. This technique successfullypredicted the permeability of several sandstones samples. We have used a sequential indicatorsimulation technique with porosity and the two point correlation function; currently, we areworking on using higher statistics, such as multipoint correlation functions and patternsimulations. We are also pursuing this technique for relative permeability estimation (Figure 2).

The diagenesis modeling is a basic framework for quantifying trends of physical properties for agiven diagenetic process. The immediate application of this method will be incorporating more

realistic diagenetic mechanisms, such as chemicaldeposition and dissolution, by altering digital rocksamples in the computer, e.g., depositing diageneticcement, dissolve minerals, or deposit small shaleparticles. By so doing, geologically-plausible variationsin the depositional environment as well as diagenesis canbe represented in the computer without having directaccess to a multitude of physical samples. The porosityand permeability of the altered samples can be calculatedto assess how these properties may vary laterally andvertically in the field. This approach places acomputational rock physics lab at the fingertips of apractitioner.

Status: This work continues, sponsored by the DOE and Stanford Rock Physics Project.

Publications:

Bosl, W., Dvorkin, J., and Nur, A., A study of porosity and permeability using a latticeBoltzmann simulation, GRL, 25, 1475-1478, 1998.

Kameda, A., and Dvorkin, J., To see a rock in a grain of sand, The Leading Edge, 23, 8, 2004.

Keehm, Y., Mukerji, T., and Nur, A., Computational rock physics at the pore scale: Transportproperties and diagenesis in realistic pore geometries, The Leading Edge, 20, 180-183, 2001.

Mese, A., Tutuncu, A., Kameda, A., Nur, A., and Dvorkin, J., Digital rock physics for sands andshales, Oil and Gas Network, 5, #3, 68, 2004.


Figure 2. Two phase oil/waterflow.



Lithology and Fluid Detection in Hydrocarbon Reservoirs

Investigators: Amos Nur, Professor; Gary Mavko, Professor; Ezequiel Gonzales, GraduateStudent; Kyle Spikes, Graduate Student; Futoshi Tsuneyama, Graduate Student; Jack Dvorkin,Senior Research Scientist, Geophysics Department.

Sponsors: The Stanford Rock Physics Consortium.

Description: Our long-term objective has been to help the domestic petroleum industry todiscover and safely produce hydrocarbons to mitigate our national dependence on foreign oil.Our principal approach is to use the rock physics to relate the in-situ lithology and hydrocarbonsaturation to seismic observables, such as the acoustic and elastic impedance, and seismic waveattenuation.

One example where systematic physics-based approach is needed is in the discrimination of sandwith commercial gas quantities from sand with residual gas during seismic prospecting. Suchdiscrimination is obviously very important, especially in the deep water where well costs areenormous. However, such discrimination may be difficult because only small amounts of freegas are required to be present in brine to lower the P-wave impedance and Poisson’s ratio of therock. As a result, seismic reflections may be only weakly dependent on gas quantity.

To solve this problem, we recognize that in real rock lithology, porosity, saturation, and theirelastic signatures are interrelated. For example, in a fining-upwards depositional cycle, the meangrain size is small which means that the irreducible water saturation is large. Large irreduciblewater saturation translates into small non-commercial gas saturation. In other words, largequantities of gas simply cannot enter sand where the irreducible water saturation is large and thecapillary forces that keep the original brine in place are strong. Once such basic logic isestablished, we may start looking for seismic attributes that can help map the shape of thereservoir to uncover its fining-upwards character. Such attributes could be pseudo-impedanceand pseudo-Poisson’s ratio (Figure 1) obtained from seismic traces within a certain frequencywindow.

We also pursue a pseudo-well generation approach where the properties of shale and reservoirsand are perturbed at a prototype well to imitate depth-related compaction, diagenesis, orvariations in a depositional setting. After a pseudo-well is generated, synthetic seismic traces arecalculated at this pseudo-well and compared with real seismic data with a supposition that if theseismic responses match, the conditions of the subsurface are also similar. In line with thiseffort, we work on creating lithological templates from which an earth model could be assembledand then synthetic seismic traces generated. We also explore how to use modern recordingtechniques which employ multicomponent seismic reflections to better map hydrocarbonquantity in-situ.




Publications:

Dvorkin, J., and Gutierrez, M., Grain sorting, porosity, and elasticity, Petrophysics, 43, 3, 185-196. 2002.

Dvorkin, J., and Alkhater, S., Pore fluid and porosity mapping from seismic, First Break, 22,February 2004, 53-57, 2004.

Dvorkin, J., Walls, J., Uden, R., Carr, M., Smith, M., and Derzhi, N., Lithology substitution influvial sand, The Leading Edge, 23, 108-114, 2004.

Spikes, K.T., and Dvorkin, J.P., Reservoir and elastic property prediction away from wellcontrol, OTC-16922-PP, 2004.


Figure 1. Synthetic seismic traces and attributes for the pseudo-well at low frequency. Fromleft to right: Gather (black) and stack (red); P- and S-wave impedance; Poisson’s ratio; GR;water saturation; total porosity; pseudo-impedance; and pseudo-Poisson’s ratio. The sandwith small gas saturation (large water saturation) has a fining-upwards shape.



Rock Physics of Methane Hydrate Reservoirs

Investigators: Amos Nur, Professor; Manika Prasad, Research Associate; Ingrid Cordon,Graduate Student; Jack Dvorkin, Senior Research Scientist, Geophysics Department.

Sponsors: The Stanford Rock Physics Consortium, Rock Solid Images.

Description: Gas hydrates are solids comprised of a hydrogen-bonded water lattice withentrapped guest molecules of gas. There are convincing arguments that vast amounts of methanegas hydrate are present in sediments under the world's oceans as well as in on-shore sediments inthe Arctic. This hydrate is possibly the largest carbon and methane pool on earth. As such,methane hydrate may be the principal factor in global climate balancing. One may also treat thismethane pool as a potential energy source. These considerations ignite the scientific andbusiness community’s interest in quantifying the amount of methane hydrate in the subsurface.Gas hydrate reservoir characterization is, in principle, no different from the traditionalhydrocarbon reservoir characterization. Similar and well-developed remote sensing techniquescan be used, seismic reflection profiling being the dominant among them.

Seismic response of the subsurface is determined by the spatial distribution of the elasticproperties. By mapping the elastic contrast, the geophysicist can illuminate tectonic features andgeobodies, hydrocarbon reservoirs included. To accurately translate elastic-property images intoimages of lithology, porosity, and the pore-filling phase, quantitative knowledge is needed thatrelates rock’s elastic properties to its bulk properties and conditions. Specifically, toquantitatively characterize a natural gas hydrate reservoir, we must be able to relate the elasticproperties of the sediment to the volume of gas hydrate present and, if at all possible, thepermeability. One way of achieving this goal is through rock physics effective-mediummodeling. The use of a first-principle-based rock physics model is crucial for gas hydratereservoir characterization because only within a physics-based framework can one systematicallyperturb reservoir properties to estimate the elastic response with the ultimate goal ofcharacterizing the reservoir from field elastic data. Rock physics relations have to be upscaled tobecome applicable to seismic reservoir characterization.

We have developed a number of rock physics models that can be used for inferring the locationand quantities of methane hydrate from seismic. These models have been successfully used byus as well as by the industry (Japex, JNOC, Schlumberger) in Nankai Trough offshore Japan; theGulf of Mexico; and on-shore in Canada to quantify natural methane hydrate reservoirs.


Publications:

Dvorkin, J., and Nur, A., Rock physics for characterization of gas hydrates, in The Future ofEnergy Gases, USGS Publications, 293-298, 1993.



Helgerud, M., Dvorkin, J., Nur, A., Sakai, A., and Collett, T., Elastic-wave velocity in marinesediments with gas hydrates: Effective medium modeling, GRL, 26, 2021-2024, 1999.

Dvorkin, J., Nur, A., Uden, R., and Taner, T., Rock physics of gas hydrate reservoir, TheLeading Edge, 22, 842-847, 2003.

Dvorkin, J., and Uden, R., Seismic wave attenuation in a methane hydrate reservoir, The LeadingEdge, 23, 8, 2004.


Figure 1. Left, impedance versus porosity in well Mallik 2L-38 in Arctic Canada, color-coded by hydrate concentration. The impedance is large due to the presence of methanehydrate in the pore space. Right, the same data (every fifth point) shown as empty blackcircles on the background of the modeled impedance strip. The modeled impedance is color-coded by hydrate concentration. The model accurately mimics the data.



Hydrogen

Goodson, Kenneth E. and John K. Eaton. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jacobson, Mark Z. “Effects of a Hydrogen Economy”. . . . . . . . . . . . . . . . . . . . . . . . .

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See Also: Cho, KJ. “Hierarchical Multi-Scale Modeling of Nano-Materials Engineering for Hydrogen Technology”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nilsson, A. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis” . . . . . . . . . . . . .

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Hydrogen 75

Fundamentals of Two-Phase Flow Phenomena in Fuel Cells Investigators: Kenneth E. Goodson, Associate Professor, Mechanical Engineering Department, John K. Eaton, Professor and Vice Chair, Mechanical Engineering Department, Carlos H. Hidrovo, Research Associate, Theresa A. Kramer, Postdoctoral Scholar, Ching-Hsiang Cheng, Postdoctoral Scholar, Eon Soo Lee, Julie E. Steinbrenner, Sébastien Vigneron, Fu-Min Wang, Graduate Researchers. Sponsor: Honda R&D Co., Ltd. Description: In the past two decades, environmental concerns and stronger emission regulations have led to a renewed interest in Proton Exchange Membrane Fuel Cells (PEMFC). Performance gains in PEMFC can be attained by utilizing microchannels (0.05 – 1 mm) to improve gas routing. However, they complicate water management particularly in terms of flooding. The complexities of water management have been previously investigated, but there still exists an urgent need for a detailed study of two-phase flow in microchannels and water transport interactions with the GDL. This work focuses on the experimental investigation, visualization and modeling of mass transport induced two-phase flow in microchannels. A series of microchannels with water injection slots in the side walls allow for distributed water injection/evaporation (including a porous wall), flow-regime visualization, thermometry, heating, and pressure measurements. These structures are microfabricated by plasma etching microtrenches in silicon and covering them with pyrex glass. Figure 1 shows the general layout of current test structures and three specific examples of test structures with different water injection geometries. Air is flown through the U-shaped channel while water is introduced through the channel perpendicular to it.

Figure 1: General test structure layout and micrographs of three specific examples.

Important flow parameters such as friction factor and Nusselt number, which govern the fluid mechanics and heat transfer characteristics of the flow, can be extracted from these measurements. Likewise, flow visualization studies provide information in terms of flow structure, regimes and transitions characteristics. These data are interpreted using compact models for heat/mass/momentum transfer and flow transition criteria. The models are based on

One 20 µm slot

Three 20 µm slots Ten 20 µm slots

10 mm

0.5 mm

Gas channel Water injection channel

Gas inlet Gas outlet

Water inlet


Hydrogen 76

1D homogeneous and separated flow formulations with regime specific closure laws. The end goal is to incorporate these models into fuel cell oriented CFD simulation algorithms. Figure 2 shows friction factor extraction from pressure drop/flow rate measurements under different water injection conditions and accompanying flow visualization images in a hydrophobic channel. From Figure 2 it can be seen that the f-Re value remains relatively constant throughout the range of pressure drops under no water injection (single phase flow) conditions. However, the f-Re values become larger at low pressure drops under water injection conditions. As can be appreciated from the images to the right of Figure 2, the injected water tends to form slugs that block a large portion of the cross sectional area of the channel and can severely impede the flow of air. The size of the slugs and blockage of the channel is inversely proportional to the pressure drop. Thus, at low pressure drops the water fills a good portion of the channel and severely obstructs the flow of air, effectively increasing the “apparent” friction of the flow (lower air flow rate).

Figure 2: Friction factor calculations and flow visualization images for a hydrophobic channel.

Status: We continue to investigate the effects of water injection on flow behavior and develop models that accurately capture the physics of some simple flows. We are also working towards the realization of more sophisticated test structures with enhanced measuring capabilities and that closer resemble actual fuel cell channels geometries and conditions. Publications: C. H. Hidrovo, et. al, “Experimental Investigation and Visualization of Two-Phase Flow and Water Transport in Microchannels”, accepted to ASME IMECE04. S. Vigneron, et. al, “1D Homogeneous Modeling of Microchannel Two-Phase Flow for Water Management Purposes in Proton Exchange Membrane Fuel Cells”, accepted to ASME IMECE04. Contacts: [email protected], [email protected].

Friction Factor Relation Constant, CHydrophobic, Pabs,in=30psi (207 kPa)

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1

Effects of a Hydrogen Economy Investigators: Mark Z. Jacobson, Whitney Colella, David M. Golden, Cristina Archer, Gerard Ketefian Sponsor: GCEP Description: The purpose of this project is to study the potential effects on global and regional climate, stratospheric ozone, and air pollution of replacing fossil-fuel based vehicles and electric power plants with those powered by hydrogen fuel cells, where the hydrogen is produced either from steam reforming of methane, coal gasification, or wind energy. The effects are being estimated with a three-dimensional numerical model of the atmosphere and ocean that is driven by emissions and that treats gases, aerosols, meteorology, clouds, radiation, and surface processes. An important part of the study is the development of emission scenarios for the model simulations. U.S. emission data were obtained from the U.S. National Emission Inventory, which considers 370,000 stack and fugitive sources, 250,000 area sources, and 1700 categories of onroad and nonroad vehicular sources (including motorcycles, passenger vehicles, trucks, recreational vehicles, construction vehicles, farm vehicles, industrial vehicles, etc.). Emission inventories for each hydrogen scenario were prepared following a process chain analysis that accounted for energy inputs and pollution outputs during all stages of hydrogen and fossil-fuel production, distribution, storage, and end-use. Emitted pollutants accounted for included CO, CO2, H2, H2O, CH4, speciated ROGs, NOx, NH3, SOx, and speciated particulate matter. Figure 1 shows a map of projected H2 emission resulting from switching all vehicles in the U.S. to fuel cell vehicles. Three scenarios have been run so far: switching the current U.S. fleet of onroad motor vehicles to hydrogen fuel-cell vehicles, where hydrogen was produced by (1) steam-reforming of methane, (2) wind energy, and (3) coal gasification. Results from the first scenario suggest that switching vehicles in the U.S. to hydrogen produced by steam-reforming of methane may reduce emission of NOx, reactive hydrocarbons, CO, CO2, BC, NO3

-, and NH4+, but increase CH4, H2, and SO2 (slightly). The switch may also

decrease O3 over most of the U.S. but short-term near-surfaces increases may occur over low-vegetated cities (e.g., in Los Angeles and along the Boston-Washington corridor) due to loss of NOx that otherwise titrates O3. The switch is also estimated to decrease PAN, HCHO, and several other pollutants formed in the atmosphere. Isoprene may increase since fewer oxidants (OH, O3) will be available to destroy it. Findings to date suggest that, even under a worst-case scenario of 10% hydrogen leakage, the conversion of the current fleet to hydrogen-fuel cell vehicles, where hydrogen is generated by steam-reforming of methane, may result in a measurable improvement in U.S. air quality.


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2

Figure 1: Map of estimated hydrogen consumption in the U.S. by county if all onroad vehicles were switched to hydrogen fuel-cell vehicles. Light blue=0-5; Medium blue=5-10; Dark blue=10-20; Purple=20-40; Green=40-80; Yellow=80-160; Orange=160-320; Magenta=320-640; Red>640 Gg/yr (1Gg=109g). See text for discussion. This figure is not final. Contact: [email protected]; [email protected], [email protected]


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Renewable Energy

Bent, Stacey F. “Hot Wire Chemical Vapor Deposition of Photovoltaic Polymer-based Films” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Brongersma, Mark and Shanhui Fan. “Plasmonic Contacts for Energy Efficient Solar Cells and Light Sources”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Horne, Roland N. “Properties of Steam/Water Flow in Geothermal Rock” . . . . . . . . . Jacobson, Mark Z. “Mapping U.S. Wind Resources” . . . . . . . . . . . . . . . . . . . . . . . . . . . McGehee, Michael D. “Nanostructured Photovoltaic Cells” . . . . . . . . . . . . . . . . . . . . . Peumans, Peter. “Organic Optoelectronics for Renewable Energy”. . . . . . . . . . . . . . . . Somerville, Chris. “Genetic Modification of Plant Cell Walls for Enhance Biomass Production and Utilization” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Walbot, Virginia. “Impact of UV-B Radiation on Corn (Zea mays L.)” . . . . . . . . . . . .

81 83 84 86 88 90 93 95

See Also: Mitchell, R. E. “Characterization of Coal-Char and Biomass-Char Reactivities to Oxygen at High Temperatures and High Pressures” . . . . . . . . . . . . . . . . . . . . . . Nilsson, A. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis”. . . . . . . . . . . . . .

50 12


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Hot wire chemical vapor deposition of photovoltaic polymer-based films Investigators: Stacey F. Bent, Associate Professor, Dept. of Chemical Engineering; Gillian A. Zaharias, Helen Shi Sponsor: CPIMA Description: The field of synthesizing and studying organic polymeric or oligomeric films for electronic applications has been rapidly expanding in the last decade. Such films have been successfully used as semiconductor layers in light emitting diodes, field effect transistors and photovoltaic solar cells. The organic starting materials are much less expensive than those for inorganic devices, and, since the films are essentially plastic, can be deposited on flexible or curved substrates. In the simplest physical picture, the delocalized pi orbitals of a conjugated oligomer or polymer chain act as a conduction band for charge carriers. A number of polymers with conjugated backbones have shown excellent promise for photovoltaic conversion, especially when mixed with a dopant or co-polymer that acts as an electron acceptor, facilitating charge transport and preventing electron-hole recombination. The majority of polyconjugated films described in the literature are synthesized by traditional “wet” chemical methods and made into thin films by spin coating or printing. The synthesis begins with a monomer in solution, and polymerization is usually induced by adding a soluble oxidant or radical initiator. For example, polythiophene can be formed by mixing thiophene in chloroform with iron(III) chloride. Once polymerized, however, most polyconjugated materials are insoluble and thus not able to be dip-coated or spin-coated onto a substrate. This obstacle has been surmounted in many cases by attaching alkyl side chains along the polymer. However, bulky or lengthy side groups can prevent the polymer chains from forming a compact film and thus can have a negative impact on electronic performance. Nonetheless, spin- and dip-coating are inexpensive, and extensive research in creating solution-processible polymers has resulted in promising photovoltaic and other devices. As an alternative synthetic approach, we are investigating hot wire chemical vapor deposition (CVD) as a solvent-free method of forming and processing organic films. Such a method has several potential benefits: 1) We may be able to deposit films with certain microstructures, having conjugated backbones without side chains, that cannot be made by conventional “wet” syntheses. 2) Well-optimized CVD reactors have been known to give rise to exceptionally compact, pinhole-free films. 3) Organic solvents in industrial processes are a primary source of groundwater pollution. 4) Although vacuum systems are necessarily expensive to set up and maintain, forming organic films by CVD allows for the easy integration of polymer deposition with existing device fabrication facilities. Moreover, only a rough vacuum may be needed in many cases for quality films. Our current project explores the possibility of using various organic precursor molecules in our hot wire CVD reactor to form films with significant polyconjugation. Filament material and temperature, substrate temperature, and chamber pressure are all varied, and internal reflection infrared spectroscopy is used as an initial probe of deposited film structure and composition.


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Inmost cases, very little is known or easily predictable about how these molecules react in a CVD environment, so a large number of experiments with different parameters is necessary to begin to understand the reactivity and chemistry of each precursor. The results will then be used to design more successful CVD procedures. References: “Hot wire chemical vapor deposition as a novel synthetic method for electroactive organic thin films,” Mater. Res. Soc. Symp. Proc., 816 (2004) I12.9. “Characterization of polyconjugated thin films synthesized by hot wire chemical vapor deposition of aniline,” G. A. Zaharias, H. H. Shi, and S. F. Bent, Thin Solid Films, in press. Contact: [email protected]


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Plasmonic Contacts for Energy Efficient Solar Cells and Light Sources

Prof. Mark Brongersma, Materials Science and Engineering Prof. Shanhui Fan, Electrical Engineering Peter Catrysse (Graduate Researcher), Electrical Engineering

Keywords: Solar cells; Light sources; Contact designs; Plasmonics; Nanopatterning; Efficiency; State of the art solar cells and light emitting devices utilize either transparent conducting electrodes, such as Indium Tin Oxide, or patterned metallic structures to collect/inject current. From an electronics viewpoint metallic contacts are preferred because their superior DC conductivity leads to lower Ohmic losses. From an optical viewpoint, transparent conductors are more favorable as they allow more light to enter/exit the structure. Truly energy efficient devices could be fabricated if electrical contacts can be fabricated with metallic-like conductivities and the transmissivity of a dielectric film. The Brongersma and Fan research groups are aiming to design exactly such contacts by exploiting the strong interaction of light with the conduction electrons in metallic contacts that gives rise to surface plasmon excitations (= collective electron oscillations). Surface plasmon excitations are able to increase the transmissivity of metallic contacts by several orders of magnitude if such contacts are patterned with specially designed nanoscale features. Large scale computer simulations (Fan), nanofabrication methods (Brongersma), and optical characterization techniques (Brongersma) are used to optimize the design of these nanopatterns. Contact via: Prof. Brongersma: [email protected]


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Properties of Steam/Water Flow in Geothermal Rock

Investigators: Roland N. Horne, Professor of Petroleum Engineering, Kewen Li, Senior Research Engineer, Allan Chen, PhD student. Sponsor: US Dept of Energy, through the Stanford Geothermal Program. Description: Steam/water relative permeability and capillary pressure are important properties for geothermal reservoir engineering, in that they have a major influence on the performance of geothermal reservoirs under development. All numerical simulations of geothermal reservoir performance require the input of relative permeability and capillary pressure values, yet actual data on these parameters has not been available. The Stanford Geothermal Program (SGP) has succeeded in making fundamental measurements of steam/water flow in porous media and thereby made significant contribution to the industry by providing both understanding of the phenomena as well as actual parameter value measurements. Two important problems left to undertake are the measurement of steam/water relative permeability and capillary pressure in geothermal rock (most of the previous study was conducted in high permeability sandstone as well-controlled test material), as well as the understanding of how steam-water boiling mixtures flow in fractures. The Stanford Geothermal Program uses both theoretical and experimental approaches to conduct the research. We use numerical simulation for modeling work and we use an X-ray CT scanner as one of our main experimental tools to measure in-situ water saturation and its distribution. We also design and construct purpose-built apparatus to conduct the experiments needed. The mechanism of two-phase flow through fractures exerts an important influence on the behavior of geothermal reservoirs. Currently, two-phase flow through fractures is still poorly understood. In this project, nitrogen-water experiments were conducted in both smooth- and rough-walled fractures to determine the governing flow mechanisms. The experiments were done using a glass plate to allow visualization of flow. Digital video recording allowed instantaneous measurement of pressure, flow rate and saturation. Saturation was computed using image analysis techniques. The experiments showed that the gas and liquid phases flow through fractures in nonuniform separate channels (see Fig. 1).

Figure 3: Examples of gas-water flow channels.


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The data from the experiments were analyzed using Darcy's law and using the concept of friction factor and equivalent Reynold's number for two-phase flow. For both smooth- and rough-walled fractures a clear relationship between relative permeability and saturation was seen. The calculated relative permeability curves follow Corey-type behavior, as shown in Fig. 2. The sum of the relative permeabilities of the two phases is not equal to one, indicating phase interference. The equivalent homogenous single-phase approach did not give satisfactory representation of flow through fractures. The graphs of experimentally derived friction factor with the modified Reynold's number do not reveal a distinctive linear relationship (as has sometimes been associated with multiphase flow in fractures).

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Status: The project is ongoing. At present the fracture flow experiments are considering steam-water flow, which in preliminary experiments has been seen to differ significantly from nitrogen-water flow. Publications: Belen, R.P., Jr.. and Horne, R.N.: "Inferring In-Situ and Immobile Water Saturations from Field Measurements", Geothermal Resources Council Transactions 24 (2000). Chen, C.Y., Diomampo, G.P., Li, K., and Horne, R.N.: "Steam-Water Relative Permeability in Fractures", Geothermal Resources Council Transactions 26 (2002). Li, K., Nassori, H., and Horne, R.N.: “Experimental Study of Water Injection into Geothermal Reservoirs,” Geothermal Resources Council Transactions 25 (2001). Li, K., and Horne, R.N.: "A Capillary Pressure Model for Geothermal Reservoirs", Geothermal Resources Council Transactions 26 (2002). Li, K. and Horne, R.N.: “An Experimental and Theoretical Study of Steam-Water Capillary Pressure,” SPEREE (December 2001), 477-482. Li, K. and Horne, R.N.: “Characterization of Spontaneous Water Imbibition into Gas-Saturated Rocks,” SPEJ (December 2001), 375-384. Sullera, M.M., and Horne, R.N.: "Inferring Injection Returns form Chloride Monitoring Data", Geothermics, 30, (2001), 591-616. Wang, C., and Horne, R.N.: "Boiling Flow in a Horizontal Fracture", Geothermics, 29, 2000, 759-772. Contact: [email protected]


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Mapping U.S. Wind Resources Investigators: Mark Z. Jacobson, Associate Professor, Cristina L. Archer, Graduate Researcher, Gilbert M. Masters, Professor, Civil and Environmental Engineering Department Partial Sponsors: NSF, NASA, EPA Description: This was a project to study the availability and characteristics of U.S. wind resources. Wind energy produces about 0.06% of the world’s energy supply today, but its globally-averaged growth rate of 30% per year over the last five years is the fastest growth rate of any energy source. Globally, total installed wind capacity at the end of 2002 was over 30,000 MW, with 12,001 MW installed in Germany, 4830 in Spain, 4685 MW in the U.S., and 2880 MW in Denmark, among others. Wind currently supplies 20% of Denmark’s electric power and 4.7% of Germany’s electric power but only around 0.1% of U.S. electric power.

This project was motivated by the fact that electric power from wind energy depends strongly on the availability and magnitude of the wind, and the total availability of wind resources in the U.S. is uncertain. The main goal of this project was to map and analyze U.S. wind resources at 80 m, the height of large, modern wind turbines. This goal was carried out by first collecting global wind data from over a thousand vertical sounding locations and several thousand near-surface wind measurement locations worldwide. Interpolation and extrapolation techniques were then developed and applied to the data to calculate winds at 80 m.

The figure below (from Archer and Jacobson 2003), shows a map of U.S. winds

at 80 m, averaged over the year 2000, generated from the project. The map identifies two

Figure 1. Map of wind speed at 80 m, averaged over all hours of the year 2000 for the continental U.S., derived from surface and sounding data.


Renewable Energy 86

previously uncharted areas of strong winds, along the southeastern and southern coasts of the United States, both near population centers. The map also indicates that 80-m winds at 25% of all monitoring sites were > 7 m/s, the threshold for annual-average wind speed allowing wind energy to be competitive with coal and natural gas in terms of price (Jacobson and Masters, 2001) suggesting that the U.S. may have ample wind power to produce a large quantity of electric power with a low direct cost. Table 1 summarizes the color coding. From Archer and Jacobson (2003). Class Wind speed at 10

m (m/s)

Wind speed at 80 m (m/s)

Identifying color for Figure 4

1 < 4.4 <5.9 Light blue 2 4.4-5.1 5.9-6.9 Blue 3 5.1-5.6 6.9-7.5 Dark blue 4 5.6-6.0 7.5-8.1 Green 5 6.0-6.4 8.1-8.6 Yellow 6 6.4-7.0 8.6-9.4 Red 7 >7.0 ≥9.4 Black

Table 1. Wind speeds corresponding to different power classes at 10 m and 80 m, for use in Figure 1.

Another finding of the study was that, when multiple wind sites are considered, the number of days with no wind power and the standard deviation of the wind speed, integrated across all sites, are substantially reduced in comparison with when one wind site is considered. Therefore a network of wind farms in locations with high annual mean wind speeds may provide a reliable and abundant source of electric power. References: Archer, C. L., and M. Z. Jacobson, Spatial and temporal distributions of U.S. winds and

wind power at 80 m derived from measurements, J. Geophys. Res., 108 (D9) 4289, doi:10.1029/2002JD002076, 2003. http://www.stanford.edu/group/efmh/winds/index.html.

Jacobson, M. Z., and G. M. Masters, Exploiting wind versus coal, Science, 293, 1438-

1438, 2001. Contacts: [email protected]

[email protected] [email protected]


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Nanostructured Photovoltaic Cells

Investigators Michael D. McGehee, Assistant Professor, Materials Science and Engineering; Yuxiang Liu, Vignesh Gowrishankar, Chiatzun Goh, Shawn Scully, Kevin Coakley, Graduate Researchers Introduction This project, funded by the Global Climate and Energy Project, involves making efficient photovoltaic (PV) cells with semiconducting polymers that could be deposited in reel-to-reel coaters. Careful analysis and optimization of each process that occurs in bulk heterojunction PV cells will be carried out and devices based on ordered interpenetrating networks of organic and inorganic semiconductors will be created. Specifically this research will lead to devices that will efficiently split excitons and carry charge to electrodes, that will have improved packing of the molecules in the organic semiconductor to enhance its ability to carry charge, and that will have a modified organic-inorganic interface to prevent recombination of electrons and holes. It is anticipated that charge recombination in the cells will be almost completely eliminated and energy conversion efficiencies in the range of 10-15% will be obtained. Background

Currently the best commercially available PV cells are made of crystalline silicon and have an energy conversion efficiency of 12%. The cost of these cells is $3 per Watt of power generated under solar AM 1.5 conditions. These costs need to be reduced by an order of magnitude to around $0.3 per Watt for PV cells to be competitive with other energy generation systems and be manufactured on a large scale. A revolutionary breakthrough in reducing the costs of PV cells may be achieved if the semiconductor were deposited from solution onto large flexible substrates in reel-to-reel coating machines similar to those used to make food packaging. Manufacturing costs would be much lower because reel-to-reel coaters use very little energy and have an exceptionally high throughput. Installation costs would be lower because lightweight flexible PV cells could be handled more easily than heavy silicon panels. Since organic semiconductors, such as conjugated polymers, can be deposited from solution, they are very attractive for PV applications. Research on organic PV cells has shown that it is important to have two semiconductors with a large interfacial area so that photogenerated excitons can be split by electron transfer.1-4 PV devices with interpenetrating networks of two semiconductors are known as bulk heterojunction cells.

The processes involved in operating a bulk heterojunction PV device are shown in Figure 1. To optimize performance of these cells, the desirable processes (1. light absorption, 2. exciton diffusion, 3. forward electron transfer, and 4. charge transport) should be maximized, while the undesirable recombination processes (5. geminate recombination and 6. back electron transfer) should be limited. This can be achieved by improving charge carrier mobility and slowing down the rate of back electron transfer so that photogenerated charge carriers can escape from the film before recombination occurs, while maintaining a thick enough film to allow most of the light to be absorbed.


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Figure 1: A schematic diagram of the energy levels in an organic heterojunction photovoltaic cell and the electronic processes (defined in the text) that occur in one.

Results and Future Plans We have made ordered bulk heterojunction PV cells by infiltrating semiconducting polymers into mesoporous titania.5,6 Currently, we are trying to make the pores straight to align the polymer chains and improve their hole mobility. We are also trying to improve exciton diffusion and electron transfer. These are important steps towards our long-term goal of enabling the reel-to-reel manufacturing of bulk heterojunction PV cells. (1) Yu, G.; Gao, J.; Hummelen, J. C.; Wudl, F.; Heeger, A. J. Science 1995, 270,

1789. (2) Shaheen, S. E.; Brabec, C. J.; Sariciftci, N. S.; Padinger, F.; Fromherz, T.;

Hummelen, J. C. Appl. Phys. Lett. 2001, 78, 841. (3) Huynh, W. U.; Dittmer, J. J.; Alivisatos, A. P. Science 2002, 295, 2425. (4) Peumans, P.; Yakimov, A.; Forrest, S. J. of Appl. Phys. 2003, 93, 3693. (5) Coakley, K. M.; McGehee, M. D. Appl. Phys. Lett. 2003, 83, 3380. (6) Coakley, K. M.; Y., L.; McGehee, M. D.; Frindell, K. M.; Stucky, G. D. Adv.

Funct. Mater. 2003, 13, 301.

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b.)

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Fig. 1: Finite-element model of the enhanced optical absorption due to a random array of 10Å diameter Ag clusters in an organic thin film.

Organic Optoelectronics for Renewable Energy Investigator: P. Peumans, Assistant Professor, Department of Electrical Engineering. Organic photovoltaic (PV) cells Traditional PV cell technologies based on inorganic semiconductors produce clean electricity at a cost per kWh that is nearly an order of magnitude higher than that of electricity generated by fossil fuel combustion. Organic PV cells have recently attracted considerable attention because of their potential to substantially reduce the cost of solar electricity by lowering the cost of the substrate, materials, processing and installation. While the power conversion efficiency of organic PV cells has increased steadily since their inception to the current state-of-the-art of 3-4%, it still falls far below that achieved in crystalline silicon (ηP~24%). Organic PV cells remain therefore uneconomical as an energy source. Our short-term research efforts focus on developing device architectures and fabrication methods for organic PV cells with power conversion efficiencies exceeding 10%. Our long-term goal is to render organic photovoltaics the cheapest known option for electric energy production. Concrete projects being pursued are: Multijunction cells: We have demonstrated that transparent metal nanoclusters contacts allow organic PV cells to be stacked in series, resulting in an increased in power conversion efficiency over single junction devices [1]. The use of thinner individual cells and the ability to adjust the absorption edge of each individual cell, allow efficiencies closer to the thermodynamic limit to be achieved. This approach is also used to construct very-high-efficiency inorganic PV cells but

requires careful control over the multilayer growth. Organic materials are inherently advantageous in this respect since heterostructure growth does not require lattice matching. We are now exploring the limits of this approach through the use of novel materials (low bandgap, band offset tuning), device modeling, growth studies, and material and device characterization. Nanoscale optical design: The presence of noble metal nanoclusters in organic films enhances the linear optical absorption of the organic material (Fig. 1), leading to a concomitant increase in the power conversion efficiency of a thin PV cell. We have developed a quantitative understanding of this effect [2] and are exploring strategies to exploit this effect to a larger extent. We will focus on reducing unwanted excitation quenching using thin dielectric insulators shells and on

optimizing the nanoscale organization of the metal structure for optimal absorption enhancement. In addition, we have discovered that the use of aperiodic dielectric stacks embedded in the substrate can lead to a 50% increase in power conversion efficiency by realizing broadband resonant cavities matched to the solar spectrum, leading to further enhancements of the optical absorption. In this project, we will use electromagnetic and device modeling, optimization techniques, dielectric multilayer stacks, nanoscale metal patterning and device growth and fabrication. As a part of this effort, we are constructing a dedicated


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Fig. 2: Combined aerosol/organic vapor phase deposition system.

Fig. 3: Simulation of phase separation in a binary mixture resulting in a bulk heterojunction donor-acceptor photovoltaic cell.

computing architecture for very-large-scale electromagnetic simulations using the finite-difference time-domain (FDTD) method. Composite systems: We are investigating the use organic composites and hybrid systems consisting of nanocomposites of inorganic nanocrystals (TiO2, CdSe), large molecules (carbon nanotubes, polymers) and small molecular weight organic materials. These systems exhibit a wider tuning range and can be used in combination with the above approaches to achieve higher efficiencies. We will further improve the quantitative models we have developed [3] and explore vapor phase deposition techniques [4]. In contrast to wet deposition techniques (spin coating, ink jet printing, dip coating), a vapor phase technique would afford the incorporation of these advanced materials into more complex multilayer structures and stacked devices with full control over the nanoscale morphology through kinetic control. An aerosol deposition tool currently under development in our laboratory (Fig. 2) allows for the deposition of inorganic nanoclusters, very large molecules, polymers and

small molecular weight materials and is scalable to roll-to-roll type processing. High performance devices can be fabricated by layering the various materials using this entirely dry process. Furthermore, the ability to deposit virtually any nanostructured material allows for the realization of complete PV cells, including a passivation layer, in a single reactor, leading to very-low-cost manufacturing. Device modeling: A hierarchy of models across multiple length scales, from molecular dynamics models to continuum device models (see Fig. 3), is used to verify the developed insights and design better structures.

Other PV-related research projects: the evaluation of new materials for increased exciton diffusion lengths and lower bandgaps, the integration of photosynthetic antenna systems into organic PV cells, organic PV cell lifetime, the effect of source material purity on the performance and lifetime of organic PV cells, innovative form factors for organic PV cells (e.g. lightweight PV cells on textile fiber), innovative fabrication techniques (e.g. vapor jet printing), p and n-type doping for increased VOC.


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Very-high-efficiency solid-state organic light sources In 1997, lighting was responsible for 8% (1775 billion kg) of the worldwide CO2 emission and costed $230 billion [5]. Efficient light-emitting diode (LED) based solid state white lighting systems have a significant potential to reduce GHG emission. Organic LEDs (OLEDs) are a promising white light source that can be manufactured at low cost and in novel, practical form factors (e.g. tiles, flexible foil). While state-of-the-art white OLEDs approach the efficiency of fluorescent lighting, 80% of the generated photons remain unused because of total internal reflection in the substrate, waveguiding and plasmon polariton emission. Using dielectric stacks and metal nanostructures, the angular and spectral distribution of the photon density of states can be altered to inhibit emission into these lossy modes, resulting in large efficiency gains and white-emitting devices with wall-plug efficiencies exceeding those of fluorescent lighting by a factor of two or more. Collaborations We work closely with research groups in Chemistry, Chemical Engineering and Material Science and Engineering for an integral approach to the above projects. This research will be supported by the Stanford Organic Electronics Laboratory (SOEL), a central state-of-the-art organic electronics research facility currently being built by the group of Prof. Peumans. References: [1] P. Peumans, A. Yakimov, and S.R. Forrest, J. Appl. Phys. 93, 3693 (2003). [2] B. Rand, P. Peumans, and S.R. Forrest, accepted for publication in J. Appl. Phys. [3] P. Peumans, S. Uchida, and S.R. Forrest, Nature 425, 158 (2003). [4] M. Shtein, P. Peumans, J. Benziger, and S.R. Forrest, J. Appl. Phys. 93, 4005 (2003). [5] E. Mills, in Proceedings from the 5th International Conference on Energy-Efficient Lighting, May 2002, Nice, France.


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Genetic Modification of Plant Cell Walls for Enhanced Biomass Production and Utilization

Investigator: Chris Somerville, Professor, Department of Biological Sciences, and Director, Carnegie Institution, Department of Plant Biology Sponsors: U.S. Department of Energy and U.S. National Science Foundation Description: Woody biomass represents an important source of biomaterials in forms such as paper, lumber and tall oils. In addition, there is widespread interest in the potential to expand the use of woody biomass in renewable energy generation and liquid fuels. The principal components of woody biomass are cellulose, lignin and several classes of non-cellulosic polysaccharides (eg., xylan, xyloglucan, pectins). These polymers comprise “cell walls” that enclose each plant cell and provide the structural framework that allows plants to assume an upright growth habit. Because of technical difficulties, relatively little is known about how the polymers are synthesized and deposited, and what controls the amount and kind of each polymer. My group is engaged in various approaches to understanding and modifying cell wall composition with a view to genetically modifying certain plants for enhanced biomass production and utilization. Our long-term goal is to develop plants that accumulate significantly higher density of certain polymers and also, to develop plants in which the composition of the polymers is tailored for specific downstream needs. Toward these ends we are engaged in identifying the genes encoding the enzymes that catalyze synthesis of the principal polymers of the cell wall. We are also dissecting the regulatory circuits that control how each of the genes are expressed. In addition, we are characterizing microbial enzymes that may be useful for probing the structure of intact cell walls and may also be useful in processing biomass to feedstocks and fermentable sugars.

A scale model of the polysaccharide organization in a dicot cell wall. The density of polymers has been reduced by two orders of magnitude to facilitate viewing. (from Somerville et al., 2004)


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Publications: Gillmor, C.S., Poindexter, P., Lorieau, J., Sujino, K., Palcic, M., Somerville, C.R. (2002) The α-glucosidase I encoded by the KNOPF gene is required for cellulose biosynthesis and embryo morphogenesis in Arabidopsis. J. Cell Biol., 156,1003-1013 Scheible, W.R., Fry, B., Zimmerli, L., Somerville, S., Loria, R., Somerville, C.R. (2003) An Arabidopsis mutant resistant to Thaxtomin A, a cellulose Synthesis Inhibitor from Streptomyces spp. Plant Cell, 15: 1781-1794.

Rhee, S.Y., Osborne, E., Poindexter, P. and Somerville, C.R. (2003) Microspore separation in the quartet 3 mutants of Arabidopsis is impaired by a defect in a developmentally regulated polygalacturonase required for pollen mother cell wall degradation. Plant Physiol., 133,1170-1180 Hamann, T., Osborne, E., Youngs, H.L., Misson, J., Nussaume, L., and Somerville, C.R. (2004) Tissue-specific expression of CESA and CSL genes in Arabidopsis. Cellulose 11,273-277 Vorwerk, S., Somerville, S.C. and Somerville, C.R. (2004) The role of plant cell wall polysaccharide composition in disease resistance. Trends Plant Sci. 9, 203-209 Somerville, C., Bauer, S., Brininstool, G., Facette, M., Hamann, T., Milne, J., Osborne, E., Paredez, A., Persson, S., Raab, T., Vorwerk, S., Youngs, H. (2004) Towards a systems approach to understanding plant cell walls. Science 306,2206-2211 Contact: [email protected]


Renewable Energy 94

Impact of UV-B Radiation on Corn (Zea mays L.) Investigators: Virginia Walbot, Professor, Department of Biological Sciences; Paula Casati, Research Associate, Department of Biological Sciences Sponsor: U. S. Department of Agriculture Description: Plants capture solar energy through photosynthesis and are the major contributors of fixed energy into biological processes. Conversion of “old” fixed carbon generated by vascular plants constitutes much of our current oil and gas reserves. Flowering plants now dominate the earth, and most species use C3 (standard) photosynthetic reactions as found in lower plants and conifers. Corn is among a handful of flowering plants that utilize a more efficient photosynthetic process termed C4 photosynthesis, which makes it a candidate for energy farming such as alcohol production. Furthermore, corn is the most important US crop in terms of acreage, value in the export market, and diversity of uses. Solar energy contains UV-C (220 – 280 nm), UV-B (280-320 nm) and UV-A (320-400 nm), but UV-C is completely absorbed by the atmosphere and most UV-B is absorbed by ozone. Consequently as terrestrial plants absorb light energy for photosynthesis, they are inevitably exposed to some highly energetic UV-B and to UV-A. Plants have evolved avoidance mechanisms such as sunscreen pigments and diverse repair processes to cope with UV exposure, because this radiation causes direct damage to proteins, DNA, lipids and RNA in cells. Human activities have decimated the ozone layer, particularly in Polar Regions, resulting in periodic higher fluence UV-B radiation that exceeds normal repair capacities. Furthermore UV-B and UV-A elicit physiological and developmental changes in corn and other plants that result in increased shielding. Using DNA microarrays we are defining the changes in gene expression that accompany responses to UV-B. We have studied gene expression from environments lacking UV-B, normal solar fluence, and supplementary UV-B in both field and greenhouse conditions. In our initial experiments (Casati & Walbot 2003) we compared the responses of plants with high levels of the effective sunscreen anthocyanin pigment, to plants with low or no anthocyanin. This analysis and dose-response studies permitted identification of gene expression changes to low, medium, and high fluence UV-B. We discovered that organs that receive no direct radiation nonetheless show gene expression changes within one hour, indicating that there is a systemic and coordinated response to UV-B treatments (Casati and Walbot 2004). An aspect of our analysis of anthocyanin, a class of flavonoid pigment, was using a combination of genetics and molecular analysis to determine how the pigment is transferred from the site of synthesis in the plant cytoplasm to the acidic vacuole. The pigment is more effective in the vacuolar environment. We were the first to provide proof of the type of pump used to transfer anthocyanin across the tonoplast membrane into the vacuole (Goodman et al. 2004).


Renewable Energy 95

We recently defined the plant ribosome – the site of new protein synthesis – as a major site of RNA damage. Because ribosome cannot be repaired, the entire molecular machine must be synthesized de novo; although protein synthesis is impaired during UV-B exposure, messenger RNAs for the proteins to build new ribosomes are selectively translated into protein. We are interested in defining the regulatory steps that permit this adaptive response. Current studies utilize a suite of Mexican and South American corn lines grown about 2000 meters near the equator; this high altitude maize lines receive a much higher fluence of UV-B than standard U.S. lines. Using the high altitude corn we are defining adaptations (genetic changes) and acclimations (physiological responses) that could be useful in breeding more UV-resistant maize. To verify results from microarray hybridization we use real-time RT-PCR to measure precisely the levels of messenger RNA for the most interesting candidate genes. We have also conduct two-dimensional gel electrophoresis to identify which proteins are altered in abundance or migration (most likely the result of post-translational modifications) after UV-B exposure; protein identification is conducted by mass spectrometry. Status: This work is continuing under a USDA grant funded through September 2006. Current efforts are directed at protein identification and the definition of novel pathways of damage repair and signal transduction that UV-B damage has occurred in the leaves. Publications: Goodman, C. D., P. Casati, and V. Walbot, “A multidrug-resistance associated protein involved in anthocyanin transport In Zea mays.” In press for the Plant Cell, 2004. Casati, P. and V. Walbot, “ Rapid molecular responses of maize to UV-B: gene expression profiling in irradiated and shielded tissues,” Genome Biology 5:R16 http://genomebiology.com/2004/5/3/R16, 2004. Casati, P. and V. Walbot, “Gene expression profiling in response to ultraviolet radiation in Zea mays genotypes with varying amounts of flavonoids,” Plant Physiology 132: 1739-1754, 2003. Contact: [email protected]


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http://genomebiology.com/2004/5/3/R16

Index by Researcher Andersson, K. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis”

12

Archer, Cristina L. “Mapping U.S. Wind Resources”

86

Archer, Cristina L. “Effects of a Hydrogen Economy”

78

Arrow, Kenneth. “Research Initiative on the Environment, the Economy, and Sustainable Welfare”

53

Avseth, Per. “Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization”

67

Aydin, A. “Structural Heterogeneities and Paleo-Fluid Flow in an Analogue Sandstone Reservoir”

26

Bent, Stacey F. “Hot Wire Chemical Vapor Deposition of Photovoltaic Polymer-based Films”

81

Bowman, Craig T. “Controlled Combustion—An Approach for Reducing Irreversibilities in Energy Conversion”

31

Bowman, Craig T. “Measurement of Species, Temperature, and Velocity in a Compact, Swirling Combustor for Validation of High-Fidelity CFD Simulations”

40

Bowman, Craig T. “Mesoscale Burner Arrays for Gas Turbine Reheat Applications”

42

Bowman, Craig T. “Process Informatics—A New Paradigm for Building Complex Reaction Models”

46

Brongersma, Mark. “Plasmonic Contacts for Energy Efficient Solar Cells and Light Sources”

83

Campbell, P.A. “Characterization of Coal-Char and Biomass-Char Reactivities to Oxygen at High Temperatures and High Pressures"

50

Casati, Paula. “Impact of UV-B Radiation on Corn (Zea mays L.)”

95

Caton, P.A. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines.”

44



Index by Researcher (Cont.)

Caton, P.A. “Homogeneous Charge Compression Ignition via Exhaust 38

Catrysse, Peter. “Plasmonic Contacts for Energy Efficient Solar Cells and Light Sources”

83

Chen, Allan. “Properties of Steam/Water Flow in Geothermal Rock”

84

Cheng, Ching-Hsiang. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76

Cho, KJ. “Hierarchical Multi-Scale Modeling of Nano-Materials Engineering for Hydrogen Technology”

9

Cinar, Yildiray. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Coakley, Kevin. “Nanostructured Photovoltaic Cells”

88

Colella, Whitney. “Effects of a Hydrogen Economy”

78

Dvorkin, Jack. “Lithology and Fluid Detection in Hydrocarbon Reservoirs”

71

Eaton, John K. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76

Edwards, C.F. “Development of Low-Irreversibility Engines”

36

Edwards, C.F. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines.”

44

Edwards, C.F. “Homogeneous Charge Compression Ignition via Exhaust Reinduction Using Variable Valve Actuation”

38

Edwards, C.F. “Measurement of Species, Temperature, and Velocity in a Compact, Swirling Combustor for Validation of High-Fidelity CFD Simulations”

40

Edwards, C.F. “Mesoscale Burner Arrays for Gas Turbine Reheat Applications”

42

Elias, Becca. “The Program on Energy and Sustainable Development”

56

Fan, Shanhui. “Plasmonic Contacts for Energy Efficient Solar Cells and Light Sources”

83




Florez, Juan. “Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization”

67

Gerritsen, Margot. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Gerdes, J. Christian. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines.”

44

Gerdes, J.C. “Homogeneous Charge Compression Ignition via Exhaust Reinduction Using Variable Valve Actuation”

38

Goh, Chiatzun. “Nanostructured Photovoltaic Cells”

88

Golden, David M. “Effects of a Hydrogen Economy”

78

Golden, David M. “Process Informatics—A New Paradigm for Building Complex Reaction Models”

46

Gonzalez, Ezequiel. “Computational Rock Physics”

69

Gonzales, Ezequiel. “Lithology and Fluid Detection in Hydrocarbon Reservoirs”

71

Gonzalez, Ezequiel. “Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization”

67

Goodson, Kenneth E. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76

Goulder, Lawrence. “Research Initiative on the Environment, the Economy, and Sustainable Welfare”

53

Gowrishankar, Vignesh. “Nanostructured Photovoltaic Cells”

88

Hanson, Ronald K. “Smart Sensors for Combustion Control”

48

Harris, Jerry M. “Monitoring of CO2 Sequestration in Geological Formations”

21

Hayes, Mark. “The Program on Energy and Sustainable Development”

56

Hidrovo, Carlos H. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76




Horne, Roland N. “Properties of Steam/Water Flow in Geothermal Rock”

84

House, Josh. “The Program on Energy and Sustainable Development”

56

Huntington, Hillard G. “The Energy Modeling Forum”

59

Jacobson, Mark Z. “Effects of a Hydrogen Economy”

78

Jacobson, Mark Z. “Mapping U.S. Wind Resources”

86

Jeffries, Jay B. “Smart Sensors for Combustion Control”

48

Jessen, Kristian. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Kaahaaina, Nalu B. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines.”

44

Kaahaaina, N.B. “Homogeneous Charge Compression Ignition via Exhaust Reinduction Using Variable Valve Actuation”

38

Kameda, Ayako. “Computational Rock Physics”

69

Keehm, Youngseuk. “Computational Rock Physics”

69

Ketefian, Gerard. “Effects of a Hydrogen Economy”

78

Klingbeil, Adam. “Smart Sensors for Combustion Control”

48

Lee, Eon Soo. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76

Lee, S. “Mesoscale Burner Arrays for Gas Turbine Reheat Applications”

42

Li, Kewen. “Properties of Steam/Water Flow in Geothermal Rock”

84

Liu, Jonathan. “Smart Sensors for Combustion Control”

48

Liu, Yuxiang. “Nanostructured Photovoltaic Cells”

88

Ma, L. “Characterization of Coal-Char and Biomass-Char Reactivities to Oxygen at High Temperatures and High Pressures"

50

Ma, Lin. “Smart Sensors for Combustion Control”

48




Mallison, Bradley. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Marquez, Sharoh. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Master, Gilbert M. “Mapping U.S. Wind Resources”

86

Mattison, Daniel W. “Smart Sensors for Combustion Control”

48

Matringe, Sebastian. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Mavko, Gary. “CO2 Sequestration in Coal Seams”

65

Mavko, Gary. “Lithology and Fluid Detection in Hydrocarbon Reservoirs”

71

Mavko, Gary. “Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization”

67

McGehee, Michael D. “Nanostructured Photovoltaic Cells”

88

Mitchell, R.E. “Characterization of Coal-Char and Biomass-Char Reactivities to Oxygen at High Temperatures and High Pressures"

50

Morcote-Rios, Anyela. “CO2 Sequestration in Coal Seams”

65

Mukerji, Tapan. “CO2 Sequestration in Coal Seams”

65

Mukerji, Tapan. “Computational Rock Physics”

69

Mukerji, Tapan. “Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization”

67

Näslund, L.-A. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis”

12

Nilsson, A. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis”

12

Nur, Amos. “Computational Rock Physics”

69

Nur, Amos. “Lithology and Fluid Detection in Hydrocarbon Reservoirs”

71




Nur, Amos. “Rock Physics of Methane Hydrate Reservoirs”

73

Ogasawara, H. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis”

12

Orr, Franklin M. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Park, S. “Hierarchical Multi-Scale Modeling of Nano-Materials Engineering for Hydrogen Generation and Hydrogen Storage”

9

Peumans, Peter. “Organic Optoelectronics for Renewable Energy”

90

Pettersson, L.G.M. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis”

12

Pollard, D.D. “Structural Heterogeneities and Paleo-Fluid Flow in an Analogue Sandstone Reservoir”

26

Prasad, Manika. “CO2 Sequestration in Coal Seams”

65

Prasad, Mankika. “Computational Rock Physics”

69

Rieker, Gregory. “Smart Sensors for Combustion Control”

48

Rolle, Matthew J. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines.”

44

Sava, Diana. “Statistical Rock Physics for Estimating Uncertainty in Seismic Reservoir Characterization”

67

Schiros, T. “Fundamental Studies of Interface Processes of Importance for Hydrogen Technology and Reactivity in Controlled Catalysis”

12

Schneider, Stephen H. “What is ‘Dangerous’ Climate Change?”

16

Scully, Shawn. “Nanostructured Photovoltaic Cells”

88

Seto, Carolyn. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Shaver, Gregory M. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines.”

44




Shaver, G. “Homogeneous Charge Compression Ignition via Exhaust Reinduction Using Variable Valve Actuation”

38

Shi, Helen. “Hot Wire Chemical Vapor Deposition of Photovoltaic Polymer-based Films”

81

Sipperley, C.M. “Measurement of Species, Temperature, and Velocity in a Compact, Swirling Combustor for Validation of High-Fidelity CFD Simulations”

40

Somerville, Chris. “Genetic Modification of Plant Cell Walls for Enhanced Biomass Production and Utilization”

93

Song, Hanho. “Dynamic Modeling and Control of Homogeneous Charge Compression Ignition Engines.”

44

Spikes, Kyle. “Lithology and Fluid Detection in Hydrocarbon Reservoirs”

71

Srivastava, Nitin. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Steinbrenner, Julie E. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76

Sternlof, K. “Structural Heterogeneities and Paleo-Fluid Flow in an Analogue Sandstone Reservoir”

26

Svrcek, M.N. “Development of Low-Irreversibility Engines”

36

Teh, K.-Y. “Development of Low-Irreversibility Engines”

36

Teh, K.-Y. “Mesoscale Burner Arrays for Gas Turbine Reheat Applications”

42

Tribbett, E. “Measurement of Species, Temperature, and Velocity in a Compact, Swirling Combustor for Validation of High-Fidelity CFD Simulations”

40

Tsuneyama, Futoshi. “Lithology and Fluid Detection in Hydrocarbon Reservoirs”

71

Victor, David G. “The Program on Energy and Sustainable Development”

56

Victor, Nadejda. “The Program on Energy and Sustainable Development”

56




Vigneron, Sébastien. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76

Walbot, Virginia. “Impact of UV-B Radiation on Corn (Zea mays L.)”

95

Wang, Fu-Min. “Fundamentals of Two-Phase Flow Phenomena in Fuel Cells”

76

Weyant, John P. “The Energy Modeling Forum”

59

Wolak, Frank A. “Energy Market Design, Performance Measurement and Monitoring”

62

Woodhouse, Erik. “The Program on Energy and Sustainable Development”

56

Zaharias, Gillian A. “Hot Wire Chemical Vapor Deposition of Photovoltaic Polymer- based Films”

81

Zerriffi, Hisham. “The Program on Energy and Sustainable Development”

56

Zhang, Chi. “The Program on Energy and Sustainable Development”

56

Zhou, Xin. “Smart Sensors for Combustion Control”

48

Zhu, Jichun. “High Resolution Prediction of Gas Injection Process Performance for Heterogeneous Reservoirs”

24

Zoback, Mark. “Assessing Seal Capacity of Exploited Oil and Gas Reservoirs, Aquifers and Coal Beds for Potential Use in CO2 Sequestration”

28



Energy Research at Stanford Universitygcep.stanford.edu/pdfs/energy_at_stanford_2004.pdfIntroduction In 1982, the Institute for Energy Studies published the original Energy Research

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