Department of Mechanical and Aerospace …...Department of Mechanical and Aerospace Engineering Thermodynamics of ceria and perovskites for solar thermochemical water splitting Jonathan

Department of Mechanical and Aerospace Engineering


Thermodynamics of ceria and perovskites for solar thermochemical water splittingJonathan R. Scheffe, David W. Hahn, Richard Carrillo, Kangjae Lee, Kent Warren

Solar Thermochemistry Workshop, Jülich, Germany, September 12th – 14th, 2017


PI: Prof. Jonathan Scheffe web: scheffelab.comemail: [email protected]

Renewable Energy Conversion Laboratory Research Themes – Thermal Sciences, Solar Energy

Conversion, Radiation Heat Transfer, Heterogeneous Kinetics, Thermodynamics of Oxides/Ceramics, Spectroscopy

Concentrated sunlight for solar fuel production -Solar Fuels

In operando Raman Spectroscopy and laser heating of reacting oxides Fe3O4 (s)→ 3FeO (s) + 0.5O2 (g)

Solar and photoluminesentroadways for enhanced lighting and power production www.wattwaybycolas.com/en

On-sun characterization and development of solar heating technologies www.articsolar.com

mailto:[email protected]

http://theconversation.com/solar-fuels-how-planes-and-cars-could-be-powered-by-the-sun-41938

http://www.wattwaybycolas.com/en/

http://www.articsolar.com/


Solar Driven Methane Reforming

Laser Based Heating Coupled with in operando

Raman Spectroscopy

Thermodynamic and Kinetic Characterization of Redox

Intermediates

3

CeO2

CeO2-δ CeO2-δ

CeO2

δH2O

TL TL

δH2

pCH4 pH2O

Qred + δCH4

2δH2 + δCO

Projects Related To Solar Chemistry


4

Solar Methane Reforming over CeO2-δReactor Experimentation Thermodynamic Modeling Kinetic Studies


Oxidizing Gd0.1Ce0.9O2-δ

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Laser Based Heating/in operando RamanHeating Gd0.1Ce0.9O2-δ

Heating GDC with 200 W laser (see re-emission through top cube) and capturing Raman spectra with the Raman probe 200 300 400 500 600 700 800 900 1000

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Experimental Methods pO2 in the system is controlled with a mixture of

H2/H2O. H2O flowrate is varied to drive reduction/oxidation cycles

Representative of expected gas compositions (e.g. high H2 during oxidation)/sample morphologies (e.g. packed bed) in thermochemical reactors

Red./Ox. extents are quantified by integrating H2consumption or production

Exemplary Results Results agree well with gravimetric

approaches

Methodology is being extended to new redox materials

Max Operating Temperature: 1873 K

Absolute Pressure Range: Vacuum to Ambient

Oxygen Partial Pressure Range: 10-30

atm to Ambient 6

Thermodynamics of Redox Materials

College of Engineering

Renewable Energy Science & Technology

• University of Florida– David Hahn, PI– Renwei Mei, Co-PI– Like Li, Post-doc

HEATS: Solar Thermochemical Fuel Production

Key Team Members:

UF Solar Fuel Reactor



Original Program Elements – 12/2011 start

• Element 1: Synthesis methodology for magnetically-stabilized bed porous structure for stability up to 1450oC

• Element 2: Continuum scale reactor model & development of lower-order reactor model

• Element 3: Identify fundamental mechanisms driving the oxidation and reduction reactor kinetics for closure of continuum reactor model

• Element 4: Design, fabricate and test critical reactor components• Element 5: Design, fabricate and evaluate performance of a 10 kW

magnetically stabilized bed low pressure solar reactor prototype Element 6: Design, fabricate and evaluate control system for the 10 kW prototype reactor

• Element 7: Design and model a 1 MW demonstration scale solar fuels reactor



Element 1 – Reactive Materials

• Achieved early success with synthesis of magnetically-stabilized structures; including exploration of:– Iron oxides– Mn- , Co- and Ni-ferrites– Yittrium- and Zirconia-stabilized structures

• Measured kinetic rates and developed detailed reaction mechanisms

• Phase-transitions between oxides (i.e. melting) within the redox temperature range resulted in reactor bed sintering

• Ultimately moved from iron-based structures to ceria-based structures to overcome sintering

10 wt% Co-ferrite in YSZ



Ceria as the reactive material

• Iron is limited by diffusion, kinetics and sintering• Ceria: Thermal stability to ~2000oC

• δ corresponds to lattice vacancies• δ is typically limited to <0.1 & is f(T,P) • δ defines H2 production capacity & reactor design

Reduction

Oxidation

CeO2 + energy CeO2-δ + δO

CeO2-δ + δH2O CeO2 + δH2



Element 2 – Modeling & Simulation

• Demonstrated efficiency (energy of fuel / solar input) via detailed continuum and kinetics model to 18-20%

• Optimized reactor cavity design for temperature uniformity via heat and mass transfer models



Element 4/5 – 10 kW reactor

• Designed and constructed a 10 kW reactor for on-sun testing on the UF solar simulator

• Milestones to demonstrate >10% efficiency and multi-cycle stability

Cavity wall

Aperture

InsulationAbsorbers

1 x

y z

θ




Inner cavity showing several tubes and diffuser plate

Rear view of reactor with tubes protruding






Blue: actual data extrapolated to 14 tubes; Orange: assuming 30 minute reduction

Solar-to-fuel efficiency

• toxidation increased from 10 to 18 min

• Gasket sealing degrading with cycles

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Funding Sources Qatar National Research

Foundation (NPRP 8-370-2-154)

Florida Department of Transportation (Task Order # 977-78)

University of Florida College of Engineering and Department of Mechanical and Aerospace Engineering

Kangjae Lee Richard Carrillo Kent Warren

Acknowledgements

Department of Mechanical and Aerospace …...Department of Mechanical and Aerospace Engineering Thermodynamics of ceria and perovskites for solar thermochemical water splitting Jonathan

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