Solar Thermal Powerpoint 7-27-2011

5/22/2018 Solar Thermal Powerpoint 7-27-2011

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University of Louisiana

CLECO Power LLC

Alternative Energy Research Center

Solar Thermal Power

PlantJonathan R. Raush, M.S., P.E.


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Overview

Solar Energy Background Solar Radiation

Available Resources

U.S. Energy Outlook

Solar Thermal Technology Concentrating Solar Power (CSP)

Parabolic Trough CSP

Steam Rankine Cycle

Organic Rankine Cycle

UL/CLECO Installation Background Information/ARRA

Technology

Goals

Cycle Analysis


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Solar Energy

Sun Characteristics

The sun is the most reliable and abundant source of energy.

9900 F at surface

36,000,000 F at center

Solar Constant

1353 W/m2(+/- 3%) .000000045% of energy emmitted

428 Btu/ft2hr


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Solar Energy

Earth and atmosphere continuously receive 1.7x1014kW of

radiation from the sun

A world population of 10 billion with a total power need of

10 kW per person would only require 1011

kW of energy Solar energy intercepted by the planet is 5000 times

greater than the sum of all other inputs (terrestrial nuclear,

geothermal, gravitational, and lunar gravitational)

Goswami, et. Al. Solar Radiation is responsible for Solar Thermal/ Wind/

Biomass/ Photovoltaic/ Hydro Energy


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Solar Energy

Of total radiation received, 30% reflected tospace, 47% converted to low-temperature heatand reradiated to space, 23% powers the

evaporation/precipitation cycle of the biospherewith


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Solar Energy

1.5x1017kWhr per year falls on land (6000 times totalenergy usage of U.S. in 2000)

Utilizing only 1% of the earth's deserts to produce solarelectric energy would provide more electricity than is

currently being produced on the entire planet by fossilfuels

Energy reaching the earth is made up of two parts Direct beam radiation

Diffuse energy in the sky

Most manmade solar collectors can convert only directenergy efficiently

Amount of direct energy depends on the cloudinessand position of the sun


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Solar Energy

In Summary:

Fraction of radiation reaches ground in form

of Direct Normal Radiation

Can be as high as 1000 W/m2

9 kWh/m2/day

Lafayette: 750 W/m2

4.36 kWh/m2/day

DNI Averaged over 24 hrs: 182 W/m2

Compare with solar constant of 1353W/m2

24 hrs x /hour


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Global DNI

Direct Normal Irradiance is the fraction of sunlight which is not

deviated by clouds, fumes or dust in the atmosphere and that

reaches the earthssurface in parallel beams for concentration.


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U.S. DNI

Lafayette: 4.36

kWh/m2/Day


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U.S. Energy Sources By Demand

Base Load

Power

Generation
http://eia.gov/totalenergy/data/annual/


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U.S. Energy Information Administration

Annual Energy Outlook


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U.S. EIA Annual Energy Outlook


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U.S. EIA Annual Energy Outlook


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U.S. Electric Capacity


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Figure 1. U.S. Energy and Geothermal Resources

Note: U.S. Total Resource Base from Characterization of U.S. Energy Resources and

Reserves, December 1989, U.S.

Department of Energy, DOE/CE-0279. Data for Estimated Accessible Geothermal

Resource and Estimated Developable

Resource are from Table 4 of this report.

0.3% total

657,000 BBOE

U.S. Total Resource Base


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Solar Energy Generation

3 Main Components Solar Collector

Energy Conversion

Energy Storage Collector Technologies

Photosynthesis converts light energy to chemical energyin plants

Photovoltaics converts sunlight directly into electricity

Solar Thermal Concentrating Solar Thermal (CSP)

Direct Solar Thermal


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Concentrating Solar Thermal (CSP)

CSP concentrates the light from the sun tocreate heat, which is transferred to a fluid. The

HTF is then used to power a heat engine,

which turns a generator to produce electricity. Heat transfer fluid that is heated by the

concentrated sunlight can be a liquid or a gas.

Heat engine types include steam engines,Stirling engines, etc.


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Concentrating Solar Thermal

Different Forms Dish: Focuses sunlight from area onto a focal point,

usually operating an external heat engine

Power tower: A field of tracking mirrors focuses

radiation onto point, creating high pressure steam fortraditional steam power cycle

Parabolic Trough: A field of mirrors focusing radiationonto a heat transfer element, which carries a fluidthrough the field, for power production

Fresnel Lens: Uses a series of long, narrow, shallow-curvature (or even flat) mirrors to focus light onto oneor more linear receivers positioned above the mirrors


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CSP projects could generate over

6 times the power needed by the U.S.


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Dish System


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Power Tower


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Power Tower


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Parabolic Trough


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Parabolic TroughHistory of Development

Archimedes212 BC
http://www.willthomas.net/Convergence/Weekly/Burning_Mirrors.htm


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History of Development

1912 first parabolic trough collector by Shuman in Cairo


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History of Development

No development until the 1970s oil crunch Research and Development efforts led to Solar

Energy Generating Systems (SEGS)


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Solar Electric Generating Stations

(SEGS)

Between 1984 and 1991, the United States built nineSEGS plants in California's Mojave Desert, and today theycontinue to provide a combined capacity of 354megawatts of electrical energy annually, power used in

500,000 Californian homes [source: Hutchinson]. SEGS I through IX (still in operation) built by LUZ

(eventually went out of business) have generated farmore power than all other solar technologies combined

Economic optimization drives plants to larger and largersizes

High O&M costs

High temp requirement restricts use to SW U.S.


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Power CycleSolarSteam Rankine Cycle

Heat transfer fluid (high temperature oil) isheated to about 740 F

Heat used to boil water, creating high pressure

steam (100 bar) High pressure steam expanded in a turbine,

which in turn spins an electric generator

Low pressure steam is then cooled andcondensed back into water to begin theprocess again


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Rankine Cycle


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T-s diagram for Ideal steam

Rankine cycle


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Organic Rankine Cycle (ORC)

Similar to Steam Cycle except that the workingfluid is an organic (carbon based) fluid often arefrigerant

Organic fluids often have lower boiling points

than water, allowing lower temperatureresources to be employed in power generation

Because of lower temperatures and pressuresinvolved, the entire system can be

compartmentalized and operated remotely,without onsite supervision and very littlemaintenance


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Why Organic Fluids?

Steam dome comparison

Dry fluid vs. Wet fluid

Condensing pressures above ambient

Low-maintenance turbines

Simplified turbine design (related to fluid density

and to smaller expansion pressure ratios

inlet/outlet)

Opportunity for Recuperation due to drying

nature


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T-s diagram for

ORC

in

out

in

out


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Working Fluid Selection


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Solar Thermal & ORC

Solar heat and ORC technology was firstattempted to be merged in the Coolidge SolarIrrigation Project in the early 1980s

Suffered from problems including low collector

performance and O&M problems with thecooling tower

ORCs have become more mainstream with use ingeothermal and industrial waste heat

applications Combining ORC technology with Parabolic Trough

technology proposed by NREL in early 2000s


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ORC Solar ThermalPros and Cons

Smaller scale ORCs have several advantages over large, centralgenerating stations Lower temperature operation

Less expensive HTF

Smaller solar field, more efficient solar field

Possibility of using air-cooling (radiator), eliminating need for largeamounts of make-up water

Simple

Can be operated remotely

Supports integration of modular systems using standardized designsand prefabrication Minimizes on-site erection

Shipment to site in containers

Potentially lower capital costs

Disadvantages Lower efficiencies

Not optimal for displacing base load power

1 MW ORC plant at Saguaro Power Plant south


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1 MW ORC plant at Saguaro Power Plant south

of Phoenix, AZ. Solargenix, APS

2006


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2 MW ORC plant at Holaniku Solar Thermal Plant

on the Big Island of Hawaii by Sopogy

2009


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Energy Storage

Stored energy allows for off peak dispatch tothe power cycle

Heat can be stored during the day and then

converted into electricity at night. Many types of energy storage in use and

under investigation

Two tank storage systems in use (hot and cold)

Thermocline energy storage (one tank)

Solid media (concrete)

Phase Change Materials (PCMs)


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Energy Storage

Advantage of CSP overPhotovoltaics is the Storage of

energy. Heat storage is a far

easier and more efficient

method than storing electricity. Solar thermal plants that have

storage capacities can

drastically improve both the

economics and the

dispatchability of solarelectricity.


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American Recovery and Reinvestment

Act of 2009

Louisiana DNR received funds to distribute for

projects

EmPower LouisianaRenewable Energy

Program

Awarded funds to the University of Louisiana

for development of a grid-tied solar thermal

power plant in partnership with CLECO Power,LLC


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Goals

LDNR goals: To encourage the development, implementation and

deployment of cost-effective renewable energytechnologies in Louisiana, to support the creation of

additional employment opportunities, and tostimulate market demand for other emergingrenewable energy systems

UL goals:1) Fulfill the Grant requirements

2) Evaluate the feasibility and commercial viability oflarger scale solar thermal power plant in Louisiana

3) Have a research/educational facility useful for futureUL/CLECO research


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Scope of Work

1) Obtain all necessary permits and site evaluations

2) Obtain bids and place orders or sign contracts forall required equipment, designs, and services

3) Prepare the site for installation4) Receive the equipment

5) Install the equipment

6) Test the completed system7) Operate the system to produce renewable power

8) Report on the findings of the project


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Preliminary Design

Located at new UL/CLECO Energy Research

Center in Crowley, LA

20kWe of net electric output to grid

245 Solar collectors oriented on N-S and on E-

W axis

Utilization of 65 kW ORC cycle power block

Two tank Thermal Storage System


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Projected Outcomes

Create or retain 2.29 full-time equivalent jobs

Produce 171,806 kWh of energy annually

Offset the production of 79.8 metric tons of

CO2 emissions


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System Schematic


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Site Plan

Solar Field

Thermal

Storage

Power Block


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Site Plan


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Sopogy

Founded in 2002 at the Honolulu, Hawaii based clean technology incubator known asEnergy Laboratories

SOlar POwer EnerGYand TechnoloGY

Manufactures MicroCSP parabolic solar trough

Smaller, lighter, lower temperature, lower capital cost

Creates a good fit with small scale ORC power generation

Operates first MicroCSP and ORC power generation facility on big island of Hawaii -2009


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Collector Performance

For UL plant:

Collector Efficiency at Design = 63.40%

Solar Collector Heating Element


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Solar Collector Heating Element

Heat Transfer

Process qin Mirror focuses radiation onto

element at 5 Conduction 5-4

Free Convection and Radiation

4-3

Conduction 3-2

Forced Convection 2-1

Process qout Reflection, Free Convection

and Radiation 3-4

Conduction 4-5

Radiation 5-7

Forced Convection 5-6


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ElectraTherm Developed ORC power generation unit, specialized for

waste heat applications; provided by CLECO. Green Machine produces 65 kWe from low

temperature (200 F) water

Incorporates patented expander, pumps, and heat

exchangers in an enclosed compartment No Recuperation


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Screw expander

Scroll compressor operating in reverse

Less sensitive to varying operating conditions

Less sensitive to condensation

Single stage

Low maintenance

Less efficient than turbine optimized to oneoperating point


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ORC Analysis

Define steady state operating points for UL plantoperating at 20 kW net

Determine cycle 1stLaw thermal efficiency

Given:

ElectraTherm Green Machine

75% Expansion Efficiency

91% Generator Efficiency

60% Pump Efficiency (Estimated)

Water cooled condensing

Water as HTF

R245fa as working fluid

15 kW of parasitic losses external to cycle


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Steady State Equations

T Di f UL C l


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T-s Diagram of UL Cycle

in

out

in

out

1

23

4


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Design Considerations


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Design Considerations

Superheating not advantageous


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Superheating not advantageous


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Design ConsiderationsHTF, in

WF,out


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Analysis, State 1

Select 20 C pinch point at WF exit from Boiler

THTF,in=96.1 C therefore Tboiler, out =76.1 C =T1

Select T1

= Tsat,g

which corresponds to

Psat=716 kPa

From tables h1=459.1 kJ/kg; s1=1.777 kJ/kg-K


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Analysis, States 2 and 3

Select 4 C pinch point at WF exit for condenser Tcoolant, in=20 C therefore TWF,out=24 C=T3

Select T3=Tsat,f which corresponds to Psat=142.4

kPa=P3

From Tables at Psat; h3,f=231.1 kJ/kg; s3,f=1.109

From State 1, assume isentropic expansion (s2=s1)

to constant pressure line at P3=P2

From tables, h2,s=429.7 kJ/kg

Then, from calculate h2=437.05 kJ/kg


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Analysis, State 4

Assume isentropic compression from P3to P4(s4=s3) and P4=P1

At P4=716 kPa and s4=1.109 kJ/kg-K; h4,s=231.6

kJ/kg and T4=24.2 C

From =.6 calculate h4=231.93 kJ/kg


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Turbine Work and Pump Work

From = .91 and 35kW desiredoutput, calculate Wmechanical = 38.5 kW

Then =38.5 kW and mWF =1.746

kg/s

Then =1.455 kW

Then =396.64 kW

And =359.6 kW


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Thermal Efficiency

Tlow =20 C (293.15 K)Thigh =96.1 C (369.25 K)

ncarnot=0.2065

ngenerator=.91Wturbine =38.5 kW

Wpump =1.455 kW

Qboiler =396.64 kW

ncycle =.0847


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Completing the Design

From energy balance around boiler candetermine required HTF flow rate

From energy balance around condenser, can

determine required Coolant flow rate


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Actual Design State Performance

Difference in actual and ideal cyclesPressure drops due to friction losses

Expander efficiency at part load

Pump efficiency at part loadTwo Phase Heat Exchanger performance

modeling

Where: Then:


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Solar Efficiency

=0.042

Actual plant with parasitic losses

=0.025


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Overall Solar to Electric Efficiency


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Potential Future Markets

Mid range solar resource areas

Distributed generation

Offsets costs at retail price instead of wholesale

Remote generation (DOE apps)

Green Power/Renewable Portfolio Standards

CSP today at 12-14 (14-17)* cents/kWh for centralgenerating

DOE goal of 5-7 (7-8)* cents/kWh by 2015 with 6 hrs

storage

DOE goal of 5 cents/kWh by 2020 with 12-17 hrs storage

*Greenpeace, the European Solar Thermal Power Industry Association (ESTIA), and the International EnergyAgencys (IEA) SolarPACES Programme have produced this report


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Questions?

Solar Thermal Powerpoint 7-27-2011

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