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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
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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
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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?