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In this session the main elements of the parabolic trough technology will be described: concentrators, receivers, heat transfer fluids, connecting elements, etc. Then, the main characteristics of today’s parabolic trough solar thermal power plants will be presented: design, operation and costs. Finally, the audience will get some ideas for future developments.
Citation preview
March 2010
Manuel Silva
Seville University
CSP TrainingLesson 2: Parabolic Trough
See also CPV
CONCENTRATING PHOTOVOLTAICS
Advantages, Interviews, Video
CONCENTRATING PHOTOVOLTAICS
Advantages, Interviews, Video
http://www.leonardo-energy.org/concentrating-photovoltaics
Solar Thermal Power Plants. Parabolic Trough Technology
Manuel A. Silva PérezGroup of Thermodynamics and Renewable
EnergyETSI – University of Seville
[email protected]://www.leonardo-energy.org/csp-training-course-lesson-2-linear-focus-technologies
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Main Concentrating Technologies
Central Receiver / Heliostats
Parabolic troughs
Parabolic dishes
Linear Fresnel Reflectors
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Solar Thermal Power Plant. Basic configuration
Beam irradiance
Concentrator
Receiver
Thermal Storage
Concentrated irradiance Electricity
Power conversion system
Thermal energy
BoilerFossil fuel Biomass
Generator
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PT power plant configuration
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Collector
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Collector
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Main elements of the collector
• Reflector (mirror)• Receiver tube• Structure• Tracking system• Connecting elements• Control system
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Applications
Process heat STP plant
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The reflector
Thin glass mirror (0.8 mm)
Thick glass mirror (3 -5 mm)
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Alternative reflecting surfaces
AluminumAlanod
Reflective films (polymers)Reflectech, 3M
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Structure
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Receiver tube
Selective coated steel tube
Glass envelope
'Getter‘ for vacuum maintenanceExpansion bellow
Glass pin for evacuation of gasesVacuum between glassand steel tubes
Glass – metal welding
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Receiver tubes
Schott PTR-70Solel UVAC-2 y UVAC-
3
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Heat transfer fluid
• Thermal oils– Caloria (SEGS I and II,
<300ºC)– Therminol VP-1 (<400 ºC)– Syltherm (Dow Chemical,
>400ºC)• Water / Steam
– >400 ºC– DISS Project
• Molten salts– Archimedes - ENEA facility
• Gasses– PSA Research Facility
State of the art
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Tracking mechanisms
Electrical motor - gearbox Hydraulic
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Connecting collectors
Flex hoses Rotating joints
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Solar field configuration (I)
1 SCA 150 m 12 SCE 1 Drive Pylon 10 Middle Pylon 1 End Pylon 1 Shared Pylon (shared with next SCA)
Cold Oil
Hot Oil
End Pylon
Drive Pylon
Middle Pylon
Shared Pylon
SCE
150 m
150 m
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Solar field configuration (2)
Cross OverPipes
1379 m
1248
m
Loop of6 SCA’s
HeadersSEGS Power Block80 MW Rankine Cycle
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A) Direct returnB) Reverse return
C) Central
Thermal losses Higher cost P balanced Lower consumption
Thermal losses unbalanced P Higher consumption
Shorter pipelines Better access to collectors unbalanced P
Solar field configuration (3)
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X
Y
N
SE
O
Z
S
C
Sol
X
YN
SE
O
Z
S
C
Sol
b) N-S trackinga) E-W tracking
Solar field orientation (Northern Hemisphere)
Maximum efficiency at noon.
Maximum yearly energy generation
Incidence angle never 0 at noon
More balanced seasonal generation
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Diámetro , D
Rayosolar
Angulodeapertura, f
Angulodeaceptancia, qReflectorParabolic
External receiver diameterD
Sun rays
Aperture angle f
Acceptance angle, q
b) Acceptance angle, a) Concentration ratio, C
Aperture, A
Absorber tube
Basic design parameters
Length, L
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Beam irradiance
interception factor, ,
Selective-coated steel tube (Absortivity = )
Glass envelope (Transmissivity = )
Parabolic mirror(Reflectivity = )
o,peak = ···
Energy balance. Optical losses
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Sun
Sun
Side view
Plant view
Shaded area
Reflecting surface
Absorber tube
L = concentrator length = incidence angle
F = focal length
Sol
F
ED
L
b) Loss of effective collector lengtha) Shading losses
Af = W x ED = W x F x tan()
Geometrical losses
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Loss of effective collector length
W
ED
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ambabsabs
conv-condabs,radabs,absL T - TLD
Q + Q=U
[W/m2
abs ºC]
UL)col = UL)abs / C
Qv,abs.
Qabs,rad.
Qabs,cond/conv. Qamb,rad
Qamb,conv
Glass envelope
Absorber tube
Thermal losses
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effeff
cos IAQ csol inouteff hhMQ thoptglobal K º0,
Energy balance (solar to thermal)
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95
96
97
98
99
100
Avail
ab
ilit
y -
%
1995 1996 1997 1998 1999
III IV V VI VII0%
10%
20%
30%
40%
50%
60%
70%Effi
cie
ncy [
%]
0
200
400
600
800
1000
1200
Dir
ect
Norm
al R
ad
iati
om
[W
/m²]
05:00 07:00 09:00 11:00 13:00 15:00 17:00 19:00 21:00
Solar to Electric Efficiency (gross)
Direct Normal Radiation
Thermal SolarField Efficiency -
Solar Efficiencies Measured at SEGS VIon July 1997 by KJC Operating Company
Typical operation curve (clear day, no thermal storage)
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Andasol-type plants (thermal storage and auxiliary boiler)
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SEGS 30 MW
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Costs
• Difficult to evaluate– Confidentiality of contracts– Volatility of prices– Only 2 – 3 providers of key elements– O&M experience restricted to US (SEGS
Plants)
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Costs (w/o TES)
Approx. 3.5 – 4 €/kWe
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Costs – Solar field
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Electricity cost
• Depends on different factors– Solar Resource– TES Capacity– Labour cost– Financial– Etc.
• Spain 2010: LCOE < 250 €/MWh• SW USA: LCOE = 120 €/MWh?
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PT Technology today, pros & cons.
• Pros:– Mature technology;
• Comercially proven, over 500 MW installed capacity;
• Extensive operational record: 9 plants operating for 20 years in USA
– Easy to finance (in Spain!)• Cons:
– Few manufacturers of key elements (recievers, mirrors…) -> limited competence
– Limited maximum temperature -> limited efficiency
– Costly, hazardous HTF– Limited TES options
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More…
• http://www.nrel.gov/csp/troughnet/• Sargent & Lundy Assessment of CSP
http://www.nrel.gov/csp/troughnet/pdfs/34440.pdf
• Look for movies at youtube, e.g:– http://www.youtube.com/watch?v=ysDXwvN
GHeM&feature=related– http://www.youtube.com/watch?v=3OLjooHY
1VA– http://www.youtube.com/watch?v=mDWSW
8BAM3U&feature=related– And more…
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