Post on 06-Apr-2018
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Advancements in Concentrating Solar
Power (CSP) Reflectors and Solar-Selective Coatings
C.E. Kennedy1National Renewable Energy Laboratory (NREL), 1617 Cole Boulevard, M/S 3321, Golden, CO
80401-3393, 303-384-6272, 303-384-6103 (fax), cheryl_kennedy@nrel.gov
E3 2007University of Minnesota, MNNovember 27, 2007
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Concentrating Solar Power Technologies
Power TowerParabolic Trough Dish-Stirling
CPV Heliostat CPV Winston Collector
Compact Linear
Fresnel Reflector
(CLFR)
Solar concentration
allows tailored designapproaches
100kW LCPV Tracking
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Goals for Improved Optical Materials >90% Specular reflectance
into a 4-mrad cone angle
Unofficially 95%
10 - 30 year lifetime Unofficially 30 y
Manufacturing cost$10.76/m2 ($1/ft2)
1992 Cost Goal
Adjusted for inflation to$15.46/m2 ($1.44/ft2)
Structural (self-supporting)mirror to $27/m2 ($2.50/ft2)
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Technical Approach Samples supplied by:
Industry
Subcontracts
Developed in-house
Optical Characterization: Perkin-Elmer (PE) Lambda 9 & 900 UV-VIS-NIRspectrophotometers (250-2500 nm) w/ integratingspheres
PE IR 883 IR spectrophotometer (2.5-50 m)
Devices & Services (D&S) Field PortableSpecular Reflectometer (7, 15, & 25-mrad coneangle at 660 nm)
Outdoor (OET) & Accelerated ExposureTesting (AET):
Atlas Ci65 & Ci5000 WeatherOmeters (WOM) (1X& 2X Xenon Arc/60C/60%RH)
QPanel QUV (UVA 340@ 290- 340 nm/ 4 h UV at40 / 4 h dark at 100%RH)
1.4 kW Solar Simulators (SS) (5X Xenon 300-500nm. 1.4 kW-SS-4 quadrants 2 RH &T, light /dark)
BlueM damp heat (85C/85%RH/dark)
3 meterologically monitored sites at Golden,Colorado (NREL), Miami, Florida (FLA), and
Phoenix, Arizona (APS)
3
2
1
3
2
1
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Reflective Layer (wet-silver)
Low-iron Slumped Glass (4- or 5-mm thick)
Acrylic (w/ high UV stability)
2nd coat Paint Layer (heavy Pb)(1% Pb)
1st coat Paint Layer (heavy Pb)
(2.5% Pb)
Parabolic Trough Glass Mirror
Architecture
Back Layer (Cu)
Three-coat
paint system
designed for
outdoorapplications
Mactac adhesive
Ceramic pad
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Original vs. New Flabeg Mirror
85
90
95
100
0 10 20 30 40 50 60 70 80
Total UV Dose (100 x MJ/m
2
)
%H
emispher
icalReflectance
APS - OLD
FLA - OLDNREL - OLD
Ci65 - OLD
Equivalent NREL Exposure Time (years)
3 6 12 15 180 24219
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Reflective Layer (wet-silver)
Low-iron Glass (3- or 4-mm thick flat)
2nd coat Paint Layer (lead-free
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Alternate Thick Glass Mirrors
65
70
75
80
85
90
95
100
0.0 3.3 6.7 10.0 13.3 16.7 20.0 23.3 26.6 30.0 33.3 36.6 40.0 43.3 46.6 50.0 53.3
Total UV Dose (100 x MJ/m2)
%
Hemispheric
alReflectance
NREL - Pilkington
NREL - Spanish
Ci65 - PilkingtonCi65 - Spanish
Equivalent NREL Exposure Time (years)1 2 3 4 50 6 7 8 9 11 12 13 14 15 1610
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Reflective Layer (wet-silver)
Low-iron Glass (~1 mm- thick)
Substrate (SS, Al)
Adhesive (PS, spray)
Paint Layer (Pb)(Pb-free)
Thin Glass Mirror Architecture
Back Layer (Cu)
(Cu-less)
Thin glass mirrors are designed for indoor applications.
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Thin Glass Corrosion
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Thin Glass Mirror
0
20
40
60
80
100
250 500 750 1000 1250 1500 1750 2000 2250 2500
Wavelength (nm)
%R
eflectance
0.0 MOBlueM 3.52 MOBlueM 7.21 MOCi65 3.16 MO
Ci65 6.15 MONREL 3.82 MONREL 9.57 MO
(Naug/Clearcoat/966
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PVD Al Reflective LayerReflectivity-enhancing Oxide
Polished Aluminum Substrate
Protective Overcoat
Aluminized Reflector
Architecture
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Aluminized Reflectors
80
85
90
95
100
0 333 666 999 1332 1665 1998 2331
Total UV Dose (MJ/m2)
%Hemispheric
alReflectance
Original
Improved Miro2Improved Miro2 Set#2
Miro/4270kk
xposure me y
1 2 3 4 50 6 7
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Aluminized Reflector Specularity
Alanod 4270/kk
FLA 11.8 m
APS 27.7 m
NREL 11 m
WOM 10.2 m0
20
40
60
80
100
0.0 3.3 6.7 10.0 13.3 16.7 20.0 23.3 26.6
Total UV Dose (100 x MJ/m2)
7-mradianSpecularRe
flectanceat660nm
APS
FLA
NREL
Ci65
Equivalent NREL Exposure Time (years)
1 2 3 4 50 6 7 8
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Aluminized ReflectorSpecular Reflectance at 7- and 25-mradians at 660 nm of Alanod MiroSun mirrors after
accelerated exposure in Blue M (dark / 85oC / 85%RH), WOM (1 sun / 60
oC / 60%RH)
chambers, and outdoor exposure at NREL, APS, FLA, and Sandia
30
40
50
60
70
80
90
100
0 3 6 9 12 15 18 21 24
EXposure Time (Months)
%SpecularRe
flectance
NREL - 25 mr
NREL - 7 mrNREL - SWV
APS - 25 mr
APS - 7 mr
APS - SWV
FLA - 25 mr
FLA - 7 mr
FLA - SWV
WOM - 25 mrWOM - 7 mr
WOM - SWV
Blue M - 25 mr
BlueM - 7 mr
BlueM - SWV
Sandia -25mr
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Silvered Polymer Reflector
Architecture
UV-Screening Superstrate
Base Reflector
Bonding Layer
Flexible Polymer Substrate
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Silvered Polymer
70
75
80
85
90
95
100
0 3.3 6.6 9.9 13.2 16.5 19.8 23.1 26.4
Total UV Dose (100 x MJ/m2)
%Hemispherica
lReflectance
UV-Screen/SS95-NRELReflecTech A-NRELReflecTech B-NREL
UV-Screen/SS95-WOMReflecTech A-WOMReflecTech B-WOM
Equivalent NREL Exposure Time (years)
0 1 2 3 4 5 6 7 8
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Advanced Selective Coating Goals
Receivers: 4 m long x 70 mm diameter 64 MWe Nevada plant
820 collectors with 24 (96
m) receivers each 19,680 receivers 82 km of receivers (50 mi)
3-4%/yr Failure Rate
~$1000/tube
To develop receiver coatingsthat have: Good optical and thermal
performance: absorptance ()
96%, & emittance () 7%>450C
High temperature stability in airat temperatures 550C
Manufacturing processes with
improved quality control Lower cost
200C (0.31 kW/m2)
300C (0.80 kW/m2)
400C (1.78 kW/m2)
500C (3.56 kW/m2)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
100 1000 10000 100000
Wavelength (nm)
BlackbodyIrr
adiance(W/m2-nm)
0
20
40
60
80
100
%Reflectance()
Direct AM 1.5 (0.77 kW/m2)
Ideal Solar Selective
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Conclusion
DOE, the WGA, state RPS mandates, and feed-in tariffs havesuccessfully jump-started growth in CSP technologies thatwould require 7 to 10 million square meters of reflector andmore than 600,000 HCEs over the next 5 years.
Commercial glass mirrors, Alanod, and ReflecTech may meetthe 10-yr lifetime goals based on accelerated exposuretesting. Predicting an outdoor lifetime based on acceleratedexposure testing is risky because AET failure mechanisms
must replicate those observed by OET. None of the solar reflectors available have been in test long
enough to demonstrate the 10-year or more aggressive 30-year lifetime goal, outdoors in real-time
Emittance excellent & absorptance of modeled coatings isvery good but further improvements are expected. However,trade-off exists between emittance and absorptance. Key
issue is making the coating and prototype developmentunderway. Patent being pursued
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AcknowledgmentsAlanod, Glaverbel, Naugatuck, ReflecTech, SAIC, and SES for providing
solar reflective samples.
Schott and Solel for providing solar selective samples.
AZ Technology and Surface Optics Corporation for high-temperature optical
measurements .Armstrong World Industries: Dr. J. S. Ross
Northeastern University: Dr. Jackie Isaacs
Penn State University: Prof. Singh, Tom Medill, and Dale Donner
SAIC: Dr. Russell Smilgys and Steve WallaceStat-Ease: Wayne F. Adams
Swisher and Associates: Dick Swisher
NREL:
Lynn Gedvilas, Gary Jorgensen, Mark Mehos, Judy Netter, CraigPerkins, Hank Price, Kent Terwilliger, and Student interns: MicahDavidson, Anthony Nelson, Michael Milbourne, and Christopher, andAndrea Warrick.
DOE supported this work under Contract No. DE-AC36-99GO10337.