Advancements in Concentrating Solar Power (CSP

8/3/2019 Advancements in Concentrating Solar Power (CSP ...

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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), [email protected]

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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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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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


7-mradianSpecularRe

flectanceat660nm

APS

FLA

NREL

Ci65


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


%Hemispherica

lReflectance

UV-Screen/SS95-NRELReflecTech A-NRELReflecTech B-NREL

UV-Screen/SS95-WOMReflecTech A-WOMReflecTech B-WOM


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.

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Advancements in Concentrating Solar Power (CSP