Concentrating solar power (CSP) technologies use large mirrors to collect sunlight to convert thermal energy to electricity. The viability of CSP systems requires the development of advanced reflector materials that are low in cost and maintain high specular reflectance for extended lifetimes under severe outdoor environments. The long-standing goals for a solar reflector are specular reflectance above 90% into a 4 mrad half-cone angle for at least 10 years outdoors with a cost of less than $13.8/m2 (the 1992 $10.8/m2 goal corrected for inflation to 2002 dollars) when manufactured in large volumes. Durability testing of a variety of candidate solar reflector materials at outdoor test sites and in laboratory accelerated weathering chambers is the main activity within the Advanced Materials task of the CSP Program at the National Renewable Energy Laboratory (NREL) in Golden, Colorado. Test results to date for several candidate solar reflector materials will be presented. These include the optical durability of thin glass, thick glass, aluminized reflectors, front-surface mirrors, and silvered polymer mirrors. The development, performance, and durability of these materials will be discussed. Based on accelerated exposure testing the glass, silvered polymer, and front-surface mirrors may meet the 10 year lifetime goals, but at this time because of significant process changes none of the commercially available solar reflectors and advanced solar reflectors have demonstrated the 10 year or more aggressive 20 year lifetime goal.

1.
Short, W. D., 1988, “Optical Goals for Polymeric Film Reflectors,” SERI/SP-253-3383, National Renewable Energy Laboratory, Golden, CO.
2.
Sahr, R., “Inflation Conversion Factors for Dollars 1665 to Estimated 2013,” Oregon State University, http://oregonstate.edu/Dept/pol_sci/fac/sahr/sahr.htm. Last modified March 4, 2003; accessed January 22, 2004.
3.
Schissel
,
P.
,
Kennedy
,
C.
, and
Goggin
,
R.
,
1995
, “
Role of Inorganic Oxide Interlayers in Improving the Adhesion of Sputtered Silver Film on PMMA
,”
J. Adhes. Sci. Technol.
,
9
, pp.
413
424
.
4.
Jorgensen, G. J., Kennedy, C. E., King, D., and Terwilliger, K., 2002, “Optical Durability Testing of Candidate Solar Mirrors,” NREL/TP-520-28110, National Renewable Energy Laboratory, Golden, CO.
5.
ASTM Standard E903-82 (Reapproved 1992), “Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres,” Ann. Book of ASTM Standards 1993, Vol. 12.02, American Society for Testing and Materials, Philadelphia, PA, pp. 512–520.
6.
ASTM Standard G173-03, “Standard Tables for Reference Solar Spectral Irradiance: Direct Normal and Hemispherical on 37° Tilted Surfaces,” Ann. Book of ASTM Standards 2003, Vol. 14.04, American Society for Testing and Materials, Philadelphia, PA.
7.
Jorgensen, G. J., Kim, H. M., and Wendelin, T. J., 1996, “Durability Studies of Solar Reflector Materials Exposed to Environmental Stresses,” Durability Testing of Nonmetallic Materials, ASTM STP 1294, edited by Robert J. Herling, American Society for Testing and Materials, Philadelphia, PA.
8.
Schweig, B., 1973, Mirrors: A Guide to the Manufacture of Mirrors and Reflecting Surfaces, Pelham Books, London, England, pp. 23–45.
9.
Sinko, J., Private Communication, Wayne Pigment Corp., Milwaukee, WI, April 27, 2001.
1.
Servais, A., et al., U.S. Patent No. 5,240,776, August 31, 1993;
2.
Servais, A., et al., U.S. Patent No. 5,296,297, March 22, 1994;
3.
Servais, A., et al., U.S. Patent No. 5,374,451, December 20, 1994.
1.
Soltys, J., U.S. Patent No. 6,017,580, January 25, 2000.
2.
Bahls, H. J., Private Communication, Lilly-Valspar, April 5, 2001.
1.
Sinko, J., U.S. Patent No. 5,378,446, January 3, 1995;
2.
Sinko, J., U.S. Patent No. 5,487,779, January30, 1996;
3.
Sinko, J., U.S. Patent No. 5,558,706, September 24, 1996.
1.
Fend
,
T.
,
Hoffschmidt
,
B.
,
Jorgensen
,
G. J.
,
Ku¨ster
,
H.
,
Kru¨ger
,
D.
,
Pitz-Paal
,
R.
,
Rietbrock
,
P.
, and
Riffelmann
,
K.-J.
,
2003
, “
Comparative Assessment of Solar Concentrator Materials
,”
Sol. Energy
,
74
, pp.
149
155
.
2.
Fend
,
T.
,
Jorgensen
,
G. J.
, and
Ku¨ster
,
H.
,
2000
, “
Applicability of Highly Reflective Aluminum Coil for Solar Concentrators
,”
Sol. Energy
,
68
, pp.
361
370
.
3.
Jechel, K., Private Communication, Energy Innovations, San Juan, CA, February 3, 2004.
4.
Ku¨ster, H., Private Communication, Alanod Aluminum Veredlung GmbH & Co. KG, Ennepetal, Germany, March 11, 2004.
5.
ASTM Standard G90-98 (Reapproved 1998). “Standard Practice for Performing Accelerated Outdoor Weathering of Nonmetallic Materials Using Concentrated Natural Sunlight” Ann. Book of ASTM Standards 2004, Vol. 14.04, American Society of Testing and Materials, Philadelphia, PA.
6.
Kennedy
,
C. E.
,
Smilgys
,
R. V.
,
Kirkpatric
,
D. A.
, and
Ross
,
J. S.
,
1997
, “
Optical Performance and Durability of Solar Reflectors Protected by an Alumina Coating
,”
Thin Solid Films
,
304
, pp.
303
309
.
7.
Kennedy, C. E., and Smilgys, R. V., 2001, “Solar Reflective Materials Produced by a Laboratory-Scale Roll-Coater,” Proc. 2001 AIMICAL Fall Tech. Conf.; 15th Int. Conf. on Vac. Web Coating.
8.
Kennedy, C. E., Swisher, R., and Smilgys, R. V., 2003, “Cost Analysis of Solar Reflective Hard Coat Materials,” Proc. 2003 AIMICAL Fall Tec.l Conf.; 17th Int. Conf. on Vac. Web Coating.
9.
Kennedy
,
C. E.
, and
Swisher
,
R.
,
2005
, “
Cost Analysis of Solar Reflective Hard-Coat Materials Deposited by Ion-Beam-Assisted Deposition,” In publication
,
ASME J. Sol. Energy Trans.
,
127
(
2
), pp.
269
275
.
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