ReflecTech® Polymer Mirror Film Advancements in Technology and Durability Testing

Abstract

One of the most promising developments for lowering the cost of utility scale concentrating solar power (CSP) is the emergence of durable reflective polymer films as an alternative to conventional curved glass mirrors. The broad adoption of wide web polymer film reflectors has been slowed by the lack of long-term weathering data. With the advent of the Ultra Accelerated Weathering System (UAWS), testing and development can proceed at a faster pace, and ReflecTech® Mirror Film has recently exceeded the equivalent terrestrial UV cumulative dosage of 25 years. ReflecTech® Mirror Film was developed through earlier collaborations between ReflecTech, Inc. (a subsidiary of SkyFuel, Inc.) and the National Renewable Energy Laboratory (NREL). More recently, through a Cooperative Research and Development Agreement (CRADA), ReflecTech, Inc. and NREL have developed an abrasion resistant coating (ARC) appropriate for application to polymer based mirror film. This hardcoat was developed to address the need for reflectors that are low in cost, high in performance and durable to mechanical cleaning methods sometimes used in the CSP environment. The combined impact of these two developments has the potential to significantly change the preferred supply choice for solar reflectors in new utility scale CSP projects. ReflecTech® Mirror Film samples prepared with and without the ARC hardcoat were subjected to accelerated exposure conditions more extreme than actual conditions. Both the uncoated and ARC films exhibit excellent weatherability with no loss in reflectance after highly accelerated exposure of over 25 years equivalent terrestrial UV. The ARC coated samples also exhibited outstanding initial abrasion resistance and adhesion to ReflecTech® Mirror Film, properties that were retained after exposure to various accelerated stress conditions including condensation cycling, thermal cycling, water immersion, and accelerated exposure to UV light. ReflecTech® Mirror Film is a commercially available product. The ARC-coated ReflecTech® Mirror Film has been successfully manufactured as a 1.5 m (5 ft) wide roll-to-roll construction in a commercial production environment and after further testing is expected to be commercially available in late 2011.