Durable Concentrating Solar Power (CSP) Mirrors

Mimi Wang, Rob Vandal, and Scott Thomsen, Guardian Industries Corp., Science and Technology Center

To convert sunlight into electricity, an array of concentrating solar power (CSP) mirrors is arranged to reflect and focus the sun light onto a receiver containing heat absorbing fluid. The hot fluid is then used to generate electric power through heat transfer mechanisms and standard steam turbine. There have been constant efforts to increase
the solar reflectivity of the mirrors and to improve the durability of the mirror backing paint for the severe environment in the solar field. The Guardian CSP mirrors successfully improved these performances by laminating a polyvinyl butyral (PVB) film
behind the mirror with a backing glass. The design allows the use of 1.6 mm thin glass for mirrors which significantly increases solar reflectivity. In addition, with PVB lamination, the mirrors do not shatter when damaged by strong winds or stones. This not only prevents subsequent damages to other mirrors, and the tube glass vacuum jackets, but also the CSP mirrors can continue to reflect sunlight, reducing the repair frequency. When compared to organic type paints, the backing glass has less vapor permeability hence provides the best protection to the mirror metals. Environmental testing has proven that this design of solar mirror is durable and retains its high reflectivity of over 93% for a long period of time.

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