Experience with mirror reflector soiling and washing methods at the Kramer Junction SEGs plants

Five 30-MW solar parabolic trough Rankine cycle power plants have accumulated over 40 plant-years of operation at Kramer Junction, California since 1986. The parabolic trough collectors at those plants, with a cumulative aperture area of 1,092,840 m2, use glass mirror panels for concentration. Performance of the plants is directly dependent on the reflectivity of the reflectors, and consequently knowledge of reflectivity degradation rates, cleaning method effectiveness, and cost/benefit tradeoffs is an important part of plant operations. This paper explores several issues associated with the soiling and cleaning of mirrors at the Kramer Junction plants, namely: reflectivity degradation and collector field performance, mirror washing methods, including water requirements and cost, and changes in reflectometer instrumentation to significantly improve data gathering.