Soiling distribution and evolution in fresnel mirrors with real operating conditions. Analysis of a plant located in southwestern Spain

Although it is evident that soiling reduces the reflectivity of mirrors, causing significant energy losses in linear Fresnel technology, the information available so far has mainly addressed mirror samples at fixed angles, with no references on the actual behavior of soiling in operational plants. This work analyzed the reflectivity values measured over two years in a four-module Fresnel installation in southwestern Spain. The main objectives were to study the evolution of soiling under actual working conditions and to verify whether soiling is distributed uniformly throughout the collectors. The average soiling rate was approximately half the rates reported by other authors who analyzed fixed mirrors. Soiling was slightly higher in the zones more exposed to traffic and environment, although the differences were not significant, and dispersion was low. This work highlighted the importance of soiling measurements in operational mirrors with sun tracking, which accumulate less soiling because they are placed upside down at night, reducing exposure time. Otherwise, the distribution of soiling was quite uniform across the solar field, making it unnecessary to take multiple measurements in different areas. These data will help to develop efficient maintenance programs to reduce cleaning costs and maximize the energy production of Fresnel plants.