Experimental soiling assessment, characterization and modelling of a highly-compact heliostat field in an urban environment

The soiling effect is presently assessed on heliostats of the very-high concentration solar tower facility located in M & PRIME;ostoles on the outskirts of Madrid, Spain, covering the lack of studies concerning Concentrated Solar Power, but also of key importance for solar-to-heat industrial applications, namely in urban areas. Specular reflectance loss was monitored with a Condor reflectometer on fifteen heliostats spaced throughout the solar field. The objectives were to evaluate the soiling effect in an urban environment during different seasons, including the measurement methodology, soiling ratio characterization, tilt angle to reduce the soiling effect and assessment of soiling intra-heliostat dynamics. Soiling rates ranging from 0.13%/day to 0.58%/day were found for this location, associated with wet and dry seasons, respectively. Special focus is given to assess long-range transports of Saharan desert dust, with soiling ratio losses of up-to 30%, and spring period due to higher atmospheric pollen concentration. Lastly, a detailed evaluation of the intra-heliostat soiling effect was performed leading to the development of soiling models to reduce reflectance loss assessment time by binding localized intra-heliostat measurements and the average soiling ratio between different heliostats with distinct tilt angles.

Automated summary

This study evaluates the soiling effect in an urban environment by monitoring the specular reflectance loss of heliostats in a solar tower facility. The results show soiling rates ranging from 0.13%/day to 0.58%/day during different seasons, with a focus on the impact of Saharan desert dust and atmospheric pollen concentration in the spring.