Automated monitoring of soiling with AVUS instrument for improved solar site assessment

Soiling of reflectors and receivers impacts energy harvesting of CSP Plants as well as operation and maintenance cost for cleaning. The identification of the proneness of a potential solar site to soiling would reduce risk and improve the performance and cost prediction. To allow for a mid- and long term monitoring of soiling rates, precise, replicable and fully automated measuring methods are needed, similar to today's solar resource assessment. Furthermore, the analysis of dust and its adhesion on solar reflectors are of interest. Tackling both aspects an instrument for automated online monitoring of soiling is presented in this article. The AVUS measurement set-up directly measures reflectance and cleanliness. Furthermore, the soiled samples are available for retrospective assessment of dust and its adhesion on solar reflectors. Three prototype instruments were built and installed next to meteorological stations at a solar thermal power plant in the south of Spain, proving the prototype function in the field and allowing ongoing monitoring of cleanliness factor and soiling rates.