Effects of dust and rainfall on the relative reflectivity of linear Fresnel reflectors

Abstract

Dust and rainfall have been key issues affecting outdoor solar concentrating systems. This study aimed to accurately evaluate the specific effects of dust and rainfall on linear Fresnel reflectors in semi-arid regions. Targeted outdoor experiments on dust and rainwater were conducted in Hohhot, Inner Mongolia, from September to December 2023. A predictive model is developed to assess the effect of rainfall on reflectivity under conditions of dust accumulation, based on the physical properties of outdoor-exposed dust. The study reveals that after 60 days of exposure, the reflectivity decreased at a rate of 0.25 % per day due to mirror dust, particularly within the 380–780 nm wavelength range, reaching 21.62 %. The rainfall leads to four distinct conditions, namely pitting, surface corrosion, gully corrosion, and overall corrosion on the dusty mirror. During the gully corrosion and corrosion stages, the reflectivity significantly improved. Rainfall below 0.4 mm barely cleaned mirror dust, whereas rainfall exceeding 26.70 mm provided substantial cleaning but reached a saturation point with additional rainfall. These findings contribute to the development of cost-effective cleaning strategies for similar climatic conditions.