Regional soiling stations for PV: Design, calibration and installation

Soiling rate (g/m2/day) and daily/annual soiling loss (%) of photovoltaic (PV) modules are primarily influenced by climatic condition of the site and tilt angle of PV modules. Therefore, for all the performance and energy prediction models used by the industry, accurate climate-specific and tilt-angle-specific soiling rate and daily/annual soiling loss data are needed. The primary focus of this work is to demonstrate the effectiveness of regional soiling stations designed to systematically collect this data and they are deployed in five regions in the United States. This paper presents information on the design, calibration and installation of soiling stations. Four of the sites are at the U.S. Department of Energy Regional Test Centers (RTC) in Albuquerque, NM; Golden, CO; Cocoa Beach, FL; and Essex Junction, VT, while a fifth site is in Mesa, AZ. Each soiling station is equipped with a data acquisition system and 10 laminated coupons tilted at angles of 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°. Each coupon contains two identical half-cells cut from a single monocrystalline silicon cell. In this test setup, the right half-cell is periodically cleaned and left half-cell is allowed to soil naturally so the above stated data can be collected throughout the year.