Cleaning frequency optimization for soiled photovoltaic modules

This study was conducted to determine the optimum cleaning frequency for cleaning Photovoltaic (PV) modules installed in Mesa (near Phoenix), Arizona, United States. By monitoring the soiling loss of PV modules mounted on a mock rooftop at ASU-PRL during May through June 2014 (highest soiling period for this site), a detailed soiling loss modeling was obtained. During the dry/soiling summer season, the daily soiling rate has been determined to be -0.061% for 20° tilted PV modules. Based on the monitored soiling rate and extensive simulation of this investigation, it is concluded that the cleaning is not economically justifiable for 20° or higher tilted residential PV modules of this and nearby sites.