Investigation of optimal tilt angles and effects of soiling on PV energy production in Pakistan

摘要

Tilt angle of photovoltaic (PV) panel strongly contributes to the amount of solar radiation harvested by the PV panel. In this paper, we model the optimal PV tilt angle for Lahore and some of the other major cities in Pakistan using the available solar radiation data from NREL and ESMAP. The model is used to propose an optimal schedule for PV tilt in Lahore involving four adjustments in a year that can provide similar to 6.6% increase in the yearly energy generation relative to a fixed tilt. The model is validated with PV tilt experiments. Moreover, a simple model is developed to estimate the upper/lower bounds of soiling losses in Lahore using the reported distributions for aerosol particulates. We show that the power loss due to soiling could be up to 10% for a lightly soiled panel and could go up to 40% for a heavily soiled panel. We further explore the tilt angle effect on the soiling losses in Lahore by doing soiling experiments. For a period of 100 days, dust deposition on a horizontal panel results in 26.2% energy loss as compared to a clean panel. For the same period, the corresponding loss for a vertical tilt was 13.5%. The variability of soiling effects with respect to tilt is used to predict an optimal tilt angle when the soiling losses are significant. These findings provide important insights into the protocols of tilt adjustments in presence of environmental dust for PV systems in Pakistan and further highlight the significance of soiling losses for the typical aerosol conditions in Lahore. (C) 2019 Elsevier Ltd. All rights reserved.