Optimum Tilt Angles of Solar Panels: A Case Study for Gansu Province, Northwest China

Abstract The article deals with optimizing tilt angles of photovoltaic panels for fixed and manually adjusted solar photovoltaic system with due south-facing orientation to maximize the output of solar electricity in Gansu province, northwest China. There are three models by Liu and Jordan, Hay and Kliein and Theilacker selected to calculate the seasonal and yearly optimum tilt angles of solar panels through Matlab programs on seven sites in Gansu province. Meanwhile, the outdoor experiment was conducted to measure the yearly sum of global solar irradiance at different tilt angles. The study found that (1) the calculated yearly optimum tilt angles by three models are close among each other especially between Liu and Jordan’s and Klein and Theilacker’s models; (2) the annual optimum tilt angles of solar panels for fixed installation could be set at model’s angle for higher latitude sites with most-rich solar energy, and latitude angle for lower latitude sites with medium-rich and less-rich solar resources; (3) the seasonal optimum tilt angles should be set at average models’ angle for manual adjustment of photovoltaic system across a year; (4) for all sites, the model’s angle could be selected for a photovoltaic system when considering limitation of land-use area.