Steep solar modules in winter bring high electricity yields

Researchers from the Wädenswil-based Renewable Energies research group at the Zurich University of Applied Sciences(ZHAW) and the electricity utility of the Canton of Zurich(EKZ) have been operating an alpine laboratory for photovoltaics in the Davos-Parsenn ski resort since 2017. According to a press release, the teams installed solar modules in various designs and installation angles in order to determine values for optimum electricity yield. The year-round tests showed that bifacial solar modules (those that absorb solar energy from both surfaces) are more efficient than monofacial ones.

A steep installation angle proved to be particularly favorable for the winter months. Not only could the solar energy be absorbed from both sides of the panel, the steep angle also resulted in less snow cover and therefore a greater electricity yield. According to a study, the bifacial solar panels installed on the Totalp near Davos at an altitude of 2,500 meters produced 25 percent more power at an installation angle of 60 degrees than comparable panels on the Central Plateau. At an angle of 90 degrees, an increase of 33 percent was recorded. According to the study, this corresponds to a yield of 2.9 to 3.1 times that of the plant in the Central Plateau.

The losses with snow cover were 8 percent at an angle of 60 degrees compared to snow-free years, and less than 1 percent at an angle of 90 degrees. "The losses due to snow cover are negligible for bifacial modules inclined at more than 70 degrees in alpine regions," Jürg Rohrer from the ZHAW is quoted as saying in the press release. According to Raphael Knecht, Head of Solar Business at EKZ, steeply inclined, bifacial modules are used in the alpine projects to maximize the winter yield. "Several years of experience with the test system now confirm our planning that losses due to snow cover are minimized," says Knecht. ce/ww