Photovoltaics in the Alps deliver up to four times more electricity in winter

Currently, many large-scale alpine plants are being planned within the framework of the so-called "Solarexpress", which are to be subsidized by the federal government. With regard to the planning of these plants, ZHAW researchers have summarized the most important findings from the measurements at the Davos-Totalp alpine test facility in a report. Above Davos at 2500 meters above sea level, the ZHAW Renewable Energy Research Group has been operating this alpine photovoltaic test facility together with EKZ for more than five years.

Alpine solar plants conserve reservoirs

The yield of an alpine solar system is divided approximately equally between the winter and summer half-year. The electricity yield in the winter half-year, i.e. from October to March, is three to four times that of a plant on the Central Plateau. According to ZHAW researcher Jürg Rohrer, however, the particularly high yields in April and May are also a major advantage. In these months, alpine solar plants achieve their highest monthly yields and the levels of the reservoirs are relatively low in each case. "This means they can make a significant contribution to the security of electricity supply," says Jürg Rohrer. "Building alpine solar can conserve reservoirs and therefore also eliminate the need for fossil-fuel backup power plants, for example."

Best in southern orientation

The measurement results give practical instructions to the planners of alpine solar plants. These plants are more sensibly built on south-facing slopes with the modules facing south. If the modules are inclined between 60 and 90 degrees, the losses due to any snow cover can be practically neglected, as the snow slides off quickly. The tilt angle of the modules affects when the yield is highest: vertical modules with a 90 degree tilt angle produce higher yields in December and January than modules with a 60 or 70 degree tilt angle. However, the latter are more productive in March-May and in summer.

According to Jürg Rohrer, Alpine solar plants are intended to supplement the expansion of photovoltaics on existing infrastructures in the Central Plateau and can in no way replace them. "We have overslept the energy turnaround and need to expand electricity generation with photovoltaics at least twice as fast as last year in the next ten years. But we also need more wind energy and, above all, the huge savings potential should be better exploited." With further research work, the ZHAW researchers are currently systematically investigating the influence of distances between module rows on the electricity yield of large-scale alpine plants. Corresponding results are expected in the summer of 2024.