Research - current projects

Winter-optimized photovoltaics

The energy yield in the winter half-year of a PV system in Switzerland is often only about one third of the whole-year yield, whereas two thirds of the energy is generated in the summer half-year. In order to counteract this commercially disadvantageous circumstance, a high tilt angle of 50° for the PV modules has been chosen in the Mont-Soleil solar plant, which not only increases the solar radiation in the winter half-year, but in particular also contributes to the fact that the snow slips off quickly the solar modules. The share of energy in the winter half-year was thus increased to around 40%.

The behavior of the Mont-Soleil solar power plant during snowfall is shown in the diagram on the left. On January 14, the site was snow-covered. Due to the low solar radiation (orange curve), the snow did not slip off and accordingly the plant output (blue curve) remained at 0 kW. Yet the loss of production was also low due to the low solar radiation. On January 15, a test area was cleared of snow to establish a representative reference state. The power curve (blue) subsequently moved in sync with the global radiation curve (orange). On the night of January 18 there was another snowfall. Thanks to the strong sunshine that day, however, the snow slipped off rapidly, as can be seen in the diagram on the left in the form of a small phase shift between the orange and blue curves.

In the case of building-integrated photovoltaics, however, the tilt angle of the PV panels is often not freely selectable, which in many cases leads to substantial losses in energy yield due to snow cover. In a broad-based research program at the PV lab at Bern University of Applied Sciences BFH in Burgdorf, various snow removal methods (electrical and mechanical solutions) are being investigated at a number of PV plants in Switzerland, including the Mont-Soleil solar power plant.

The measuring campaign of the PV lab with regard to the snow problem and its evaluation as well as its interpretation in the overall economic context has not yet been completed and will therefore continue in 2019.