The photovoltaic system with a capacity of 117 kWp was commissioned on 27 March 2009. It is the largest roof-integrated solar installation on an existing farm building in the canton of Bern. This installation with a surface area of 870m2 produces about 113,000 kWh per year. This provides power to 21 average homes with 90% energy loss, or to 113 urban houses renovated to Minergie-P standards.
With the roof of its farm building, the Guggisberg family demonstrates how farmers can become energy producers. The farm is located at an altitude of 900metres above sea level and enjoys excellent sunlight conditions. The installation is very well integrated into the ridge and pitch of the roof; it almost reaches right up to the sides and the gutters.
About two metres of rainwater per square metre (nearly two tonnes) fall on Grimsel; if you imagine that this water falls from a height of 400 metres, you could obtain hydroelectric power amounting to 2kWh/m2a. If the Guggisberg family were to plant trees or shrubs to harness their energy, it would produce 3 to 5 kWh/m2a per square metre of surface area of biomass. Now the Bern-based operation generates 130 kWh/m2a of solar power.
Per square metre of photovoltaic surface area, they therefore generate 40 times more energy from sunlight than using biomass and 65 times more than hydroelectric power. However, unlike biomass and pumped storage hydroelectric power plants, solar power cannot be stored. Each form of energy thus has its advantages and disadvantages. It is a case of using it wisely.