Use of combined alternative energy. View of the solar panels and biogas tank at a sewage works. Methane from the sewage degradation is collected and stored in the corrugated tank just left of centre. The methane is then used to fuel a combined heat and power system (30 kilowatts electricity, 60 kW heat). This is supplemented by the solar panels (peak 140kW) and a large wind turbine (250kW). Together, these sources provide most of the electricity demanded by the sewage works. The site is at Fehmarn, Germany.