German Central Solar Heating Plants with Seasonal Heat Storage

The German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety considers central solar heating plants with seasonal heat storage as a key technology to meet the targets for the reduction of CO₂ emissions. Central solar heating plants with seasonal heat storage are designed for solar fractions of approximately 50 per cent. Solar collectors are installed preferably on large roofs and the seasonal thermal energy store is built into the underground for space and aesthetical reasons. Central solar heating plants with short-term heat storage are designed for a solar fraction, based on the total heat demand for space heating and hot water preparation, of approximately 15–20 per cent. Since 1997, the first central solar heating plant with borehole thermal energy store in Germany is being operated in Neckarsulm. In addition to solar fraction, the efficiency of solar-assisted district heating systems can be evaluated by the amount of solar heat per m² collector area delivered into district heating net.