Solar District Heating Systems for Small Districts with Medium Scale Seasonal Thermal Energy Stores

This contribution deals with recently realized as well as planned small solar district heating systems with seasonal thermal energy stores in Europe. It focuses on systems with less than 1 000 m2 of solar collector area and less than 1 000 m3 volume of seasonal thermal energy store. Different technical characteristics of systems in Poland, Spain and Germany are shown. As high storage efficiency in small systems is difficult to achieve, particular attention is given to the design of the seasonal thermal energy stores and other components such as high temperature heat pumps that are necessary to reach an efficient operation of the plant.