The Central Solar Heating Plant with Aquifer Thermal Energy Store in Rostock, Germany

The first central solar heating plant with an aquifer thermal energy store (ATES) for seasonal heat storage in Germany has been built in Rostock in 1999. The heating system supplies a multifamily house with a living area of 7000 m2 in 108 apartments. On the roof of the building solar collectors (Solar Roof) are mounted with an area of 980 m2. The ATES operates with one doublet of wells and is located in a depth of 15 to 30 m. The Paper gives information about the heating system and the investigations that have been performed during the design phase. Furthermore the resulting design values and information about the monitoring program are presented. Introduction Stopping global warming of the atmosphere caused by burning of fossil fuels requires a substantial reduction of the fossil fuel consumption. In Germany, 30 % of the energy consumption is used for heat supply of residential buildings. Besides, this field offers the highest potential for energy savings. Central solar heating plants are the most economic opportunity for the use of solar energy in housing estates to support domestic hot water (DHW) preparation and room heating. In connection with a seasonal heat store more than 50 % of the fossil fuel demand of an ordinary district heating plant can be replaced by solar energy. The first pilot plants with seasonal heat stores in Germany show good performance and energy savings in the expected range (HAHNE et al. 1999). Altho ugh there have been several problems with the initial operation of the plants, mainly concerning the interconnection between the solar and the conventional heat supply system, the technical part of large solar systems is fully understood. From the economical point of view, solar produced heat can not yet compete with fossil heat production. A substantial part of the investment cost of a central solar heating plant with seasonal storage (CSHPSS) is caused by the seasonal heat store. Formerly built pilot-plants in Germany are equipped with hot-water tanks, gravel-water stores or duct stores. However, the aquifer thermal energy store in Rostock is expected to achieve a decisive reduction of the cost for this component. TERRASTOCK 2000, Stuttgart, Germany; August 28 until September 1, 2000 Seite 2 Description of the heat supply system The aquifer store is integrated in the heat supply system for a multifamily house in Rostock-Brinckmansdorf, NorthGermany. The building has 108 apartments with a total living area of 7 000 m2 in eleven terraced houses. Figure 1 shows a simplified hydraulic scheme of the heat supply system. The heat is produced by a solar system with a collector area of 980 m2 that is mounted on the building as a Solar Roof, a heat pump that uses the ATES as heat source and a gas condensing boiler. To overcome the discrepancy between the large amount of solar energy in summer and the heat demand for space heating in winter, the aquifer works as a seasonal store that is heated up in the summer-period by the solar system and unloaded in autumn and winter directly or by way of the heat pump. To increase the amount of directly usable solar heat (not by way of the ATES), a buffer store with 30 m3 is integrated as well. heating circuit 1 heating circuit 2 heat pump boiler buffer store cold water W1 W2 W3 collectors