Seasonal Storage of Low Temperature Heat in Big Water Reservoirs

Abstract

Seasonal storage of heat for house heating would be very attractive as the house heat demand is high in the winter and very low or zero during the summer. If big thermal storage systems could be safely constructed at acceptable costs the sources for this low temperature heat could either be operated all the year round (high efficiency, lower capital costs) or solar as well as waste heat which mainly or likewise arise during the summer could be used for (peak) heat demand in the winter. Mainly the following two applications of seasonal heat storage would be of great interest:

• 1.1. District heating systems based on combined generation of heat and power (CHP) could be operated at optimal efficiency all the year round. In the summer and whenever the heat demand is lower than heat production the surplus energy could be stored and extracted in the winter when the demand is higher than the rate of production.

• 1.2. Central solar heating plants (CSHP) with seasonal storage could be operated theoretically without any other complementary heat source like fossil fired boilers or heat pumps. They would use in winter time mainly the heat collected during the summer and stored in the reservoir.