Geothermal storage for seasonal heat utilization

12.06.2025

Source: E & M powernews

Geothermal storage systems can contribute to seasonal heat and cold storage. A background paper shows technical possibilities and examples.

Geothermal storage systems can store heat in summer and make it available again in winter. At the same time, they enable buildings to be cooled using the same system. The German Geothermal Energy Association (BVG) presents the current state of research into the seasonal storage of geothermal energy in a background paper entitled "Geothermal storage", the association announced on June 12. According to the association, seasonal heat storage systems are a "key element" in the rapid decarbonization of heating networks.

Several technical approaches can be considered for seasonal storage. According to the German Geothermal Energy Association, borehole heat exchangers (BTES) can be installed almost anywhere. The pipe systems installed vertically in the ground store heat similar to the principle of a heating blanket. One example is Crailsheim in Baden-Württemberg, where around 260 residential units as well as a school and a sports hall are supplied with solar heat and seasonal storage.

Aquifer heat storage systems, which store heat in thermal water layers, would also work efficiently. The recovery rate can be up to 80 percent. This principle is already being used in the Reichstag building in Berlin to supply heating and cooling. Further aquifer systems are currently being tested at two locations.

A third concept envisages the subsequent use of former mining infrastructure as a heat storage facility. Mine Thermal Energy Storage (MTES) is currently being researched in Bochum and Freiberg, among other places. Mine water is used as a thermal storage facility.

"Not only does the ground not send a bill, it actually helps to save money: In many cases, the combined use of the ground for heating and cooling buildings can drastically reduce investment costs. In the case of geothermal probe systems, up to two thirds of the costs for heating alone are possible," adds Gregor Dilger, Managing Director of the German Geothermal Energy Association.

In addition to the technologies, the background paper also looks at regulatory, social and ecological aspects. It also looks at other forms of storage such as CO2-based concepts and combined heat and power storage. According to the BVG, the aim is to provide a basis for decision-making for the increased expansion of seasonal heat storage.

In light of the requirements of the heat transition, the BVG sees considerable potential for geothermal storage in Germany. Integration into existing and new heating networks is seen as a key lever for decarbonization.

Author: Heidi Roider