Storing Summer Heat for Winter

June 22, 2026

Source: E & M powernews

The University of Duisburg-Essen is conducting research on seasonal heat storage systems in three projects. The goal is to be able to use excess summer heat to supply heating networks in the winter.

In the summer, heat from sustainable energy sources is often available in abundance, while in the winter it is urgently needed. Seasonal heat storage systems could bridge this gap. However, for this to work, seasonal storage systems must not only be climate-friendly but also economically viable to operate. This is where three projects at the University of Duisburg-Essen (UDE) come in.

“With our projects, we are laying the scientific groundwork so that municipalities, municipal utilities, and energy providers can safely and economically harness this potential in the future,” said project leader Christian Thommessen from the Chair of Energy Technology. “The findings will serve as a guide for the entire heating industry as they develop their own projects.”

Scientific Foundations for Municipalities and Utilities

UDE is participating in the Federal Ministry for Economic Affairs’ “URBAN ARENA Seasonal Heat Storage” funding program with three projects. The “HANSE,” “LEEZE,” and “BISAM” projects are investigating how excess heat from renewable energy sources can be stored over extended periods and used for heating in the winter. According to the university, UDE is the only German university represented in this funding program with three projects.

According to the Chair of Energy Technology, the projects are intended to provide technical, economic, and planning foundations for the use of seasonal heat storage systems. The researchers are collaborating with municipal companies and engineering firms on these projects. They are examining both the integration of the storage systems into existing heating networks and issues related to site selection and economic viability.

Earth-tank heat storage in Lübeck is being studied

In the project “HANSE—Hydraulic and Techno-Economic Analyses for Grid-Connected Systems with Seasonal Earth-Tank Heat Storage Systems Using the Example of District Heating in Lübeck,” the UDE is collaborating with Stadtwerke Lübeck and the engineering firm Ramboll. The consortium is assessing the feasibility of a seasonal earth basin heat storage facility in the Lübeck metropolitan area.

The storage facility is intended to utilize heat from solar thermal systems as well as from heat pumps that draw energy from wastewater and river water. The partners are analyzing potential sites from geotechnical, hydrological, and planning-law perspectives. In addition, they are simulating the storage system’s operation in conjunction with various heat generators over several years.

LEEZE Investigates Sites with High Groundwater Levels

In the project “LEEZE—Long-Term Energy System Analysis for Ground-Source Storage in Urban District Heating Networks,” researchers are taking a closer look at the use of seasonal ground-source storage in cities with high groundwater levels. Such locations have often been considered difficult or unsuitable for such storage solutions.

In collaboration with Stadtwerke Münster and Ramboll, the UDE aims to identify potential sites and conduct district heating network simulations. One of the goals is to develop a set of criteria for planning seasonal ground-storage reservoirs in densely populated urban areas. The results are expected to provide insights into the conditions under which such systems can be implemented even at challenging sites.

Repurposing a Former Coal-Washing Plant in the Third Project

In the project “BISAM—Investigation and Evaluation of a Fundamental Repurposing of Former Coal Mine Building Complexes,” the focus is on a former coal washing plant in the Ratheim district of Hückelhoven. Together with WEP Heat, Energy, and Process Technology and the civil engineering firm W+G, the UDE is investigating whether the structure can be used as a seasonal heat storage facility.

The facility has a diameter of approximately 100 meters and is located near a district heating network. The researchers are analyzing the structural suitability of the existing building, possibilities for grid integration, and the economic and environmental impacts of a conversion.

If the concept proves feasible, the facility could be among the first repurposed existing structures in Germany to store heat from renewable energy sources on a seasonal basis. The project thus also addresses the question of what role former industrial and mining sites can play in heat supply in the future.

Author: Heidi Roider