Evaluation of the potential for geological heat storage in Denmark

In Denmark both wind power and district heating are integrated parts of the energy supply and according to the politically adopted plans for a transition toward a fossil free energy supply by 2035 all electricity and heat production must come from renewable energy sources. However, extensive periods with surplus of both solar and wind power calls for innovative ways to store this energy and make it available when needed. By the concept of Geological Storage surplus electricity can be converted to heat and along with surplus heat from solar panels and as well as surplus of industrial heat stored in the ground for later use. Furthermore, implementation of heat storage can make it possible to expand district heating supply without building new production facilities and subsurface heat storage will often be the only possibility, especially in city areas, due to areal limitations. Though the potential is large, the experience with this concept is currently relatively limited. This project aims to explore the possibilities to store and retrieve heat from relevant geological formations in Denmark to be used at larger and smaller district heating plants as well as other relevant industries when needed.

Since technically and environmentally sound solutions for geological storage of heat to a large degree depends on the local geological settings and depths, it is essential to identify potentially favorable geological conditions and the related possible technical solutions. In this project selected geological settings will be investigated and the potential, risks and investment costs of different types of storage facilities and geometries will be examined.

The aim of the project is to provide district heating companies and other relevant industries with maps and guidelines to facilitate planning and construction of storage facilities in connection with their current power plants.

One part of the work regarding shallow energy storage will be based on present experience and data from an existing test plant at Brædstrup District Heating. This work will focus on possible ways to upscale such a test plant using novel combinations of proven technologies. The present project will draw on experience from previous projects investigating deep and shallow geothermal potentials in Denmark