Potential of geothermal energy for heat transformation in cities

6 May 2021

©Matt Palmer

Geothermal energy is a key technology for realizing the urban heat transformation. As regards deep geothermal energy, it feeds existing or newly built district heat systems with renewable heat and thus replaces existing systems based on fossil sources and CHP.

In what way and to what extent can geothermal energy contribute to implementing local heat transformation strategies? What are existing best practice examples? Which obstacles can local authorities face concerning the regulatory framework and city planning and how can they overcome them?

Check the strategies of three cities from the Decarb City Pipes 2050 project to learn more about the potential of geothermal energy for cities!

Shallow geothermal energy potential in urban areas: the example of Vienna

In Vienna, there is a potential of shallow geothermal in urban areas. To map it as precisely as possible and allow the municipality to make enlightened choices in its heat mapping, the Federal Agency for Geology of Austria explores existing resources for shallow geothermal energy and possible limitations. Cornelia Steiner, an expert in hydrogeology and geothermal energy working for the Federal Agency, gave an overview of the integrative management of shallow geothermal energy use the Agency put in place. It created a web portal for shallow geothermal energy and gives a clear overview of existing installations in Vienna. Based on thermal groundwater use for heating and/or cooling or installed as borehole heat exchange, those installations rely on different hydrogeological conditions, based on the aquifer’s groundwater characteristics.

A key instrument for integrating shallow energy sources in Vienna’s heat supply is the Spatial Energy Planning (SEP), which is part of the Green Energy Lab ( It includes a traffic light map disclosing information on potential limitations for shallow geothermal projects. Challenges for mapping resources identified in Vienna are changing input parameters (which could be overcome by interactive maps), the quality of input data as well as limitations due to resources with competing usages.

Apart from shallow geothermal energy, Vienna is also looking into deep geothermal energy potential and installations as a solution for decarbonizing the city’s district heat system.

Estimating the potential of deep geothermal energy: following the Dublin region’s example

District heating has been identified as the key solution to decarbonizing the Irish heat sector in densely populated areas, and geothermal energy is going to play a fundamental role here. However, while shallow resources are relatively well characterized and accessible across the whole country, it is more complicated when it comes to deeper resources. To significantly increase the installed capacity, Ireland can build on a strong support for climate friendly technologies, strong local and internal geological networks, a dynamic geoscience SME sector and District Heating demonstrator projects underway.

In the course of building up a regulatory framework for district heating in Ireland, the government, together with Geological Survey Ireland (GSI) is examining of the potential of geothermal to contribute to district heating and the development of a dedicated district heating roadmap. To tackle the lack of subsurface knowledge, GSI is looking into a deep geothermal pilot project in Dublin and has initiated the mapping of key data at national level. To enrich this mapping, Codema and local authorities have shared their latest heat demand maps and studies as well as planners for urban subsurface management and district heating. As research shows, potentials for geothermal heat in the city of Dublin, particularly in the South County Dublin, are significant. A demonstrator project would apply knowledge transfer in the EU-funded Hotlime project and could serve as best-practice example for other European cities.

Geothermal strategy and projects in Munich

The city of Munich, together with its publicly owned utility Stadtwerke München (SWM), is aiming for fully decarbonizing its district heat system by 2040. Based on new and even more ambitious climate goals of the city, the transition of Munich’s heat sector may need to be completed by 2035. Today, roughly about one third of Munich’s households are connected to the district heating grid. Deep geothermal energy is already a reality in the city – and it will be the backbone of Munich’s renewable heat supply of the future.

The area benefits from favourable geological conditions: thermal water in limestone layers (“Malm”) in the subsurface of Munich’s and its southern region, high temperatures of ~100°C and depths of ~3000 km under the city). Thanks to this, Munich is a true frontrunner in developing urban geothermal energy solutions. The city area already counts two installations in operation, and a third one will be connected to the grid in the winter season of 2021. This new plant, which will be built on the grounds of an existing CHP plant in the south of Munich, will have an installed thermal capacity of more than 60 MW, serve more than 80,000 people with renewable heat and will be Germany’s biggest geothermal energy plant. It will largely contribute to SWM’s plans of providing the major share of district heating with deep geothermal energy until 2040 (2035). More installations are already in the planning phase – including new installations in the city area as well as the connection of existing plants in the southern region to the city’s district heating grid by new transmission lines.

Of course, there are key challenges to further realise the geothermal potential in Munich. The main one is linked to the specific requirements for building geothermal plants in dense urban areas, particularly regarding a lack of suitable areas and competition of usage. The question of high investment costs and risks comes second, followed by the need of high-quality data on the subsurface. To continue developing geothermal capacity, the next step will be exploring the potential and feasibility of geothermal storage (aquifer storage). The Decarb City Pipes 2050 project allows the city to gather valuable information and provides an excellent network for proceeding both on the structural (city planning) as well the research side of geothermal energy.

Main takeaways

Looking at geothermal energy to feed your heat transformation strategies means involving different actors, with different roles and responsibilities. The city government, local (publicly owned) utilities and federal geological institutes have to work hand in hand to unlock the potential of geothermal energy for urban energy transitions in heating. It is also key to develop pilot projects to work on investment problems and a better mapping of data. When available, geothermal energy can be one of the fast lanes towards decarbonised heating systems.