5 April 2022 | revised on: 15.07.2022

18 metres long, around five metres high, and highly efficient: Mannheim-based energy company MVV is building a river water source heat pump along the bank of the Rhine by the GKM power station in Mannheim. The heat pump extracts thermal energy from the river and uses it to produce heating water. Around 90 stakeholders from industry, politics, and science were present to witness the official start of construction.

A large proportion of Germany’s CO2 emissions can be attributed to the supply of heat. Large-scale heat pumps (LHPs) could help the country to reduce these emissions. They utilize river water or waste heat from power plants as a heat source and exploit these to reach a suitable temperature level. Thermal energy is subsequently fed into district heating networks (see infobox below “What is a large-scale heat pump?”).

A river water source heat pump of this kind is now being used at the GKM power station in Mannheim. It is part of the Living Lab for the Energy Transition entitled “Large-scale heat pumps in district heating networks – installation, operation, monitoring and system integration”, which the German Federal Ministry for Economic Affairs and Climate Action is providing with around € 21.3 million in funding. The various project partners involved are integrating LHPs into a total of five district heating networks at various types of location in Germany. The aim is to promote the decarbonization of heating supplies.

Construction measures start in April

The official ground-breaking ceremony yesterday marked the start of construction and civil engineering works at the Mannheim power station. Around 90 stakeholders from industry, science, and politics were in attendance. Guest speakers at the event were Thekla Walker (Minister of the Environment, Climate Protection and the Energy Sector Baden-Württemberg), Dr. Peter Kurz (mayor of the city of Mannheim), Dr. Hansjörg Roll (Chief Technical Officer at MVV Energie AG), and Holger Becker (Commercial Director at GKM). During her speech, Thekla Walker emphasized that the Living Lab for the Energy Transition “Large-scale heat pumps in district heating networks” is an important project for promoting the use of this technology at other locations, as crucial know-how has been amassed in the Mannheim project.

Once the water source heat pump has been successfully put into operation, the Mannheim-based energy company is planning to install further LHPs. These plans serve MVV’s aim to achieve carbon neutrality by 2040 and to subsequently become climate positive. To this end, Mannheim and the surrounding region is planning to convert to a carbon-neutral district heating supply by 2030. The use of river water source heat pumps plays an important role in this regard. “From 2023, the innovative river water source heat pump will count among the green technologies through which we are gradually replacing heat from the GKM,” explained MVV CTO Dr. Hansjörg Roll.

The river water source heat pump is set to go into operation in early summer 2023. This will be followed by a roughly three-year operational phase in which research and development measures will predominantly take place. The new LHP is expected to supply thermal energy for around 3,500 households.

District heating network utilizes thermal energy in river water

At the Mannheim site, one of the largest heat pumps in the collaborative project will be implemented with a thermal power of approx. 20 megawatts. Its output is equivalent to that of roughly 2,000 conventional household heat pumps. Energy company MVV expects that the new technology will lead to the reduction of up to 21,000 tonnes of CO2 each year in the long term.

In addition, the heat pump retrieves river water via a water inlet structure, which is pumped below ground to the system. It then uses the thermal energy extracted from the waters of the Rhine via a heat exchanger to heat water from the return flow of the district heating network from 60 degrees Celsius to up to 99 degrees Celsius. The heated water is then directly fed back into the district heating network or is temporarily stored in a thermal energy storage system (capacity of 1,500 MW). The Rhine water, which is cooled by around 2 to 5 degrees Celsius due to the heat released to the heat exchanger, then flows back into the river.

What is a large-scale heat pump?

Depiction of a large-scale heat pump.
© 2020 Johnson Controls
Depiction of a large-scale heat pump.

Just like a conventional, decentralized heat pump, an LHP also extracts thermal energy from an external heat source and passes this energy on. The difference, however, is that the recipients of this energy are usually district heating networks, which operate at higher temperatures than heating systems in a single-family home. The LHPs need to be adapted for these temperature levels. Operating parameters such as pressures, temperatures, and sometimes even coolants differ greatly from smaller heat pumps. In contrast with decentralized heat pumps, LHPs are able to utilize large, natural sources of heat and industrial waste heat sources with high energy potential at a low temperature level. LHPs are not often situated in direct proximity to heat consumers or cannot be accessed by individual consumers due to their size. They enable an efficient, electricity-based heat supply, particularly in areas with a high heating demand that are supplied with district heating. Further information on LHPs can be found on the online portal industrie-energieforschung.de.

Large-scale heat pumps also being built at other locations

Respective power plant operators and energy suppliers are also building LHPs close to existing heat production sites at the four other locations of the Living Lab dedicated to this technology: in Stuttgart (EnBW Energie Baden-Württemberg), Rosenheim (Stadtwerke Rosenheim), Berlin-Neukölln (Fernheizwerk Neukölln), and Berlin-Köpenick (Vattenfall Wärme Berlin). As part of these efforts, they are working closely together with scientists from the Fraunhofer Institute for Solar Energy Systems (ISE) and the University of Stuttgart. The teams are testing on site how the LHPs can be efficiently integrated into the existing infrastructure and their operation optimized. In addition to technical findings, the experts aim to discover how regulatory and economic frameworks must be adapted in order to better establish LHPs on the district heating market.

Launch of the Living Lab for the Energy Transition offer practical innovations

The LHP project is a Living Lab for the energy transition. Funded by the Federal Ministry for Economic Affairs and Climate Action, the project involves innovative technologies being tested in practical applications and under real-world conditions. The Living Labs focus on the systematic interaction between energy provision and energy demand on the level of a specific district or one or several select cities. Some of the Living Labs even stretch across several federal states. Experts can subsequently use the findings obtained through the project to make a decisive contribution to Germany’s efforts to fundamentally restructure its energy system. The Living Labs for the Energy Transition are a valuable way of testing innovations before they establish themselves in the energy industry and thus represent a crucial support for the success of the energy transition.

In the field of energy-optimized districts, five Living Labs for the energy transition have been launched:

DELTA – Darmstadt Energy Laboratory for Technologies in Application

LHPs –Large-scale heat pumps in district heating networks

IW3 – Integrated household heating transition in Wilhelmsburg


SmartQuart – Smart energy districts

Five Living Labs for the Energy Transition have also been launched in the field of sector coupling and hydrogen technologies. Further information and an overview of all projects can be found at energieforschung.de. (bs)


Project partner
MVV Energie AG

Tel.: +49 711 126-0

©aryfahmed – stock.adobe.com

Net-Zero Heating

More than half of the energy consumed in Germany is used to heat our homes, offices, and shops, as well as to make heat available for industry and commerce. The transition to renewable heat, inevitable waste heat, and CO2-free fuels needs to be well organized.


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