Large heat pump makes coal phase-out possible

24.04.2026

Source: E & M powernews

The coal phase-out in Hanover reaches the next stage: a 30 MW heat pump is being built at the central sewage treatment plant.

Following the decommissioning of the first coal block in March, Enercity is preparing to replace coal block II. The decentralized mix of various biomass plants will now be joined by several large heat pumps, power-to-heat plants and the expanded heat extraction from the waste incineration plant. The utility is thus further diversifying its generation portfolio in order to minimize its dependence on individual fuels, according to a company statement.

The new large-scale heat pump with an output of 30 MW, whose components have now arrived at the Herrenhausen sewage treatment plant, will supply climate-neutral heat for up to 13,000 households in future. The central components, including motors, compressors and the two central heat exchanger packages, come from the Swiss manufacturer Friotherm.

Winter-stable heat from the sewage treatment plant

"Within just a few days, the installation team assembled the individual components weighing up to 50 tons in front of the hall and pulled them into the building with millimetre precision using rails," said Michael Hartung, Managing Director of Enercity Contracting GmbH, commenting on the progress of the project. In the coming weeks, the units will be connected via several hundred meters of piping.

According to Enercity, the municipal sewage treatment plant in Hanover offers ideal conditions for the use of the technology because the temperature of the treated wastewater remains stable at around 12 to 16 degrees even in winter. This makes the plant particularly valuable as a medium-load generator because it can also provide heat when demand is particularly high.

Phasing out coal and the heating transition

With an annual heat generation of around 130 million kWh, the large heat pump will cover around seven to eight percent of Hanover's total district heating requirements in future. The integration into the existing system has been prepared: Electricity and district heating connections were made last year.

The system is scheduled to be fully installed by the end of 2026, after which it will go into regular operation. According to Enercity, it is investing a total of around 56 million euros. The project is being funded by a grant of 22.5 million euros from the "Federal Funding for Efficient Heating Networks" (BEW) program.

By the end of winter 2027/28, the coal-fired power plant is to be completely replaced by a climate-neutral plant portfolio. At the same time, the district heating network is to grow considerably: from around 360 kilometers today to around 550 kilometers in the future. By 2040, Enercity aims to supply around 18,000 buildings in Hanover with climate-neutral district heating - around four times as many as today.

Technical data of the large heat pump

• Heat source: purified clear water from the sewage treatment plant
• Source temperature: 12 to 16 degrees (stable in winter)
• Thermal output: 30 MW
• Annual heat generation: around 130 GWh
• District heating flow temperature: around 95 degrees
• Supply potential: arithmetically 13,000 households
• Share of district heating demand in Hanover: 7 to 8 percent

Author: Günter Drewnitzky