CHP networks electricity and heat

05.12.2025

Source: E & M powernews

CHP remains relevant even in a climate-neutral energy system - for peak loads and as an efficiency component of heating grids. This is shown by examples from municipal utilities and suppliers.

Municipalities, and with them suppliers and municipal utilities, are faced with the question of how they can heat in a climate-neutral way in the long term and at the same time reduce the burden on the entire energy infrastructure. Both can be achieved with CHP energy concepts.

Today, larger CHP plants in particular are usually integrated into a system consisting of a heating network, storage, heat pumps and, increasingly, power-to-heat plants. According to a short CHP study by Frontier Economics, around two thirds of installed CHP capacity and almost all systems are integrated into the distribution grids in a decentralized manner. This also reduces the need to transport energy over long distances. Many heating customers are supplied via these flexible "heating network systems". At the same time, they make important contributions to supply and system security in the electricity sector - and are already doing so today, as examples show.

EWE relies on biomethane and heat pumps

The EWE subsidiary TEWE, for example, commissioned a new heat generation system in the Erkner Mitte boiler house this fall. After just over a year of construction, the combination of large heat pumps and a biomethane cogeneration plant supplies climate-neutral district heating for the small town of Erkner (Oder-Spree district in Brandenburg). The conversion of the central boiler house has increased the proportion of renewable energy in Erkner's heating network to over 50 percent. This is thanks to biomethane as fuel for the CHP unit and the use of new heat pumps. Previously, heat was generated exclusively using natural gas boilers. The main customers are municipal facilities, housing companies and public buildings.

With an electrical output of 360 kW and a thermal output of 400 kW, the biomethane CHP unit generates electricity and heat simultaneously. The heat pump technology combines an air-to-water and a water-to-water heat pump, both operated with natural refrigerants. This allows heating water to be heated up to 80 degrees Celsius - supplied from environmental heat and a heat storage tank. The expected coefficient of performance (COP) is 3 to 4. The heat pumps are operated with electricity from the company's own CHP unit - which also reduces the load on the electricity grid. In winter, an existing natural gas boiler supports the supply.

CHP will continue to be an important component of the transformation plan for the decarbonization of district heating for the city of Gotha. The Thuringian municipality's goal is to generate 100% climate-neutral district heating in Gotha by 2045. This summer, Stadtwerke Gotha installed an innovative CHP system at the eastern combined heat and power plant in Gotha-Siebleben.

The new system consists of a gas-fired combined heat and power plant with a thermal output of 2.2 MW, which will cover part of the peak load during the heating period. The two other components are a power-to-heat system, which generates heat using surplus electricity from renewable energies, and an air heat pump, which uses the ambient temperature to generate heat.

The heat pumps, which have very high efficiency levels during this time, are to run in summer. In the event of high heat loads in winter and a high electricity price, the CHP unit also secures the heat supply. "With the commissioning of our iKWK plant, we are reliably supplying heat from renewable energy sources," explained Sven Anders, Managing Director of Gothaer Stadtwerke Energie. Ferdinand von Stryk, Head of Generation and Heating Network at Stadtwerke, summarizes the functionality of the innovative system, which is intended to promote the green transition in Gotha, as follows: "Heat pumps as base load units and gas engines, whose peak load replaces gas boilers in winter."

The combination of these three technologies should save around 230 tons of CO2 per year in future and supply around 400 households in Gotha.
The high investment of 5.2 million euros should pay off threefold: The plant should help to make better use of renewable energies, noticeably reduce gas consumption and buffer price fluctuations on the energy markets.

A number of municipal utilities across Germany have opted for an innovative CHP system. On the one hand, because it is subsidized, but also because of its economic and system-beneficial properties. Stadtwerke Duisburg, for example, has built an iKWK plant at the Huckingen sewage treatment plant. It is currently the largest CHP plant at a wastewater treatment plant in Germany and uses the thermal energy of the treated wastewater to supply district heating. The system is supplemented by two hydrogen-capable combined heat and power plants and an electric heat generator at the Hochfeld site.

Stadtwerke Bietigheim-Bissingen also put its first innovative CHP system into operation last year with the commissioning of the Energiezentrale Mitte (EZM). The plant is operated in conjunction with other plants in an electricity market-oriented manner, links various heat generators and connects two previously separate district heating networks in the city. It consists of a combined heat and power plant, environmental heat pumps and an electric boiler. Depending on the electricity price, the iKWK generators can be used in a targeted manner: When the electricity price is high, the CHP units run, when the price is low, the heat pumps run, and when the price is negative, the electric boiler is used. In the winter months, the heat is mainly generated in the CHP unit at the central energy center. As soon as the outside temperatures allow, the environmental heat pumps will start operating.

CHP remains a central component of the heat transition

Especially in the winter months of November to February, combined heat and power generation from CHP remains sensible in order to ensure security of supply and economic efficiency. This was also the result of a study by Prognos. In a presentation at the annual CHP congress in Dresden in mid-May, Marco Wünsch from Prognos AG emphasized the system-supporting role of flexible CHP plants - for example to cover the residual load or as heat generators when electricity prices are high in winter.

As most applications in transport, buildings and industry will be electrified by 2045, the demand for electricity will increase significantly. At the same time, the seasonality of generation will increase and prices will rise as a result. According to the study by Frontier Economics, CHP can play a decisive role in closing the capacity gap of 17,000 to 21,000 MW by 2030. According to Prognos, an expansion of power plant capacities is also necessary. These plants would fulfill different functions in the future - both as base load and peak load power plants.

CHP plants will also ensure a reliable supply of heat in times of low renewable feed-in and high electricity prices. "CHP is the backbone of district heating," emphasized Johannes Dornberger from AGFW, another speaker at the Dresden CHP Congress. Although the variety of technologies will increase in the future, CHP will remain a decisive factor due to its efficiency. The economical use of fuels will also remain important in a climate-neutral energy system. Hydrogen, biomass and unavoidable waste heat are scarce but necessary resources. According to Prognos, around 30 percent of district heating requirements will still be covered by CHP and biomass in 2045.

Karlsruhe plans hydrogen-compatible CHP plant

Stadtwerke Karlsruhe is also continuing to rely on CHP as a building block to securely cover district heating. They want to build a new CHP plant with a heat output of around 50 MW and an electrical output of around 50 MW on the Stadtwerke West CHP plant site in Karlsruhe. Operation could start in 2029. The plant would then be part of the future district heating generation facilities, which are intended in particular to replace the thermal output of the EnBW hard coal-fired power plant.

According to the supplier, the planned plant is significantly more efficient than the separate supply from boilers and gas-fired power plants - and even CO2-neutral in the long term if green hydrogen is used. "By building a CHP plant, we as a municipal utility could make a key contribution to security of supply. At the same time, we are ensuring that the energy supply remains reliable, affordable and regionally anchored in the future," said Michael Homann, CEO of Stadtwerke Karlsruhe, commenting on this decision.

System integration through storage and sector coupling

The Agora study "Climate-neutral Germany 2045" also continues to assign a key role to CHP in a largely electricity-based energy supply. While heat pumps, electric boilers and seasonal storage cover the basic demand, flexible hydrogen-based CHP plants secure the supply in times of high demand and low feed-in from wind and solar power. Their operation should be exclusively electricity-led, so they only run when high electricity prices meet a demand for heat.
Seasonal heat storage and flexible operating modes make this possible. The combination with heat pumps, electrolysers and power-to-heat plants creates an integrated system that can absorb both electricity and heat peaks. This means that CHP will remain a central component of the energy system in 2045 - but with a different operating profile: rarely in use, but system-critical in its function.

Despite these positive examples, both utilities and industrial companies are reluctant to invest in new CHP systems. "There is uncertainty in the market as to where the journey for and with combined heat and power generation is heading," said Andreas Rimkus, the new President of the German Combined Heat and Power Association (B.KWK) since September. Associations and companies are calling on the German government to set the course quickly and clearly: an extension and substantive reform of the Combined Heat and Power Act (KWKG), an update of the tenders, a coordinated electricity market design and coordinated heating legislation. This is the only way the industry can make its contribution to security of supply and the heating transition. Because the fact that "CHP is part of the energy system of the future has now been recognized in many places," said Rimkus when asked by E&M.

Author: Heidi Roider