FlexKWK Energy transition: New concept for combined heat and power generation

FlexKWK reacts to fluctuating prices on the market and compensates for bottlenecks in local networks.

Heat storage

Introduction of one of a total of six heat storage devices into the heating cellar of the plant in Oberhausen.

Project aims

The generation of electricity and heat according to demand is an important component of the energy transition. In the Flex KWK project, Fraunhofer UMSICHT demonstrates a new combined heat and power generation (CHP) concept. The operation of a combined heat and power plant is flexibly adapted to the demand for electricity. At the same time, heat storage devices and a power-to-heat system ensure that the heat demand of the heat sink can be met at any time. Following the successful integration of a Flex KWK plant into a local heating island in Oberhausen, Fraunhofer UMSICHT identifies further promising locations and favorable framework conditions.


The future energy system will be characterized by renewable energies. Energy from wind and sun must be used optimally for this purpose – and sufficient energy must also be provided on windless, cloudy days and at night. One solution is to use flexible CHP plants that supply electricity when there is not enough energy available from renewable energy sources. However, they can be switched off if there is a high level of renewable electricity generation.

The operation of such plants becomes economical because the energy markets react sensitively to the fluctuating power generation from wind and sun; prices rise with low renewable power generation and fall with high proportions of wind and solar power in the grid. This also leads to a situation in which more electricity is generated than is consumed. This results in negative electricity prices. Conversely, this means: Whoever generates electricity has to pay for it. This means that permanently running CHP plants will no longer be profitable in the future.

The combination of CHP plant, heat storage and power-to-heat concept developed by Fraunhofer UMSICHT delivers flexible electricity and can cover the heat demand of the heating network at any time.


As part of the Flex KWK project implemented by Energieversorgung Oberhausen AG (evo) and scientifically supported by Fraunhofer UMSICHT, a Flex KWK plant for an existing heating network was erected in the Oberhausen district of Barmingholten. A combined heat and power plant, a large heat storage device, and an electric hot water generator supply to a total of 150 residential units. The settlement is a flexible local heating island: Electricity is produced when it is needed. The resulting heat is stored and made available according to the requirements of the heating network.

Fraunhofer UMSICHT evaluates and optimizes CHP concepts under different market conditions, taking into account the measurement data obtained from practical experience.


Project partners

Energieversorgung Oberhausen AG (evo)

Funding information

Federal Ministry for economic affairs and climate action


Duration: January 2016 to January 2019

Website: www.bmwk.de