CHP Accumulator System




Fernwärme Ulm


The practice used a water-based system as a heat accumulator - and essentially, also an electricity accumulator - in order to respond to heat consumption peaks and increase the general efficiency of the region's combined heat and power (CHP) plant. The heat accumulator used in the project is a steel tank containing 2.400 m3 of water.



  • Find a simple solution to the challenges of both heat and electricity consumption management
  • Adapt the solution to make it environmentally (reduced CO2 emissions) and economically efficient
  • Reduce the necessity of relying on fossil energy


Main information:

In order to increase the sustainability of its production, Fernwärme Ulm GmbH (FUG) decided to combine two technologies: CHP (combined heat and power) and accumulation technologies, using a water-based heat accumulator.

The basis of the practice constitutes a heat accumulator that is connected to FUG’s waste-fuelled power plant. A thermal store allows for a time delay between heat production and consumption, storing the energy produced by the combustion of waste and residues at low consumption times and using it at peak times, thus reducing the use of fossil energy during peak load times.

Additionally, the heat accumulator responds well to renewables-based electricity generation. When sufficient electricity is produced by renewable energy sources, the waste combustion system feeds less electricity into the grid and loads the accumulator instead. When renewable energy production decreases during less sunny or windy times, the waste combustion system feeds the maximum possible amount of electricity into the grid, and the heat accumulator supplies the missing district with heating instead. In this way, the accumulator essentially takes on the additional role of an electricity accumulator.


Additional information:

"Fernwärme Ulm GmbH" or "FUG" is one of the principal district heating suppliers in Ulm (Baden-Württemberg). Thanks to its district heating network and its generating facilities in three locations, FUG is able to respond to 46% of the city's heating needs. FUG also invests in and develops technologies in order to reach the sustainability goals of the German energy transition concept, especially focusing on the production of renewable energy and on the reduction of CO2 emissions.


RGI gratefully acknowledges the EU LIFE funding support:

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Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the LIFE Programme. Neither the European Union nor the granting authority can be held responsible for them.