Ariadne analysis "Change in district heating in the context of the coal phase-out and the current gas crisis".

Source: Energy & Management Powernews

The concept of successively converting district heating from coal to renewables is under pressure because gas is crumbling as a bridge. Ariadne researchers therefore propose low-temperature networks.

The gas crisis brings the previous plans for a conversion of the heat networks in trouble. Because the once cheap energy source gas, as a bridge in the conversion of coal to renewable thought, makes the purchase of district heating more expensive than thought and thus currently unattractive. Researchers from the science consortium "Ariadne," a Copernicus project funded by the German government, are working on alternatives.

With a new report on the transformation of district heating, the authors Alexander Burkhardt and Markus Blesl (University of Stuttgart) now have considerations on how the conversion of district heating networks to low-temperature networks can be accelerated. The two scientists advise more speed in this area above all because persistently high gas prices could have a negative impact on district heating network providers' plans to build new combined heat and power (CHP) plants.

Gas and energy crisis can trigger push for district heating

A lowering of the temperature in the networks results fundamentally from the replacement of fossil fuels with renewable energies. Fossil CHP provides a grid temperature of more than 100 degrees Celcius. With a growing share of renewables in district heating generation, which is expected to rise from the current 17 percent to 45 percent by 2030, the temperature must gradually drop to 60 degrees Celcius.

The Stuttgart scientists hold out hope that the "current gas and energy crisis could trigger a boost for district heating." This is under the condition that gas CHP as a bridging technology, contrary to the original plans, is only used to a limited extent.

The faster switch to low-temperature networks for the integration of renewable energies, however, requires regulatory assistance:

• The existing district heating networks should be divided into several sub-networks.
• A separation of non-sinkable process heat demands is to be carried out.
• A higher pump capacity is necessary.
• In addition, the two researchers write, a hydraulic balancing of house connection stations is necessary to improve the efficiency of existing structures.

The criticism of the Stuttgart scientists of the previous district heating planning is comprehensive. For far too long, they say, it has been a topic thought of in isolation by building owners, heat supply companies or cross-utility companies.

Tackling heat supply more intensively on a larger scale

In this regard, they say, faster implementation of municipal heat planning and the transformation plans of the Federal Promotion for Efficient Heat Networks (BEW) is essential. The support under the BEW, which is to be welcomed in principle, is still based in part on the CHP Act, which does not automatically mean a claim to fossil-free generation.

The transformation of district heating basically provides for the increased use of biomass or biogas. In addition, technological developments make the use of electricity in power-to-heat plants possible. In addition, there are large heat pumps that draw their thermal energy either from surface waters, waste heat (industry, wastewater) or the environment. Finally, the combustion of synthetic fuels - hydrogen, gas - in CHP plants is also technically conceivable.

The Ariadne analysis "Change in district heating in the context of the coal phase-out and the current gas crisis" is available for download on the Internet as a PDF.

Author: Volker Stephan