District heating

District heating and local heat networks provide thermal energy from a central source to multiple buildings through a shared distribution network. Heat is generated at one or more central plants and delivered to consumers via insulated pipelines in the form of hot water or steam.

Both concepts are based on the same principle. The primary difference lies in the scale of the network and the area served. District heating systems typically supply entire urban districts or cities, whereas local heat networks generally serve smaller areas such as residential developments, business parks, industrial sites, or campuses.

Operation of district heating networks

In a district heating network, heat is generated centrally and distributed through a network of supply pipes. After transferring thermal energy to the connected buildings, the cooled water returns to the plant via a return line, where it is reheated and recirculated.

A variety of heat sources can be integrated into heat networks. In addition to combined heat and power (CHP) plants and biomass-fired facilities, renewable and low-carbon heat sources are becoming increasingly important. These include geothermal energy, solar thermal systems, industrial waste heat, and large-scale heat pumps that upgrade ambient or waste heat to temperatures suitable for network operation.

Role in the energy transition

Heat networks are widely regarded as a key enabler of the decarbonization of the heating sector. They make it possible to utilize heat sources that are often uneconomical to exploit at the individual building level while facilitating the integration of renewable energy and industrial waste heat. Particularly in densely populated urban areas and industrial clusters, district heating and local heat networks can significantly reduce dependence on fossil fuels and help lower CO₂ emissions.

Industrial heat pumps in district heating networks

Industrial heat pumps can play an important role in the supply of district heating and local heat networks. They utilize sources such as industrial waste heat, river water, wastewater, and other low-temperature heat sources, upgrading them to the supply temperatures required by the network.

This enables existing heat networks to be progressively decarbonized while unlocking previously unused heat sources. As a result, large-scale and industrial heat pumps are becoming increasingly important in modern and low-temperature district heating systems.

Industrial companies can also continue to use district heating as an energy source even as network supply temperatures are reduced during the transition to next-generation heat networks. High-temperature heat pumps can raise the temperature of district heating to the levels required for industrial processes, enabling the generation of hot water or process steam.