Sustainable heating in towns and cities
For towns and cities, local and district heating networks represent an environmentally friendly alternative to individual heating systems using fossil fuels. Renewable sources of energy and heat, advanced heat storage systems and the utilisation of waste heat enable local and district heating networks to make an economically viable contribution to the reduction of CO2 emissions.
The ISH trade fair offers insights into the latest developments in the field of local and district heating networks, their characteristics and their contribution to climate-friendly heating of buildings. An overview:
The difference between local and district heating
Local and district heating systems work in the same way. The main differences are the supply radius, the connected load and the heat source:
- Local heating networks supply smaller areas such as housing estates or individual neighbourhoods with a connected load of 0.5 to 5 MW. They often use decentralised generation plants such as combined heat and power (CHP) plants.
- District heating networks provide heat to cities and regions, with a supply radius of up to 30 km. The connection load is generally between 50 and 500 MW. In most cases, the heat is centrally generated in large power plants.
The structure of local and district heating networks
Local and district heating networks have several main components with the heat being produced by a variety of different heat-generation plants, e.g., combined heat and power plants, biomass plants or geothermal power plants.
The primary network of highly heat-insulated transport pipes carries the heating medium to the consumer at feed temperatures of 95 to 130 °C and return temperatures of 45 to 70 °C. High-performance network pumps ensure the heating medium circulates continuously while transfer stations with efficient heat exchangers provide for hydraulic separation between the primary and secondary circuits.
The secondary network distributes the heat within buildings with typical feed temperatures of 60 to 90 °C and return temperatures of 30 to 50 °C.
Energy sources for local and district heating
A key benefit of local and district heating networks is their flexibility with respect to the source of heat:
- Renewable energies: geothermal or solar-thermal energy systems feed heat into the grid via heat pumps.
- Combined heat and power (CHP): the simultaneous generation of electricity and heat from fuels such as natural gas, biomass or hydrogen can achieve efficiency levels of up to 90 percent.
- Waste incineration plants: With a typical thermal firing output of 50 to 150 MW, waste can be efficiently recycled into heat.
- Biomass plants use renewable raw materials such as wood chips to generate heat. They cover an output range of 1 to 50 MW and are often combined with ORC processes to generate electricity.
- Industrial waste heat: With temperature levels of 30 to 500 °C, waste heat from industries such as cement, steel, chemicals and food has a significant potential for heat supply. Moreover, innovative high-temperature heat pumps permit an even more efficient use of waste heat.
Cold local heating networks: heating on demand
Cold local heating networks simplify the integration of waste heat and renewable energy sources for heating. Heat is supplied at a low feed temperature of 40 to 70 °C and heated to the correct temperature for heating and hot water supply via a water heat pump at the consumer's premises.
Prosumer: bidirectional, decentralised heating networks
Bi-directional heating networks pave the way for supplying heat based on the prosumer principle, according to which buildings not only consume heat, but also return any surplus to the system. This fosters the integration of decentralised sources of heat, such as solar thermal energy or micro-CHP units, for sustainable and resilient heating.
Power-to-heat: sustainable grid stabilisation
Power-to-heat technologies facilitate the integration of surplus electricity from renewable sources. Large-scale heat pumps and electric heating rods in combination with thermal storage units, e.g., in hybrid heating systems, can convert surplus electricity into heat and thus contribute to grid stabilisation. In this connection, innovative latent-heat storage systems or thermochemical storage units promise higher energy densities with lower losses.
State-of-the-art local and district heating networks combine energy efficiency, environmental friendliness and economic efficiency. As part of the heating transition, innovative concepts for local or district heating and sector coupling are essential to ensure sustainable cities and communities. Find out more at ISH 2025 to unlock the full potential of heating networks for your municipality or company.