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Local heating networks - challenges in construction and implementation

Local heating networks offer sustainable energy supply solutions, but their implementation is complex. This article sheds light on the challenges and solutions involved in building such networks - from different temperature requirements in the network to innovative technologies for narrow, historic city centre areas. Read how local heating networks contribute to CO₂ reduction and why careful planning is crucial for success.

 

 

Local heating networks are local energy supply systems that deliver heat via a network of pipes to various buildings in a given area. Warm or hot local heating networks require the pipes to be insulated, while cold local heating uses non-insulated pipes to absorb additional heat from the surrounding earth.
Nowadays, local heating networks often use renewable energies such as solar thermal energy, geothermal energy or industrial waste heat as heat sources. In the past, the main sources were natural gas, wood and district heating from fossil fuels.
In warm networks, this so-called anergy is first fed into one or more energy centres and raised to the desired temperature level - e.g. 55°C - via a central generator (e.g. a heat pump system, which we discuss in more detail in this article) and possibly a heat exchanger. Cold local heating networks, on the other hand, work with decentralised heat pumps - the temperature is then only raised to a usable level in each individual building.
Local heating networks are particularly suitable for densely populated areas and neighbourhoods, where they can make a significant contribution to reducing CO2 emissions and increasing energy efficiency by efficiently distributing the heat generated to the connected buildings.

Construction of heating networks

The construction of a local heating network involves several steps:

1. Demand analysis and planning: First, the heat demand of the future supply areas is analysed. Possible future energy savings and new connections are also taken into account. A site analysis provides an overview of the possible energy sources available on site. Based on this data, the network is planned with the positioning of the technical centres, the connections, the positioning of the storage tanks and the dimensioning of the pipes.

2. Selection of heat sources: Suitable renewable heat sources such as solar thermal, geothermal or aquathermal energy are identified in the immediate vicinity and integrated into the concept.

3. Construction of the infrastructure: The main and distribution pipes are laid, heat generation plants - so-called energy centres - are installed and, if necessary, heat storage tanks are integrated.

4. Connecting the consumers: In the final step, the buildings are connected to the local heating network, with any existing heating systems being converted to the new heat source.

Challenges and solutions in the implementation of local heating networks

Grid temperature - Inhomogeneous building structure with different temperature requirements

Challenge: In existing and mixed neighbourhoods, the heat demand varies considerably due to different building ages and usage structures. This makes a standardised supply via a local heating network difficult.

Solution: One solution is to segment the network into different temperature zones that are tailored to the specific requirements of the individual buildings. Hybrid systems that supply both high and low temperature heat can also be used. Sometimes, however, an individual consumer, such as a manufacturing business that requires particularly high temperatures, needs to be excluded from the network and supplied differently. Another option is to supply these businesses with the required temperature via their own booster heat pump.

Limited space - no open spaces for geothermal energy

Challenge: In densely built-up urban areas, there is often a lack of open spaces for the use of near-surface geothermal energy in the form of probe fields or collectors.

Solution: Alternatives such as utilising waste heat from industrial processes or waste water heat from the sewage system can overcome space problems. In new buildings in particular, it is often possible to install the geothermal probes below the floor slab, for example in the underground car park. As a supplementary heat source, the integration of solar thermal or photovoltaic-thermal systems on roofs should also be considered as a space-saving alternative.

Additional areas of land for central energy centres

Challenge: As a rule, additional land should be available close to the neighbourhood for central supply concepts.

Solution: Early involvement of urban planning and cooperation with property owners can help to identify suitable areas. In addition, several decentralised systems that require smaller areas can be considered as an alternative.

Existing pipes/lines in the ground - Transformation networks

Challenge: Existing underground infrastructure can make it difficult to lay new cables. It is important to observe clearances, which vary depending on the type of pipe.

Solution: Thorough mapping of the existing infrastructure and careful planning of the route are essential. Modern trenchless installation techniques can help to minimise the disruption caused by roadworks in inner-city traffic, for example. Sometimes it is also possible to use existing pipes and lay new ones - this can sometimes be a cheaper and more practical solution, especially in cities. However, the pipes for cold local heating generally have larger diameters, so it is always necessary to check in advance whether such a solution is feasible.  

Shutting off the net

Challenge: If subsequent heat consumers are connected or maintenance work is carried out, the heat supply for all connected consumers in the entire network fails.

Solution: The installation of shut-off valves and secondary circuits enables flexible handling of the network. This means that individual houses or sections can be maintained or connected independently of each other. Shut-offs should be planned at the junctions to existing and future consumers as well as on a street-by-street basis. Some pipework suppliers can even drill into filled pipes and place branches there if this has not been taken into account in the planning.

Hydraulic control system

Challenge: Hydraulic imbalances impair the efficiency and reliability of the network.

Solution: Careful hydraulic planning and the use of pressure equalisation and control valves are crucial to ensure even heat distribution. Digital monitoring systems help to monitor and adjust the pressure in real time so that the system is always running efficiently. This can also be done remotely by a service provider or contractor hundreds of kilometres away. Regular maintenance of the system also helps to prevent malfunctions during operation.

Management of the engery sources – digital tools

Challenge: Controlling the various heat sources requires precise and coordinated control, as not every source is always equally available. For example, waste water can fail on some days of the year when the sewer is being cleaned. Industrial waste heat is also not always reliably high.

Solution: The use of digital control and monitoring tools enables efficient and flexible control of the heat sources. These tools can optimise energy generation in real time and react to fluctuating feed-ins on the source side as well as fluctuating demand - for example during the course of the day. In order to compensate for these fluctuations, buffer or buffer storage units are installed that can store the heat for several hours. Seasonal storage is also an option if the heat yield varies between summer and winter.

Planners must know and be able to use all sources

Challenge: Planners must have comprehensive knowledge of the various heat sources and their integration into the network.

Solution: Commissioning specialist planners for energy sources and grids is essential. Cooperations and partnerships between experienced specialists ensure comprehensive expertise in all planning and construction phases. To this end, we have also founded NETZ-WERK REGENERATIV together with partners. In addition, the use of planning software facilitates the integration of various heat sources and the laying of heating networks.

Summary

The implementation of local heating networks is a complex task that involves numerous technical, economic and organisational challenges. Successful implementation and smooth operation require careful planning, the use of modern technologies and close co-operation between all parties involved. But it is worth facing up to these challenges: local heating networks make an important contribution to achieving climate targets and offer a sustainable and efficient solution for heat supply.

Sources:
  • Umweltbundesamt: Nachhaltige Nutzung erneuerbarer Energien (https://www.umweltbundesamt.de/sites/default/files/medien/479/publikationen/texte_27-2022_nachhaltige_nutzung_erneuerbarer_energien_in_effizienten_gebaeuden_und_quartieren.pdf)
  • Stadt Stuttgart: Entwicklungen in Stuttgarter Quartieren (https://www.stuttgart.de/leben/umwelt/energie/energieleitplanung/entwicklungen-in-stuttgarter-quartieren.php)
  • Umweltbundesamt: Wärmewende (https://www.umweltbundesamt.de/sites/default/files/medien/5750/publikationen/2021-04-26_cc_18-2021_waermewende.pdf)
  • dena: Studie Wärmeversorgung (https://www.dena.de/fileadmin/dena/Publikationen/PDFs/2023/Studie_Waermeversorgung.pdf)
  • Stadtquartier 2050: Leitfaden Klimaneutrale Quartiere (https://www.stadtquartier2050.de/images/D3_2_1_LeitfadenKlimaneutraleQuartiere_final.pdf)