Expanding district heating faster and more sustainably __

Expanding district heating faster and more sustainably
16. February 2024 7 min.

The world is striving for the so-called "Net Zero Emissions by 2050" as a goal. This means that CO2 emissions are to be completely reduced to zero by 2050. But this requires much greater efforts than before. In the field of district heating, the energy efficiency of existing solutions must not only be quickly optimised, but also switched to renewable heat sources, e.g. bioenergy, solar thermal energy, large-scale heat pumps and geothermal energy. In addition, the integration of secondary heat sources, such as waste heat from industrial plants and data centres, must be promoted.

However, it is not only heat generation that poses major challenges; pipeline networks must also enable rapid but sustainable conversion and expansion with flexible solutions. Compared to metal systems, plastic pipes have clear advantages to offer in order to achieve the ambitious goals. The best example of this is the pre-insulated polypropylene piping system aquatherm energy.

A forward-looking solution for district heating and beyond

aquatherm energy is specially designed for 4th generation district heating and other applications with continuous temperatures up to 75 °C. The pipe system is also suitable in sectors such as local heating supply, district cooling supply, water distribution, refrigeration systems, biomass plants, biogas plants, geothermal energy, swimming pool technology, ground-mounted heating, ground-mounted cooling, thermal water pipes, cooling technology, connection to heat pumps, lawn heating systems, and air conditioning systems. aquatherm energy sets new standards in terms of efficiency and adaptability in modern energy infrastructure.


A key advantage of this system is its agility. The medium pipes used are characterised by a simple and effective installation and connection technology – plastic welding. This technique allows for a quick and safe installation, suitable for projects of all sizes.


Another key aspect is the flexibility of aquatherm pipes. They can be easily cut and adjusted, which means significant time savings and efficiency during installation. This feature is particularly advantageous in complex installation scenarios where tailor-made solutions are required.


In addition, aquatherm energy stands out due to the possibility of custom-made products. aquatherm can produce customer-specific moulded parts within a very short time, which are not available in the standard range.

The advantages of aquatherm energy compared to steel pipes:

  • 70% lighter than steel
  • Minimised trench size compared to steel pipes
  • No expansion arcs required
  • 50% less working time than steel pipes
  • Corrosion resistance inside and outside
  • Resistance to incrustation
  • Lower pressure loss due to reduced pipe roughness
  • More cost-effective installation


Long-term reliability of aquatherm energy

The physical and chemical properties of the system are carefully matched to the specific requirements of each project. This makes aquatherm energy a reliable choice for long-term applications.

Over 50 years of service life

aquatherm PP-R/PP-RCT pipelines have a predicted service life of more than 50 years. This long-term reliability is a critical factor that reduces both maintenance and replacement costs over time.

Peak temperatures up to 100°C

The piping is designed in such a way that it can easily withstand peak temperatures of up to 100°C, even in the event of short-term faults. This ability to cope with extreme temperature fluctuations makes the system particularly robust and reliable in demanding environments.

Continuous temperatures up to 75°C

The pipes are designed for continuous operation at temperatures up to 75°C. This feature is particularly advantageous in applications that require constant temperature control, such as district heating or cooling.


District heating: An untapped potential in the global heat supply

In 2022, about 9% of the world's final heating demand in buildings and industry was covered by district heating, according to the IEA. The most powerful district heating networks impressively demonstrate the great potential of the technology: it enables an efficient, cost-effective and flexible large-scale integration of low-emission energy sources into the heating energy mix.

However, despite these impressive benefits, the decarbonisation potential of district heating remains largely untapped. Fossil fuels continue to dominate the supply of heating networks worldwide. They account for about 90% of total heat production – especially in the two largest markets, China and Russia.

The challenge is to harness the enormous potential of district heating to pursue a more sustainable and efficient path in global energy supply. However, this transformation will require a concerted effort from governments, energy providers and industry to shape a sustainable future.

Recently, a number of district heating markets around the world have experienced considerable momentum, especially in Europe. Since 2022, district heating has been receiving increased political support due to energy security concerns resulting from the current energy crisis. This development is reflected in various initiatives and projects around the world.

  • Various European countries saw an increase in new network connections in 2022, including Germany and France.
  • At the beginning of 2023, China launched its first project to use waste heat from nuclear power plants in district heating networks.
  • The City of Vancouver, Canada, is expanding its District Heating Network capacity by adding 6.6 MW of wastewater heat recovery systems to capture latent heat from wastewater using heat pumps.
  • In April 2023, the European Union allocated €401 million to support Czech green district heating.
  • In the United Kingdom, in March 2023, the Energy Security Act introduced regulation of heat networks to allow for the heat zones. The Committee on Climate Change has estimated that by 2050, around 18% of the UK's heat consumption could be supplied by heating networks.
  • In Denmark, in March 2023, the parliament passed a regulation to support geothermal energy and passed a law that will exempt geothermal heat projects from the price regulation already in place.
  • Finland's first geothermal heating plant was commissioned in 2023 in Varisto with an expected heat supply of 2600 MWh per year.

Types of district heating

Not all district heating is the same – there are different heat sources that are used to transport the heat via pipelines. Here are the most important techniques:

Solar thermal district heating

In 2021, 44 new large-scale solar heating systems were installed globally with an impressive total capacity of 142 MWth. China accounted for the largest share of this, commissioning three-quarters of global plants.

Large-area heat pumps

While the integration of large-scale heat pumps into district heating networks is not a new concept, it is playing an increasingly important role in decarbonisation. These heat pumps are able to collect waste heat from a wide variety of sources and make it usable, such as data centres, subway tunnels, industrial plants or electrolysers.

Especially in urban areas, where heat demand is concentrated, wastewater is a highly potential source of waste heat. In Europe, almost 4,000 wastewater treatment plants are located in close proximity to district heating networks, which could potentially provide up to 175 TWh of heat per year. This corresponds to about one fifth of the current district heating supply in Europe. A successful example is Katri Vala's heating and cooling plant in Helsinki, Finland, which has been in operation since 2006. It uses large heat pumps with a heating capacity of 126 MW, which use wastewater for space and water heating in residential buildings, as well as a cooling capacity of 80 MW with cool seawater to cool office spaces.

A current example of the commissioning of the heat pump at the end of 2022 is the Qwark3 project in Berlin, which combines heating, cooling and power supply via heat pumps. In Europe, projects for 13 new geothermal heating and cooling plants connected to district heating were approved in 2021. In the Danish city of Aarhus, the development of Europe's largest geothermal district heating plant was announced at the beginning of 2022, which is expected to be partially commissioned by 2025.

Geothermal district heating

The use of geothermal energy in district heating is becoming increasingly important worldwide, as recent projects in the United States and Iceland show. In the U.S., an ambitious district heating and cooling project based on the use of 200 geothermal wells was announced in 2022. Another example of the efficient use of geothermal energy is Iceland, where a local heating company introduced a new geothermal district heating system in Höfn to replace the previous electric heating system in 2021. To support the switch to district heating, the company also offers subsidies to those who connect to the district heating network.


References with aquatherm energy

Gateshead Energy Centre: Combined electricity and district heating

In Gateshead, a project was realised to expand the existing district heating network, which efficiently produces both heat and electricity. The new energy centre provides energy directly to public buildings, businesses and private households via a three-kilometre underground network of heating pipes and high-voltage cables. Thanks to the advanced technology, the energy centre can use up to 85% of the waste heat generated during energy production and transfers it effectively.  aquatherm energy was chosen for the heating network. The pre-insulated pipes were laid in trenches just 80 metres long, which significantly reduced disruption to local residents as fewer road closures and diversions were required. This also led to significant cost savings. The corrosion-resistant aquatherm energy PP-R pipes are just as economical in operation: compared to conventional steel pipes, they enable energy cost savings of 15 % and a significantly superior thermal efficiency. Read more.


Project Orsolina28: Heat and water for artistic spaces

The Orsolina28 project in Moncalvo, Italy, presented a unique challenge: The connection of the tent domes to the hot and cold water supply as well as heating and cooling had to be designed efficiently and ecologically. The solution was found in aquatherm products, which are made from environmentally friendly polypropylene and have significantly lower CO2 emissions than steel pipes.

The underground aquatherm energy variant was chosen for the construction project, which is ideal for the safe and efficient transport of water over longer distances. The system consists of a carrier pipe made of fibre-reinforced plastic, which is known for its corrosion resistance, durability and flexibility. It also offers excellent insulation properties, which are reinforced by rigid PUR foam and supplemented by a PE casing pipe to protect against damage to the soil. In total, around 630 metres of the aquatherm energy pipe system were laid to supply drinking water, heating and cooling to the tent domes. Orsolina28 is therefore not only a place dedicated to art, but also an example of sustainable and efficient construction that harmonises with its surroundings. Read more.


Pooling know-how through international cooperation

Associations, cooperation programmes and initiatives play a crucial role in fostering expansion and innovation in the field of district heating. The District Heating and Cooling Technology Collaboration Programme (IEA DHC TCP) has taken a leading role in research in this field since the 1980s and now has 16 member countries, including Ireland since the end of 2022 and Estonia and the Netherlands in 2023. In addition, the Sino-Danish Clean and Renewable Heating Centre was launched in 2022, a cooperation between the Danish Energy Agency (DEA), the China Renewable Energy Engineering Institute (CREEI) and the UNEP Copenhagen Climate Centre (UNEP CCC). This centre aims to promote the exchange of knowledge and expertise between Denmark and China in the field of clean and renewable district heating.

Which piping system for which application?

As diverse as the solutions for modern district heating are, aquatherm energy offers a range of highly developed pipe solutions that are tailored to specific requirements. Here is an overview of the aquatherm energy pipe range:

aquatherm energy green SDR 9 MF RP

This piping system made of fusiolen® PP-RCT, with a special fibre filling in the middle layer, is ideal for the installation of drinking water networks. The combination of high-quality materials and innovative technology makes it a reliable choice for drinking water applications.

aquatherm energy blue SDR 11 MF RP/17,6 MF RP

Specially developed for applications outside of drinking water installations, this system offers greater flow rates due to lower wall thicknesses of the pipes. aquatherm blue is therefore an efficient solution for a wide range of applications.

aquatherm energy blue SDR 11 MF RP OT

The newly developed oxygen-tight, multi-layer plastic composite pipe meets the requirements of DIN 4726 by means of an integrated diffusion barrier. In combination with the aquatherm green system, aquatherm blue OT covers all requirements for the installation of air conditioning and heating systems as well as in system technology and offers a comprehensive solution for demanding applications in building technology.



aquatherm presents a wide range of pre-insulated piping systems that have been specially developed for industrial applications and extensive building complexes such as hotel resorts. These systems allow hot or cold liquids to be transported with minimal energy loss, making them an ideal solution for a wide range of applications. Especially in the area of district heating and cooling as well as local heating and cooling, aquatherm energy stands out. The underground variants of the piping systems play a decisive role in the safe and efficient transport of heating and cooling water over long distances. They make it possible to supply individual buildings as well as entire cities or conurbations with the necessary heat for heating and hot water or cold for air conditioning.

Detailed information on specifications can be found in the current aquatherm energy guidelines, which you can download here.