Future-proofing district heating

Heat pumps are here to stay, but how can the UK follow Europe’s lead of using them as part of sustainable district heating systems? Alex Bradley investigates

Heat pumps are revolutionising the heating industry around the world and fast becoming the renewable technology of choice. Governments in Europe have long been committed to heat pump technology, setting a goal of 40 per cent of all their residential buildings to be heated by electricity by 2030.1
Furthermore, according to the European Heat Pump Association (EHPA), there were 3m units sold in 2022. This coincides with many EU Member States having already published plans to ban new gas boilers, which can readily be replaced by electric heat pumps or district heating in urban areas. 2
The Scandinavian heat pump model has been noted for its successful implementation and widespread adoption in Denmark, Norway, and Sweden. These nations have made significant progress in transitioning to low-carbon heating systems, with heat pumps playing a crucial role.
By now, everyone is aware of the net UK’s zero targets set for 2050. The government already has put legislation in place for this – the Heat and Buildings Strategy states that it is necessary to phase out all-natural gas fired appliances and change to low-carbon technologies such as hydrogen, heat pumps and new heat networks. Part L of the Building Regulations also introduces a fabric-first approach and ensures buildings are being built to standards which limits the heat output requirements.
Indeed, to achieve carbon neutrality by 2050, it is crucial that the way in which buildings are heated is reviewed to determine the most suitable solution. The government has acknowledged that district heating (also referred to as heat networks) forms an important part of its plan for future sustainability in heating homes as well as improving energy costs.
District heating or a communal heat network refers to heating provision for multiple properties from one central heat pump system. Heat pumps are modular, so district heating schemes can be designed to heat any number of properties of all sizes, from flats to detached houses. Schemes can also be retrofitted to existing properties or installed in new builds. Heat pump systems can also run in tandem in multiple bases and plant rooms to provide heating and hot water for an almost limitless number of homes under one district heating scheme.
As the latest heat networks have been designed to work at lower temperatures (i.e. flow temperatures of 50-60°C), they are already a more cost-effective alternative to fossil fuels due to the use of air source heat pumps. The UK has already seen more heat networks now utilising commercial heat pumps on the primary system; the heat pumps are often fitted on the outside of a building then connected via the heat network to next generation heat interface units (HIUs) inside the property (also known as “fourth-generation heat networks”). This configuration is often seen in projects involving apartments and offices.
These fourth-generation systems are supported by the latest CIBSE CP1 2020 heat networks Code of Practice for the UK. This stipulates the minimum system requirements, as well as guidance on improving energy efficiency. By focussing on the low temperatures at which heat pumps operate, the document has also led to the development and specification of heat networks with these technologies at their core.
As a result, manufacturers have developed HIUs specifically designed to be used in conjunction with renewables. These units comply with CP1’s stipulation for the maximum return water temperature from the domestic hot water (DHW) heat exchanger to the district not to exceed 25°C. While most HIUs on the market can operate and sufficiently provide DHW or space heating at lower operating temperatures, not every model will have low enough return temperatures to meet CP1 2020. So, specifiers and contractors should be looking to use products specially designed for use with heat pumps.
Studying the heat pump strategies implemented by the Scandinavian countries – including their policies, regulations and incentives – would allow us to learn and understand the main reasons for their success. This would then allow further goals and targets to be set, with policies and regulations tailored to suit accordingly. Yes, we have already mentioned the existing UK legislation, but there are other aspects, such as financial incentives, tax breaks, grants, or subsidies that could make heat pumps more affordable.
End user awareness and education is equally important, especially in providing them with the key knowledge about the benefits of heat pumps and how they can contribute to reducing carbon emissions.
Finally, for professionals, training and accreditation is essential. We need to ensure that there is a sufficient workforce skilled in heat pump installation, maintenance and repair. In order to do so, there need to be more training programmes and certifications in place to allow installers to maintain high-quality standards.
The UK can certainly build upon the foundations it already has in place and adopt a heat pump strategy that will accelerate the transition to more sustainable heating systems in line with net zero targets. Although there is still a long way to go, we only need to look at Europe to see the positive impact of heat pump technologies.

References

1) https://www.theecoexperts.co.uk/heat-pumps/top-countries
2) European Academies Science Advisory Council (EASAC) report – “The Future of Gas” (2023) https://easac.eu/fileadmin/user_upload/EASAC_Future_of_Gas_Web.pdf

• Alex Bradley is commercial director at Modutherm