Every year, Europe wastes around 2,860 TWh/y of accessible heat. Strikingly, that equates to about 90% of the annual heating and hot water demand across the EU27+UK’s residential and service sector buildings. If the UK is to make the most of this incredible untapped resource, we must think much bigger than the typical zoned / neighbourhood level heat plans that are so prevalent today Andy Sloan, managing director, COWI in the UK, observes.

The UK is not unfamiliar with the concept of thinking bigger on heat, in fact the UK’s first district heating network which was built in the 1960s piped waste heat from Battersea Power Station under the Thames to warm 3,000 homes and 50 businesses in Pimlico, London.

Yet while countries like Denmark accelerated district heating deployment from that date onwards, the UK focused on building out its gas infrastructure instead. As a result, today, around 65% of homes in Demark are connected to district heating while in the UK the figure has hovered around 3% for a decade or more with a not overly ambitious target of achieving 18% by 2050.

In the past five years, Denmark’s commitment to sustainability as a cornerstone of urban planning has seen the country become even more ambitious with its district heating schemes by using long distance pipework to transport waste heat from sources such as industrial sites and power plants to be used in populous areas and by high heat users.

Connecting waste heat with heat offtakers

One of the better-known examples of this long-distance district heating network approach is the ‘triangle area’ – a 123-kilometre-long district heating network operated by TVIS which runs along the Danish coastline from Bredballe through to Kolding via Fredericia and Middelfart. Waste heat is taken from several sources including a power plant, energy from waste plant and refinery and redistributed in a highly efficient manner across four municipalities in the ‘triangle area’. Altogether the scheme serves more than 60,000 domestic customers, a dairy and a horticulture site. Network extensions, which bring new customers and waste heat sources to the network, are made regularly and approval has just been granted for a 7km extension.

Over the past few years, the UK has shown more interest in the potential of waste heat, most recently committing £65 million to fund five projects that will pipe waste heat from data centres into more than 10,000 homes. Yet, there are thousands more opportunities to divert waste heat from being released into the air or sea and put to good use. However, if the UK is to fully realise the opportunity presented by waste heat, and of district heating more generally, a step change is needed away from the current zoned approach that is prevalent today.

Zoning – where heat plans are divided into smaller neighbourhood schemes – risks missing the benefit of economies of scale and utilising heat sources such as industrial sites and wastewater treatment plants that sit outside of the designated zones. It will also take longer. Instead, planning should be approached at a regional, or even national level and be executed jointly by both the public and private sector.

Scotland, the home to the UK’s first long-distance heat network?

Take Scotland for example. Scotland intends to connect an additional 650,000 homes to district heating by 2030. This could be achieved by establishing a handful of larger schemes using long-distance pipework to take advantage of low- or no-cost waste heat. Or it could be achieved by creating hundreds of smaller schemes. There are pros and cons to both approaches however, establishing many smaller sites will be less efficient, more complex and time-consuming to manage and generally will have access to less variety of heat sources.

Some view the initial outlay for regional or national heat infrastructure as a barrier, however there is also an enhanced level of certainty to the return. Investors can be certain that the heat load will remain. The city of Glasgow, for example, has had city status since the 12th century. People will continue to live there for many lifetimes and need heat and hot water to do so. In step, heat sources will also remain abundant. Take the growth of the data centre market – between now and 2028 it is expected to grow 5% a year and achieving net zero is high on the agenda of the world’s biggest data users such as Microsoft and Google making waste heat offtake partnerships ideal.

A further benefit of long-distance heat infrastructure is that it is heat source agnostic and new sources can be added as they become available, helping to decouple consumers from gas price shocks. The Port of Esbjerg’s district heating network, which is currently fuelled in part by the local coal-fired power plant, will soon be switched to heat pumps powered by the offshore wind farm adjacent to Esbjerg City. Soon, waste heat from the production of green hydrogen at the Port will also supply the network.

Scale up the approach and learn from Denmark’s experience

As the UK remains early in its district heating journey now is the time to deepen the connection between the UK and Denmark to realise the potential to leapfrog the UK’s progress in the same way that Africa achieved telephone connectivity at a fraction of the cost by investing directly in mobile rather than cabled communications.

Denmark's pragmatic approach to district heating, focusing on long-term sustainability and efficiency, offers valuable insights for the UK’s energy strategy. Pursuing long-distance heat networks, 'Heat Highways', to maximise the use of waste heat sources, sees Denmark increasingly future- and shock-proof its supply of heat and hot water. Greater use of public-private-partnership, along with a scaling up of ambition to a regional or national level would help the UK to capitalise on the potential of waste heat in the same way and in doing so, support the country to achieve its net zero goals more efficiently and cost-effectively.