District heating sounds like a futuristic term but it has been around for a long time. Even in the 1960s the UK had some district heat networks, according to Crispin Matson, Ramboll UK head of energy. They just were not very efficient and earned the technology a bad name.
Today, according to Matson, the situation is very different. And he ought to know because Ramboll is a Danish design consultancy that has been involved in the development of heat networks in Denmark for more than 40 years. Some of the heat sources used are technology that the waste and recycling industry will be familiar with: energy-from-waste (EfW) plants.
Across Copenhagen, 98% of houses are connected to the district heat network, and it extends out from the city centre some 30km into the suburbs. It is powered by not just one heat source but eight: four power stations and four EfW plants. Recently an older EfW plant was replaced with a new one, complete with an artificial ski slope on its roof.
Imagine that in the UK? ‘Nimbyism’ and health concerns have meant that most of our EfW plants are not built near residential areas. Not so in Denmark. “They seem happy to have plants right next to houses,” says Matson. “They have a lot of controls in place. I am no expert on the standard of controls they employ, but it does not seem to be an issue.”
An exception to this in the very built-up area of Deptford, south London, is South East London Combined Heat and Power (Selchp). Built in the 1990s, it supplies heat to a district heating network and proves that the technology can work in the UK. In fact it is now mandatory for all new UK developments to connect up to a heat network. So far only developments such as the Olympic Park in east London have hooked into the technology.
Currently, just 2% of buildings in the UK are connected to heat networks compared with 60% in Denmark, and this is mainly in London. However, Sheffield has an established network – one of the oldest in the UK at 25 years – as does Nottingham, and Leeds is being considered for a scheme. So why the renewed Government interest in district heat networks? It’s all down to carbon reduction.
By 2050, around 18% of UK heating will need to come from heat networks in order to meet carbon targets cost effectively, according to the Committee on Climate Change. The Department of Energy and Climate Change published its heat strategy in 2013.
Before this, the concern had been on how to reduce traditional energy use such as electricity. But carbon targets mean we also need to look at how to decarbonise heat. Matson says the Government is leaning towards a system where, ideally, “in the cities we should look at using heat networks and in the suburbs heat pumps”.
As well as reducing carbon there are other sweeteners such as lower energy bills for householders by as much as 20%. And the more widespread a network becomes, the more efficient it becomes because the heat loss from underground pipes gets proportionally smaller.
However, there are barriers, such as the fact that many heat sources are not that centrally located – such as EfW plants, which otherwise would be ideal heat sources. So there is a challenge to connect them to the buildings.
A district heat network is also an expensive venture because there is a lot of infrastructure needed to make it work. You have to connect to the heat source, install a pump, lay double underground pipes and then connect to the buildings. However, Matson says “the good thing is that these systems can last up to 60 years so you can look at payback over quite a long period of time”.
The Government has been undertaking a series of feasibility studies to look at all the cities in the country to see where we have sources of heat, where the demands is and whether it makes economic sense to join them together. It also has £320m in capital funding to help district heat network projects get off the ground. This is open to public and private enterprises.
Matson says: “The hope is that district heating networks, by 2030, can be up to 40% of buildings in the UK. In theory it could be half or one-third of traditional gas fired boilers. It’s definitely a good way of decarbonising heat.”
Back in the 1960s and 1970s, the UK invested heavily inNorth Sea oil and gas. But the tide has now turned and district heating networks are back on the agenda – and it looks like they are here to stay.