District heating – What is it, how does it work, is it viable in the UK?

District heating systems can help to reduce energy bills and cut carbon emissions, providing an alternative means for heating homes in the United Kingdom
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District heating has been around since the late 1800s. It has enjoyed waves of popularity on mainland Europe over the past century-and-a-half but like two-pin plugs and driving on the right side of the road, it has never taken off in the United Kingdom.

There was a brief dalliance with district heating during the 1960s and 1970s, mainly in new council-owned properties.

Those installations from 50 years ago are now coming to the end of their lifespan, leaving many local councils with the choice of finding district heating system repair methods, replacing worn and damaged sections as part of upgrades, or abandoning the concept all together.

As councils grapple with such decisions regarding the future of their systems, now is as good a time as any for the wider UK to debate whether district heating could play a larger role in heating homes and businesses across the country.

What is district heating?

District heating systems distribute heat generated by a central source through pipes and into properties, warming up homes and business connected to the network.

The easiest way to understand it is to imagine the street you live on. Rather than each house having an individual boiler heating it up, there is a larger boiler from which a network of pipes supplies the heating needs of every house on the street.

How does district heating work?

Now comes the clever bit. The central source in a district heating system will often be an appliance or process which produces heat as a by-product.

Rather than allow this heat to go to waste, district systems capture it and use it to heat water, which is then transported through pipes and into homes in much the same way as a CHP plant works in industry.

Birdshill Holly was the American mechanical engineer who pioneered the idea of district heating in the city of Lockport, New York. As industry came to America, Holly realised that he could recover heat from industrial processes at little cost and then sell it on for a profit.

Given that district heating is now being used to drive down bills as part of a shared energy economy, it is somewhat ironic that the man behind it came up with the concept as a means of making money.

Where is district heating used?

Taking Holly’s idea, the Soviet Union discerned that the heat produced by its heavy industry could be used to keep the homes of its workers warm.

District heating become city-wide heating as factories were connected to domestic properties via vast networks of underground pipes.

Comrades in the Eastern Bloc would complete a daily shift at their plant before returning to a home now being kept warm by the heat that their earlier work had produced. That was the theory, anyway.

Scandinavia too soon got in on the act, hardly a surprise given the culture of cooperation which the Nordic countries are famous for. Rather than heavy industry, their district systems were connected to power plants.

Power plants enabled states to make better use of their energy supplies when it came to producing heat at a central source, rather than having inefficient and often wasteful boilers in every home in the country. Throughout the 1970s, managing how fuel was used was particularly important thanks to the OPEC crisis.

District heating proved to be so popular that it is now a legal requirement in Denmark that inhabitants of cities have to connect to their district heating system. In Copenhagen, 89 percent of the city’s heating needs are supplied by district heating.

Those fossil-fuelled power plants are on their way out, too. The Danes are now connecting their district heating systems to renewable energy sources such as wind and hydro.

Knowing that in the not-too-distant future, every city in the country is going to be heated by a zero-carbon source means that Denmark is on track to meet its commitment to fossil-free heating and electricity by 2035.

District heating in the UK

The UK took a different approach, driven by its discovery of vast resources of natural gas in the 1960s. Whilst some local councils opted to pipe heat into the properties they owned, the vast majority of the country was instead connected to gas.

Once this gas reached a home or place of work, it was down to the occupant’s boiler to provide warmth for the property. A much less energy efficient way of going about things, but they were less enlightened times when it came to climate change and the UK was well-stocked for gas, so why not?

21st century Britain however is different. The UK is now a net importer of natural gas and rising energy bills are causing many people to wonder if there might be a better way of heating homes than burning through money and damaging fossil fuels.

District heating is back on the menu. The first line of the London Underground was opened in 1863 and over 150 years later, the heat it produces is belatedly being pumped into the homes of Londoners.

The Tube is kept at a steady 25°C all year around with pipes set to take some of that warmth directly into properties in the capital.

London wants to reduce its reliance on national energy infrastructure with the aim of supplying 25 percent of its energy through decentralised sources by 2025.

District heating schemes like the one involving the Underground and new developments at Canary Wharf and Southbank have a huge role to play in meeting that target.

According to the Energy Saving Trust, there are now over 17,000 district heating schemes in the UK and half a million properties are connected.

Those numbers will only increase over the coming years through innovation, a desire to be more sustainable and ultimately, the cost savings that district heating can bring.

The downside of district heating

There is one downside to and that is when part of the system fails. When an individual boiler stops working, it is just one home that is impacted and left without heat. Should something go wrong in a district heating system, then that problem potentially extends to many properties.

Damaged pipes are the biggest cause for concern but even the problems posed by cracks, holes or breaches are becoming lessened thanks to the advancements made in leaking pipe repair kits, which make fixing such issues a much quicker and easier process than they used to be.

With the pipes in a district heating system often running underground through confined tunnels, the usual repair method for a water pipe on the public supply network of a pipe repair clamp is not viable because of the space constraints.

Repairs provided by materials such as epoxy putties, self-fusing silicone waterproof repair tapes and composite pipe repair bandages provide the flexibility needed to seal holes and cracks and wrap damaged areas.

Pipes can now be permanently repaired in under 30 minutes, meaning that any disruptions to heating supplies caused by a leak can now be kept relatively brief.

The success of district heating systems in Scandinavia and the manner in which they have seamlessly become part of life in London show that the concept not only has a future in the UK, but that it could thrive.

For cheaper bills, less harm to the environment and great energy security, district heating is the way to go.

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