This technical guide explains the concept of district heating and how such heat distribution networks can be used to deliver significant eco-friendly, energy efficient heating solutions for both domestic and commercial occupiers.
The guide explains what district heating is, how it works, current trends and opportunities for adoption. It concludes by considering both the benefits and drawbacks of this type of centralised heating system.
What is district heating?
District heating, also sometimes known as a heat network, is an engineering system whereby heat is generated centrally and then distributed through a network of pipes to many different buildings, offices, factories or other facilities.
District heating systems might supply space heating or hot water to either commercial or residential buildings, in a way which is both lower-carbon, and cheaper than each home or commercial building generating its own power.
Often, neighbourhoods or businesses embracing this type of networked heating scheme generate their power using renewable technologies, and might also capture waste heat from other sources too.
Is district heating the same as communal heating?
Well, yes and no… although in essence both heating systems may seem very similar, the main difference is one of scale.
Community heating projects usually apply to only one building, or a couple of buildings located very close together, such as an apartment block or a few houses on an estate.
District heating is a different concept altogether, with the system servicing buildings often miles apart.
Smaller community heating projects usually use gas boilers, but larger district heating systems are more likely to embrace alternative sources of energy such as heat pumps, waste heat from factories or other infrastructure, or generate heat using biomass.
There is also larger infrastructure needs to transport the heat to and around buildings which may be quite some distance apart.
How does district heating work?
In most district heating systems, power is produced centrally.
This might be achieved using a biomass boiler, combined heat and power or CHP, or traditional oil or gas boilers in smaller systems.
The original district heating systems used a traditional fossil fuel boiler to heat water, which was then pumped around the radiators in the houses or businesses being heated.
This method is simple and efficient, and although it still involves fossil fuels and traditional technology, it’s still more efficient than every flat, house or office having their own small boiler.
Combined heat and power (CHP)
CHP boilers are also commonly used in centralised heating networks.
CHP systems take the heat produced during the electricity generation process and use this to heat buildings.
This heat is usually supplied in the form of steam, and again passes through a network of pipes into individual properties.
The enormous CHP boilers are usually powered by fossil fuels such as gas or coal, but increasingly alternative technologies such as biomass, heat pump, solar energy or geothermal energy are becoming increasingly common.
Heat is distributed around customers using a network of insulated pipes and units designed to capture and store heat until peak times.
Modern network heating systems
Modern district heating systems aim to reduce energy waste by capturing heat which is generated during the working day, and funnel it back into homes across the day, especially during the mornings or evenings when demand is at its highest.
For example, a common district scheme might take the heat recovered from the air conditioning system in a large building, and redirect this into heating the water of the local swimming pool.
Other systems suck heat from underground train tunnels, and use the heat to subsidise the energy bills of all the houses connected to the network.
Where is district heating headed?
Many other countries are far ahead of the UK in terms of the number of houses which are connected to a district heating system.
However, the idea is catching on in the UK, and with encouragement it’s increasingly being considered for new-build housing developments.
Thousands of UK homes are now benefitting from district heating systems, and planning is currently underway to use excess heat from a range of novel sources including the London Underground, where waste heat will be used in Islington homes.
What’s slowing the adoption of network heating in the UK?
One of the main issues with district heating is that it is much easier to construct the system when a new development is being built than it is to retrofit the system to existing buildings, housing estates or business parks.
Retrofitting into existing properties also requires residents and occupiers to be on board with the scheme and be reassured that they won’t carry the potentially high capital costs of the installation.
This is still fairly new technology in the UK, and every project will have its own teething problems.
However, the main problem isn’t with the heat itself, but with the control of that heating.
Many district heating systems charge a flat rate to customers rather than billing for the heat they use.
This means customers have little incentive to save energy by turning down the thermostat, improving insulation etc. and they tend to heat rooms more than if they were footing the bill.
Older district heating systems often offer very little user control at all.
Unlike smaller, individual heating systems where room temperatures can be carefully controlled, many district or communal heating systems will have one centralised thermostat, if any.
Again, this can lead to overheating in properties and significant energy wastage.
Some modern district heating systems combine advanced control technology with some sort of metering, allowing individual users to be billed for the amount of heat they use.
Although this sounds a fairly simple concept, currently it is surprisingly rare in industry.
Many home owners and businesses are reluctant to switch from a system which charges them on a flat rate into one where they are being charged for what they use, out of fear their bills will rise.
From the heat generating providers point of view, supplying heat on a flat-rate basis allows them to accurately forecast revenue in the future.
However, having a flat rate system penalises consumers who are trying to be environmentally friendly and reduce their energy charges.
Converting from a flat rate into a metered system can be expensive, and without a great deal of enthusiasm on either side, it rarely happens.
What are the benefits of a district heating system?
There are a range of important benefits that come with a district heating system including:
What are the drawbacks of district heating?
Despite the significant environmental benefits to this form of centralised heating network there are some drawbacks that also need to be considered.
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