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Decarbonizing heat supplies

by Steve Hodgson

District heating is coming back into fashion in the UK, with new schemes extending into new-build and private sector developments. While the British district heating sector has tended to cater for high- density public sector housing and local government buildings, some schemes now cover commercial buildings. Private sector developers are also opting for locally-based heating networks, which often incorporate gas and waste-fired CHP units.

Recent weeks have brought several district heating developments. E.ON has announced a new district energy scheme for 330 housing association homes being built in south London. A new heating network is being built by Cofely to link a waste-to-energy plant to local authority and church buildings in Coventry. Train line operator Network Rail is adding its new HQ building to the retail and residential buildings connected to the Milton Keynes heating network, which has been operated by Thameswey since 2007.

But district heating could go much further, given time and political will.

In a fascinating glimpse into a low-carbon future, a new study by Delta Energy & Environment suggests how UK domestic heat markets could be decarbonized by 2050, with district heating networks having to play a very major role under all of the scenarios studied. This would mean both the development of many new networks, and the expansion of existing schemes.

The UK is currently formulating plans to substantially decarbonize both its electricity and heating markets to meet highly ambitious carbon reduction targets. The debate on the power markets is all about continued use of gas (with or without carbon capture and storage) versus new renewables and/or new nuclear power. But planning for decarbonizing heat throws up a host of interesting alternatives to the gas-fired single home boiler that dominates UK domestic heating today. And the message is that most of the alternatives feature local, decentralized energy.

Electrically-driven and gas-fired heat pumps, micro-CHP and solar thermal systems could serve huge numbers of homes in rural and suburban settings. Meanwhile, district heating networks fuelled by zero-carbon fuels such as biomass or municipal and other wastes could heat higher density developments in cities and town centres. Strict decarbonization would require entirely removing natural gas from the system, but the report identifies a more likely scenario, in which gas-fired boilers and micro-CHP units retain a role in low-density housing.

Although 2050 is a long way away, even to this timescale decarbonizing domestic heat is not going to be easy. It will require massive intervention by government and regulators to first cut overall thermal demand from buildings and to develop district heating schemes to run on zero-carbon fuels ” as well as parallel moves to substantially decarbonize the electricity system. However, the message for the UK district heating and micro-CHP sectors is that massive market expansion may be on the way. Many northern European countries will have similar situations.

Indeed, it’s not just the gas-dominated UK in which interest in district energy systems ” that supply heating and/or cooling according to the season ” is growing. Britain is ahead of most of the world in its decarbonization agenda, but much of the developed world is not so far behind. And a city or town with an established heating (and/or cooling) network is in a good position to see traditional coal or gas-based sources gradually replaced with waste, biomass, solar thermal or geothermal inputs, as fossil stations close down and new, lower carbon thermal stations are connected to networks.

And we are not just future-gazing here. With abundant wood fuel supplies, many Scandinavian district energy schemes have operated largely or entirely on biomass or waste fuels and even ‘waste’ heat from industry for many years. North America is following suit and I see that a heating network in Paris uses geothermal heat alongside fossil fuels.

Decarbonized heat has never been out of fashion in some countries; its more widespread adoption is closer than many of us think.

Steve Hodgson
Contributing editor, COSPP

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