Waste heat from the Underground to warm offices and homes

Waste heat from one of London Underground's tube lines will be used to warm homes in the capital from this winter.

Warm air from from the Northern Line channelled to support the London Borough of Islington's district heating will provide offices and 1,350 homes with heat by the end of 2019.

Dubbed the first of its kind in Europe, the Bunhill 2 project is a joint undertaking between Islington Council, Transport for London (TfL) and engineering firm Ramboll.

The council hopes the system will make London more self-sufficient in energy, cut carbon emissions and reduce heating bills for residents, while tube passengers can expect cooler tunnels.

District heating, also known as heat networks, is the supply of heat and hot water from a central source to a group of buildings.

Bunhill 2's central source is a ventilator shaft in the abandoned City Road tube station, located on the Northern Line between Angel and Old Street.

Ramboll has designed a heat pump that captures the excess heat from the ventilation shaft, before it is warmed to around 70 degrees Celsius. This will then be transferred into Islington's heat network to supply heat and hot water to properties.

Over the summer months, the system is designed to be reversed so that cool air can be piped into the tube tunnels.

The hunt for alternative sources of renewable heat in cities has gained pace in light of the climate crisis, and the UK government's resultant ban on gas-fired boilers in new-build homes from 2025.

According to the Greater London Authority, there is enough heat wasted in London to meet 38% of the city's heating demand. The expansion of district heating networks like Bunhill 2 could see this increase to 63% by 2050.

Lucy Padfield, director of district heating at Ramboll said: "We believe that the use of large-scale heat in this way connected to urban district heating systems will play a major part in decarbonising the UK's heating energy demand.

"The use of heat pumps utilising industrial waste heat sources is more carbon efficient than gas-fired combined heat and power, the usual source of heat for district energy schemes", she added.

Bunhill 2 district heating system is currently expected in late 2019.

[edit] About this article

This article was written by the Chartered Institute of Architectural Technologists (CIAT). It is based on a CIAT press release entitled 'London Underground's waste heat to warm hundreds of homes' and was published on the CIAT website in August 2019. It can be accessed HERE.

Other articles by CIAT on Designing Buildings Wiki can be found HERE.

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--CIAT