With the Project:
Bunhill 2: Using waste heat from the London Underground to heat homes
The London Borough of Islington commissioned the Bunhill 2 project with an aim to expand its existing Bunhill heat network. Bunhill 2, the first of its kind in the world, supplies cheaper, cleaner and greener heating by using waste heat emissions from the London Underground network. With the network being expanded to supply a further 500 homes on a nearby council estate and add capacity for 1,000 more in a new-build development, a new energy centre was required to provide additional supply capacity.
The original Bunhill Heat Network began operating in 2012, initially supplying three council estates (600 homes in total), two leisure centres and some office buildings. Heat was supplied by a 2.2MW gas-fired combined heat and power (CHP) plant, with the original boilers of the sites retained for backup. Council tenants received a 10% discount on their heating charges compared to the standard tariff and it was estimated that the annual carbon savings were around 2,000 tonnes. In the next few years, two new build private developments with around 200 homes and some commercial space were added to the network.
The council sought to extend the network to a large estate of around 500 homes and increase the capacity of the network to allow more connections in the area, including a new built development of around 1,000 homes. The new energy centre is forecast to reduce carbon emissions by around 500 tonnes per year compared to the existing heating supply for the newly-connected dwellings, previously heated by gas boilers. Two potential sources were assessed: a London Underground ventilation shaft and an underground electrical substation.
The new energy centre is constructed around a 1MW heat pump that uses warm air expelled from a disused London Underground ventilation shaft to create hot water for the network. The system is also designed to allow the fan in the ventilation shaft to operate in reverse in the summer, when warm air drawn in from the atmosphere it is cooled by the heat pump coils, providing cooling for the London Underground tunnels, helping make journeys more comfortable on the Northern line.
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