22 Dec 2017
by ReUseHeat Project

Heat recovery from the London Underground in Islington, UK

An expansion of Bunhill Energy Centre in Islington is a part of a project to capture waste heat from London Underground tunnels. Heat recovered is used to warm local homes and lower the energy bills.

Description

Temperatures in London’s tubes can get high and currently most of this energy is discharged through ventilation systems all over London. Most of this heat is produced by the train system, of which a great part is form braking losses, mechanical losses and drivetrain. Only a small part of the heat is produced by passengers. Currently, most of the heat is absorbed in the tunnel walls and approximately 10 % of the heat is removed by mechanical ventilation.

The EU-funded CELSIUS-project, a platform of networking and knowledge-sharing regarding barriers to district heating and cooling solutions, aims to demonstrate heat recovery from London Underground’s ventilation system through an electric heat pump system. Hereby, energy is extracted and used to produce local district heating. The Bunhill Energy Centre already through a previously project in 2012 created a local district heating system to warm two leisure centres, three communally heated council houses and one private housing development, covering 805 units in total. The existing system consist of a 1.9 MW CHP gas engine and 115 m3 thermal storage with 1.5 km of district heating pipework.

The CELSIUS-project aim to expand this network with 454 homes and include excess energy from London Underground, potentially further supplying 1000 homes. Removing heating from the tunnel system in winter, when it is mostly needed above ground, can help cool surrounding walls and hereby lower overall temperatures during summer. Heat extraction during winter enables more absorption capacity for the tunnel walls during summer.

Finned tubes within the ventilation shaft capture heat from the air. The ventilation shaft expels exhaust air at a rate of 30 m3/s with a temperature of 22°C in winter and 28°C in summer. A feasibility study found that the heat capacity of the ventilation shaft would be approximately 400 kW. By increasing fax expelling air rate to 70 m3/s the heat capacity would be increased to 1000 kW. Hereby, low-grade waste heat is recovered from the ventilation shafts through a air-to-water heat pump. Two 237 kW CHP gas engines, which produce electricity, can power the heat pumps when electricity prices are high. The heat pump can accordingly operate without connection to the national electric grid, when both heat pump and CHP’s are operating. The CHP’s can further operate without the heat pumps, hereby exporting electricity to the national grid.

 

Facts about this case

Installed heat capacity: 1 MW heat pump and 2 x 237 kW CHP gas engines.
Heat source: Excess heat from London Underground ventilation system (22-28 â—¦C)
Potential: 10 % of heat losses from the London Underground is from ventilation.
Support: FP7-supported CELSIUS-project
Organization: Islington Council
District heating network: +1000 units
Link to web page: http://celsiuscity.eu/
Contact information: CELSIUS-project
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Source: Greater London Authority

 

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