Heat recovery from the London Underground in Islington, United Kingdom

Location: London, United Kingdom

Population: 8,899,375 [Greater London]

Climate: Oceanic

Duration: ~ 2014 – 2017 (source)

Sector: District energy

Funding sources: Public

City networks:  C40

Savings: 500-tonne reduction in CO2 emissions per year.

Solutions: Bunhill Energy Centre in Islington is being expanded as part of a scheme to recover waste heat from London Underground tunnels (source).

Multiple benefits: The warm recovered is utilized to heat nearby houses, lowering energy bills (source).

The heat generated in London’s tubes is currently dissipated through ventilation systems. The railway system generates most of this heat through braking, mechanical, and drivetrain losses. Passengers emit just a small amount of heat. Currently, most heat is absorbed by the tunnel walls, with mechanical ventilation removing around 10% (source).

Objective – To demonstrate heat recovery from the ventilation system of the London Underground through an electric heat pump system.

Solutions – Installing a heat exchanger in the vents used to collect hot air from the London Underground is the technological option for recovering heat from the network. Using a heat pump can provide hot enough water to be utilized in a district heating network.

LO2 and LO3 are two of London’s demonstrators. The technologies exhibited are connected to:

• Capturing waste heat from electrical transformers and tube ventilation shafts, and including a thermal storage. Removing heating from the tunnel system in winter, when it is largely needed above ground, can aid in cooling nearby walls and, as a result, decrease overall temperatures throughout the summer. Heat extraction in the winter allows for greater absorption capacity of the tunnel walls in the summer.
• Bunhill seed network expansion. Bunhill Energy Centre developed a local district heating system in 2012 to heat two leisure centres, three communally heated council residences and one private housing complex, totalling 805 units. The CELSIUS initiative seeks to add 454 households to the network and integrate London Underground’s excess energy, potentially adding 1000 homes.

The project’s primary stakeholders include Islington Council as the District heating network operator and London Underground as the Ventilation shaft operator.

Funding – Full procurement and preliminary stage are completed for the project and Colloide engineering systems has been appointed as principal contractor.

Islington Council, Transport for London, and the Mayor of London collaborated on the ground-breaking extension of the Bunhill Heat and Power district heating network. It was funded by Islington Council, which owns and operates the network, and a grant from the European Union’s CELSIUS project (source).

Innovation – The project’s main novelty is that London’s heat recovery from an underground railway has never been done commercially. The biggest technical concern is the fouling of the coil (air to water heat exchanger) in the ventilation shaft by dirty and polluted railway air. Therefore, the project produced a coil wider than the average spacing between heat exchanger fins to limit the coil’s ability to trap particles and a washer mechanism to wash the coil automatically. The project team worked closely with London Underground to conduct heat exchanger coil experiments on the network.

Success factors – 1) Process optimization in the realization phase. It avoided delays by twin monitoring the procurement and planning/authorization procedures; 2) Acquiring expertise. To assure the project’s success, the council carried out a public procurement process to engage a client engineer to establish specifications, supervise the design process, act as clerk of works, and give general technical direction and experience. As the client, they also selected a highly experienced project team to monitor the project for the council; 3) Obtaining assistance. The project’s primary goal is to deliver cheaper and greener heat to Islington residents. To receive full support for the investment, the project team had to demonstrate with certainty that the initiative would create minimum savings. We employed a complicated energy modelling tool to reproduce the operational circumstances and unpredictability in energy markets to provide outputs in heat pricing and values for connected buildings.

Significant outcomes

• Expanded district heating system and cheaper heat source;
• Those who are connected will contribute to a 500-tonne reduction in CO2 emissions per year (source);
• Reduced energy bills.

Synergies with local policies:

• Zero Carbon London. London’s net-zero aim will be moved from 2050 to 2030. District heating networks are an essential aspect of the Mayor’s Plan to make London carbon-free by 2050. Heat networks connect buildings to low-cost, low-carbon, waste, and renewable energy sources to provide them with heating and cooling (source).

Political alignment:

• Carbon Plan. The Plan outlines how the United Kingdom would accomplish decarbonisation within the context of energy policy. Over the years 2023-2027, demands a 50% reduction in emissions relative to 1990 levels. The government will provide financial assistance to district heating networks;
• Heat and buildings strategy. This document outlines the government’s aim for high-efficiency, low-carbon buildings that promote business and job growth. The strategy’s major aims are to cut energy expenses, develop markets for low-carbon heat systems, and evaluate the viability of hydrogen for heating (source). The strategy also addresses the topic of district heating from different angles.

Marketability: The replication potential of the project shows the highest levels in:

• Adaptability to different climate conditions;
• Easiness-to-operate (no need for specific technical requirements), and;

The opportunity of integrating waste energy sources.