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Reusing waste heat from London Underground

As the UK strives to achieve a net zero target by 2050, innovation has become more critical than ever. This year we have seen a key advancement in this area – reusing waste heat from London Underground. Keep reading to find out all the details about this innovative game-changer.

Bunhill 2 energy centre – the first of its kind

Experts estimate that the total wasted heat in London could provide for up to 38% of the city’s heating demand. Companies at the forefront of innovation are developing new ways of reusing this wasted heat, for example from the Tube. This is how the Bunhill 2 energy centre came to life this year. And, surprising as it may sound, it is the first of its kind in the world. Located in the London Borough of Islington, it is an exemplary case of how energy from waste can decarbonise urban areas.

Back in 2012, the Bunhill 1 was open in the same neighbourhood. A gas-fired combined heat and power (CHP) engine powers this energy centre. The CHP is the most common source of heat for energy provision in cities. This is precisely what makes the Bunhill 2 Energy Centre so unique. It has been designed with the highest sustainability standards in mind to minimise the carbon emissions in the area.

Reusing waste heat from the Tube to keep 1,350 homes warm

The project opened in May this year (yes, in the midst of the pandemic). It had a total cost of £16.3M and is helping to provide heating and hot water not only to 1,350 homes but also to a school and two leisure centres. This is achieved without burning any fossil fuel. On the contrary, it reuses waste heat from London Underground. In particular, it takes hot air coming up from the Northern line to help power the heating network.

How does the new energy centre work?

The new heat pump system is located in a disused London Underground station – City Road. Danish engineering consultancy company Ramboll was responsible for the design of the energy centre. They carried out a feasibility study which found that the waste heat from the London Underground ventilation shaft could be utilised by heat pumps. Ramboll established a design temperature of 70ºC. The system can also work in both directions. During the winter, it can use the hot air coming up from the Tube to provide heating and hot water. It can then invert the ventilation fan to pump in fresh air during summer to cool down the Underground system.

The 2m diameter fan is installed in an existing six-storey ventilation shaft. The heat pump captures heat from the warm exhaust air. This heat is then used to heat a refrigerant gas, called ammonia. After the ammonia reaches a certain temperature, it is pushed through a compressor. This process converts the gas into a hot liquid which heats the pipes around it. The hot pipes are then used to heat water that runs through a new network of insulated underground pipes. When the hot water reaches nearby council housing estates, it uses heat exchangers connected to their heating and hot water systems.

Reusing waste heat from London underground to hit sustainability targets

Reusing waste heat from London Underground seems to be a win-win solution. It allows Northern line passengers to enjoy cooler tunnels during the summer, whilst local residents benefit from sustainable energy. Besides, the wider community in London benefits from fewer carbon emissions and better air quality as a consequence of removing the traditional gas combustion for heating.

This innovative project aligns perfectly with Islington Council’s target to hit zero carbon by 2030, a really ambitious target. It is estimated that the Bunhill energy centre is helping to reduce carbon emissions by 500t each year. Heating bills are also expected to be reduced by 10% compared to other districts.

The Mayor of London, Sadiq Khan, said:

It’s great to see this highly innovative project up and running, recycling waste heat from the Tube to provide a low-carbon, affordable way of heating local homes and businesses. I’ve set London the target of being carbon-neutral by 2030. It’s an ambition that will require innovative projects like Bunhill to help deliver it. If we’re truly going to tackle the climate emergency we will need progressive partnerships between local authorities, City Hall, TfL and others as was demonstrated so perfectly by this project.’

Bunhill energy centre and its idea to reuse waste heat from London Underground have set the bar for sustainable innovations in urban areas. We are hoping that more projects like this will soon see the light. Sustainability-centred schemes need to become a priority if we are to tackle climate change.

What do you think about this sustainable innovation? Let us know in the comments below.


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