Cities tapping their excess heat to reduce emissions

LONDON • The London Underground is the oldest subway system in the world, so it might seem an unlikely source of innovation for one of the thorniest problems facing humanity in the 21st century: climate change.

While public transit is usually more environmentally friendly than other methods of travel, the Underground is playing a more direct role in a groundbreaking experiment to reduce greenhouse gas emissions from buildings.

The local council for the Borough of Islington in London has developed, planned and installed a way to provide heat and hot water for several hundred homes, a school and two recreation centres - all using otherwise-wasted thermal energy generated mostly by the electric motors and brakes of the Underground's trains.

Islington's project is just one of many innovations by cities around the world to provide heat to residents and businesses while reducing greenhouse gas emissions and saving people money.

A neighbourhood in Vancouver, British Columbia, is also recovering waste heat, but from sewage.

Stockholm, too, is using heat from sewage, as well as tapping data centres and other sources to supply heat for much of the city.

Buildings are also a major source of urban greenhouse gas emissions, largely because heating, cooling, cooking and electricity largely rely on fossil fuels.

"If you can start to use a whole array of waste heat streams, you're taking out a big chunk of greenhouse gas emissions," said Professor of Earth Sciences Jon Gluyas at Durham University in Britain who specialises in geoenergy, carbon capture and storage.

In Islington, which stretches from north London to the British capital's centre, the innovation - which took more than five years to plan and build, and began operations in March last year - was to feed in heat from the Underground.

Typically, the hot air from the Underground is released into the air through stations and ventilation shafts. But in this particular case, air is drawn from a ventilation shaft at an abandoned Underground station into an energy centre where a series of heat transfers takes place, eventually leading to delivery of the heat to the buildings in the network.

The fans in the shaft can also run in the other direction to send ambient air into the Underground to cool it in the summer months.

"For our residents, locally, this is absolutely the right thing to do," because it saves money in an area where many residents struggle to afford heat, said Mr Keith Townsend, the Islington council's director of environment and regeneration. "And this is a perfect solution for big cities across the world."

Over in Vancouver, the False Creek Neighbourhood Energy Utility - the Canadian city's sewage and wastewater heat recovery system - serves several densely populated, centrally located neighbourhoods yet produces 60 per cent less emissions than typical buildings in the city.

Heat from wastewater and sewage now provides about 70 per cent of the space heating and hot water for the 43 buildings connected to the network, with the remaining 30 per cent coming from natural gas, though the goal is to end that by 2030.

"Every time we take a shower, do the dishes or do a load of laundry, the water is still hot when it goes down the drain," said Ms Ashley St Clair, Vancouver's senior renewable energy planner.

She added: "It's flowing under our streets, and we're already collecting it through the traditional infrastructure of wastewater pipes, and to be able to tap into that waste heat is really the ultimate circular economy."

In Stockholm, data centres are increasingly becoming part of the energy mix, said Mr Erik Rylander, the head of heat recovery for Stockholm Exergi, a heating and cooling company.

Since starting in 2017, Stockholm Data Parks, a collaboration between the Swedish city and Exergi, has offered companies different locations to build new data centres and participate in the heat recovery system. The companies are paid for the heat they provide to the network.

"If you establish a data centre in a cold place like Sweden, it's stupid to waste the heat, because heat has power and value in a cold country," Mr Rylander said.

Because of the heat generated by data centres and other sources, Stockholm was able to close the city's last coal-fired power plant, Mr Rylander added.

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