Excess Subway Heat to Warm London Homes

With a ridership of more than 1 billion passengers per year, the London Underground (better known as "the Tube") ferries an impressive number of residents and tourists across the city. It's also impressively hot due to its very old, rather deep clay tunnels with few ventilation shafts, which lock in excess heat from the metro system and make many a Londoner sweat on their daily commute. The hottest stations without air conditioning routinely get to 86 degrees Fahrenheit (30 degrees Celsius) or more. And rising temperatures due to global warming don't help.

But one enterprising collaboration between the London borough of Islington and Ramboll — a consulting company that works on many issues, including energy and urban design — will harness some of that excess subway heat for the benefit of Londoners, with a completion date for the project as early as late 2019.

Ramboll had been commissioned by the Islington Council to "deliver a district-wide heating network to provide cheaper and greener heat to 1,350 homes plus community buildings in north London" according to their press release. Of those 1,350 dwellings, the Islington Council and Ramboll have already brought cheap, green energy to more than 800 through the Bunhill Heat and Power Network. But the Islington Council wanted to do more in order to reach their goal of providing efficient and sustainable heat to the remaining homes.

So Ramboll proposed extracting wasted heat from the London Underground's Northern Line — specifically, through a ventilation shaft connected to an abandoned Tube station — to serve as an "innovative low-carbon heat source" for 500 homes in north London. How? The plan is to use heat pumps to harness the excess heat of the London Underground and hike up the heat to 70 degrees Celsius (158 degrees Fahrenheit) for use in heating homes and community centers.

According to the press release, Ramboll says that these heat pumps that recycle industrial heat will prove to be a far more efficient (and cheaper) use of carbon than gas-powered energy sources, which is a great win for the residents of North London whose homes will be fueled by the waste energy from the Northern Line. Riders on the Northern Line will sigh in relief at cooler tunnels on their commute, and all Londoners will reap the benefits of reduced air pollution and lower carbon emissions.

Could this innovative model be applied to other cities with notoriously hot subway systems and more high-density housing? With the concerns of climate change looming, leaders all around the world are hoping to decarbonize or remove carbon from the global economy in order to move toward a carbon neutral future by 2050. Schemes like the one in Islington could be the first step in getting there.