When I walk down the sidewalks during frigid winter days in Washington, D.C. I like to seek out the sidewalk grates where warm air escapes from the subway system under foot, offering a moment of relief from the cold.
While those moments are great for thawing out numb hands and feet, the heating vents aren't the most efficient use of such a vital resource in those cold winter months.
In London, they've come up with a better use: capturing the heat from its subway to heat nearby homes. Mayor of London Boris Johnson recently announced the project saying that it will connect with the Bunhill energy centre and heat network, an underground network of pipes that heats homes using heat waste from power stations. This latest project will heat about 700 homes in the London borough of Islington.
The scheme is just one part of London's goal of generating 25 percent of city’s energy from local sources both by 2025.
"We need to do everything possible to create a more secure, cost-effective and sustainable heat and power supply for London," said Matthew Pencharz, the Mayor of London’s senior advisor on environment and energy. "By supporting locally sourced energy and heat networks which can reduce bills and lower carbon emissions, we can not only save money but also drive innovation, jobs and growth in this burgeoning sector."
But it's not the only example of a city turning to waste heat for power. Paris is working on a similar project for its subway system. In Sweden, they're looking to a geothermal system that captures heat given off by its daily commuters.