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Body heat, new green energy source?

  • environment

Harnessing waste body heat in Stockholm's central station

With scarcer resources and rising energy prices, cities are seeking more sustainable ways of heating buildings. A project in Stockholm could offer a solution: it uses body heat from commuters to heat a nearby office building.

Stockholm central station is Sweden’s busiest, with some 250,000 commuters passing through every day. Each idle person produces around 100W of body heat, but when shopping, eating and rushing around, people produce even more heat. Normally this heat is a waste product, which is removed through ventilation systems. But in 2010, the company that owns the station came up with a novel idea: to use the waste body heat to heat a 13-storey office building nearby, owned by the same company.

Engineers developed a way to convert the heat gathered in the ventilation system into hot water using heat exchangers. It is then transported 90m away to the office building. Construction of the system cost around €21,200, and for a project of this scale, the results pay for themselves. The company estimates that the building’s energy costs have fallen by around 20%, making it more environmentally friendly and rendering the building itself more valuable.

This system works especially well in countries like Sweden, where winters are cold and gas prices high. The initial cost is rapidly recuperated in energy savings, but in countries where these factors do not apply, the cost of transporting the heat from building to building may not be worthwhile.

The project is not the first of its kind. In fact, similar projects exist around the world, but at the time of building, this was the first example where the heat was transported to a different building. Other projects have traditionally used body heat as a heat source within the same building.

However, since 2010 similar initiatives have appeared, for example in Paris where heat from people and trains in a metro station is being used to warm 17 apartments in a nearby public housing complex. In this case, however, the housing complex and station are connected by a staircase, so there was no need to construct an additional channel to transport the heat. The scheme is expected to slash the housing complex’s carbon emissions by a third compared to a boiler connected to a district heating system.

Meanwhile in Stockholm, the team behind the project is now exploring other opportunities to harness this green energy. They are, for example, considering the possibility of transferring heat to and from residential areas and office buildings between day and nighttime. For cities like Stockholm, this potential could represent a step ahead in the fight against climate change, limited resources and soaring energy prices.