Using heat from the human body as energy to heat buildings

Stockholm Central Station sees more than 250,000 passengers pass through it every day. And the strange thing is that these people have no idea that their body heat is being harnessed for energy.

The more passengers move around Stockholm’s central station, the more energy they produce. In 2017, engineers at Swedish real estate company Jernhusen figured out how to use this excess energy to heat another building in the same area.

Using body heat to heat a building has been used in crowded buildings such as shopping malls and cinemas in the winter. What is different about Stockholm Central Station is how engineers are collecting the excess heat and transferring the energy between the station and the 13-storey Kungbrohuset office building, located more than 30m away.

The system at Stockholm Central Station works like this. A heat exchanger is installed in the station's ventilation system. It absorbs excess body heat and uses it to warm water in an underground tank. The water is pumped through pipes to another building and fed into the main heating system.

This system helps reduce 25% of the office building's electricity costs.

In other countries like the US, the financial benefits of investing in insulation, pipes and pumps may not be apparent, but in countries like Sweden, where electricity is expensive and winter temperatures are very low, the benefits are clear.

In addition, this method has some other limitations such as the buildings must be located close together to avoid heat loss if it needs to be pumped over long distances.