17 Sep 2020

The buildings heated by human warmth

Please note that this article was originally published here by BBC Future

From a stuffy metro station in Paris, to a large shopping mall in the United States, human body heat is helping to lessen the need to burn fossil fuels for warmth.

This seven-storey corner building’s milky white facade blends in well with its neighbours on Rue de Beaubourg, in the heart of Paris. The area is known for its more conspicuous occupants – just a short stroll away is the Centre Pompidou, a contemporary museum and an extravagant 20th-Century architectural statement. By comparison, the building at number two Rue de Beaubourg looks modest, but it is perhaps even more unusual in its design, though you wouldn’t know it from the outside. Since 2015, the building has been drawing its warmth from the hustle and bustle of human body heat in a nearby metro station. The air temperature inside the metro tunnel is around 10C (18F) higher than outdoors. This heat mainly come from human bodies moving around the station and the heat generated by the trains, says Genevieve Littot, climate and energy strategist at the social housing construction company Paris Habitat, which designed the heat extraction system. “A staircase connects the basement of the building to the metro tunnel,” says Littot. “The installation extracts warm air from the metro tunnel through the existing passageway, as the warm air passes through a heat exchanger to produce hot water, which is used for space heating.” This waste heat provides up to 35% of the heat needed for Beaubourg building’s 20 apartments and a commercial premises downstairs. Littot adds that it helps to minimise further carbon emissions through using a district heating system, which is more efficient than heating buildings individually. The Paris project is hardly alone in this regard. Different innovative projects with energy saving designs are emerging around the world to mitigate carbon emissions. Buildings and construction account for over one-third of the world’s final energy use and nearly 40% of energy-related carbon emissions. Currently, only a tenth of energy used for heating comes from renewable sources, according to the International Energy Agency (IEA).

The potential to reduce emissions from heating is therefore huge – especially considering that half of the world’s total energy consumption is used to heat homes and other buildings. But so far, the move towards renewables has been sluggish – the IEA has predicted that the share of clean heating technologies has to double by 2030 to stand a 50% chance of keeping global climate change below 1.5C.

Next stop, clean heating

One of the most ubiquitous sources of heat inside buildings is, of course, the human body. And buildings where, at least in ordinary times, people gather in large numbers have the greatest potential to put that stuffy, human-warmed air to good use. Bustling train stations in particular have proven to be a popular place to experiment with harnessing human body heat. Sweden has made a name for capturing the body heat in its busy Stockholm Central station – about 250,000 people passed through it each day, pre-Covid-19. That heat is used to warm a 17-storey building named Kungsbrohuset nearby, helping to reduce energy consumption of the building by up to 10%. “We take in seawater to cool the ventilation in Kungsbrohuset and the Stockholm Central Station,” says Roger Björk, technical manager at Folksam, which owns Kungsbrohuset. “When the water returns, it is pretty hot . Then we recycle the water to generate heat in our district heating system.” The district heating system utilises a number of other sustainable sources besides body heat, including geothermal heat, burning of unrefined biomass – waste wood, straw, forestry residues and so on – and surplus heat from industrial buildings. That heat is then distributed to homes and buildings across the country through underground pipes. Ulla Janson, senior lecturer at the division of building services at Lund University, says district heating systems have been a powerful way to heat buildings up. Half of Sweden’s entire heating demand in the residential sector in 2017 was satisfied mainly through use of heat pumps and utilising waste heat in district heating. Please visit: https://www.bbc.com/future/article/20200908-the-buildings-warmed-by-the-human-body to read the full version of this article.