Body Heat: A New Source of Energy for Buildings?

In a few countries around the globe, governments are using an innovative method to warm buildings using body heat. The long-talked-about idea is finally becoming a reality, but it is not yet widely used. A resting male can generate between 100 and 120 watts of energy, most of which is lost as excess heat. However, capturing this heat for other applications is complicated. In recent years, significant progress has been made in the body heat power generation industry, but scientists believe that applications of body heat can be much more widespread if managed effectively. 

In 2015, in Paris, a seven-story building on Rue de Beaubourg in the center of the city was transformed to use the warmth from human bodies moving around a nearby metro station as a source of heat. As the air temperature in the metro station is roughly 10oC higher than outdoors, due to crowds of people and heat from trains, it can provide heat for other applications. A heat extraction system "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," according to Genevieve Littot, a climate and energy strategist at the social housing construction company Paris Habitat, which designed the heat extraction system. The waste heat contributes around 25 percent of the heat needed for the 20 apartments as well as commercial spaces in the Beaubourg building. 

Around half of the world's total energy consumption is currently used to heat homes and buildings, demonstrating how much projects like these could contribute to decarbonization efforts. However, very few places are using these types of technologies at present, with many opting for alternatives such as solar heating or electric heat pumps, or simply sticking to gas. 

Sweden is one country looking to utilize body heat more to reduce its conventional energy use. around 250,000 people pass through Stockholm Central Station every day, which the government decided could support its heating aims. The heat generated at the station is extracted to warm the nearby 17-story Kungsbrohuset building, reducing energy consumption in the building by around 10 percent. Roger Björk, the technical manager at Folksam, the company that owns Kungsbrohuset, explained, "We take in seawater to cool the ventilation in Kungsbrohuset and the Stockholm Central Station… When the water returns, it is pretty hot [warmed by body heat]. Then we recycle the water to generate heat in our district heating system."

Sweden is not only using body heat as a source of heating for buildings. Its district heating system uses geothermal heat, biofuel from waste, and surplus heat from industrial buildings transporting heat through underground pipes to buildings countrywide. The Scandinavian country has been exploring alternative ways to power buildings since the energy crisis of the 1970s, with heat pumps and the use of waste heat in district heating now providing most residential heating needs. 

Another example is the massive Mall of America, in Minnesota in the U.S., which does not use a central heating system. The mall maintains its 21oC year-round temperature using passive solar power through 1.2 miles of skylights, heat generated from lighting and body heat. It also has over 30,000 living plants and 300 trees, which act as air purifiers. 

Governments worldwide are looking to expand the use of body heat for other applications. For example, hospitals could benefit greatly from the use of excess body heat and heat generated from machines. However, distributing the heat evenly and effectively throughout the building is both necessary for vulnerable patients and complicated. Nonetheless, the Klinikum Frankfurt Hoechst hospital in Frankfurt, Germany is putting the technology to the test. It has more than 1,000 triple-glazed windows, to enhance insulation. The hospital uses a ventilation system to preheat fresh air before it flows into the room to maintain indoor temperature and avoid unpleasant odors.

There are many more obvious places where body heat could be captured and transferred to provide heat where needed, such as concert venues, nightclubs, airports, and other commercial spaces. In 2023, a nightclub in Glasgow announced plans to use the body heat released from people on the dance floor to power heat pumps and provide sustainable heating. The Scottish tech start-up BODYHEAT plans to use the heat generated in a nightclub, from up to 1,000 dancers, to either sustainably cool down the building or to store heat underground for later use. The SWG3 nightclub stated, "We're hugely excited to reveal our plans to introduce a state-of-the-art renewable heating and cooling system to the SWG3 complex, transforming body heat from clubbers and gig-goers into a source of energy to be used again." 

In Europe, a 30m2 studio using electricity for heating and hot water consumes around 4,350 kWh of energy annually, meaning that harnessing the heat of 430 people sharing a space for around an hour could provide enough energy to power a small home. This demonstrates the huge potential for using body heat from crowded spaces to provide cheap, carbon-free power.  

By Felicity Bradstock for Oilprice.com

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