DAILY SCIENCE

Innovative personal cooling system uses half the energy of traditional AC
By drawing heat radiated from a person's body rather than cooling and dehumidifying air, radiant-cooling panels could cool people in outdoor spaces using little energy
September 10, 2020

This was the second hottest year on record, and the needle is likely going to keep moving towards the red because of climate change. The thirst for energy-hogging air-conditioning is only going to make the issue worse. So researchers have been racing for environmentally friendly cooling technologies.

The latest is an innovative energy-efficient technology called the Cold Tube that can cool people in sweltering summer months by absorbing the body heat a person emits. By providing personal cooling, the system uses about half the energy of traditional cooling systems.

“Air conditioners work by cooling down and dehumidifying the air around us, an expensive and not particularly environmentally friendly proposition,” said Adam Rysanek, professor of environmental systems at the University of British Columbia. “The Cold Tube works by absorbing the heat directly emitted by radiation from a person without having to cool the air passing over their skin.”

Photo by Lea Ruefenacht

 

The principle behind the Cold Tube, which Rysanek and his colleagues reported the technology in Proceedings of the National Academy of Sciences, is simple. It relies on heat flowing from hotter objects to colder ones.

The system is composed of several rectangular wall or ceiling panels through which chilled water is circulated. So when a person stands near the panels, the body heat they radiate moves towards the panels. This feels like cool air flowing over the body even when the surrounding air temperature is very high.

Chilling the water consumes energy. But because there is no need to dehumidify and cool large volumes of air, the system achieves a significant amount of energy savings.

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Such radiant cooling technologies haven’t been adopted widely because in humid environments, the low temperature results in condensation on the panels. So the researchers wrapped their panels in a novel membrane that is airtight and repels humidity.

In the paper, they report results from a outdoor cooling pavilion that they built in Singapore. At temperatures of 30°C and humid conditions, people in the pavilion felt cool and comfortable, and the panels did not build up condensation.

These materials could quickly rapidly provide cooling comfort to people in outdoor spaces such as bus stops, summer fairs, concerts, and public markets, “all without wasting cooling energy to the air,” the team writes. But, said Eric Teitelbaum, lead author of the paper and senior engineer at Singapore–ETH Center, “the mission is to adapt the design for indoor spaces that would typically use central air conditioning.”

Source: Eric Teitelbaum et al. Membrane-assisted radiant cooling for expanding thermal comfort zones globally without air conditioning, PNAS, 2020.

Image: Borodox

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