Researchers from the University of California and Singapore-ETH Center created a device, named Cold Tube, that cools people without air conditioning (AC).

Exterior of Cold Tube demonstration pavilion. Source: Lea Ruefenacht

Cold Tube absorbs heat emitted through radiation from a body without needing to cool the air around them. Cool Tube is made of rectangular walls of ceiling panels that are kept cold by chilled water circulating within the device. Heat naturally moves via radiation from a hotter surface to a colder surface. When a person stands near Cold Tube’s panel, body heat is radiated from the body and towards the cool panel, creating a cooling sensation.

Cold Tube is a unique cooling system because it doesn’t have to be combined with a dehumidification system like AC units. Cold Tube condenses water without drying the air around the panels. There is an airtight humidity repelling membrane that encases the chilled panels to prevent condensation while allowing radiation to travel through.

In 2019, the team built an outdoor demonstration unit of Cold Tube in Singapore. Fifty-five members of the public were allowed to visit the unit and provide feedback. Participants reported feeling cool or comfortable when standing near Cold Tube, even though the average air temperature was 86 degrees Fahrenheit. During this demonstration, the panel stayed dry.

Cold Tube could be used for outdoor spaces and events, like summer concerts or bus stops. But the team’s goal is to adapt the design so it can be used in indoor spaces that would typically use AC.

Researchers plan to demonstrate a commercially viable version of Cold Tube by 2022.

A paper on Cold Tube was published in PNAS.