A new, lower-energy alternative to air conditioning works by sucking the body heat out of nearby people. With “membrane-assisted radiant cooling,” the researchers tested a pedestrian pavilion in tropical Singapore and found 79 percent reported feeling comfortably cooled by the pavilion despite air temperatures of 29 to 30 degrees celsius.
Alternatives to air conditioning are a huge area of interest for scientists, because AC is extremely energy-dense and costly. In contrast, radiant cooling is maybe best known today as a part of clever home engineering: panels in the floor or ceiling, filled with circulating cool water, absorb ambient heat and create a cool effect. You can feel the same idea if you have a glass of ice water on a hot day: hold your hand near it and you’ll feel coolness radiating off of it.
But you’ll also see a key downside: lots of condensation. This happens to radiant cooling panels in humid climates, too, which makes the finding in Singapore even more exciting. The cooling effect of the “cool tube” worked even at high relative humidity in the tropical climate.
“A thermally transparent membrane is used to prevent unwanted air cooling and condensation, a required precursor to deploying radiant cooling panels without humidity control in tropical environments,” the researchers explain in their new paper, published in Proceedings of the National Academy of Sciences.
What results is a revolutionary radiant cooling system that, like an anti-fog glasses lens or the defroster in your freezer, prevents extra water from causing problems in the system. There’s a funny paradox in trying to study a radiant cooling system, because to measure the temperature of the membrane requires placing a sensor within the radiantly cooled area. Instead, researchers controlled the temperature of the cooled water carefully so they could document at what temperature condensation would finally start to accumulate.
The airtight membrane is the superstar here, and the researchers say taking dehumidifying out of the equation could finally push radiant cooling into wide and public use. “Because the Cold Tube can make people feel cool without dehumidifying the air around them, we can look towards shaving off up to 50 percent of typical air conditioning energy consumption in applicable spaces,” researcher Eric Teitelbaum said in the statement.
Our outdoor architecture already controls our weather experience in many ways, from simple overhead shelters to the space heaters used at transit stops in many cold cities. In warm climates, home design uses natural cooperation with the weather, like windows aligned with natural patterns of air circulation and pergolas to block the hottest sun. And even in office settings, one of the biggest bastions of full-blast air conditioning, researchers are exploring ways to cool individuals to their own comfort levels.
Now, the radiant cooling wall could join the growing number of technologies that seek to supplement and eventually replace energy-costly air conditioning, or even bring restorative cooling to places that have never had air conditioning because of the energy burden and high related cost. All it takes is some cool water and a membrane.
Image credit: Screnshot/ Cold tube walk-through