Another Radiative Cooling Advancement

solar

The more I learn about radiative cooling systems the cooler they get. These cooling systems absorb heat from an enclosed space and send the heat directly into outer space. It sounds like science fiction but it exists now. The heat gets converted into infrared waves and emitted upwards away from the planet where the waves pass through the atmosphere to release their heat into the coolness of space.

In experiments, the team showed that the device was able to lower the temperature inside a test unit by more than 12 °C (22 °F) under direct sunlight, and by more than 14 °C (25 °F) in a simulated nighttime test.

The mirrors are more advanced than they might sound, too. Made with 10 thin layers of silver and silicon dioxide, they’re designed to be selective in how they handle different wavelengths. They reflect the mid-infrared waves from the emitter while absorbing the visible and near-infrared waves from the sunlight. That prevents the Sun’s warmth from cancelling out the cooling effect, improving the efficiency.

As an added extra, the heat absorbed by the mirrors can be put to good use – in this test, the team used it to heat water to 60 °C (140 °F).

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A Team Cools the Planet by Sending Heat to Outer Space

desert and stars

Aaswath Raman, a material scientist at UCLA, has looked into the past to solve today’s problems. He has led a team that’s created an impressive device that uses radiative cooling to help cool anything by sending heat into outer space. This sounds like it’s right out of science fiction, but it is very real and is based on sound science that’s been ignored for decades. A basic example of radiative cooling is how temperatures drop on buildings overnight due to the lack of sunlight, in this case the heat just goes into the atmosphere. Using Raman’s new device the heat can get transferred into outer space because the material used reflects a very particular wavelength which won’t get trapped in the atmosphere.

In a few years the Stanford group had its first prototype. Placed outside in the hot California sun, it felt cold to the touch. It was a giddy, counterintuitive sensation, even to Raman.

Yet even after he convinced himself that daytime radiative cooling was possible, it wasn’t until a trip to visit his grandmother in Mumbai that Raman started to see how it could also be useful.

A growing number of homes in Mumbai had air conditioners in their windows, something he rarely saw during childhood visits. That’s an unqualified victory for people’s health, Raman said; exposure to extreme heat can lead to a range of illnesses, from respiratory illness to psychological distress.

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Improved Air Conditioner Beams Heat Into Space


Air conditioner suck up a lot of energy in hotter months by dumping heat from inside buildings to the outside, ironically heating up neighbouring locations. A Stanford research team developed a more efficient cooling system for AC by pre-cooling water that circulates through the machine. It cools water during the night by essentially beaming the eat out into space, which surprisingly uses less energy than current solutions.

For the new fluid-cooling system, the researchers made radiative panels that were each one-third of a square meter in area; they attached the panels to an aluminum heat exchanger plate with copper pipes embedded in it. The setup was enclosed in an acrylic box covered with a plastic sheet.

The team tested it on a rootop on the Stanford campus. Over three days of testing, they found that water temperatures went down by between 3- and 5 °C. The only electricity it requires is what’s needed to pump water through the copper pipes. Water that flowed more slowly was cooled more.

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Cheap and Easy Ways to Keep Cool Without Air Conditioning

I’m one of those people that can’t handle unrelenting heat and so I’m always looking for ways to stay cool. I’m also one of those people who doesn’t like air conditioning (for reasons beyond the obvious power consumption), as a result I love tips on how to make your home cooler in easy ways.

At Treehugger they have a list of 10 ways to alleviate the need for AC. Some require a few years to take effect (like growing a shade tree) while others can happen right away like opening the windows.

The windows on your home are no just holes in the wall that you open or close, they are actually part of a sophisticated ventilation machine. It is another “Oldway”—People used to take it for granted that you tune them for the best ventilation, but in this thermostat age we seem to have forgotten how.

If the Treehugger list is not enough for you, don’t worry! We’ve looked at energy-free ways to stay cool in the summer before:

Keeping it Cool Without Air Conditioning

Green Ways to Stay Cool in Summer Heat

Keeping it Cool Without Air Conditioning

In really hot countries air conditioning in buildings might seem like a necessity; however, it is possible to design buildings that stay cool in the heat without even using electricity. In Burkina Faso there is a school that was specially designed to stay nice and cool by manipulating airflows.

There’s not much electricity to go around, Kéré says. “So there is no air-conditioning. It’s too expensive for a country like Burkina Faso.”

So when he designed this secondary school for Dano in his native land, he built it with innovative, elegant, distinctive and yet simply constructed split-level roofing and ceiling structures that funnel warm air up and out of the buildings.

Tall window slats that can be adjusted control both light and heat. Three to a room, they pull air into the classroom. Heat rises.
To use that movement of air, a series of narrow “chimney” gaps between the convex wave shapes in the highly insulating concrete and brick ceiling pulls the hot air up and out the roof.

Read more and see pictures here.

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