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).
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.
London’s tube system is literally heating up the city – and that’s a problem. A hundred years ago their subway stations were places to cool down during hot summer days and people had to wear sweaters while commuting. Today, this is no longer the case. The trains are heating the earth which in turn makes the entire tube too hot.
Cooling the tube is now a pressing issue and nifty ideas are being tried. New systems being tested tend to be green and benefit other parts of the city. Basically they are trying to transfer the heat to places that want it to save costs.
An experiment in Islington is trying that very thing using heat from the tube tunnels to warm up a municipal heating service provided to a housing estate. The advantage of this scheme is that it can remove heat in winter when it’s needed above ground. It may seem mildly annoying that surface users don’t want heat in summer when you’d think the tunnels are at their most oppressive, but in fact removing heat in winter helps during the summer.
If the clay surrounding the tunnel can be cooled in winter, it has more capacity to absorb heat in the summer.
As it happens, at this particular trial, the fans can also be reversed so that during the summer months, they can suck cool night time air down into the tunnels as well.
During winter snow is cleared from the roads and put into massive piles to melt when warmer weather returns. This might seem simple enough, but it’s a big challenge dealing with the snow because of the sheer volume in colder climates like Canada. Researchers in British Columbia are proposing that the snow gets taken to special facilities that can benefit from all that snow – for cooling buildings during the summer.
It’s like a return of the once very profitable ice king.
Snow cooling technology is currently used several other countries, including Sweden, where a 60,000 cubic-metre pile of stored winter snow is used to cool the Sundsvall Hospital during the summer.
Hewage and his colleagues determined that in Canada, it would take about a playground’s worth of snow to cool a neighbourhood of 200 to 300 homes for the summer. In the winter, the snow could be compacted and used as a skating rink, he said.
With current energy prices, the system is more economically feasible in Ontario, where rates are high. B.C. has an abundant supply of cheap hydro power.
“But, of course, the environment has a price, too. So if you consider all of the aspects — environment, economic and also the social dimensions — I believe this is a good technology for Canada,” Hewage said.
Keeping buildings cool in the summer is hard enough as it is and we have access to air conditioning technologies. Now, there’s a better way to keep buildings, cars, and whatnot thanks to some research out of Stanford University. Their new approach to cooling entire structures doesn’t require electricity and means that air conditioners won’t be needed and thus a huge decrease in energy consumption can be achieved.
A team of researchers at Stanford has designed an entirely new form of cooling structure that cools even when the sun is shining. Such a structure could vastly improve the daylight cooling of buildings, cars and other structures by reflecting sunlight back into the chilly vacuum of space.
“We’ve taken a very different approach compared to previous efforts in this field,” said Aaswath Raman, a doctoral candidate in Fan’s lab and a co-first-author of the paper. “We combine the thermal emitter and solar reflector into one device, making it both higher performance and much more robust and practically relevant. In particular, we’re very excited because this design makes viable both industrial-scale and off-grid applications.”