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Air conditioner of the future: Radi Cool’s Xiaobo Yin and
Ronggui Yang show the thin film that cools buildings without using power. (Photo: Radi Cool.) |
THE crazy weather KZN has experienced recently, with 20° Celsius
fluctuations in temperatures from one day to the next, is not only
uncomfortable, but dangerous, warns Aadyl Gany, an air conditioner technician in
Pietermaritzburg.
Gany says meteorologists predict that 2017 will be the hottest year
on record, and the third year in a row with record high temperatures.
He says the human body is only comfortable in a very narrow range
of temperatures and heat stress suffered over a few hot and humid days with
temperatures between 30° C to 35° C is as dangerous as, for example, running on
a 45° C day.
“Climate change has already exacerbated the extremes we were used
to. A decade ago, 32° C was normal in the middle of summer. Now we are closer to
40° C.
“This means we are approaching Dubai temperatures, which makes air
conditioners no longer a luxury but a necessity, especially for older or not
very fit people,” Gany said.
As specialist installer for Save Supermarkets, Gany says he can
recommend the store for offering a wide range of devices that will keep
customers cool, with solid warranties. “The latest floor-standing units sell for
R42 999 and a smaller indoor unit goes for some R6 999, but customers who don’t
have this kind of money can go old school with a four-setting fan from R199,” he
said.
The bottom line, he warns, is that the summer looks to be another
scorcher and people need to plan ahead.
He says that apart from being an investment in health, air
conditioners add more value to a home than a swimming pool, as they can both
cool the house in summer and warm it in winter.
Radiating heat into space
Meanwhile, the future of airconditioners looks to take the shape of a shiny plastic film.
Radi Cool, a start-up from the University of Colorado Boulder,
developed a plastic film that delivers noon-time radiative cooling power of 93
Watts per square meter under direct sunshine — more than double that of its
nearest competitor.
When backed with a silver coating, Radi Cool’s metamaterial film
showed an average cooling power of over 110 Watts over three continuous days and
a noon-time cooling power of 93 Watts between 11 am to 2 pm.
Radi Cool published a paper in Science in February,
in which it describes its metamaterial film as a “glass-polymer hybrid
material”. The founders of Radi Cool, Xiaobo Yin and Ronggui Yang, in 2015
received a $3 million federal grant from the U.S. Department of Energy’s
Advanced Research Projects Agency-Energy to develop a new film that provides
cooling without needing a power input at the University of Colorado Boulder and
have since patented their shiny film.
They exploit the little-known radiative cooling effect, which
exploits tiny “gaps” in the Earth’s amospheric “roof”.
These gaps allow infrared waves with amplitudes between 8–13
micrometres to radiate through the “roof” into space, instead of being bounced
back. When heat can radiate into icy space off a surface, it quickly becomes
several degrees cooler than the surrounding air, causing frost to form on the
surface even in broad daylight. Several companies are now making surfaces that
radiate this precise range of infrared waves into space, with Radi Cool’s system
currently the cheapest and most effective. Radi Cool said in a statement their
material can be scalably manufactured at a low cost through roll-to-roll
manufacturing processes.
They compete with SkyCool Systems, a Stanford University start-up
whose founders were the first to see the potential in a tiny atmospheric gap.
SkyCool has patented a nano-shaped tin foil with a cooling power of 40,1 Watts
per square metre — less than half as effective as Radi Cool’s film. Still, the
Skycool “tin foil” panels are 4,9˚C cooler than ambient air.
In Australia, another company calling itself Skycool is selling
“heat reflective paint”, which also makes use of radiative cooling. This white
roof paint renders an interior as much as 14˚C cooler than the ambient air —
even during Australia’s extremely hot summer.
All three companies are looking to expand, and would welcome trade
inquiries.
The savings in electricity from the new systems can be big. Nick
Fernandez, an energy analyst at the Pacific Northwest National Laboratory, in
2015 published a study that showed up to 70% energy savings are possible when
the new radiative cooling systems are coupled with a hydronic radiant cooling
system — a rare but highly efficient way of cooling buildings that works by
circulating water instead of blowing air. — WR.
