One way to keep cool this summer is to coat your roof with what is claimed to be the whitest paint ever made. Created by engineers at Purdue University in the US, the coating reflects 98.1% of sunlight – shattering the previous record of 95.5%, which is also held by the team led by Xiulin Ruan.
What is more, the paint is a good emitter of radiation at wavelengths that pass very easily through the atmosphere, which reduces the temperature of the coating via a process called radiative sky cooling. This means that the coating can be cooler than the surrounding air.
According to the team, a painted roof of about 9 m2 could deliver a cooling-power equivalent of about 10 kW – which is greater than a typical domestic central air conditioning system.
Seasonal problem
This is one catch, however, if you live in an area with cold winters. The team points out that at 6 °C the paint surface can be a chilly -4 °C, so the paint could increase your heating bills.
One solution would be to paint your roof black in the autumn, perhaps using Vantablack – which incorporates carbon nanotubes to absorb 99.9% of visible light.
Purdue University must be a very cool place to be because researchers there have also joined forces with Air Squared and Whirlpool Corporation to develop a refrigerator for use in space. While fridges for experiments and biological samples operate on the International Space Station (ISS), they are not very energy efficient and therefore not practical for food storage. As a result, astronauts tend to rely on canned and dried food with a shelf life of about three years. Fridges could extend the lifetime of stored food by another three years and also increase the range of food that can be stored.
While the vapour-compression fridges used in kitchens on Earth are very efficient, they rely on gravity to keep the liquid and vapour phases of the refrigerant in the right places. Similarly, the motor driving the system is lubricated using a gravity-based system.
But now, Leon Brendel and colleagues have developed a refrigeration system that does not rely on gravity and should operate in microgravity environments such as the ISS. In their lab, they have shown that the fridge will operate upside down – or at any angle, for that matter.
Parabolic flights
The next step is for Brendel and four other members of the team is to fly with their fridge on parabolic flights run by the company ZERO-G, which uses a specially outfitted A310 to create a microgravity environment for about 22 s.
“This is a once-in-a-lifetime opportunity for me. I can’t wait to board the plane,” says Brendel in the video above.