We’re caught in a vicious cycle of confronting rising temperatures across the planet and combating them with air conditioning — which in turn causes global warming. A problem worth throwing a lot of science at, if anything.
Fortunately, we may be close to a solution.
Researchers at the Hong Kong University of Science and Technology (HKUST) have developed an elastocaloric cooling device that they say is 48% more efficient than previous attempts.
Built on a cooling principle that is completely different from the vapor compression method that enables traditional air conditioners to do their job, this system completely eliminates the need for greenhouse gas emitting refrigerants in air conditioning units.
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What is Elasto?
It's also pretty new to me. The researchers' device works by using the elastocaloric effect. This is when a solid material reversibly changes shape and undergoes a phase transformation when an external mechanical force is applied or removed. Due to the difference in entropy between its two coexisting phases, the material can either cool down or heat up.
Now that you mention it, this sounds familiar
Yes, that's because you read it so well. The electrocaloric effect was first discovered in 1980 by physicists Rodríguez and Brown – but it wasn't thought to have any potential for cooling or similar applications.
More recently, we saw a breakthrough in September 2023 when HKUST researchers achieved cooling to 50 Kelvin. Not bad at all.
How is this new device better?
A team at the University of Hong Kong has developed a multi-material stepper using nickel-titanium (NiTi) shape memory alloys that can change shape when cold and return to their original shape when heated.
“They selected three NiTi alloys with different phase transition temperatures to operate at the cold end, intermediate end, and hot end, respectively,” the researchers explain. “By matching the operating temperatures of each unit with their corresponding phase transition temperatures, the overall superelastic temperature window of the device was extended to over 100 K, and each NiTi unit operated within its optimum temperature range, significantly improving cooling efficiency.”
This system allowed their devices to cool to a full 75 Kelvin without the need for harmful refrigerants. It also saves much more energy.
OK, so when are there better air conditioners?
It’s hard to say. But hopefully sooner than a bunch of glaciers melt. The amount of energy we use just to cool homes and buildings will more than double by 2050, according to the International Energy Agency, a French nonprofit that coordinates research and education on energy efficiency.
It will also be fun to see how much competition this will spur among researchers investigating similar energy-efficient technologies.
Last year, researchers at the Luxembourg Institute of Science and Technology developed a system based on the electrocaloric effect, in which materials such as ceramics and polymers undergo a reversible temperature change when an electric field is applied to them. Their device produced a temperature difference of 20 Kelvin without any observed degradation.
LIST's researchers note that much of the electricity used to power electrocaloric cooling devices could be reused and therefore highly efficient. The technology could also see applications such as cooling electric car batteries.
An article on the research was published in the journal Nature EnergyLet the cooling wars begin.
Source: HKUST