Air conditioning, refrigeration, and other cooling technologies account for more than 20 percent of today's global energy consumption, while the refrigerants they use have a global warming potential thousands of times greater than carbon dioxide. In a recent study in the journal Science, a team led by Maryland Engineering Professors Ichiro Takeuchi, Reinhard Radermacher, and Yunho Hwang introduced a high-performance elastocaloric cooling system that could represent the next generation of cooling devices.

Takeuchi calls it "a completely different, completely green, environmentally friendly cooling technology, which bypasses chemical refrigerants to essentially rely on pushing and pulling pieces of metal to create cooling."

Caloric materials—including magnetocaloric, electrocaloric, and elastocaloric materials—can undergo phase transition and release, and absorb heat upon application of various fields and mechanical forces. The key feature is the compression and release of fatigue-resistant nickel-titanium (NiTi) tubes configured in a versatile, multimode heat exchange architecture.

"More than a decade ago, we were just playing with a NiTi wire," Takeuchi said. "By stretching it, you could get a substantial cooling effect one could feel by hand. That was when we started thinking about applying the concept to a cooling device."

Video showing live operation of a multi-mode elastocaloric cooler (at 10x speed). Superelastic NiTi tube bundles are compressed using hydraulic actuators. In this configuration, there are two top bundles and two bottom bundles operated in concert in direct work recovery mode in order to deliver 150 W of cooling power. The left plot is monitoring the temperature of the cooling medium (water) at outlet points of the bundles (blue: top; red: bottom). The right plot shows the temperatures of the heat source (blue) and the heat sink (red) as a function of time. Credit: Maryland Engineering

The team says it's possible to improve the performance of its system enough to make the technology commercially viable within several years. A current prototype can produce 200 watts of cooling capacity, enough to power a compact wine fridge, with plans to expand to window units, whole-house cooling systems, and commercial HVACs eventually.

Source: Elastocaloric cooling system opens door to climate-friendly AC (phys.org)