Elastocaloric cooling a system for the future

University of Maryland researchers in the US have developed a high-performance elastocaloric cooling system they say could herald the next generation of cooling devices.

Eight years in the making, the prototype system relies on pushing and pulling pieces of metal to create cooling, rather than using a refrigerant circuit containing a working fluid.

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. Indeed, much work is being done to develop cooling devices using these materials.

The key feature of this system 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,” says team leader Professor Ichiro Takeuchi. “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.”

Small scale refrigeration systems such as wine coolers seem to be the best application in the initial stages. Takeuchi says the team plans to have a commercial wine cooler in several years.

According to the researchers, a current prototype can produce 200W of cooling capacity, enough to power a compact wine fridge. In the future, the team plans to expand the technology to window units, whole-house cooling systems, and eventually to commercial HVAC systems.

Its implementation is not without hurdles, however. One of the biggest challenges to its commercial viability is the driving mechanism.

“We are currently using a hydraulic actuator for compressing NiTi tubes,” Takeuchi says. “These actuators work, but they are too big and expensive to be used for cooling appliances, and have low energy efficiency.

“To get around this problem, we are developing new elastocaloric materials based on Cu, which can be driven with a smaller stress actuator. The other challenge is materials: we need new materials, and we need to be able to mass-produce them.”

Read the research paper “High-performance multimode elastocaloric cooling system” here.

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