A new eco-friendly refrigeration device has been developed that offers record-breaking cooling performance and is set to transform industries reliant on cooling while reducing global energy use.
Researchers at the School of Engineering of the Hong Kong University of Science and Technology (HKUST) have boosted efficiency by over 48 per cent. The new elastocaloric cooling technology opens a promising avenue for accelerating the commercialisation of this disruptive technology and addressing the environmental challenges associated with traditional cooling systems.
Traditional vapour compression refrigeration technology relies on refrigerants with a high global warming potential. Solid-state elastocaloric refrigeration based on latent heat in the cyclic phase transition of shape memory alloys (SMAs) provides an environmentally friendly alternative, with its characteristics of greenhouse gas-free, 100 per cent recyclable and energy-efficient SMA refrigerants. However, the relatively small temperature lift between 20 and 50 K, a critical performance indicator of the cooling device’s ability to transfer heat from a low-temperature source to a high-temperature sink, has hindered the commercialisation of this emerging technology.
To overcome the challenge, the research team led by Professor SUN Qingping and Professor YAO Shuhuai from the Department of Mechanical and Aerospace Engineering has developed a multi-material cascading elastocaloric cooling device made of nickel-titanium (NiTi) shape memory alloys and broke the world record in its cooling performance.
They selected three NiTi alloys with different phase transition temperatures to operate at the cold, intermediate, and hot ends, respectively. By matching the working temperatures of each unit with the corresponding phase transition temperatures, the overall device’s superelastic temperature window was expanded to over 100K. Each NiTi unit operated within its optimal temperature range, significantly enhancing the cooling efficiency. The built multi-material cascading elastocaloric cooling device achieved a temperature lift of 75 K on the water side, surpassing the previous world record of 50.6 K. Their research breakthrough, titled “A Multi-Material Cascade Elastocaloric Cooling Device for Large Temperature Lift”, was recently published in Nature Energy, a top journal in the field.
Building on the success in developing elastocaloric cooling materials and architectures with many patents and papers published in leading journals, the research team plans to further develop high-performance shape memory alloys and devices for sub-zero elastocaloric cooling and high-temperature heat pumping applications. They will continue to optimise material properties and develop high-energy efficient refrigeration systems to drive the commercialisation of this innovative technology.
According to industry estimates, space cooling and heating account for 20 per cent of the world’s total electricity consumption and are projected to become the second-largest source of global electricity demand by 2050.
“In the future, with the continuous advancement of materials science and mechanical engineering, we are confident that elastocaloric refrigeration can provide next-generation green and energy-efficient cooling and heating solutions to feed the huge worldwide refrigeration market, addressing the urgent task of decarbonisation and global warming mitigation,” Prof Sun said.
Image: Hong Kong University of Science and Technology (HKUST)
