Revolutionary environmentally friendly refrigerator breaks world performance record

HKUST’s new refrigerator breaks world records with a 75K temperature increase and 48% efficiency improvement using environmentally friendly materials.

Researchers from the School of Engineering at the Hong Kong University of Science and Technology (HKUST) have developed an environmentally friendly refrigeration device with record-breaking cooling performance. With an efficiency improvement of over 48%, the new elastocaloric refrigeration technology opens a promising path to accelerate the commercialization of this breakthrough technology and address the environmental problems associated with conventional refrigeration systems.

Challenges and innovations in refrigeration technology

Conventional vapor compression refrigeration technology is based on refrigerants with high global warming potential. Solid-state elastocaloric refrigeration technology based on latent heat in the cyclic phase transition of shape memory alloys (SMAs) offers an environmentally friendly alternative with its properties as greenhouse gas-free, 100% recyclable and energy-efficient SMA refrigerants. However, the relatively low temperature rise between 20 and 50 K, which is a key performance indicator of the refrigeration device’s ability to transfer heat from a low-temperature source to a high-temperature sink, has hampered the commercialization of this new technology.

World record in cooling efficiency

To meet this challenge, the research team led by Prof. Sun Qingping and Prof. Yao Shuhuai from the School of Mechanical and Aerospace Engineering developed a multi-material cascading elastocaloric cooling device made of nickel-titanium (NiTi) shape memory alloys, breaking the world record in its cooling performance.

They chose three NiTi alloys with different phase transition temperatures for cold-, middle- and hot-end operation. By matching the working temperatures of each unit to the corresponding phase transition temperatures, the superelastic temperature window of the entire device was extended to over 100 K and each NiTi unit operated within its optimal temperature range, significantly improving cooling performance. The multi-material cascading elastocaloric cooling device achieved a temperature rise of 75 K on the water side, surpassing the previous world record of 50.6 K. Their research was recently published in Natural energy.

Future prospects and environmental impacts

Building on the success in developing elastocaloric cooling materials and architectures with numerous patents and articles 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 pump applications. They will continue to optimize material properties and develop highly energy efficient cooling systems to advance the commercialization of this innovative technology.

Cooling and heating of spaces accounts for 20% of global electricity consumption. Industry estimates suggest that these areas will be the second largest source of global electricity demand by 2050.

“We believe that with the continuous advancement of materials science and engineering, elastocaloric cooling can bring about next-generation environmentally friendly and energy-efficient cooling and heating solutions in the future to serve the huge global cooling market and address the urgent task of decarbonization and curbing global warming,” said Prof. Sun.

Reference: “A multi-material cascaded elastocaloric cooler for large temperature rise” by Guoan Zhou, Zexi Li, Qiuhong Wang, Yuxiang Zhu, Peng Hua, Shuhuai Yao and Qingping Sun, May 23, 2024, Nature Energy.
DOI: 10.1038/s41560-024-01537-3