Chinese researchers make breakthrough in green cooling technology

BEIJING -- A group of Chinese researchers has achieved a breakthrough in refrigeration technology by discovering a new cooling effect that can help simultaneously realize low-carbon emission, high cooling capacity and high heat transfer efficiency, according to a study published on Thursday in the journal Nature.

Refrigeration technology is one of the cornerstones of modern society. Widely used vapor-compression cooling contributes to about 2 percent of China's GDP, but also consumes nearly 20 percent of its electricity and generates 7.8 percent of its carbon emissions.

To address the need for greater efficiency and emission reductions, researchers have in recent years developed solid-state caloric materials. These materials absorb and release heat via changes in pressure or magnetic fields, thus preventing emission concerns.

However, such materials have a fatal flaw, as solids don't transfer heat well, thereby making them inefficient when there is a need for large-scale use.

A research team led by Li Bing from the Institute of Metal Research, Chinese Academy of Sciences discovered the dissolution barocaloric effect in an NH?SCN salt solution. When pressure is applied to such a solution, solid NH?SCN precipitates and releases heat. In the event of depressurization, the salt rapidly dissolves in the solution while absorbing a large amount of heat.

At room temperature, the solution's temperature can drop by nearly 30 degrees Celsius within 20 seconds, with even greater cooling performance achieved at higher temperatures, far surpassing the capabilities of current solid-state caloric materials.

This new method unifies the refrigerant and heat-transfer mediums into a single fluid, achieving low carbon emissions, high cooling capacity and high heat transfer efficiency all at once, the study notes.

Based on this discovery, the team designed a four-step cyclic system including pressurization for heating, heat dissipation to the environment, depressurization for cooling, and delivery of cooling capacity.

Simulations show that a single cycle of this system can achieve 67 joules of heat absorption per gram of solution, with an energy efficiency as high as 77 percent, demonstrating significant potential for engineering and commercial applications.

The study not only provides a novel refrigeration principle, but also lays a critical scientific foundation for the development of efficient and environmentally friendly next-generation cooling technologies, such as cooling systems for large-scale data centers.

According to the Global Cooling Watch 2025 issued by UNEP, the cooling demand could more than triple by 2050 over 2022 level, which would almost double cooling-related greenhouse gas emissions.