Hong Kong Scientists Build Zero-Emission Freezer at -12°C

A team at Hong Kong University of Science and Technology has built a freezer that could help save the planet, one ice cube at a time.

Their new device reaches temperatures as cold as -12°C without using any of the harmful refrigerants found in nearly every freezer on Earth today. Instead, it uses a special nickel-titanium alloy that releases cooling energy when compressed, similar to how a rubber band feels warm when stretched quickly.

Professor Sun Qingping and his team published their breakthrough in Nature this month. The desktop-sized prototype successfully froze water into ice within two hours during outdoor testing. It maintained a stable temperature of -4°C even when the outside air hovered around room temperature.

Traditional freezers rely on chemicals called hydrofluorocarbons, which trap heat in our atmosphere far more effectively than carbon dioxide. The freezing industry alone pumps out roughly 330 million tons of CO2-equivalent emissions annually. That's like adding 70 million extra cars to the road every year.

The new technology works through three clever innovations working together. The team developed a super-elastic alloy with high nickel content that stays flexible even at -20°C. They paired it with a calcium chloride solution that won't freeze at sub-zero temperatures, allowing heat to transfer efficiently. Eight cascaded tube units create enough surface area to handle the extreme compression needed without breaking.

The device achieved an impressive 36-degree temperature difference, cooling from 24°C room temperature down to -12°C. At peak performance, it delivered 1.43 watts of cooling power per gram of material.

The Ripple Effect

This isn't just about better freezers. The technology opens a path to decarbonizing an industry the same size as air conditioning. Every supermarket, ice cream truck, medical facility, and home freezer could potentially switch to this emission-free alternative.

The timing couldn't be better. Global demand for freezing continues climbing as temperatures rise and populations grow. If widely adopted, this single innovation could prevent emissions equal to what 330 million tons of CO2 represents each year.

The research team is now working to scale up the technology from desktop prototype to commercial production. Unlike previous elastocaloric devices limited to room-temperature air conditioning, this system proves the technology can handle the demanding sub-zero temperatures the freezing industry requires.

Climate solutions often feel distant or theoretical, but this one is refreshingly concrete: a working freezer that makes ice without warming the planet.