Cold without the compressor: Boffins build better ice box

A thermoelectric material called CHESS is pretty cool

Scientists at Johns Hopkins and Samsung have developed a nano-engineered thermoelectric material that is twice as efficient at material-level cooling as existing alternatives, paving the way for broader adoption of solid-state refrigeration technology.

Commercial refrigeration and air conditioning tend to use compressors that pump vaporized refrigerant through a cooling system. The chemicals used in this process aren't great for the environment, and it's bulky and energy intensive at scale.

Thermoelectric cooling offers an alternative approach, sending electric current through specialized semiconductor material. It's used in wine coolers, mini-fridges, cooled seating, and a handful of other consumer products, but has limitations – it works in a narrower range of ambient temperatures, offers less cooling capability, and hasn't been compatible with high-volume semiconductor fabrication.

Researchers at the Johns Hopkins Applied Physics Laboratory (APL), in conjunction with Samsung Research engineers, have devised thin-film thermoelectric materials that deliver a twofold boost in material-level thermoelectric performance compared with bulk alternatives.

They describe their work in a paper published in Nature Communications, "Nano-engineered thin-film thermoelectric materials enable practical solid-state refrigeration."

The technology is called CHESS, which stands for controlled hierarchically engineered superlattice structures. According to Johns Hopkins, CHESS was initially developed for national security applications – cooling chips and engine components – and has been used to provide cooling in medical prosthetics.

The Nature Communications paper documents the researchers' claim that thin-film thermoelectric components are ready for mainstream refrigeration applications. The research team said it achieved thermoelectric cooling that was almost 100 percent more efficient at room temperature (300 K, ~80°F, ~27°C) than other thermoelectric materials. And when implemented in thermoelectric modules built with the CHESS materials, the efficiency improvement amounted to about 70 percent.

What's more, the CHESS thin-film material can be grown using metal-organic chemical vapor deposition (MOCVD), a scalable, industrial process. This should make it easier to commercialize – an effort that's already underway.

"Beyond refrigeration, CHESS materials are also able to convert temperature differences, like body heat, into usable power,” APL researcher Jeff Maranchi told the Johns Hopkins news service.

"In addition to advancing next-generation tactile systems, prosthetics and human-machine interfaces, this opens the door to scalable energy-harvesting technologies for applications ranging from computers to spacecraft – capabilities that weren’t feasible with older, bulkier thermoelectric devices." ®