Is magnetic cooling the future of cool?

Scientists have attempted for years to push magnetic cooling over the gap between fundamental research and applied technology. One of these scientists is Vitalij Pecharsky. Twenty years ago he and fellow Ames Laboratory scientist Karl A. Gschneidner Jr. discovered a gadolinium alloy that allowed magnetocaloric cooling to occur at room temperature. He is leading an effort today to finally advance magnetic cooling into homes and businesses. “The first big question is whether this technology is still worth pursuing, and the overwhelming sentiment is ‘yes,’” Pecharsky says. “The potential gains in energy efficiency are too significant to ignore.”

Cooling eats up as much as one quarter of US daily energy consumption, according to the Department of Energy. Magnetic cooling works by exploiting the magnetocaloric effect, a temperature change of a material caused by exposing it to a changing magnetic field. Duane Johnson, chief research officer at Ames, says it could reduce by 20 to 30 percent the energy cost of refrigeration. “That’s roughly equivalent to the US import of oil every day, energy-consumption wise. The potential economic and societal impact is enormous, if you think about all the ways in which we use cooling technology.”

Earlier this year, Pecharsky and Johnson helped organize “Advancing Materials for Efficient Cooling,” a workshop where academics, national lab scientists and industry representatives met to discuss the limits of electrocaloric, elastocaloric and magnetocaloric solid state cooling. “Everyone agrees we need better materials, it’s as simple as that,” Pecharsky says. “We have only a few families of materials that have a reasonable magnetocaloric effect. Almost 20 years ago we called it giant—a giant magnetocaloric effect. Now we know that it was just reasonable, even though at that time it was just about the strongest known. We could make a device with these reasonable materials, but in order for them to become commercially successful, we will need stronger effects that can be triggered by smaller fields.”

For a consumer, a magnetic refrigeration system would appear to operate much like the traditional vapor-compression models used in homes and businesses today. “But for the manufacturer this is a radical departure,” says Pecharsky, “replacing a compression unit with an entirely different system. Current refrigeration technology is highly refined, relatively inexpensive to build and cost-effective to operate. Until science can provide them and their consumers with a big advantage, it won’t be financially viable for them to retool production.”

Johnson says the key to attracting manufacturers is developing materials that are controllable within a range of temperatures for which various forms of cooling systems are used. Pecharsky concurs. He believes the improvement in materials wouldn’t need to be a large one to push the technology toward successful commercialization. “If we could incrementally improve the magnetocaloric effect using inexpensive and readily available elements, it wouldn’t even begin to push the theoretical performance limits of these materials and would still easily be the more efficient technology,” he says. “Scientifically speaking, I am confident we can get there.”