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Inside Iowa State
July 23, 1999

Prototype in the works

by Susan Dieterle, Ames Lab Public Affairs
Every time Karl Gschneidner Jr. and Vitalij Pecharsky tell someone about magnetic refrigeration technology, they hear the same question: "Where can I see it?"

The scientists at the U.S. Department of Energy's Ames Laboratory have explained that they haven't had the funding to build a working prototype. But that's about to change.

Ames Laboratory and Milwaukee-based Astronautics Corp. of America have embarked on a three-year project to build a prototype rotary magnetic refrigeration unit.

Through a cooperative research agreement, the energy department will give $750,000 toward the prototype project. Astronautics, a leader in magnetic refrigeration technology, will match that amount through in-kind contributions of personnel, research, services and facilities.

"Building the prototype is a crucial step in moving magnetic refrigeration technology into the marketplace," said Gschneidner, an Ames Lab senior scientist and distinguished professor of materials science and engineering.

Ames Lab and Astronautics have collaborated for the past eight years. In 1996, they built a proof-of-principle apparatus demonstrating that magnetic refrigeration was a reliable, competitive technology. It operated for 18 months, achieving cooling power 20 to 100 times greater than previous units.

If successful, the prototype would be the first magnetic refrigerator capable of sustained operation and generating enough cooling power for commercial applications.

The technology is based on the magnetocaloric effect -- the ability of some materials to heat up when magnetized and cool when removed from the magnetic field. Using these as refrigerants would provide an environmentally friendly alternative to volatile liquid chemicals, such as chlorofluorocarbons and hydrochloro-fluorocarbons, used in traditional vapor-cycle cooling systems.

Gschneidner said initial findings indicate that magnetic refrigeration is about 20 percent more energy efficient than traditional systems. Although magnetic refrigeration technology initially would cost more, consumers could earn back the difference within about five years through energy savings.

The scientists have discussed a system that would move the refrigerant materials continuously through high and low magnetic fields on a rotating disc. Water or antifreeze will be used as the heat-transfer fluid between the magnetic refrigerant and the heat exchangers.

Gschneidner, Pecharsky and senior physicist David Jiles will concentrate on optimizing the performance of the alloys, and developing a source for the magnetic field that is more cost-effective and convenient than super-conducting magnets. Astronautics will design, build and test the prototype.

Large-scale applications using magnetic refrigeration, such as commercial air conditioning and supermarket refrigeration systems, could be available in five to 10 years, Gschneidner said. In 15 years, the technology could be available in home refrigerators and air conditioners.

Gschneidner and Pecharsky also are investigating magnetic refrigeration for use in air conditioning systems for electric vehicles.

Gschneidner said the outward appearance of a magnetic refrigerator probably won't change very much.

"We would just replace the compression system with the magnetic refrigeration system," he said. "It probably wouldn't look much different from the outside."

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Revised 07/23/99