Ames Laboratory, U.S. Department of Energy, Ames, Iowa
Ames Laboratory, U.S. Department of Energy, Ames, Iowa
AMES, Iowa -- Two scientists at the U.S. Department of Energy's Ames Laboratory at Iowa State University have earned DOE honors for discoveries that could revolutionize the future of refrigeration.
Karl A. Gschneidner Jr., senior scientist at the Laboratory, and Vitalij K. Pecharsky, associate scientist, received the 1997 Materials Sciences Award for "Significant Implication for Department of Energy Related Technologies" in metallurgy and ceramics.
The scientists discovered a new class of materials made of a gadolinium-silicon-germanium alloy that are the key to magnetic refrigeration systems, which are more energy-efficient and environmentally friendly than current gas-compression coolers. The new materials also broaden the practical applications of magnetic refrigeration and make the technology more cost effective.
Magnetic refrigeration is based on the magnetocaloric effect -- the ability of some metals to heat up when they are magnetized and cool down when removed from the magnetic field. Conventional systems use liquids that are expanded and compressed to cool the air inside the refrigeration unit while drawing the warmer air outside. However, the liquids most commonly used are either chlorofluorocarbons, which have been linked to ozone depletion, or ammonia.
"One of the driving forces behind this is that people are worried about the greenhouse effect and global warming, and they want to cut down on the emissions from power plants," says Gschneidner, an ISU Anson Marston distinguished professor in materials science and engineering. "Obviously, if you can save 30 percent of the electricity to power all of the air conditioners, refrigerators, freezers and other refrigeration equipment, that means a lot less carbon dioxide and other environmentally unfriendly substances going into the atmosphere."
Because it eliminates the need to expand and compress a liquid, magnetic refrigeration consumes less electricity and can operate at 60 percent efficiency, or greater. The maximum efficiency of conventional systems is about 40 percent, but most units run at about 25 percent.
The materials discovered by Gschneidner and Pecharsky are two to 10 times more effective in their cooling power than prototype alloys. Also, their operating temperature can easily be changed over a wide range -- from about 30K (-400 F) to 290K (65 F) -- without losing the magnetocaloric effect.
The discovery helps make magnetic refrigeration more competitive with conventional technology. Gschneidner and Pecharsky teamed with Astronautics Corporation of America last year to unveil the first gadolinium-based magnetic refrigeration unit. It has been operating since December 1996, far surpassing the few days of operation recorded by similar units. It has also achieved cooling power 20 to 1,000 times greater than previous units.
Magnetic refrigeration is expected to be commercially available in five to 10 years. Its initial uses will likely be for climate control in buildings and large-scale refrigeration. The wide temperature span of magnetic refrigeration could also cut the cost of producing liquid hydrogen, a clean and endless alternative fuel source. It may also expand into smaller-scale applications, such as air conditioning for homes and cars.
Pecharsky adds that magnetic refrigeration "has a great potential to be scaled down to miniature applications, which is impossible with gas compressors."
Although magnetic refrigeration systems will cost more than conventional systems, Gschneidner says the energy savings will earn back the difference within five years. "And as the efficiency of magnetic refrigeration improves, the savings will come faster," he adds.
The Materials Sciences Awards are given annually to recognize scientists at DOE laboratories throughout the country for outstanding research. "We think we're doing good research, but it's always nice to have other people recognize your efforts," Gschneidner says.
Ames Laboratory is operated for the DOE by ISU. The Lab conducts research into various areas of national concern, including energy resources, high-speed computer design, environmental cleanup and restoration, and the synthesis and study of new materials.
Contact: Karl Gschneidner
ph: 515-294-7931
Susan Dieterle
ph: 515-294-1405
Last revision: 4/17/98 sd
Home | Comments | Search | Disclaimer