Active Magnetic Regenerator Refrigerator
Summary:
In the early 1990s, SDIO gave seed money to the Astronautics Corporation of America (Milwaukee, WI) to continue development of Astronautics' low temperature (15 K to 7 K) cryogenic refrigeration technology for compact, lightweight space-based cooling systems. This work is being done primarily at the Astronautics Technology Center (Madison, WI). Astonautics spun off this work into an internally funded device that resulted in an active magnetic refrigerator prototype. The device, also developed in part with DOE funding, has terrestrial applications for large industrial cooling needs as well as domestic refrigeration and climate control technology (for electric vehicles). This technology has tremendous potential benefits over conventional refrigeration methods in terms of efficiency, impact on the environment, and inexpensive production of liquid hydrogen.
Technology Description:
The Astronautics Technology Center (Madison, WI) has developed a magnetic refrigerant based on the principle of magnetic cooling, or the magnetocaloric effect. Astronautics has developed a 500-watt prototype device called an active magnetic regenerator refrigerator (AMRR), which is currently used to cool a 20-gallon water tank. The refrigerant is comprised of spherical particles of gadolinium (Gd) spheres, a paramagnetic material that heats up as it enters a magnetic field and cools as it departs the field. In this case, a helium-cooled superconducting niobium-titanate magnet is used to provide a 5-Tesla magnetic field; the field induces magnetism in Gd spheres that are immersed in flowing water, which is the heat-transfer medium. The water heats and cools as the Gd is alternately magnetized and demagnetized.
One of the main benefits of the AMRR is that it uses water as a heat transfer fluid, replacing expensive and environmentally hostile chlorofluorocarbons. Another benefit is that the magnetocaloric effect is intrinsically highly efficient (nearly 100 percent Carnot efficiency because it is a thermodynamically reversible process). However, the necessary use of a heat transfer liquid reduces the practical Carnot efficiency to about 70 percent, which still compares favorably with the 25 to 60 percent efficiencies of conventional refrigerators. Department of Energy's (DOE) Ames Laboratory (Ames, Iowa) researchers Karl Gschneider and Vitalij Pecharsky have also worked with Astronautics on materials containing Gd alloyed with silicon (Si) and germanium (Ge) that have the potential to achieve even greater cooling capacities and higher efficiencies. The cooling capacity of the paramagnetic Gd alloy can be manipulated by varying the relative amounts of Si and Ge. Magnetocaloric devices also have wide operating ranges, on the order of 20 K (-425° F) to 300 K (80° F), depending on the heat transfer medium and operating regime.
MDA Origins:
SDIO contributed seed money through an Air Force (Wright-Patterson AFB) program to Astronautics to develop cryogenically cooled materials for space-based cooling
applications. Astronautics continued the effort with internal funding and a grant from DOE, resulting in the first tests of a magnetocaloric refrigerator in 1995.
Spinoff Applications:
Researchers have identified two chief application areas for environmentally friendly and highly efficient magnetocaloric refrigerators. The first area is large-scale commercial refrigeration and cooling, including refrigeration of supermarket display cases and the cooling of large office buildings and food warehouses. The second area comprises smaller-scale cooling needs such as central air conditioning for households and climate control systems for electric vehicles. Cooling systems for electric vehicles require a lot of electrical power, representing a significant drain on the vehicle’s battery supply. The operating range of electric cars can therefore be increased if their cooling systems can be made more efficient.
Commercialization:
Astronautics has presented to established automakers a proposal outlining a magnetocaloric source for electric vehicle cooling needs. Astronautics is interested in collaborating with players in the industry to bring the AMRR to market.
Company Profile:
Astronautics Corporation of America is a large commercial and government contractor based in Milwaukee, WI, employing approximately 2,300 people. Astronautics designs and manufactures high quality avionics instruments, displays, and guidance systems. Its products are used throughout the world in a wide range of military and commercial applications for ground, sea and aerospace. Astronautics' facilities are located in Wisconsin, New Jersey, North Carolina,Texas, Mexico, and overseas.
The Astronautics Technology Center in Madison, WI, designs and develops cryogenic systems.
Contact Information:
Dr. Carl Zimm
Astronautics Corporation of America
Technology Center
5802 Cottage Grove Road
Madison WI 53718
Tel:608-221-9001
Fax:608-221-9104
email: zimm@astronautics.com
Dr. Karl Gschneider, Jr.
Anson Marston Distinguished Professor
Senior Metallurgist
Iowa State University Ames Laboratory
255 Spedding
Ames IA 50011-3020
Tel:515-294-7931
Fax:515-294-9579
email: cagey@ameslab.gov
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