As the Earth’s average temperature continue to rise, those of us in already-warm climates may find ourselves increasingly tempted to crank up the A/C. But traditional air conditioners are huge consumers of energy: According to the U.S. Department of Energy, residential air conditioning accounts for 16 percent of all household electricity use in the United States.
One day in the not-too-distant future, magnetic air conditioners may help us keep our homes cooler inside without making temperatures hotter outside. A traditional air conditioner works by changing a liquid refrigerant to a gas (absorbing heat from the outside air in the process), then compressing and cooling the gas to convert it back to a liquid. Magnetic air conditioners take an entirely different approach to cooling, using magnets instead of compressors and refrigerants to cool the surrounding air.
The Magnetocaloric Effect
Magnetic air conditioners are based on a phenomenon known as the magnetocaloric effect. Magnetic materials heat up when they are exposed to a magnetic field, then cool down when the field is removed. The magnetocaloric effect was first observed in iron samples by a German physicist named Emil Warburg in 1881, but the change in temperature was too small for any practical application. In recent years, however, separate groups of researchers have developed magnetocaloric metal alloys that produce a significantly larger magnetocaloric effect at room temperature.
How will magnetic air conditioners work?
Magnetic air conditioners cool the air by quickly and repeatedly exposing a magnetocaloric material to a magnetic field. In one prototype designed by Astronautics Corporation of America in conjunction with the U.S. DOE’s Ames (Iowa) Laboratory, a wheel containing the rare-Earth element gadolinium spins through the field of a stationary magnet. As the disk spins, the gadolinium alloy heats up, then cools as it passes through a gap in the field, cooling the water that surrounds it as it makes its trip.
Environmentally Friendly Technology
In a magnetic air conditioner, the alloy acts as the “refrigerant,” and plain old water provides the heat transfer, eliminating the need for the decidedly unfriendly hydrochlorofluorocarbons (HCFCs) used in traditional air conditioners. While the earliest magnetocaloric alloys were either toxic or prohibitively expensive, the latest magnetocaloric materials are cost-effective and environmentally safe.
Magnetic air conditioners do require electricity, but the motor that spins the disk containing the magnetocaloric alloy is expected to be much more efficient than the compressor required to run a traditional air conditioner. According to a 2011 article in Scientific American, Astronautics hopes to have a prototype by 2013 that uses just two-thirds as much electricity as a conventional air conditioner to provide the same amount of cooling.
Is there a magnetic air conditioner in your future?
In addition to the researchers mentioned above (Astronautics and DOE), several private companies, universities and government agencies around the world are exploring magnetic cooling technology for industrial and domestic applications including air conditioning, refrigeration and climate control.
The National Laboratory for Sustainable Energy at the Technical University of Denmark runs its own “MagCool” project, while research at Penn State and other U.S. universities has advanced the understanding of magnetocaloric principles, helping us understand why one material might cool more efficiently than another. In 2009, BASF and Delta Electronics announced a corporate partnership to develop new magnetocaloric cooling systems and “explore the opportunities of magnetocaloric power generation.” But as much as we’d love to get our hands on this new technology today, commercial availability of magnetic air conditioners is still at least a few years away, and the first uses will most likely be industrial rather than residential.