by Aaron Beth
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The future of refrigeration technology has been within our grasp for more than 80 years. Since the early 1920s and into the 1930s several prominent inventors (Albert Einstein among them) were developing green technologies capable of reducing green house gases long before green house emissions were part of the American psyche.
Aside from developing the theory of relativity and discovering the law of the photoelectric effect, Einstein, along with Hungarian physicist and former student Leo Szilard, collaborated on ways to improve home refrigeration technology. Their invention has been termed the “Einstein Refrigerator.”
The Einstein Refrigerator was a modified version of an absorption refrigerator invented in 1922 by two students, Baltzar von Platen and Carl Munters of the Royal Institute of Technology in Stockholm, Sweden. It had no moving parts and produced “cold” from a heat source such as propane, electricity, or kerosene. Platen and Munters’ invention was put into production in 1923 by the Swedish company AB Arctic. Electrolux, the world’s second largest appliance company next to Whirlpool, purchased AB Arctic in 1925, and began selling units worldwide. In that same year Servel, an American company, purchased the rights to manufacture gas refrigerators exclusively in the U.S.
A side note: I was fortunate to have serviced a Servel refrigerator in the late 60s. It was a single-pressure absorption refrigerator, had no moving parts—not even a circulating fan, and did not require electricity to operate. It was noiseless and had a small burner similar to a gas hot water heater underneath the unit, as well as a gas line connection.
The Einstein Refrigerator had four main parts: boiler, condenser, evaporator, and absorber. The unit charge consisted of a quantity of ammonia, water, and butane. Einstein and Szilard obtained a patent for their invention on November 11, 1930.The Einstein Refrigerator was not immediately put into production, however. The Swedish company AB Electrolux quickly bought up the patent to protect its own absorption refrigeration technology. And despite the breakthroughs, Einstein and Szilard’s refrigerator was shelved in 1930 in favor of a new technology; vapor/compression utilizing hydrocarbon refrigerants (better known as freon)became the industry standard. Now, concerns over ozone-depletion and greenhouse gases are warranting a new look at Einstein and Szilards invention.
Malcolm McCulloch, an electrical engineer from Oxford, whose passion is green technology, is leading a project to revive Einstein’s invention. McCulloch believes that by modifying the design and replacing the ammonia gas Einstein used, he’ll be able to improve upon Einstein’s efficiency by up to 400 percent. Thinking forward, McCulloch wants to insert a solar powered heat pump into the non-electric refrigerator. “No moving parts is a real benefit because it can operate without maintenance. This could have real advantages in remote areas,” he said.
Magnetic refrigeration is another example of green technology on the rise. It’s a cooling system based on the magnetocaloric effect, which was first observed in 1917 by French physicist Pierre-Ernest Weiss and Swiss physicist Auguste A. Piccard. The first working magnetic refrigerators were constructed by several groups beginning in 1933 and were developed for cooling below about 0.3K (-458.86F). Instead of ozone-depleting refrigerants and energy-consuming compressors found in conventional vapor-cycle refrigerators, this style of refrigerator uses gadolinium metal that heats up when exposed to a magnetic field, then cools down when the magnetic field is removed.
At the U.S. Department of Energy’s Ames Laboratory, researchers have successfully demonstrated the world’s first room temperature, permanent magnet, magnetic refrigerator. The refrigerator was developed by Milwaukee-based Astronautics Corporation of America as part of a cooperative research and development agreement with Ames Laboratory.
“We’re witnessing history in the making,” Ames Laboratory senior metallurgist Karl Gschneidner Jr. says of the revolutionary device. “Previous successful demonstration refrigerators used large superconducting magnets, but this is the first to use a permanent magnet and operate at room temperature.”
“Our fridge works, from a conceptual point of view, in a similar way [to freon fridges] but instead of using a gas we use a magnetic field and a special metal alloy. When the magnetic field is next to the alloy, it’s like compressing the gas, and when the magnetic field leaves, it’s like expanding the gas. This effect can be seen in rubber bands: when you stretch the band it gets hot, and when you let the band contract it gets cold,” explains managing director Neil Wilson.
Initially tested in September 2004 at the Astronautics Corporation of America’s Technology Center in Madison, Wisconsin, magnetic refrigeration technology is undergoing further testing. The goal is to achieve larger temperature swings that will allow the technology to provide the cooling power required for specific markets, such as home refrigerators, air conditioning, electronics cooling, and fluid chilling.
Researchers working in GE labs have used a special magnetic material to achieve temperatures cold enough to freeze water. The breakthrough system, which is projected to be 20 percent more efficient than current refrigeration technology, could be inside your fridge by the end of the decade.
The system uses a water-based fluid flowing through a series of magnets to transfer heat, rather than a chemical refrigerant and a compressor, significantly lowering any harm to the environment and simplifying the process of recycling of old refrigerators. This technique, cooling without adding extra energy by using magnetism, can be used to attain extremely low temperatures, as well as the ranges used in common refrigerators. “This is a big deal,” says Venkat Venkatakrishnan, a leader of the research team. “We are on the cusp of the next refrigeration revolution.”
GE teams in the U.S. and in Germany decided to build a cascade from special magnetic materials, where each step could lower the temperature just slightly. “We are taking a chunk of heat and pushing it down the ladder, from the cold insides of the refrigerator to the warm room outside” Venkatakrishnan says.
It took them five years to achieve cooling of just two degrees Fahrenheit. Not much, but enough to show that the idea was working. “We started with a huge machine that didn’t do very much, but we’ve moved to a prototype that’s about the size of a shopping cart,” says Michael Benedict, design engineer at GE Appliances. “The goal is to get this thing down to a size where you can put it in the refrigerator.”
That goal got closer when the team’s materials scientists developed a new type of nickel-manganese alloy for magnets that could function at room temperatures. Design engineers arranged the magnets in a series of 50 cooling stages. Today they are capable of reducing temperature by 80 degrees. “We are focusing on magnetic refrigeration as a potential replacement for all the refrigeration technologies currently in use,” Benedict says.
The GE team has run demonstrations for experts from the Department of Energy, attended by staffers from the White House and the EPA. “Nobody in the world has done this type of multi-stage cooling,” Venkatakrishnan says. “We believe we are the first people who shrunk it enough so that it can be transported and shown. We were also the first to go below freezing with the stages.”
The team is now working to achieve a 100-degree drop in temperature at low power. “We’ve spent the last 100 years to make the current refrigeration technology more efficient,” Venkatakrishnan says. “Now we are working on technology for the next 100 years.” (Click here to see a working model of a GE magnetic refrigerator in action.)
The potential for greener refrigeration technology is currently being developed in several laboratories around the world, and the results look promising. If I had to bet on which technology will revolutionize the industry, I’d go with magnetic—it’s cleaner, safer, and more efficient. Whichever way the technology goes, it’s certainly time to take a new look at an old discovery.