spinnerholic
01-30-2009, 06:31 PM
January 30, 2009, 2:57 pm
By Nick Chambers
Go to http://greeninc.blogs.nytimes.com/2009/01/30/climate-friendly-refrigerator-magnets/?hp for graphics I couldn't copy. This sounds ~great~!
A magnetocaloric material (a) heats up when magnetized (b). When demagnetized and cooled (c) it experiences a sharp temperature drop (d). The property has promise as an everyday refrigerant. (Image: National Institutes of Standards and Technology)
Back in the 1980s, substances such as chlorofluorocarbons, or CFCs, which were used in everything from hairspray to refrigerators, were singled out as major causes of ozone depletion.
After the introduction of the Montreal Protocol, these ozone-depleting substances were phased out and replaced with substances deemed safer for the ozone — including hydrofluorocarbons, or HFCs.
Fast-forward 20 years. The ozone problem has largely faded to the back burner, but now we’re faced with a potentially larger environmental problem as we learn more and more about global warming. And guess what? HFCs happen to be tens of thousands of times more potent as greenhouse gases than carbon dioxide.
Of course, gases like HFCs account for less than 2 percent of annual emissions in the U.S., but their cumulative affect on the climate can be substantial.
Now it appears that researchers from the United States and China have discovered a new metal alloy that could make refrigeration using HFCs a thing of the past.
As illustrated above, the refrigeration technique works by using something called the “magnetocaloric effect.” In simplest terms, this describes the proclivity of some magnetic materials to heat up when they are placed in a magnetic field, and more important, to cool down sharply when they are demagnetized.
It is this temperature drop that can be substituted for the traditional gas refrigeration cycle using HFCs.
Magnetocaloric refrigeration techniques have actually been around since the mid 1930s. Up until this point, however, they have been restricted to industrial and scientific uses because of the incredible expense and toxicity of magnetocaloric materials, which can contain gadolinium and arsenic.
To get around these restrictions, researchers working at the National Institute of Standards and Technology developed a magnetocaloric metal alloy that functions at room temperature and doesn’t contain any particularly toxic materials.
The alloy the researchers discovered is a mixture of manganese, iron, phosphorus and germanium. Not only is this alloy much cheaper and less toxic than current magnetocaloric materials, it reportedly also rivals gas compression technology in terms of efficiency.
According to Qing Huang, an N.I.S.T. crystallographer, the team’s current findings are just the beginning, and the unique crystal structure of their alloy allows for further refinement.
“Understanding how to fine-tune this change in crystal structure may allow us to get our alloy’s efficiency even higher,” says Mr. Huang. “We are still playing with the composition, and if we can get it to magnetize uniformly, we may be able to further improve the efficiency.”
By Nick Chambers
Go to http://greeninc.blogs.nytimes.com/2009/01/30/climate-friendly-refrigerator-magnets/?hp for graphics I couldn't copy. This sounds ~great~!
A magnetocaloric material (a) heats up when magnetized (b). When demagnetized and cooled (c) it experiences a sharp temperature drop (d). The property has promise as an everyday refrigerant. (Image: National Institutes of Standards and Technology)
Back in the 1980s, substances such as chlorofluorocarbons, or CFCs, which were used in everything from hairspray to refrigerators, were singled out as major causes of ozone depletion.
After the introduction of the Montreal Protocol, these ozone-depleting substances were phased out and replaced with substances deemed safer for the ozone — including hydrofluorocarbons, or HFCs.
Fast-forward 20 years. The ozone problem has largely faded to the back burner, but now we’re faced with a potentially larger environmental problem as we learn more and more about global warming. And guess what? HFCs happen to be tens of thousands of times more potent as greenhouse gases than carbon dioxide.
Of course, gases like HFCs account for less than 2 percent of annual emissions in the U.S., but their cumulative affect on the climate can be substantial.
Now it appears that researchers from the United States and China have discovered a new metal alloy that could make refrigeration using HFCs a thing of the past.
As illustrated above, the refrigeration technique works by using something called the “magnetocaloric effect.” In simplest terms, this describes the proclivity of some magnetic materials to heat up when they are placed in a magnetic field, and more important, to cool down sharply when they are demagnetized.
It is this temperature drop that can be substituted for the traditional gas refrigeration cycle using HFCs.
Magnetocaloric refrigeration techniques have actually been around since the mid 1930s. Up until this point, however, they have been restricted to industrial and scientific uses because of the incredible expense and toxicity of magnetocaloric materials, which can contain gadolinium and arsenic.
To get around these restrictions, researchers working at the National Institute of Standards and Technology developed a magnetocaloric metal alloy that functions at room temperature and doesn’t contain any particularly toxic materials.
The alloy the researchers discovered is a mixture of manganese, iron, phosphorus and germanium. Not only is this alloy much cheaper and less toxic than current magnetocaloric materials, it reportedly also rivals gas compression technology in terms of efficiency.
According to Qing Huang, an N.I.S.T. crystallographer, the team’s current findings are just the beginning, and the unique crystal structure of their alloy allows for further refinement.
“Understanding how to fine-tune this change in crystal structure may allow us to get our alloy’s efficiency even higher,” says Mr. Huang. “We are still playing with the composition, and if we can get it to magnetize uniformly, we may be able to further improve the efficiency.”