What's Hot in Refrigeration
Green refrigeration is a twofer: It eliminates harmful chlorofluorocarbons (CFCs) that eat away at the ozone layer and can save big bucks on your utility bill, since refrigerators use more electricity than any other household appliance.
New Energy Star refrigerators represent a big improvement on old-school energy guzzlers, but what about not using any electricity at all? A recent article in Scientific American points that that the scientific principle making refrigeration possible doesn’t need electricity. Making cold is as simple as sweating.
The key is the energy exchanged when liquids turn to vapor and vice versa—the process that cools you when you sweat. By far the most common approach, the one used by the refrigerator in your house, uses an electric motor to compress a refrigerant—say, Freon—turning it into liquid. When the pressure created by the compressor is released, the liquid evaporates, absorbing heat and lowering the temperature.
Absorptive chillers like solar refrigerators use a heat source rather than a compressor to change the refrigerant from vapor to liquid. The two most common combinations are water mixed with either lithium bromide or ammonia. In each case, the refrigerating gas is absorbed until heat is applied, which raises the temperature and pressure. At higher pressure, the refrigerant condenses into liquid. Turning off the heat lowers the pressure, causing that liquid to evaporate back into a gas, thereby creating the cooling effect.
Don’t worry: It’s simpler than it sounds--and innovators have begun churning out greener technologies almost as fast as a Sub-Zero produces ice. Solar refrigerators are being used in areas with limited access to electricity, but in the U.S., which accounts for most of the world's electricity use, the technology has made few inroads. Luckily, it won’t take a quantum leap to get there: Einstein himself invented a non-electric refrigerator back in 1930, and electrical engineers at Oxford are working hard to bring it back.