Einstein's green refrigerator making a comeback

September 25, 2008 by Lisa Zyga, Phys.org weblog
Einstein Refrigerator
In 1930, Einstein and Leo Szilard designed a refrigerator that required no electricity and had no moving parts.

While almost everybody knows how Einstein revolutionized physics with his theories of relativity, many people may not know that the great scientist had a domestic side, too. Well, sort of - in 1930, Einstein and his former student Leo Szilard designed a refrigerator that required no electricity and had no moving parts. However, as refrigerator technology became more efficient, Einstein's design was nearly forgotten.

Now, Malcolm McCulloch, an electrical engineer at Oxford, is trying to bring Einstein's refrigerator back. McCulloch explains that the design is environmentally friendly and could prove especially useful in developing countries, where demand for cooling appliances is quickly increasing.

McCulloch's team has recently built a prototype of Einstein and Szilard's refrigerator. Instead of compressing man-made greenhouse gases called freons, as typical refrigerators do, the prototype uses pressurized gas to keep items cold. The refrigerator just requires a way to heat the liquids, and McCulloch has been working on developing a solar energy system to meet this requirement.

The refrigerator is based on the idea that liquids boil at low temperatures when the surrounding air pressure is low.

"If you go to the top of Mount Everest, water boils at a much lower temperature than it does when you´re at sea level, and that´s because the pressure is much lower up there," McCulloch said.

In their refrigerator prototype, the scientists filled a flask with liquid butane (which is also commonly sold as a liquid in cigarette lighters and as a gas for cooking). Then the scientists introduced a new vapor to decrease the air pressure, which decreases the liquid boiling temperature, causing the butane to boil. As the butane boils, it takes energy from the surroundings, and lowers the temperature inside the refrigerator.

Although Einstein and Szilard´s original design was not as efficient as the freon refrigerators that replaced them, McCulloch plans to improve the design by using different kinds of gases. He predicts these improvements could quadruple the refrigerator´s efficiency.

The fact that the refrigerator has no moving parts could also be advantageous, he explains, as it would require minimal maintenance and so could be particularly useful in rural areas.

McCulloch emphasizes that the refrigerator is still just a prototype, but he hopes to one day commercialize it. The work is part of his team's three-year project to develop robust appliances that can be used in locations without electricity.

via: The Guardian

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4.8 / 5 (5) Sep 25, 2008
4.6 / 5 (7) Sep 25, 2008
Einstein refrigerators are supposed to be less lethal (no moving parts) but haven't some still leaked and killed their owners with concentrated ammonia fumes?

I'm not saying they have, just raising the question, I know a little about them but not much...
4 / 5 (2) Sep 25, 2008
This article was rather unclear... It says there is no need for electricity, but then posits a need for solar cells?

Rather confusing, plus they didn't really explain what the mechanism for heat transport is...
5 / 5 (5) Sep 26, 2008
It doesn't need electricity, but needs a way to heat the gases. Solar thermal power could be used for heating, which is not solar electric cells, but the simpler collector method.
4.8 / 5 (4) Sep 26, 2008
Check out this article about the Zeer_Pot - an invention by Mohammed Bah Abba, a teacher from Nigeria. It keeps food fresh without electricity, using wet sand and evaporative cooling:
not rated yet Sep 26, 2008
Dometic makes Refrigerators and Freezers that are sealed and use an Ammonia Cycle and propane or electricity and has no moving parts. Servel used to produce this type of refrigerator for rural areas.
not rated yet Sep 26, 2008
these types of refridgerators are already in wide use in RVs. Nothing new here.
not rated yet Sep 26, 2008
"Coool" :)
not rated yet Oct 03, 2008
This is similar to the gas adsorption refrigerator. These use ammonia, water and hydrogen. It seems the Einstein version replaces the hydrogen with butane. In either case, the partial pressure of hydrogen is much higher on the evaporator side than the condensor side. This reduces the partial pressure of ammonia, causing it to boil. The key to the operation is the hydrogen (or butane) is not soluable in water, so it can't cross a water trap boundary. Here's a link that explains all this:
not rated yet Oct 09, 2008
I have done a lot of research on this topic; the Einstein cycle is scientifically different from the adsorption cycle. The Einstein cycle uses the ammonia to make the butane evaporate, and condense due to partial pressure. This is the complete opposite of the adsorption cycle. The Einstein cycle is reversible like the compression cycle ware the adsorption cycle is not.

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