By Joel Johnson at 6:35 am Mon, Dec 8, 2008
A prototype device from a team at Stanford acts as a super-charged, twenty-four-hour cold pack when heated over a fire and then left to cool. Its purpose? To keep vaccines at proper temperatures in areas with no electricity.
How a Zero-Electricity Fridge Will Bring Medicine to the Developing World [Esquire]
Nice! This is the opposite of the nice little hand-warmers that I have, where you boil them to set them, and then click a little button to heat them up again.
I’m a little confused by the physics, though. The hand-warmer is naturally two mirror chemical reactions, one endo-thermic (to re-set the solution) and one exo-thermic (to produce heat).
I’m guessing that this is just one long ento-thermic reaction, which gets kick-started by heating it high enough. Would it be theoretically possible to produce the same effect in a reaction that gets kick-started at room-temperature, thus creating a permanent cooling pack (from which, naturally, you could create a energy source, which would provide “free” energy until the entire world turns to ice…)
Nothing new here. A refrigerator similar to the one in article was available in the US in the 1930’s. (Sorry, I can’t find a web link)
Absorption refrigerators have been available for about a century and are still widely used in RV’s and other situations where electricity is problematic.
Most modern absorption refrigerators usually use natural gas or propane, but, like the refrigerator in the article, they can be designed to use any heat source.
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