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Old 11-25-10, 11:36 AM   #14
AC_Hacker
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Quote:
Originally Posted by Ryland View Post
So if Ben takes his 40 gallon tank, puts Calcium Chloride in it and hooks that to the wood stove then he could heat it up to a higher temp and get more out of it then if he had heated the 210 gallon tank of water and without killing the fish.
Yes, that would be correct... but I can't be responsible for the fish. The phase change material, in this case a Eutectic Salt Calcium Chloride would store more energy in the temperature range discussed.

40 gallons of water converted to quarts = 40 x 4 = 160 quarts

Since the phase change of hydrated calcium chloride happens at about 82 degrees, and the heat taken up and released in changing from a solid to a liquid is about 237.8 BTU per quart,

160 x 237.8 = 38,048 BTU

I'm not sure what the specific heat of hydrated calcium chlporide is, but there would be heat taken up and released both above and below the phase change temperature. I seem to remember that the specific heat of a similar PCM material was about half that of water. But the serious action (heat storage and release) takes place at the phase change temperature, and since 82 F is very close to the desireable comfort level for humans, it's worth looking into.

There was a ton of work done by Mária Telkes and others on another similar PCM material called Glauber's Salt, but there was a problem with long-term reversability. Turns out that Glauber's Salt (AKA: Sodium sulfate deca-hydrate, or Na2SO4·10H2O) over time would begin to change into Sodium sulfate hexa-hydrate (Na2SO4·6H2O), also a phase change material only with a temperature of phase change that was outside the comfort level of humans. In spite of all the work and all the patents the long-term reversability was not overcome.

Nevertheless, there is a home high in the mountains of Utah, built by a guy named David Allen that uses several solar energy storage techniques, one of which uses Glauber's Salt. He obtained his PCM material here.


He used black ABS tubes with the PCM inside, and glued caps to both ends, and arranged the tubes in a rack that was hit by full sunshine every day (see image above, #5) and released it's stored heat to the rest of the house during the non-sun hours. By the way, the heat is self-circulated to the rest of the house without the use of mechanical blowers due to the intentional design of the house. Really, really clever.

BTW, the image above is hyperlinked to the page that discusses the overall design.

But, regarding PCM and Eutectic Salts, Calcium Chloride Hexahydrate, seems to hold the best promise. That's why I posted the patent. So, since the winter is upon us, and driveway ice-melting products are available in the stores, it's a good time to do some experiments with the stuff.

(* I like the idea of ABS tubes of PCM material stored vertically in a water bath, inside of a chest-type freezer. That would be a cheap way to get the structure, the insulation, the re-purposing of junk, etc. *)

Regards,

-AC_Hacker
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Last edited by AC_Hacker; 11-25-10 at 12:05 PM..
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