A while back I heard a reference in passing to building a solar water heater using the radiating coils off the back of a dead refrigerator. (one that has already lost it's charge of course) I guess the idea was that the tubing is already fixed in a backing and held in position. Just tack the whole sheebang into a black-painted, window covered box and plumb it in.

The problem: I can't for the life of me remember where I heard this. I can turn up no references in archives, or on the internet. Has anyone else heard of doing this? Perhaps even tried it? or abandoned it as unfeasable...

What do you think?

-- James in ID (jlfinkbeiner@yahoo.com), February 20, 2002

Answers

Jack: I think I remember that from an old TMEN issue. I've never tried it but my guess is it would work, but not well. The reason is the tubes in the refrigeration condensor are so small that it would be difficult to get a sufficient amout of water thru it to do much good.

On the other hand if it were to be used during a period of minimal hot water demand so as to give it a chance to build up temperature it might help in that case. Couldn't say for sure in either case.

-- john (natlivent@pcpros.net), February 21, 2002.

I think it was a M.E.N. article. The idea is to have the collector plumbed into an insulated tank, and it slowly heats during the day. The tank should be above the collector a minimum of 18 inches to circulate automatically. The best time to use the energy stored this way would be just before the temp starts to drop,(maybe 3-4 pm?) whether you're using the heated water "as is" or using it as a pre- heater going into your regular hot water heater.

-- IveyNelson (iveynelson@aol.com), February 21, 2002.

I agree with John, it should work, but not very well. The tube is only 1/4", or maybe 3/8" at most, with a large number of fins containing a small area (to radiate heat, not absorb it). Just opposite of what you want, a large diameter tube, 3/4" or 1" with one or two large surface area fins. You could try an experiment -- hook the coil up to a small water pump (low pressure 1/4' tube, like a evap cooler pump) and use a bucket of water as your storage tank. See if a larger scale setup would be worth while. The results would be interesting - let us know what you find out.

-- Joe (CactusJoe001@AOL.com), February 21, 2002.

I buuilt a pool heater with black plastic tubing and a black box with a window over it,,worked great

-- Stan (sopal@net-port.com), February 21, 2002.

Interesting concept, does anyone know of a web site that allows you to play/calculate such such things?

I'm sure that there are formulas for figuring such things out, I just need a very user friendly format, never liked math enough to want to be an engineer.

-- BC (desertdweller44@yahoo.com), February 21, 2002.

James: I'm not an engineer but in response to what BC said here's a coupla tips to get some idea of what the coil is capable of before going to all the trouble, only to find out it ain't gonna work.

1 btu = the amount of heat necessary to raise the temperature of 1 pound of water 1 degree F

1 gallon of water = 8(?) pounds

You'll need some way of measuring the flow of water in gallons/minute thru the coil after you hook up some kinda pump. Measure the temperature of the water going into the coil and the temp coming out of the coil.

For example if the temp rise was 10 and the flow rate was 1 gallon/minute then that'll equate to 80btus/minute. Multiply by 60 for btus/hr etc.

Another thot for that frig carcass is to use it as a breadbox solar water heater. Remove the door. Install a hot water heater core (uninsulated tank) in the frig compartment, paint it flat black, and put some glazing material where the door used to be.

-- john (natlivent@pcpros.net), February 21, 2002.

John is right.

1 btu = the amount of heat necessary to raise the temperature of 1 pound of water 1 degree F

1 gallon of water = 8(?) pounds

Now taking this into consideration....

1 average size chicken gives off 8 BTU's an hour, so taking that into consideration, you can roost X# chickens on your system to keep that water warm!

If you also take into consideration all the poo the chickens will generate, throw some organic matter on top of that, composting will begin and you willhave warm water all day while the chickens are away from their nightly roost eating.

-- LurkyLu (lurkylu@yahoo.com), February 22, 2002.

Lu: Thats 8 btus/LB/HR

-- john (natlivent@pcpros.net), February 22, 2002.