I was thinking on the same line in using copper tubing or even plastic and use the reflective foil insulation as a heat shield. I also have an a pool pump I no longer use and thought I could pump a continuous flow of water through tubing and into the barrels. Any engineers out there?

Sounds like a fairly hefty pump.
It would be a good idea to check that the pump doesn`t cost more to run than the value of heat collected, otherwise its actually cheaper heating the water by conventional means :)

Well it can keep a 24' round pool clean. I guess another way to look at is to compare the costs of running a pump versus a electric heater

I think I'll use the copper tubing as well, as it seems a lot of work to get the refrigerator coils plus the diameter is really small. I can't imagine you'd need a very big pump to run water through a 3/8 inch line. I'm still in a quandary about whether to make it a closed system with antifreeze and a heat exchanger in the barrel, or just run water straight through. With water I'd have to drain the system every night it falls below 32 degrees to prevent freezing. If I use antifreeze in a closed system I'd need two pumps, one to move the antifreeze through the system and one to circulate the water through the barrels.

I think that you will find that the water will not freeze as long as it is moving. The movement of the water in the pipe creates friction and heat. The same principle as leaving your faucets dripping in your house. I THINK :)

I don't know what effect the freezing temp would be if continously circulating the pump. I had 92 degrees in my GH the other day when it was only 22 outside and that is with an auotvent open @ 75. So how warm would the water get if circulating water through tubing / barrels . The heat from the water should continue after the sun goes down but how long is the answer

Wouldn't the physical properties of water (hot rises, cold sinks) make it possible for the heat to cause water motion? Make the water from the reservoir flow from the bottom of the barrels into the heating coils. Heated water from the coils flows UP -powered by heat and by the pressure of colder water flowing in behind it- and lands on top of the reservoir water. It should be able to operate a an open system with the opening being in the reservoir.

Okay, now it's time for an engineer reality check - would this work? I'm going to try it, but haven't had the spare time to put something together yet.

It would work fine, you`d have to have the tank above the solar panel.
The water temp needse to rise a fair amount before you got a convective current going.. probably a couple of hours.
Its a passive solar hot water heater so very hot water but only a limited quantity.
With a pump you could heat a much larger amount of water just a few degrees per pass through the collector like a swimming pool collector.
The best method will depend on how much water you want to heat and how hot :)

How bout this setup, seems like it would work even better, with goodies that you can easily get at Lowes or HD? www.sunnyjohn.com/indexpages/shcs.htm

What about using SALT, that might solve your freezing problems, from my experience and the description of the system you should be fine. If you want the system to last from 5-10 years, you are going to have other problems before the salt corrodes anything.

The copper should be fine, however I don't know what the coils are made of so that's the only things i might worry about. Pool pumps are typically plastic and most of them are designed for both fresh and salt water. Anti-freeze is evil! It sounds like you want to help the environment, so stay away from it. Do it the way nature does, There is lots of liquid water in the artic circles- because its salty.

Instead of the small refrigerator coil I would go to a salvage yard and get some condenser from Auto air conditioner.

these are typically the size of the radiator they would make much more heat than a fridge coil.

Keep this in mind:

In physics, the best absorber is also the best radiator. If you have the absorber inside an insulated chamber, based on the "black body" theory, energy will escape in the form of radiant energy thru clear glass, doesnÂt matter it's double or triple insulated.

This happens as long as, and as soon as, the outside energy level is lower then the absorber..

dcarch

When I was a kid, sometime last century, we had a solar water heater. The tank must be higher than the coils for it to work without a pump. Our house was very old and the tank was in the peak of the attic and it was insulated with sawdust. We lived in FL on an island and generally we had plenty of sun, but with the sun did not shine we took COLD baths. Of course the pitch of the roof was steep and Cedar shingled. So long ago and so simple.

halfNosed Jack and the Dawg

If you are in the warm climates you can get hot water for free without solar. Solar is too expensive and to many moving parts. If you have an air conditioner you can get hot water for a fraction of solar. If you are interested let me know. Ben

I use these heaters to heat my swimming pool. Each panel is 20' long by 2' wide. Here I show 4 panels, but I now have 6. On a good day, it pumps at 5 gallons a minute and raises the water temp by about 30 degrees. Look for "Sungrabber pool heater" on ebay.
{{gwi:289989}}From Misc

web4deb I don't know if you still come on here this thread is really old but I would like to know about your set up to heat your greenhouse using the Sungrabber pool heater. If you see this I would greatly appreciate any info, thanks.