[gobug]

There is a description of how to set up a roof top solar hot water system in the book Back to Basics.

If you have free firewood this one is good. Build a well pump house size building out of cinder blocks. Fill the walls with sand. Build a fire box vented to outside the cider building for inflow and out flow of air and exhaust. Make sure there is a doorway to feed the fire box from the outside of the cinder building. Then put a system of copper pipe inside the cinder building running into the house and tank. After you have done that fill the inside of the cinder block with sand. I am not sure if they used regular sand or green sand.

When you have this completed you start up the fire heat the sand and the water gets hot in the pipes flows out to the tank. From my understanding you don't have to keep the fire going constantly as the sand holds the heat. The guy talking about it said he heated it only every three days sometimes.

There are other technical things you may need to think through. The above is just what I remember from seeing it years ago.

obo

Obo, thanks for the pointers. I have a few questions. 1) Do you recall the material and ~size suggested for the fire box? 2) You say "fill the walls with sand" and later "fill the cinder block with sand" -- is this the same step? or do you mean that the void space in the cinder blocks and the space between the cinder block and fire box are all filled? 3) do you think the sand will get hot enough to damage solder joints? 4) do you think there is a balance in the fire box size and the amount of copper piping? 5) can you direct me to more information?
Grateful thanks,
gobug

 

[gobug]

1) sorry no I don't
2) Fill the walls then fill in all around the pipes too. When I think about it I am not sure it was copper pipe could have been galvanized. Was almost two decades ago.
3) I am not sure how hot it gets or how hot before solder melts.
4) I am not sure but IMO I don't think you would want to have solid copper pipe but more a coil around the fire box and on top of the fire box.
5) I am not sure as I said it was almost two decades ago. Seems like though it was in Mother Earth News. Here is a link to old Mother Earth News online articles. You may find it in there. If not contact Mother Earth News and they may know more. If you don't locate it you may have to do a trial and error on your best research on solder melting points, cubic foot of fire heat ratios and sand density retention rates.

http://www.motherearthnews.com/menarch/archive/index.html

Hope that helped. Let me know if you build it and how you did it and how it works.

obo- thanks for the link. gobug