Greg wrote:
>Im curious, what material are these drums made of. I acquired four large
>white poly-ethylene (sp?) drums several years ago, which sounds like
>what you are talking about. I think there were originally used to ship
>soft drink syrup...
Hi Greg, This solar project has been fun so i was happy to
get your response. The drums i'm using are blue and contained
vanilla flavoring. They are food grade and probably the same
material used in your barrels. Each barrel still had about half
a gallon of vanilla which has made working in the greenhouse
a heady experience <grin>.
>What is the benefit of sinking them halfway in the ground? Or is this
>just a way to get more usable space from your greenhouse.
There is always a gap between theory and practical results, but
here is the theory: The ground is a good insulator when dry and
also works as a good place to store heat. The problem is getting
the heat down and then retrieving it. The barrels serve this
function by helping to store heat (water transports it down) and
returns the stored heat by simple convection (heat rises in liquids).
The water in the barrels also functions as heat storage. I've not
bothered to calculate the heat gains and losses because it is easy
to add barrels and measure their impact. Since this is a small
greenhouse (8x12 feet) it is possible to fill it without much effort.
This is the same theory that was used on our house and it seems to
work well. We also found it works in reverse. If you allow water
near a house it will wick the heat away. During the sixties there
were books with tables showing all this but they are now difficult
to find. One of our local libraries had all the books a few years
ago but last i checked they were gone.
Anyway, if all this works you will have to endure my bragging
and carrying on about tomatoes in late winter <grin>.
>Project sounds interesting, keep us informed. I am building a 12x16 shed
>which I'd like to turn into a greenhouse space by adding some south
>facing glazing...
That sounds even better. If the north side is insulated and
the south side is designed to conserve heat it should beat
my free standing greenhouse. This computer looks into a sun
room designed exactly like that. Right now i see stevia
still growing and several tropical plants with leaves.
jeff (wishing solar heat was more popular)
