On Mon, 8 Mar 2004 22:58:07 -0000, David Hill wrote:

Following my posting re reverse thermostat, I have been wondering just what
ideas the collective brains on this group could come up with for
Greenhouse/poly tunnel heating.
We get a lot of questions re Gas , electric or paraffin heating, but surely
we can come up with something free/cheep and useable.

I seem to remember talk of having bottles of water with washing soda in
solution in them, the idea being that when the temp dropped to below 50 then
the soda would crystallize giving off heat, and when the water was over
about 60 then the soda would absorb heat as it went back into solution.
Now have this in tanks with some sort of heat exchanger taking heat from the
top of the house in the day and heating the tanks.........

I saw a report on Austrian telly a while ago about a chap who uses flexible
rubber/polythene pipes of water to heat the soil under his cold-frames
during the winter. The water was heated by the sun in a normal
central-heating radiator painted black and the water pumped round slowly by
a small, cheap solar-powered pump. He didn't heat the cold frames directly,
just the earth underneath, and this acted as enopugh of a heat sink to
allow him to grow many vegetables in the winter when the ground is normally
frozen solid for months.
Extrapolate that to the milder British winters and it might keep a green
house warm enough. You might be surprised how much heat you can collect
even in the winter.

--
Tim.

If the human brain were simple enough that we could understand it, we would
be so simple that we couldn't.