"David Hill" wrote in message
...
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 see no thermodynamic advantage in that, compared with any massive black
material in the tunnel to absorb heat during the day and release it during
the night. But you are likely to find that the amount of heat you can trap
in this way is nowhere near enough to keep your greenhouse warm over night.
Let's face it, winter is winter because there is not much heat sculling
around.

Franz




--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk