[savbo]

Hi all

One for a wintry night....

When I was a ranger we had storage bays full of fresh woodchip. These got VERY hot just a few centimetres down and stayed like that for weeks. I always wondered how we could capture that heat.

Now I have an allotment I've been wondering whether I could heat my greenhouse for a few months Jan-April. Ideas I've knocking around include a heat box (6'x3'x3' insulated box or even an old washing machine), filled with chip, then a heat collector (either some kind of metal vessel (old gas bottle?) or a coil of black water pipe or an old radiator) connected to a radiator or underfloor heating in the greenhouse. Would it need pumping or would the rising heat of the water give us a trickle of circulation? Would you need a thermostat? Would it just not give enough heat (if an electric heater is 2KW I can't see it pumping that out)?

Thought it might be an interesting one for people to bat around. If it's a non-starter maybe I'll go for Dick Strawbridge's heat store idea...

savbo

[greendog]

ive seen programmes about old time gardeners who used to heat frames by burying a thick layer of raw manure and they used to grow pineapples. i would imagine a lot depends on whether you want a warm greenhouse or just frost free  its bound to give heat to the greenhouse but a lot of factors will affect how much

[Yorkie]

I have known some compost and similar heaps spontaneously combust when too hot, and would invite caution if you can't guarantee that won't happen.

Another thing to bear in mind is that it might create a lot of condensation, which you don't want in an unventilated cold greenhouse - recipe for fungal problems.

[savbo]

thanks for comments - I have seen a hotbed in use and wanted to see if something more engineered and predictable was possible. I was thinking of having the box outside the greenhouse both in terms of space needed and the moisture/spores issue...

[kenny199]

ive seen programmes about old time gardeners who used to heat frames by burying a thick layer of raw manure and they used to grow pineapples. i would imagine a lot depends on whether you want a warm greenhouse or just frost free  its bound to give heat to the greenhouse but a lot of factors will affect how much

I have seen this at "The Lost Gardens Of Heligan" .It inspired me to try it with toms in a greenhouse and got toms end May and they went on longer as well.