Hello one and all, long time lurker here making my first post! Big thanks to Paul and all the rest of you wonderful folks who make such great contributions. I wonder if anyone could give me a few pointers...
I'm currently working on a permaculture farm in the north of Scotland, it's early days for the place - coming up to the end of the first year. We've got a polytunnel to extend our growing season and we've been scratching our heads over how to heat it...
My initial plan was to build a rocket mass heater of the half-barrel bell variety and run it along the length of the tunnel, using the beds inside as the mass.
Then I remembered about Jean Pain and his amazing water heating woodchip piles and thought I'd investigate those a bit more. My thinking was to run a kind of closed circuit piping system through the beds to heat them. Or, to drip feed into water butts inside the tunnel which would act as thermal batteries, and then irrigate the polytunnel with the water...
It was then pointed out to me the benefits of capturing the CO2 given off from the heap and piping it into the tunnel; the plants would love it.
I researched a bit more and came across
http://www.builditsolar.com/Projects/Sunspace/NewAlchemycompost.pdf (possibly on your forum) about using
compost to heat and raise CO2 levels in a greenhouse. They run a perforated pipe through a large compost pile set against their north wall and blow heat and CO2 through their veggie beds. Moisture from the bed was also carried along and condensed, keeping the roots hydrated. Seemed promising!
So, my ponderings now are... digging a big ol' trench along the middle of polytunnel where the central walkway would be, filling it up with woodchips and other good stuff, running perforated pipe through it and up into the veggie beds. It would mean a fair bit of digging and shifting but all the CO2/heat given off from the pile would be put to use and it being in the polytunnel and in the ground would insulate it. And if it's lower than the veggie beds hopefully convection should circulate everything for me..?
Any thoughts..? Is it all possible? Would a trench variation on the Jean Pain pile work or does it need to be in a big ol' mound for proper operation? Will I just keep thinking of different approaches and never actually get anything done?
I've attached a little sketch, hope you can make sense of it. The tunnel is 18.5 by 5.5 metres... 2.5 metres high. The trench in the sketch is 16cubic metres, not sure if this is too small or overkill.
Any composting experts out there?
Many thanks
Sean