Thanks for your input guys, so fast!
Some really good ideas. Although some seem too complicated for me to do right. I love the idea of insulating the bins to the outsides and digging it down a bit to help with the height. I was thinking to put 2 bins together on each side of the tunnel. On the inside walls how about zig zagging some 25mm black htpe pipes up and fixing them to the cage walls with zip ties. (would this be big enough?) Should keep them out of the way of the pitch fork when turning the pile. steel pipes would be better of course but the cost of the project woud likely run out of control, running it as 4 separate systems might be useful if something were to leak and i will need to fix it without losing the whole crop. for the same reasons id like to keep the medium as water to avoid any biohazard. I wasnt going to have a base just to dig down where the legs of the structure for a couple of feet or til I hit something substantial bang some rebars into that and set the legs in concrete.
It goes down to -20c here too but I think at those times of year there is so little light nothing would grow anyway. might be best to empty the system for Dec Jan and Feb. We will see how it works before making that decision. It snows up to May here so I was really looking to extend the season a few months rather than grow oranges in January. Also in the location ithere is no electricity, its not impossible to get some there but it will cost. getting air into the pile by means of a couple of 110m pipes with some holes drilled in might be a better option for me.
