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I'm designing a hydroponics system for a difficult spot, and I'd like to draw on the /hmg/ brain trust.
It's a hoophouse with no power, but available water. For reasons that I can't get into, I have to utilize a hydroponics setup.
picrel is my general design. I have access to a large number of large, flat trays, about 25"x28" and 1" deep. I plan to use these as the grow beds.
The plan is to have a raised reservoir with the nutrient solution that trickles down narrow vinyl tubing into the first tray. I've experimented, and a simple t-joint works pretty well to make a sort of water aspirator to suck in air along with the water and help aerate the nutrient solution as much as possible.
This aerated solution bubbles into the first tray, which has its own drainage tube on the far end. This drains the solution (again aerating it) into the next tray, and so on. Crucially, it's positioned so that there's always a little bit of water standing on the bottom of the tray, though naturally this water is constantly being aerated and exchanged as the solution flows.
The trays will be covered with sheets of XPS foam cut to size, with holes drilled for flexible foam collars or net cups to hold the plants.
The idea is to have sort of nutrient film/deep water culture hybrid, by having slow flow with a small amount of aerated water always on the bottom of the tray. Each tray holds ~2 gallons when partially flooded this way. Ideally I'd have a reservoir of 20-30 gallons that I could refill (from a second bottom reservoir that the last tray would drain into) with a hand pump once or twice daily.
I'd be growing greens and herbs. My main concern is temperature--I'm in the northeast and though summer nights are much cooler, I worry that with a thin 'film' of water in the bottom of the tray, the whole system could warm to ambient (90+F in the dog days of summer) and I'd end up with a lot of dead plants. Any way around this? Or is it less of an issue than I'm thinking?
