3/2/14:Today is a very big day for me. After 3 years of planning and 2 years of building, I have unplugged the extension cord and my greenhouse is running off 100% solar energy. Inside I have a subterranean air exchange fan, pond pumps (soon to be automatic watering system) and greenhouse fan that are now PV-powered with nighttime battery storage to run the pumps.
Shown here is the charge controller, fuse panel and battery that I have inside the greenhouse. Yes, I used a truck box because it was laying around and it is waterproof!
The "cabinet" with plywood mount for electroinics.
Deep cycle marine battery I bought at Sam's for $82. If I need another I should have room.
I found the Victron MPPT charger to be a bargain at $104. So far it is charging nicely. The fuse panel is made for a boat and I think I found it on eBay. Should keep dampness at a minimum.
The school bus fan was a nice find at Auto Zone for $15 and it only draws one amp. I cut off the cigarette lighter plug and wired it into the fuse panel.
The black hose into the filter is fed by a 1.3amp dc pump (submerged, lower-right) I found on Amazon. It was fairly cheap, claims 30000 hour life and moves about 3 gallons per minute. I left the AC pump attached with a series of valves in case of failure, but it is officially off.
Update 3/16: Pump has been running constantly and pulling very little charge from battery. After just a few hours of bright sun each morning the battery is back up to full voltage and the charge controller starts floating.
Update 4/21/14: The pump has not shut off yet. Battery maintains approx. 14.1V charge constantly. Very nice!
Update 6/30: I bought a 12V dc timer and added another 15watt dc pump (that moves water nicely, if you were wondering!) for an off-grid, automatic watering solution. Like last year, I used an old hose with holes drilled in it, except the holes didn't line up exactly with this year's crops, but it's working OK. I think the pump and timer ended up costing $30 on Amazon. They work great!
Update 11/24/14: The pump shut off today! Maybe it was because the PV panels were blocked by snow on the lower half for 4 days. Anyway I cleared the snow and the pump came back on when the sun came out.
Update 3/10/15: The pump never shut off again. It was a very snowy winter, but I just went out after a storm and cleared the snow from the panels. Everything is running perfectly!
Update 4/25/15; Check out my new drip irrigation system that runs off the white timer above!