Suggestions and knowledge *needed !

[otterbob]

I am placing this in the general forum because it touches on many different topics----

I am going to build an off-grid greenhouse that operates on a 12 volt battery/bank.

I am planning {and testing components} before I build it and this post represents where I am at, and what I would like to do.
The prototype greenhouse "structure" {on-grid} has been working for 6 years now.

The “power” ,,,
Goal is to use one or more marine { Boat } battery's for a 12volt DC system.
Over the years I have built a 12 volt generator from a Delco alternator that is internally regulated and powered by an old lawn mower engine. This system works well. All bugs have been worked out !
This will backup my Air 404 wind generator I have, but not yet installed. Small solar panel may be added later.


The “water system”,,,
I will be using a 95 Gal Stock tank inside the greenhouse for a cistern.
This has work well for a 110 volt Irrigation system.
I do not want to use a sureflo or other low volume pump { but I could }
Current idea is to use a 12 volt marine duty transfer pump from harbor freight.
I bought one on sale to “play” with and like it so far { life of pump might be an issue at a later time }.
It is rated at 50 psi for a 35 ft head.
To keep volume up and and the pump from cycling too often I was thinking I would add a “bladder tank” and plumb everything with 1/2” pvc.
I am thinking a standard pressure switch from my 110volt bladder tank / pump system should handle the 12volt on/off cycling of the pump.


The “automated irrigation system”,,,
To create the irrigation system I would like to use lawn sprinkler items , But,,, They run off 110volts AC generally dropped to 24 volts with some 24volt DC

The Toro DDCWP controller says it runs on 2- 9 volt battery's and it says it will work with the DCLS-P DC Latching Solenoid , I can not find specs on the “DCLS-P DC Latching Solenoid” but one picture showed 9V on the label .
I would like to get components that would allow me to keep my 12 volt system without inverters.


The “Air inflation system” { dual layer poly }
I am considering an Attwood or Jabsco marine blower for boat air exchange.
I will have to manufacture an adapter for installation.


Suggestions/ideas welcome !!!

Otter Bob

[plowman]

here are some things to think about 12v 24v system.
if 24 hooked up in series or parallel i would use
solar battery chargers mounted in the roof on the
blower i would put a timer on it so it would not
run all the time.

good luck on your project

[Backwoods_Bob]

Well, sounds like you know what you want outta that greenhouse.
The only comment I can make is can you adapt the design to use no power at all?

Could water be supplied by gravity?
How 'bout natural convection for ventilation?

- Just sayin.'
I've lived off grid for ten years now and I find the very best way to manage it is by adopting methods that don't use power at all to work.

Myself, I wanna build one of these some day -
http://www.undergroundhousing.com/images/greenhouse_book.jpg

http://www.undergroundhousing.com/

Might help extend my growing season a bit.
I'm up in northern washington at 3,200'
I underestand your at some 6,000' in Colorado?
Hows your growing season? I can't get ripe tomatoes without a greenhouse.

[randallhilton]

The “water system”,,,
To keep volume up and and the pump from cycling too often I was thinking I would add a “bladder tank” and plumb everything with 1/2” pvc.

(See the "BUT" below). The bladder tank would be good for your proposed system. The 1/2" pvc would be not so good unless you use multiple solenoid valves so that each 1/2" run of pipe could be limited to the GPM demand that the 1/2" pipe could carry. It's a common misconseption that a smaller pipe size will help maintain pressure. It does keep the pressure up at the source, just the same as partially closing a valve would do, but you'll suffer a pressure loss the further down the pipe you go. Your sprinkler heads are designed to deliver x amount of GPM at y pressure so what would happen is that the heads nearest your source would be happy, the heads at the end would starve. (as a master plumber and one time irrigation guy this is my bailiwick)

BUT

(this is not so much my bailiwick)
I'm a late comer to getting off the grid but we made a serious commitment to a Victory Garden here in town. Along with that, I'm designing a rain catch system which can provide household necessities as well as irrigation. Since we would have to make a tank of water last between Texas rain showers (a frog strangler followed by a dry spell) it would be important not to squander water. So, I did some research and figured out how much water (gallons per week, not minutes of watering) the various plants need and we've organized our garden plots accordingly. On our test plot, I set a 10 gallon tank about 3 feet above the bed (any height would be enough), then simply laid some 3/4" pvc on the bed, and piped it in a rectangle so that there's no dead end on the piping (this balances the pressure/volume). I drilled holes in the pipe using the SWAG method. For my test bed, 10 gallons once a week is sufficient (we have lots of mulch on the bed) so all I have to do is fill the reservoir and let it trickle out through the holey pipe. When it's empty, the bed is watered enough. My only issue was that I didn't level the bed enough so I had to prop up one end of the piping. Amazingly, my SWAG hole sizing/placement resulted in relatively even distrubution of the water and the plants grew just fine.

So . . . what I'm saying is, you might be able to set up an arrangement with reservoirs for each sort of watering requirement - optionally use a toilet ballcock to controll the fill level in each reservoir. You'd have to cobble together a way to dump the reservoirs once they get full. (I can think of a couple of ideas but they're not simple enough yet -- simple takes more thinkin' than complicated does). I'm guessing you want this thing to run automatically so you don't have to remember to do the watering.

The benefit is that you use much less water and the pressure requirement is much lower since you're simply lifting a few feet to fill the reservoirs. This could mean a cheaper pump using less energy. The rest is gravity. In a pinch, you could even hand carry water to each reservoir and still get the desired water application without having to hand water everything individually.

Lots of loose ends but this is just a different way of thinking about it.


The “automated irrigation system”,,,
To create the irrigation system I would like to use lawn sprinkler items , But,,, They run off 110volts AC *generally dropped to 24 volts with some 24volt DC . . . I would like to get components that would allow me to keep my 12 volt system without inverters.


Look around a little more - there are irrigation contollers designed for DC systems but you'll need to switch to DC solenoids on the valves. I haven't used them so these are out of my bailiwick but I know they're out there. You probably won't need them if you use the reservoir idea.

Remember -- you said "Suggestions/ideas welcome !!!" you didn't say they had to be good'uns. ;D