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solar irrigation for a remote orchard site

Posted by seth jones 
solar irrigation for a remote orchard site
April 02, 2017 04:15PM
Hello all
Wondering if anyone has experience with affordable solar irrigation systems. We're putting in a 2.5 acre second orchard starting this spring. G.222, G.935 on tight grid (adding Bud118 next year) and want to drip irrigate for a couple years. We dont have electric at the site. It's on a gradual slope so will probably need enough pressure to push the water uphill slightly.

Recommendations and warnings are welcome. The water source will either be a shallow collection pond, if possible or we'll have to use IBCs filled at our main pond and pulled across the road on a trailer to start. Hope to have a system in place by mid June. Help.


Seth Jones
East Hollow Cider
Petersburgh, NY
Cider From Here
Re: solar irrigation for a remote orchard site
April 02, 2017 08:09PM
Why need for solar?
If I follow you well, your orchard is on a slope, and you are already considering using IBCs that would be pulled at the site of the orchard.
Then, following this reasoning, I would bring the IBCs at the highest point, and the water would then simply flow by gravity.

Jolicoeur Orchard
Zone 4 in Quebec
Author, The New Cider Maker's Handbook
Re: solar irrigation for a remote orchard site
April 02, 2017 08:34PM
Thanks Claude
Hmm. Could be I am asking the wrong question. Would a gravity fed irrigation system across a gradual slope have enough pressure for the emitters (or holes) to drip at an adequate rate? My experience is on level ground and without back pressure the flow is very reduced. It would sure be simpler if it would! Anyone done this?
Re: solar irrigation for a remote orchard site
April 02, 2017 09:14PM
I have no experience with large-scale applications like this, but perhaps my own experience with moving water in a solar greenhouse is germane. (This may get complicated... I learned a lot of lessons along the way.) 12 volt pumps (designed for solar) are remarkably efficient in terms of the amount of water they can move with only relatively small inputs of energy from a P-V panel. (My little setup will easily pump 10 l/min, using just a 90Watt P-V panel, which cost me $150). You will have to do your own arithmetic to determine how much water you need to move, and hence how big a pump and how big a panel you need, but on the whole, I think it is entirely economically feasible to pump water from A to B using a solar panel. What is not nearly so feasible is seeking to run the system continuously, rather than only when the sun shines, (or more accurately, only when there is an adequate amount of light - it will work even in cloudy-bright weather). This requires battery storage, and that costs easily twice as much as the P-V panel itself. Personally, the way I would approach this would be to install a storage tank at a high point in the orchard, and plan on pumping the total amount of water you need, during sunny periods, and allowing gravity trickle irrigation to distribute the water over time. (ie. forget about trying to store solar energy in battery banks - store the energy in the pumped water itself).

There were some wrinkles I learned in the course of my own installation. My panel was labelled "12 Volt, 90 Watt". Seems pretty straight-forward. Except that a "12 Volt" panel does not actually put out 12 Volts - it puts out as much as 22.5 volts in full sun. The "12 Volt" rating means it will charge a bank of 12 Volt batteries, (which actually requires a minimum of 14.2 volts). If you connect something designed simply to run on 12 volts, you will fry it. (Took less than 60 seconds in my case). This caveat does not extend to appliances specifically designed for direct connection to solar panels, (which may actually tolerate as high as 24 volts without complaint, but will still operate down to below 12 volts). Or, the alternative is to insert a "voltage regulator" into the circuit - a simple black box, available on eBay for very small amounts of money, which will adjust the input to put out a standard 12 volts., (and actually cut off the load if the voltage falls too low).

It is probably important to note that I was not assembling my system from "official" components purchased from fancy solar equipment vendors. Most of the bits came form China, purchased over eBay, mostly at prices less than $20 apiece. But once I cottoned on to the points where things could go wrong, my cheap kludged system works entirely satisfactorily.

Broomholm Orchard
Zone 5b in Nova Scotia
Re: solar irrigation for a remote orchard site
April 04, 2017 07:30PM
My orchard is also somewhat removed from my dwelling. It is a good 1200 feet by the crows flight, and another 200 feet above in elevation. I get there via a road with two switchbacks and grades that approach 12%. The orchard itself is only slightly flatter. I have tried gravity feeding from multiple food totes manifolded together with 3" PVC and reduced to 1/2" black pipe for transmission down rows. Grade ranged from near flat to over 10%. The results were non intuitive. If I can find the Colorado School of Mines paper on it I will back post. Long story short, the friction between water and the pipe in the 1/2" causes a variation in pressure over the length of the pipe, such that holes closest to the water source flow stronger than those away from it. This action is exacerbated as your head pressure drops. Start with 1200 gallons and you might be tempted to just make the holes with less flow slightly larger. Bad move. As you approach even 600 gallons, even the holes you thought were doing fine are now showing signs of variation. My lengths were approximately 400'.

In the end, I now irrigate with a food tote pulled behind my tractor. I have a small Honda generator on the trailer that powers a transfer pump (http://www.homedepot.com/p/Wayne-1-2-HP-Cast-Iron-Portable-Transfer-Utility-Pump-PC4/100067909) which I can switch on and off at the tractor through a wiring harness which sends the 110v forward to an in use box with a light switch. From there the 110v travel back to the pump. The pump draws water from the tote, and pushes it though a hose that runs back to the tractor to my seat. From there I roll up on two trees and give them 20 seconds irrigation each, which is how long the pump takes to move 5 gallons. Each tree has a well/berm around it out to the drip edge on the down hill side to catch and retain water. Not as set and forget as drip, but you are never taken aback when your emmiters plug up with gunk in July.

Pressurizing a drip system is not an option, it is mandatory. In addition, I would recommend pressurizing to the same level as those fancy drip systems are prototyped at, which is city pressure, which is probably towards 80 psi. Again these systems are mostly engineered and tested in controlled settings that even if they have an outdoor lab it is liable to be as flat as a QC table. If you are intent on using drip, you need to match those conditions as closely as possible to get results. I struggled with drip years ago. The emitters are a constant source of consternation as because they drip so slow, sediment in the water dries and builds up in them. Generally I never got a season out of the things as they regularly failed. Constant monitoring will be your only defense against one tree getting enough, and another nothing. Given the cost, I would go for a more personal approach, and you won't get fooled again...

Lakes Region NH @ 1200' or so

393 planted towards a 440 goal mixed apple, pear, plum and apricot...
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