Need help with AG irrigation Solar setup. Newbie.

[chumpy36]

Hello all,

I am starting a project for a farmer in south Georgia (US). He uses a main detention pond to supply water for his irrigation pivots. He gets water to the pond through pumping well water out using 3 phase electric pumps. In addition is collects water in several ponds on the property which are supplied with rainwater runoff. He uses gas powered pumps to transfer the water from the ponds to the main detention pond. This lowers his (costly) use of well water.

He uses A LOT of gas and maintenance to keep the gas pumps going. I'd like to show him that solar would be more efficient and better for the polar bears. So I want to put together a proof of concept system that won't break the bank. If I can show him a solar system will work, he would roll it out to other places on the farms.

Right now, the gas pump is a 3" inlet pipe (trash pump) submerged in the runoff pond. It then goes to a mile long 8 inch PVC pipe that has a maximum head of 90 feet. There it empties into the detention pond where it is pumped out.

The system is not mission critical. It's just nice to have the "free" water instead of pumping it out of the ground. Usually they fill up a large tank with gas and it runs for 48 hours then they refill etc.

I'm thinking of using a well pump like the Grundfos SQ Flex (for direct DC operation), a controller and a pv array. The existing gas pump SUPPOSEDLY pumps 290gpm at zero head. My thoughts are I could get by with much less GPM since the pump will be running more often (as long as the sun is out).

Amy help on what I need? Would be willing to entertain a cheap system (Chinese etc) for this proof of concept before buying stuff to last.

Am I correct in thinking I need the following?

PV panels (sized based on pump requirements)
Solar controller
DC cutoff
some sort of mounting system
Float switch for when supply pond is low

Any gotchas or ideas of what to use?

I think maybe 3-5 HP well pump? 4k PV array and suitable controller?

Thanks much!

 

[OzSolar]

I'm thinking of using a well pump like the Grundfos SQ Flex (for direct DC operation), a controller and a pv array. The existing gas pump SUPPOSEDLY pumps 290gpm at zero head. My thoughts are I could get by with much less GPM since the pump will be running more often (as long as the sun is out).

Sounds like a really interesting project.

I wouldn't go any further until I did a bit more math to the compare the total weekly(?) need vs the total potential weekly (?) production with solar.

You mentioned 48 hrs and 90' of head. Derating that 290 to 250 for some SWAG and I get 720,000 gallons.

The 25SQF-7 looks like the pump to use.

40 gpm x 6 hours day x 7 days = ~100,000 gallons.

I'm not saying those are the numbers for your application, just offering an illustration for how I'd look at it. You'll have to pick out your own variables and do the math.

 

[chumpy36]

I'm excited about the project. Should be lots to learn. Thanks for the pump rec. I think we can get by with a much lower pump rating as it will be running all the time. Do you have any recs for panels and a controller?
Thanks again

 

[OzSolar]

I'm excited about the project. Should be lots to learn. Thanks for the pump rec. I think we can get by with a much lower pump rating as it will be running all the time. Do you have any recs for panels and a controller?
Thanks again

I fear that I've not done a good job helping you understand what you're up against.

Back of the napkin math indicates there's no possible way you can this with a solar pump.

A solar pump won't be running all the time. 7 hours per day at rated flow rate is best case.

The operation, as you've described it, needs much more water that a single SQF can provide.

Until you better identify how much water you actually need I sure wouldn't be making any assumptions.

 

[chumpy36]

Well, that's the part that's hard to nail down. This isn't a situation of NEED. This is sort of gravy. It just lowers the cost of pumping water from the ground for pivots to use. So, I think moving whatever water is available in timeframe of longer than a week would be good. They only run the pump during the growing season so that could be expanded to other times. If we can get something like half the amount of water in twice the time, I think we would be fine. So, instead of 750k gallons in a week. More like 300k gallons in 2 weeks. The thing that is eating them up is fuel and maintenance.
Does that make any sense?

J

 

[OzSolar]

I'm following you better now.

I've been playing around with some pumps from Alibaba and have been impressed so far. You can buy ten (or more) of them for price of one SQF. Keep in mind it's also going to take you 10X's longer to figure out which one you need and a month or longer to get it once you do.

Not trying to talk you out of the SQF by any means, it's a great pump! I've installed dozens. No issues and a few are over 20 yrs old still going.

Below is a snip from the spec sheet of one pump from a company of been buying pumps from to give you an idea of what you're up against.

 

[chumpy36]

So the last one seems like it would fit my needs. The solar panel config is roughly 3200 watts? Then I would just need a solar controller yes?

Thanks for the help

 

[OzSolar]

So the last one seems like it would fit my needs. The solar panel config is roughly 3200 watts? Then I would just need a solar controller yes?

Thanks for the help

The pumps typically come with thier own controller.