# Solar power for well



## Rocky69 (Jun 2, 2012)

Ok, I bought a small 6acre farm. There is a well powered by AC that works great.

I need to add solar power to it. There is so much information I don't know where to start.

From what I've read I need a panel to charge a battery and an inverter to change the battery to AC.

How big a panel? How big a battery? More than one battery?


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## The_Blob (Dec 24, 2008)

some specifics about the pump motor and well would help us to help you...


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## BillS (May 30, 2011)

Trying to run a motor that runs a pump sounds like a lot of electricity for a solar panel. Maybe even if you lived in Arizona it would have to be 4' x 8'. I think you'd be better off with some type of manual pump.


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## FatTire (Mar 20, 2012)

The_Blob said:


> some specifics about the pump motor and well would help us to help you...


Yeah, need the voltage and hp rating off the pump motor.

Also, a general location (state, and north south east west of that state). Also, off grid or grid-connected?


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## FatTire (Mar 20, 2012)

Oops, also are you filling a tank, or is it direct demand?

Well pumps last longer if they fill a tank periodically rather than cycling on and off every time there's a demand, but you'd need more battery capacity for the former due to longer run time


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## The_Blob (Dec 24, 2008)

BillS said:


> Trying to run a motor that runs a pump sounds like a lot of electricity for a solar panel. Maybe even if you lived in Arizona it would have to be 4' x 8'. I think you'd be better off with some type of manual pump.


+1 :congrat:

after some specifics that probably would've been my recommendation as well... of course, some people can't operate a manual pump, so another alternative might need to be devised :dunno:

... always something


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## FatTire (Mar 20, 2012)

Well pumps aren't that big of a motor, the right combination of panels and batteries could do the job no problem.

Most likely it's a 3/4 hp pump, that's about six and a half amps @ 120 volts... Or ten twelve volt batteries in series running for one hour, charged by one 3x5 panel for six hours, the average peak efficiency period for pv systems


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## NaeKid (Oct 17, 2008)

This has been discussed several times here on the board - I just located one of the latest ones for you ...

http://www.preparedsociety.com/forum/f20/12v-pump-slow-filling-water-tank-7827/

If you are looking to run house pressure, use an RV-based 12-volt water-pump to run from a cistern-style tank that is filled by a 12-volt pump that runs only during day-light-hours. For the night-time, the RV-pump would need to have a basic RV-style (deep cycle) battery put into the circuit.


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## J-stets (Jul 2, 2012)

*solar power for well pump*

Hate to burst bubbles, but to operate a 3/4 HP submersible well pump with a solar system gets costly. First, a 3/4 HP is likely 240V. 1/2 HP might be either 120 or 240. But if 120 it will be twice the amps of a 240 unit. Both require a DC to AC inverter. Second, while they operate at "X" amps once they get going, they also require a huge initial surge often 5 to 10 times their rated amps, and they need this for a few seconds. So an inverter (DC to AC) has to be able to provide this. Generally, this means an inverter rated at a minimum of 5,000 - 7,000 watts, and either for 120 or capable of delivering 240. In fact, submersibles often hit their LRA amperage briefly during start up, meaning Locked Rotor Amps rating, which is often 10 times their running amps.

Then, there's a factor about the batteries. While a group of batteries may be able to supply the inverter and handle the normal running amps for a certain period of time, once again, unless the battery capacity is sized for the huge initial draw, the pump will not be able to start up. So it has to be a amp-hour capacity based on the start up, which will be a larger capacity.

Then, for an hour of total pump operation per day, for a typical submersible, you can figure it will take a minimum 500 watt solar array all day to recharge the battery for the one hour of pumping. So 2 hours total pumping, then 1000 watts of solar all day, etc.

This is why many people just get a $600 - $1000, 5,000 - 8000watt generator. It's very doable with solar, but not affordable for many.


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## LincTex (Apr 1, 2011)

J-stets said:


> In fact, submersibles often hit their LRA amperage briefly during start up, meaning Locked Rotor Amps rating, which is often 10 times their running amps.
> 
> This is why many people just get a 5,000 - 8000watt generator. It's very doable with solar, but not affordable for many.


Correct... It's also why everyone is always asking what size gen is needed to start their "ABC brand and size" well pump. It's the number one reason why people find out the hard way they didn't buy a large enough generator.


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## hiwall (Jun 15, 2012)

It looks like the best way would be a DC pump like one of these-
http://www.coburnett.com/waterpumping.htm


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## J-stets (Jul 2, 2012)

yes, LincTex- folks use their pump's Avg rated amps, so like just say 8A @240 or 16A at 120, and figure a 2500 watt generator will be OK. But the submersible may draw 30 amps for a few seconds to get going and there is often a spike of up to 60 A or more for a few milliseconds, and in the case above it requires a minimum of a 5000 watt generator that can handle the few seconds of 30A and the 60A for maybe 100 ms.

In solar powered systems, the batteries are rated based on capacity and time, so any single battery in the system might have say, 100 amp-hours over 100 hours, because the load is smaller, but maybe only 85Ah over 20 hours, maybe 60Ah over 8 hours, and if asked to handle a huge draw down maybe 40Ah or less depending on the load. Unlike engine start batteries which are designed to deliver large cranking amps within their top 20% state of charge, but can't be recharged over and over, or especially hundreds or more times, the deep-cycle battery can be recharged, but they don't offer the massive cranking amps. The combo start-deep cycle tend to try to do both, but they typically can't deliver as much CCA like a pure start battery, and they can't be recharged as many times as a true deep-cycle.


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## J-stets (Jul 2, 2012)

hiwall said:


> It looks like the best way would be a DC pump like one of these-
> http://www.coburnett.com/waterpumping.htm


The issue with these (shown on the page) is that it's tough to run a whole property with flow rates this low, depending on the pumping depth and total head, without some large reserve tanks and then a pressure pump for night use. And remember, the flow rates shown are during peak sun and ideal clear skies. The Grundfos solar-direct series can be scaled with far greater flow rates at various depths and for overcast conditions. They're also more expensive of course, but to pull an AC pump and replace with a solar powered pump, since they both won't fit in common well casings, and have close or the same flow rate during daylight sun-hours it pretty much dictates going to a Grundfos class. Since they can operate with AC or DC input to the controller, they can also be configured with AC or generator auto-switching, so when PU power goes down the solar takes over etc. Because of much higher flow rates, a much smaller reserve is needed for night use or any backup, and during the day there's a lot more water available. It's likely the company sells these or can get them.


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