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Solar water well

Posted: Wed Apr 10, 2019 4:25 pm
by Oilpan4
I have a 16 inch bore 120 foot deep well with 12 feet of water in it. It is capable of pumping 100gpm continously, no problem.
It's about 300 feet from the house.
The water coop has raised their surcharge from $45 a month to $55 and we constantly have water outages from crumbling improperly installed water lines. So I'm kind of done with them.
I already have spent $900 getting the locked up irrigation motor, line and pump pulled out. Need to finish it.

I have a few 100 watts of panels from my illegal grid tie pilot array experiment and a 24v 255ah forklift battery and mppt Morningstar tristar cc.
Already plan on having at least 2 pumps for redundancy. One pump will run straight off solar power in parallel with the charge controller. The other pump will run off a the battery. The charge controller will power a relay that will turn off the pump if battery voltage falls below 21v.

The pumps I'm looking at look like they should do 1/2 to 2/3gpm with 24v and closer to 1gpm with closer to 48v.
Our water bill is for about 3,000 gallons per month.
Worst case scenario is all 3,000 gallons need to be pumped with 24v power.
So I would need 6,000 minutes at 200w.
Gives us 1.2 million watt minutes, which reduces to 20,000 watt hours or 20kwh. Per month.
My battery should be able to power 200w for 24hr straight no problem. That's about 5kwh, my new forklift battery should be able to put out 6kwh if the amp draw is under 10 amps before hitting 21v, more if the amps are lower. That should give me around 700 gallons per 24hr from that pump.
Seems like plenty of pump capacity and I only have a 500 gallon tank.
So I'm good on the battery and pump system.
I would probably set it up with float switches to relays that turn off the panel pump when full, on at around 450 gallons. Then turn the battery powered pump on at 300 gallons, off at 400 gallons.

For the direct solar to pump system I want to be able to run both pumps and still charge the battery and have enough cc capacity to utilize all the panels power to charge the battery if no pump is running.
To do that I will need 280w to run the one pump off direct 48ish volt raw panel power, 200 watts for the battery pump and want at least 200 watts of panel for the battery so the battery can absorb at least 1kwh per day even if both pumps run all day.
Ideally only the direct solar powered pump will run during the day for 100 minutes max.
Ideally the battery powered pump will only run once every few nights.
So I will just round that to 700 watts of capacity.
Then to charge the battery with 700 watts I will need 30 amps of charge controller capacity. I already have one 15 amp Morningstar tristar mppt, will need a second one.
Around these parts I should be able to make about 3.5kwh per day with 700 watts of fixed panels. I only have 200 watts of framed mono panels at the moment and a lot more frame less semi flexible panels. I would prefer to use mono panels I can rack.
If the panel powered pump runs for 2 hours during the day that should leave about 2.5 to 3 kwh for the battery, probably a bit less in the winter.
Seems over paneled but it won't be so over paneled during winter.
For backup I have my home made alternator welder, it uses and externally excited DR44G alternator converted to external rectification it can supply at least 100 amps at 30v.
Also installing rain water collection, but rain here is infrequent and unreliable.

That's just to get water to the surface.

So with a 500 gallon tank starting full, 700 gallons per day of battery powered pump water and 600 gallons of direct solar to pump capacity that's 1,800 gallons I could use in one day if I needed it. There's 1,440 minutes per day.
So 1.5 gallons per minute of pressurization capacity and a big pressure tank is all I really NEED...

Pressurization can be accomplished with a much simpler 12v based RV system.
About 6 years ago I pretty extensively dyno tested several RV diaphragm pumps. I found "1gpm" surflo pumps pretty consistently made 2L per minute, for every gpm they were rated for when ran at 50psi and drew 5 amps.
So to pressurize 100 gallons per day I only need about 17ah of 12v battery capacity.
But to pump and pressure 1,800 gallons per day I probably need a little over 300ah of 12v power.
For the pressurization system it will be at the house so it doesn't have to be 100% solar powered, I can toss a 100 watt panel up some where, small cc on a large AGM deep cycle marine battery and a 120v battery tender, all of which I already have.
But let's say I want to be able to run 4gpm for say 2 women taking a shower ( in seperate showers you dirty minded person ). I would need a total pump capacity of up to 8 gpm to hold 50psi.
I do have some Delavan and surflo plumps, maybe 4 or 5 gpm total, enough to at least get started.

Re: Solar water well

Posted: Thu Apr 11, 2019 6:35 am
by Lothsahn
I don't understand. Do you have questions or are you just stating things?

You start by saying that you need 3000 gallons a month, and you're engineering for 1800 gallons a day? If you can pump 600 gallons per day of direct solar and a 500 gallon tank and you consume 100 gallons a day, you don't need batteries at all. Just a supercapacitor should be sufficient, or a small battery for voltage stability.

OTOH, you will need battery capacity if you want constant pressure, unless you have a complex air high pressure tank and regulator feeding into your water tank.

If you're engineering all of this and have a 500 gal water tank, I might consider using a compressor to pump up a high pressure tank (since it sounds like you have a lot of space), and use compressed air to store the energy and regulate water pressure, eliminating the need for batteries entirely. This would allow your example two women to take an hour long shower each day and still have 4 gallons left over.

Re: Solar water well

Posted: Thu Apr 11, 2019 9:46 am
by Oilpan4
Just putting it out there to see if there is a better way, maybe I missed something.

It's seriously over built for when relatives visit, I have some irrigation to preform, possible wild fire threat to fight, if I want to fill up a hot tub, ect.

I was going to pump water to the surface with deep well submersible pumps to an open storage tank then use smaller RV water pumps to pump into a pressure blatter tank for domestic use. These pressure blatter tanks are commonly used on single pump well systems where the well pump brings the water to the surface and pressurizes it.
I have been dealing with wells since I was 15 when we inherited my grandfathers house and moved to rural maine. I was the one that kept it going since we didn't have a lot of money to call out a proper well service company. Luckily the difficulty level of a typical home well system isn't any where rocket or robot surgery.

As I plant more trees my 3,000 gallons per month can easily double.
My high usage days could easily go to 300 to 400, maybe even 500 gallons.

With a lot of this alternative energy stuff people focus on the idealized system. Where main considerations are average use, best case scenarios, ect, then tend to ignore or down play peak use, unusual or exceptional conditions, demand growth, redundancy.
I know building for the average is a lose-lose scenario.
To me the average use is the bare minimum starting point. Then I try to predict peak trends, system demand growth and exceptional conditions.

Re: Solar water well

Posted: Thu Apr 11, 2019 10:42 am
by smkettner
You plan to pump a 120' rise with 24 volts?

I would sooner have a regular 240vac well pump driven by an inverter off a 48+ volt battery.

Add battery and solar as needed. For a long term permanent solution install I would have a lithium battery.

Maybe I missed something.

Re: Solar water well

Posted: Thu Apr 11, 2019 10:59 am
by Oilpan4
It says it's rated to do 60 meters on 24v.
All I need is about 37 or 38 meters of total dynamic head, that's 108 feet from the water level in the well to the surface, plus the 5 feet or so for the tank plus the force of over coming the resistance of being pumped through the pipe and elbows.
I won't know fore sure till I drop the pump down the hole with a line attached, power it up with 24 and or 48v and see what comes up.
I don't have a 48v battery. But I do have a almost new aside being dropped once 560lb 24v battery warehouse tug battery.

I have ordered the deep well pump. Will see how it goes.

Re: Solar water well

Posted: Thu Apr 11, 2019 4:11 pm
by LeftieBiker
I don't have a 48v battery. But I do have a almost new aside being dropped once 560lb 24v battery warehouse tug battery.
I don't know how high a rating you can get, but there are boost converters that will double the voltage (and halve the capacity) of that battery's output.

Re: Solar water well

Posted: Thu Apr 11, 2019 7:06 pm
by Oilpan4
If this 24v centrifugal pump can't reach the surface then I will try a 24v submersible diaphragm pump. They won't have any trouble achieving 52psi of static head pressure.
My little 12v surflo and Delavan pumps can pump 50psi no problem, but they aren't submersible. The diaphragm pumps have a very fine mesh screen that may clog easy so I will have to pull it often to clean it.

Re: Solar water well

Posted: Thu Apr 11, 2019 8:33 pm
by smkettner
52 psi is about 120 feet. Seems marginal at best.

Re: Solar water well

Posted: Thu Apr 11, 2019 9:24 pm
by Oilpan4
That's just to reach the surface.
Simple 2 chamber 12v powered diaphragm pumps can reach 100 to 150psi no problem.

Re: Solar water well

Posted: Fri Apr 12, 2019 11:09 am
by ripple4
One time i did the math on a water battery at household scale, called pumped hydro at the utility scale. basically using solar to pump water up and recouping most of the energy with a multi-Kw turbine on its way back down. I based the idea on those multi-1000 gallon water/fuel bladders the army uses, but one of those large inflatable pools might be cheaper. it was not impossible. maybe with big enough reservoirs the electrical battery would not be needed because the potential energy of water is sort of a battery by itself.