Solar Well Pump System Critique

[hpinson]

I wonder if I could ask for comment and critique on a solar well pumping system for my build site. I'm a few days from going ahead with this.  The well is located far enough from AC power to make solar practical. Plus, it will be a fun and I hope educational project. I could go AC, but the cost of copper over a long run makes the price comparable.

The well is 305 feet deep

Casing is 4"

Water output is 1/2 GPM - very low but reliable

Static head is 180'

Pump will be located at 290'

Water column holds about 81 gallons.

I'm pumping into a 1000 Gallon tank, above ground for now.  The tank is to provide water for camping while we build, for construction, and for fire suppression. Ultimately it will be for cabin water supply and I hope to bury the tank.

The pump is a SunRotor Helical Rotor SR-4, a new-on-the-market competitor to the expensive Grundfos and Lorentz pumps.

Specs are here: http://www.sunrotor.com/SR-4

Cost is quite reasonable at $1300 compared to 2K-3K for the grundfos. The warrentee is as good.

It uses a controller box, which has dry pumping protection on a 30 minute timer, and a full-tank sensor. This pump curves are the best I've seen for such a low output well. At this depth, the company claims I can dial it down to approach the 1/2 GPM output of the well.

The pump will be powered by 2 Conergy 235PA Volt 235W Panels. They are about 30 volts / 7.8 amps each at best.  I live in a place where the sun shines through most of the year.  Specs are here:

http://www.conergy.us/PortalData/3/Resources/products/photovoltaics/pdf/ConergyP_235PA_TD_ENG_180111_LR.pdf

I'm concerned that these may be overkill.

Wiring will be with the solar panels connected in parallel out to a double-pull single phase on-off switch (no fuse or breaker) that acts as a disconnect for the panels, and then to the control box, to the pump using 12/3 submersible cable.

Submersible 18/2 wire runs from the controller above ground to the dry-run protector sensor placed just above the pump, and to the tank-full sensor in the storage tank.

Couplers, check valve, and Pitless adapter are stainless steel, so there will be no leeching of lead as in bronze fittings..

Pipe will be 1" Schedule 80 PVC Pipe, and pre-threaded. I'm getting more than enough.

In addition I'm getting a waterproof splice kit, a roll of safety rope, and a roll of 2" pipe wrap tape to bind the electrical cable to the pipe in the well.

Would a lightning arrestor of some sort be a good idea?

Am I missing anything?

I hope if nothing else, this description is helpful to someone in a similar situation.

-- Thanks
Harlow

[UK4X4]

well over specified !

you are basing your panels on lift V's requirements for 24/7/365 pumping


You should take into account usage !

and use a couple of batteries and charge controller for your worst case consumption-

it will cut your costs of surface gear way down- ie 1 small panel and a couple of sears car batteries

I don't have time to spec it out right this moment - but take a guess at average water usage / week

or worst case scenario.

Full spec sheet is here- i could not see the graphs on the original link

http://www.sunrotor.com/sites/default/files/SR-4%20Spec%20Sheet.pdf

[Squirl]

Wire size/run seems a little off.

http://www.windsun.com/Hardware/Wire_Table.htm

The spec sheet calls for 3 - 12v panels wired to 36v.  It would probably to cut down on wire size.  It would take the amps from 15 to 10.  It would almost double the length per gauge.  I can't find a 36 volt wire size chart.
You might be able to interpolate from the 24-48v one here:
http://backwoodssolar.com/reference/wire_size.htm

[Squirl]

After reading the manual again the next morning the pump can take up to 48v. DC.  I would get 2- 205 to 215 watt panels at around 24v and wire them in series up to 48v.  This would drop your amps to around 8. And you could go with a smaller wire gauge like 6, according to the chart.

[UK4X4]

So here's a worked example- do I have enough solar for my usage...

lets say you use all 1000 gallons a weekend .

at 0.5gal per min you'll need power for about 33 hrs or 1.4 days of power to refill the tank

you have 7 days of sun- at aprox 7hrs per day of full power
so you have about 49 hours a week of full power.

Your pump if you take a rough figure uses about 12 amps of power at your-depth -and rate

So how much power do you use

33 hours X 12 amps = 396 amp hours

Given your perfect conditions every day you have 49 hours a week to produce that power

396/49 = 8amp /hour required

If you wanted to stick to max 36 V

You'll want 3 x 12 v panels to produce 288 watts of power

or for example 1 off   Suntech Solar Panel 280 Watts 35.20 Vmp

Batteries would be required to store the energy supplied on the days you were not pumping !

Sizing them is another math lesson !

[hpinson]

I talked with Sunroter, and it seems whatever the panel configuration I choose, that at this depth, it will need a very heavy wire gauge to avoid extreme DC voltage drop off-- 6 GA or more likely 4GA wire. That changes the economics of this rather drastically given the price of copper.  

There is an alternate pumping sytem that may avoid this.

Simple Pump: http://www.simplepump.com

It meets the low flow requirement and the motor is at the well-head instead of 300 feet down the well.

Does anyone have experience with this?

Thanks for valuable advice. And I do mean valuable.  This community is the best  

[hpinson]

Yecats, 4/3 copper wire is running $7-$8 a foot.  The Simple Pump system is looking quite attractive. I'll detail my experience with it in this thread for those who are interested.

[hpinson]

I've gone ahead with the purchase of a Simple Pump system.  It will be a few weeks before delivery and then installation, and I think I will move my experience with the install and operation to my build thread here: http://countryplans.com/smf/index.php?topic=10231.0