Running 220v pump from solar

Welcome to the forum Cummins13.

Very difficult to design a "cost effective" system to run such a well pump for a short period per day. Just a really quick rule of thumb design:

• 1.5 HP pump would need about 5x running current (guess at 2,000 watts to run) to start... Near 10 kWatts.

Very roughly, you would need a minimum of:

• 5 kWatt AC inverter
• 500 AH @ 48 volt battery bank (to support starting surge current)
• 2,000 Watt minimum (5% rate of charge) Solar array based on battery bank size

If you go with some other battery chemistry--For example LiFePO4 type with very high surge current ratings... Call it a 1x Capacity (pretty high discharge rate):

• 10,000 Watt surge * 1/0.85 AC inverter eff * 1/46 volts minimum voltage * 1.0 discharge rage = 256 Amp peak surge ~ 256 AH @ ~48 volt Li battery bank minimum based on surge current
• ~2,000 Watt load * 1/0.85 inverter eff * 0.5 hour per day operation * 1/48 volt batter bank * 1/0.50 discharge of battery bank = 49 AH @ 48 volt Li battery bank minimum (based on energy used)
• ~2,000 Watt load * 1/0.52 system eff * 0.5 hours per day * 1/3.0 hours of sun minimum = 641 Watt array minimum for Li based battery bank

The above numbers are very rough... But close enough (within 20% or so) of the accurate numbers (just using rules of thumbs and minimum hours of sun per day) to give you some idea of sizing such a system.

Now, the alternative... Get a small pump and run it for 2-6 hours per day directly from solar panels... This is also known at "slow pumping". As long as you have sun, then you pump. Use a larger water tank to "store energy" for bad weather. If you need water during the deep winter (no sun, bad weather), a backup genset will usually be more cost effective than trying to do it with a battery bank (adding batteries increases the cost of power by something like 4x--Plus batteries only last 3-8 years or so--for typical batteries).

A "solar friendly pump" is not cheap (probably $2,000 to $3,000 for a ~900 Watt Grundfos pump).... But they are very good pumps and will last you many years with little in the way of maintenance (no batteries to monitor, no batteries to fill, no batteries to replace after X years, no charge controller+AC inverter that need to be replaced every 10_ years, etc.).

Grundfos Solar Submersible Well Pumps (SQF family direct from solar panels--expensive. SQ family is AC only, but much more solar AC inverter friendly).
http://www.solarpumps.com/pumpintropage.html
http://www.solar-electric.com/wind-and-water-products/sodcwapu.html (more solar pumps)

There are alternatives to use with standard induction motor well pumps (VFD--Variable Frequency Drive) which can give you soft start and variable speed (RPM) control. And if you change the pump to a 3 phase pump, VFD drives can work very nicely with those type of motors... VFDs are pretty nice and can be pretty AC inverter/Battery system friendly, but do have their issues too.

BB. wrote: »

Re: Working Thread for Solar Beginner Post/FAQ

Some discussions about VFD (Variable Frequency Drives)... Basically a variable frequency inverter with (typically) three phase output. Used to soft start motors (handy for 3 phase well pumps, or pumps with well head starting capacitor) and can also turn an AC motor into a variable speed motor (very handy for pumping applications).

WELL PUMP and Inverter QUESTION
Wind/solar for large scale pumping etc (out of my depth!)
could use knowledge - using Gould jet pump - transfering from 230vAC to ? DC (new link/thread 10/27/2012)
Help required to design off grid system (information on possibilities to connect "standard VFDs direct to solar panels) (new link 1/13/2013)

-Bill

Note, pumps like the Grundfos pumps, more or less have internal/integrated VFDs inside them.

And there are now companies beginning to offer VFD's with "solar panel" front ends--Has made a very nice solution for many parts of the world where cost of pumping (electricity, fuel, support equipment) is expensive.

LiFePO4 (or similar chemistry) batteries may work out OK for you... But Li batteries tend to be pretty expensive (2-4x the cost of lead acid) and are a bit on the "bleeding edge" of technology (you will have to do a lot of self education to design/maintain your own system). Not to scare you away--But be prepared for lots of questions and details if you choose this path.

In the end, you probably need to do a few paper designs (different choices) and see what works best for your needs.

I will stop typing here--Questions?

-Bill