Can I Use Solar for 220 volt AC Well Pump?

Re: Can I Use Solar for 220 volt AC Well Pump?

In general, the first place is to start with understanding the load.

A typical AC induction motor well pump will need around 3-5 times is rated wattage for an inverter to start it. Say your pump needs 1,000 watts to run, you will probably need a 2,000 watt or larger inverter to run it (it also depends on the inverters--some are much better at supporting surge loads than others).

All About Inverters
Choosing an inverter for water pumping

Since well pumps are a major load (both surge and running)--Working to reduce those loads can be a big help in reducing the costs providing the power.

For example, there are VFD controller (variable frequency drives). These drive three phase (or well pumps with an external capacitor at the well head) can can "soft start" or even limit pump RPM/Power (if pump is larger than you need, the VFD can "throttle back" on its output frequency and reduce peak power usage).

Another option is to get well pumps with soft start (Grundfos SQ series are an example). An in well pump that will use much less power (more efficient, VFD built in pump).

Or, you can get pumps that will work directly with AC or DC power (inverters, generators, battery banks) or even directly with Solar Panels (Grundfos SQF series--not cheap at ~$1,700 or so--not in business, just a guess). If you use solar panels direct--You pump into a cistern/storage tank while the sun is shining and use gravity or a small DC (or AC) pump for home pressure (with bladder tank).

A version of the above is "slow pumping"--Just a few GPM filling the cistern (low peak power, very efficient pump), and the cistern supplies the "peak" water flows.

The money you put "in the well" can save you the money that you would have to put in an off-grid solar+battery+inverter system.

-Bill

Re: Can I Use Solar for 220 volt AC Well Pump?

How is the system going to be setup? Is this grid tied (solar panel to Grid Tied AC Inverter to AC mains), off grid (solar+battery bank+AC inverter), or panels to VFD (fairly recent "invention")?

VFDs allow the pump (motor) to operate at different RPMs other than fixed frequency (50 or 60 Hz input). Gives you the option to slow the pump down to operate at lower power/more efficient volume pumping. Also supports "soft start" (starts at near zero Hz and brings pump up to speed/frequency slowly).

And pump power consumption is highly dependent on pump type, lift, water flow. Have you measured the Pump's current draw (AC Clamp Meter) or Power (Clamp Meter+Voltage Phase measurements using a power meter)?

The amount of array really depends on your pump's power needs and AC power system type (GT, off grid, VFD connected array).

A grid tied system (no battery) is fairly standard and usually the most cost effective. The Solar Array and GT inverter are sized to "turn the utility power meter backwards" and credit the amount of power the pump uses. This also depends on your billing agreement with the utility. In some regions (such as California, where it can literately take a Power/Electrical Engineer to design the system and calculate all the ins and outs of peak power usage, kVA usage, time of day, seasonal, 15 minute peak power usage/and even power fed back to grid, etc.).

Off Grid power is the most expensive (battery bank is very costly, and somewhat inefficient). Used if there is no Utility power and/or utility power is unreliable. Can be 3 to 10x the co$t per kWH vs utility power.

Using a solar array to VFD is relatively new technology (and not very common yet) to use the solar array to power the pump directly. Can be cost effective and has been used in regions of the world where utility power is expensive or not available. The solar panel provides power to the input of the VFD, and the VFD outputs the power needed to the pump and based on available sunlight (i.e., the pump turns relatively slowly during morning/late afternoon sun, and at "full speed" during the middle of the day). Great for pumping to a storage tank/ponds or flood type irrigation. For sprinkler irrigation, probably not so great--Changing sun gives you changing flow rates/pressure--Sprinkler emitters and drip irrigation may not work well under changing water conditions.

-Bill