Letter Re: Solar Well Pump

Hand pumps are not the only alternative to grid-powered electric well pumps. When we were researching the available options, hand pumps with a solar option was our first choice. The problem was that they would not produce the volume of water required. We needed a system that would be capable of pumping enough water to satisfy the requirements of all the livestock plus supply domestic water, if needed. (This was approximately 1500 gallons per day as a design parameter.) Consultations with the folks at Simple Pump indicated their pump could not produce enough water.

That left a solar submersible pump as the only option. The next question was whether to pump to a large enough reservoir to have backup capacity. This option would require a large storage tank, plus a distribution pump in the tank to pump to a pressure tank, and battery backup for the distribution pump. The other option was to pump directly to the pressure tank. While not cheap, pumping directly to the pressure tank was a lot less expensive than pumping to storage.

We recently completed the installation of such a system in one of our wells, and it is up and working. The system seems quite satisfactory. The heart of the system is a Grundfos submersible SQ Flex pump. Grundfos is unsurpassed in the quality of their pumps. The SQ Flex line of pumps is made for solar or wind systems. The Flex in the name indicates the flexibility of the pump, at least to me. The pump will run on AC or DC with no modification. It will also run on a wide range of voltage in either AC or DC mode. If memory serves the voltage range is something like 19-300 volts. There are a large number of different pumps in the SQ Flex line. Choosing the right one depends on the depth at which the pump will be set and the gallons per minute required. We chose a pump that we set at 250 feet (60′ static water level) that would produce six gallons a minute.

The pump is controlled by Grundfos controls that allow the user to choose the source of power input. By plugging in a pigtail that comes with the control we can operate on grid or generator power. If we unplug from the grid/generator, the control switches automatically to solar. We view grid/generator power as backup for the system.

The system is powered by four 180 watt pv panels. (Since this is an overview, I won’t go into any detail on how things are connected.) There is a battery bank to power the pump for 24 hour operation, and a charge controller that handles power distribution. Since the entire system is DC, there is no need for an inverter.

In the course of installing the system I’ve learned quite a bit. That said, I’m not knowledgeable enough to have designed the system. For that, and as a source for all the components, I relied on the knowledgeable people at Oasis Montana (http://oasismontana.com/). I can’t speak highly enough of them. They were a pleasure to deal with and invaluable if we had questions.

A hand pump is a less expensive alternative than the system described here. However, if you want a system you do not have to physically operate on a daily basis or one that will produce a larger volume of water than you can get from a hand pump, a solar pumping system is something to consider. – G.L.