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All About Solar Powered Water Pumps

Remote Greenhouses need Soloar Water Pumps

Solar powered water pumps have been growing in popularity since 2012. Submersible well water pumps
located in remote areas have previously required power from a generator or engine, with all of the noise
and fossil fuel pollution that comes along with those energy solutions. The lure of operating pumps far
from the grid, without the noise, without the pollution, and without the need to refuel generators or
motors, is huge.

Solar Panel Technology makes Solar Powered Water pumps possible
Solar Panel Technology makes Solar Powered Water pumps possible

Of course, the reduced life cycle cost is a big factor as well. The maintenance costs and operational costs
for a solar well pump are much less than for a diesel powered pump.

Fact: Operation and Maintenance Costs for a solar powered submersible well water pump are between 70% and 85% lower than a diesel powered well water pump

Typical applications for solar pumps include:

  • Remote Homes
  • Crop Irrigation
  • Livestock Watering
  • Game Reserves
  • Ground Water Control
  • Drinking Water in Underdeveloped Countries

The first important thing to know about solar powered water pumps is that the actual physical installation
of the pump and motor are the same as for any other submersible well pump. The bore sizing is the same
(3 inch, 4 inch, etc…) as is the hole itself. The well driller will not need to do anything different than
normal. Also, installing the pump in the hole is the same as any other well pump.

Solar Powered Water Pump Operating Diagram
Solar Powered Water Pump Operating Diagram

The only disadvantage to solar powered water well pumps is the acquisition cost. You can expect to pay
50% to 120% more for a solar powered well pump versus an AC motor well pump. This extra expense is
due to the solar panels (photovoltaic array), and the necessary pump controllers and inverter, depending
on which particular pump you are purchasing.

However, the payback period, even when conditions are less than optimal, is under 5 years. A study was
conducted on a large project in Jordan involving 55 solar water well pumps. The pumps were specified in
2010, and the study was complete in 2014. This study was done on pumps using solar panel technology
that is now a decade old. And still, the total cost per kWh (kilowatt hour) was $0.136 / kWh for solar and
$0.239 for diesel generators! That is a total cost of solar pumps at 44% below that for diesel, and this cost
takes into account the additional acquisition cost of the solar pumps and photovoltaic arrays.

Solar Powered Water Pump System
Solar Powered Water Pump System

Of course, this economic analysis doesn’t include the reduction in CO2 emissions (100% less for solar),
particulate matter emissions (100% less for solar), and noise reduction (95% less for solar).
Another feature of solar well pumps is that they are typically capable of running off of any renewable
power source. Windmills and batteries can be used to power most solar pump models – and most can also
run off of the grid or a generator, if your circumstances change or the pump is relocated. Be sure to check
with the manufacturer of any pump prior to purchase if this is important to you.

Some pump companies provide solar panels along with their pumps. Others expect the owner or installer
to provide the photovoltaic arrays and support equipment. Make sure to keep this in mind as you
compare products.

PWS Stainless Steel Solar Well Pump - Solar Panels not Included
PWS Stainless Steel Solar Well Pump – Solar Panels not Included

Running your pump directly off of the solar panels is the lowest cost way to operate. However, you may
want to include a battery as part of your solar pump package. This will keep you covered in case of the
need to operate at night or in cloudy conditions. Of course, there is some efficiency lost by having the
solar panels charge the battery, and the battery then power the pump

Solar Irrigation System at Wilderstead – the 16 acre homestead surrounded by wilderness, in northern Ontario near Lake Superior

Lastly, there are many local, county, state, and federal incentive plans to individuals and companies that
implement a solar powered pumping solution. These inventives can make your Return On Investment
impressive indeed, and bring your payback period to well under 5 years.

Solar well pump in rural part of Punjab India brings much needed water to local community

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Well Pump Checklist

So you need a well pump and you’re not a pump expert.  How can you even begin to look for a pump?

The first thing to know is what size (diameter) well you have.  Well pumps are typically available in 3, 4, 6, and 8 inch sizes.  Most residential well pumps are 3 or 4 inch.  Knowing this will narrow down your search tremendously.

Next, you need to know the electrical service you have available.  In the USA, typical residential service is single phase, 120 Volt.  This voltage can be a little bit confusing, as well pumps and other equipment and appliances are often labeled as 110V or 115V.  Actually, these are all equivalent.  The 110V and 115V items are intended to run on 120V service; they are simply rated to be able to operate on lower voltage.  

Other somewhat common electrical service possibilities are single phase 230V, three phase 230V, and three phase 460V.  

If you know these two bits of information (example:  I need a 4 inch well pump for single phase, 120V electrical service) you will be well on your way to selecting a pump.  Even if you intend to hire a professional to figure out everything else, these two items are essential to begin.

Of course, the entire reason you want a pump is to provide a flow of water at acceptable pressure to your home or for some other service.  

How much flow do you need?  One good way to determine this is to simply see what the existing pump (if there is one) provides.  Flow is measured in Gallons Per Minute (GPM), and pressure is either measured in PSI or in “feet of head”.  This will be expressed as “10 GPM @ 90 psi” or something similar.

If you don’t have an existing pump, or don’t know how much flow or pressure it provides, there are guidelines to follow.

The minimum recommended flow for any well pump is 5 GPM.  

There are two common ways to size a pump for flow for a residence:

1.  Add up the water using fixtures in the home, and have a flow in GPM equal to the number of fixtures.  For instance, if you have 2 sinks, 2 bath tubs, 1 kitchen sink, 1 dishwasher, and 1 washing machine, you would need a 7 GPM pump.  

2.  If you are concerned about having plenty of water at peak usage times (often the morning), you need to take into consideration how much water could be used at any one time.  For instance, showers typically use 5 GPM, so if you have two showers and want to be able to use both without any water shortage, you would need 10 GPM. 

Recommendations are as follows:

  • 1 Bathroom = 7 GPM
  • 1.5 Bathrooms = 10 GPM
  • 2 Bathrooms = 14 GPM
  • 3 Bathrooms = 17 GPM

Your exact situation may have different requirements, the figures above are simply general guidelines.

As for what pressure you need, your well pump needs to generate enough pressure to get water up out of the well and to your house, at the PSI you want at your house.  Maybe you want 60 psi available at your house.  Your pump will need to generate enough pressure to get the water out of the well PLUS that 60 psi to provide adequate service.  In order to determine how much pressure is required to get the water out of the well, you will need to know the depth of the well and the water level.  Also, if piping runs horizontally once the water is above ground, you will need to know how far that is.  With this information, along with the pipe size, the number of elbows, and the number of valves, filters, and other obstructions, a pump professional can calculate the psi of the pump that you need.