Solar Water Pumping
First there were skins filled with water that had to be carried from a source of water to the point of usage. Later, after animals were domesticated, they were used to carry the water and operate rudimentary pumps to accomplish the same thing. Over thousands of years, the nature of pumping water has changed many times and made gigantic leaps in technology.
Now we have a device that uses the awesome power of the sun to pump water in places where the power companies seldom venture. Many farmers and ranchers are finding out that by using solar powered pumps they can now graze their cattle on pastures that were previously unproductive due to the lack of livestock water. They can now turn that remote property into income because they are able to graze and water the livestock in close proximity to each other, not worrying about the stock walking off their weight gains to access drinking water.
Villagers in dusty African towns can now have clean drinking water and water for cleaning thanks to solar water pumps. Wells in the desert are especially good sites for solar pumps since the brighter the sun, the more water they produce. Actually, some small scale irrigation is being practiced using the power of the sun to drive pumps to drip irrigate plants. This ability to produce water with sunshine in desert villages has freed many laborers, traditionally women and children, from the time consuming task of hauling water from distant springs. This additional free time allows families to spend more time caring for gardens and livestock, preparing nutritional food and leading healthier lives.
Yet, many people have never heard of solar water pumping and are amazed to find out that the technology has been around for three decades. In the early days of solar pumping, simple DC water pumps like those found in motor homes and campers were attached to batteries and a solar module or two was attached to the batteries to replace the current drawn by the pump. We actually still use this technique on a limited scale today but solar pump technology has come a long way since those early days. We now have several excellent solar submersibles, solar pumps for really deep applications and high quality solar surface pumps for extremely high lifts; all designed specifically to run off of the sun. All of this is accomplished without the use of batteries.
While batteries may seem like a good idea, they have a number of disadvantages in pumping systems. First, batteries reduce the efficiency of the overall system. The solar modules’ operating voltage is dictated by the battery bank and is reduced substantially from levels which are achieved by operating a pump solar direct. Batteries also require additional under and over-charge protection circuitry which adds to the cost and complexity of a given system. For these reasons, and the increased maintenance involved, only about 5% of solar pumping systems employ a battery bank and we suggest you avoid them unless they are part of your existing residential solar system.
Learn from Experience
When planning a solar water pumping system it is always a good idea to have someone available who has done this before. However, if your neighbor has one already and your wells and water requirements are very similar, it is possible to just duplicate theirs. Typically, solar water pumping systems are designed simply to bring water to the surface and dump it into a stock tank. This doesn’t lend itself to water for domestic household use because it is not pressurized and water is only pumped during daylight hours. For pressurized water systems where the home is powered by a renewable energy system, there will most likely be batteries and an inverter for household loads and we can just use that inverter to run a high efficiency AC pump wired and plumbed into the house as if it were a traditionally powered home.
Types of Solar Pumps available and in common use:
Submersible Diaphragm Pumps
Usually operates at 24 to 30 volts and limited to heads (maximum water lift) of 225 feet or less. These pumps require a pump controller to match solar array output to motor demands to avoid premature motor failure. Examples of this type of pump include Kyocera SD pumps, SunPumps SDS pumps, and ShurFlo 9300 series pumps.
Submersible Centrifugal Pumps
Operate at higher voltages of 45 to 120 volts DC and higher. . These pumps require a pump controller to match solar array output to motor demands to avoid premature motor failure. If high volumes of water at moderate (50’ to 100’) lift are required, this is a good pump to use. Examples of this type of pump include Kyocera SC pumps, SunPumps SCS pumps, and some of the Grundfos SQ Flex pumps.
Submersible Helical Rotor Pumps
Operate at higher voltages of 45 to 120 volts DC. These pumps require a pump controller or internal electronics to assist in getting the pump started after periods of inactivity. These are very sophisticated pumps but have a high water to power yield. They are most efficient at the 40 foot to 180 foot range. These are sometimes referred to as the Archimedes Screw Pump and are a fairly new arrival on the solar water pumping scene. Examples of this type of pump are the Dankoff ETA pump and some of the Grundfos SQ Flex pumps.
Surface Diaphragm Pumps
Available in either 12, 24 volts DC or 120 volts AC. These pumps perform best if operated from a 12 or 24 volt battery bank or from grid power. They are good for delivering small quantities of water from a surface source up to about 100 feet in lift. Suction is only about 10 feet so they need to be located close to the surface of the water being pumped. On rare occasions they can be used in an array-direct (with pump controller) but we have found that life expectancy is greatly reduced. Examples are ShurFlo 2088 pumps and RV pressure pumps.
Surface Centrifugal Pumps
These pumps are less common in the solar water pumping field than they were in previous years and use impeller pumps connected to DC motors of various voltages from 24 to 120 volts DC to move larger volumes of water over relatively low lifts. These pumps require no pump controller since they do not start under load. They have minimal suction capacity. If they are used in pressurizing applications, they require a flooded inlet and a suitable battery bank. An example of this type of pump is the SunPump SC pump and the SunPump SCB Piston Pumps. These pumps are usually operated at 45 volts to 240 volts DC and are excellent for lifting surface water to extreme heights. A DC motor drives a pressure pump similar to that used in a car wash to create enough pressure to push water to heights exceeding 1000 feet. These pumps are built to your specification by our friends at SunPumps.
Floating Centrifugal Pumps
These are high volume, low wattage pumps but need to be floated on a pond, ditch or cistern. They lack the ability to lift water very high but are good for keeping livestock out of riparian zones where contamination from animals is of growing concern. They operate from 12.5 to 30 volts DC and require no controller. Examples are the Sun Motor M-3 and M-20 pumps.
Once the backbone of the deep well, solar pumping industry these pumps are great for pumping from very deep wells or wells that have too small a diameter to get a submersible pump into. While the hardware to make this pump is relatively expensive there is very little to fail and life expectancy is measured in decades. They can operate from 30 volts DC for very shallow wells to over 200 volts DC if water is very deep. These units require special controllers for starting and running under heavy loads. They operate on the same principle as oil field pumps. An example is SunPumps SJ series pumps.
Determining your pump type
As you can see from the above list of pump types there are many application factors to take into account when choosing the appropriate pump for any given pumping situation. For this reason, we usually like to talk to the customer before sending out a pumping system to ascertain that the system will perform as desired. We have included a Water Pumping Questionnaire which you can print and fax to us so that we can make sure your system is properly designed.
Solar Power + Water Pumping
= A Natural Mix
Generally, water is needed most when the sun shines the brightest. Solar modules generate maximum power in full sun conditions when we typically need larger quantities of water. Because of this "sun-synchronous" matching, solar is an economical choice over windmills and engine-driven generators for most locations where there is no utility power. Owners of solar pumping systems enjoy reliable water delivery that requires no fuel and very little attention.
Water Pumping Questionnaire
Download and fill out this questionnaire to help us determine your water pumping system requirements.
Daily Water Requirements
Each person, for all purposes= 75 gal/day
Cow/calf pair=10 to 30 gal/day
Each horse, dry cow or beef= 10 to 20 gal/day
Each milking cow=35 gal/day
Each sheep=2 gal/day
Each hog or 100 chickens= 4 gal/day
*actual requirements may vary