Because of the remote areas that they are often found in, adequate sources for both agricultural and livestock watering can at times be problematic and expensive. This is usually because of the long runs of wire and piping required to run a pump or deliver the water to the desired destination. Not too long ago our grandfathers would harness the power of the wind, with the mechanical windmill to pump water out of the ground right to the source where it was needed. Unfortunately this is becoming a forgotten practice, primarily due to the inefficiency of the windmill compared to the cost and liability to maintain the equipment against the ravages of time and the intense mechanical stress that extreme weather conditions can exact. While we would be more than happy to introduce you to a romantic or two who still service old windmills, they're primary uses are still best put out on the windy plains far away from our mountainous county.
Here in the hills and valleys of the Ozarks wind can often be sparse and unreliable. To this effect the old time windmill has now been replaced by remote solar pumping, and to some degree the use of proper rainwater retention. Both of which, when properly designed can deliver on demand water for a fraction of the energy and cost of conventional delivery. In addition, these systems can be placed far off in remote areas previously ruled out by conventional means.
New technologies in pump design have allowed pumps to work efficiently at very low power levels. This means that only a modest solar arraignment is needed to draw up water from deep within the ground or an even smaller arraignment to simply transfer water from any source on the surface. Without the need for batteries these pumps can pump all day long and store up water for when it is needed most. Such a small footprint and simple design makes your water supply secure, always available, and independent from problems on the grid.
Solar Water Pumping
Especially for rural folks, solar water pumping really makes a lot of sense. Conventional water pumps can use an incredible amount of energy to draw up water out of the ground. They are also vulnerable to problems on the grid. If the power goes out, often times so does the water supply. Many times a reliable source of water is needed far away from a reliable source of electricity needed to run the pump. These are insecurities easily avoided with a solar based water pumping system.
Modern solar pumping systems work similarly to the iconic windmill of days past. Drawing up small amounts of water with little energy and storing it for later on-demand use. Without the need for batteries nor a large power source, nor complicated equipment, a solar pumping system is great way to ensure a secure and reliable source of water at any place and time.
The sun is the natural source of energy for an independent water supply. Solar pumps operate anywhere that the sun shines, and the longer it shines, the more water they pump. Photovoltaic modules, the power source for solar pumping, have no moving parts, require no maintenance and last for decades. A properly designed solar pumping system will be efficient, simple and reliable.
How it works
Solar water pumping systems operate on direct current. The output of the solar power system varies throughout the day and with changes in weather conditions. The nature of variable electricity in the form of direct current (DC) is quite different from conventional, steady alternating (AC) current from the utility grid or a generator.
To use solar energy economically, the pumping system must utilize the long solar day, drawing a minimum of power. This means pumping more slowly than conventional pumps. Pumping at rates of less than 6 gpm requires different mechanisms from the conventional (centrifugal) pumps. Small solar pumps are unique, both electrically and mechanically.
The most efficient pumps are "positive displacement" pumps. They pump a certain amount of water with each rotation. If it is cloudy, the pump will receive less energy and thus pump a little slower. A positive displacement pump will pump approximately half as much water with half as much energy.
Conventional AC pumps are usually centrifugal pumps that spin at a high speed to pump as many gallons per minute as possible. They also consume a large amount of power. If you run a centrifugal pump at half speed, it pumps one quarter the pressure. Their efficiency is very low at low speeds and when pumping against high pressure.
Solar powered pumps can provide an equal volume of water per day without the high and inefficient energy demands of a large capacity AC pump. Instead of pumping a large volume of water in a short time and turning off, the solar pump works slowly and efficiently all day. Often a solar pump will work fine in a well with a recovery rate too slow for a conventional AC pump.
If your water sources are remote from power lines, add up your long-term costs of fuel and repairs on generators, or the cost of utility line extensions. Now consider the savings with a solar pump that needs attention only once every 2 to 20 years depending on the model.
Submersible Pumps
If you are pumping from a well, we have solar pumps that can deliver from 1 gallon per minute to over 75 gpm. The smallest pumps, the low-power diaphragm pumps from SHURflo and SunPumps, operate from two 50- to 100-watt solar modules, depending on the head (vertical distance) they are pumping. They can pump 500 to 1000 gallons per day and lift water 200 feet. These pumps require service every 2 to 4 years.
If you have a higher lift, need more water, or want a pump that does not require service for 10 to 20 years, the Grundfos SQFlex pump is a good choice. The SQFlex can lift water over 600 feet and can pump over 20,000 gallons per day at lower lifts. The SQFlex pump can be powered by solar modules, a wind generator, a fuel powered generator, and inverter or the utility grid or a combination of several of these.
For greater water needs or deeper wells, the Grundfos SQ-series AC submersible pump can easily be powered by an inverter or generator. Larger, custom-designed solar powered pumping systems can be supplied by SunPumps. Contact us if your needs fall outside of the flow or lift specifications found in the following pages.
Surface Pumps
Surface pumps are less expensive than DC submersibles, where applicable. A surface pump is not submersible. It can draw water from a dug well, spring, pond, river or tank, and push it far uphill and through a long pipeline to fill a storage tank or to pressurize it for home use or irrigation, watering livestock, etc. The pump may be placed at ground level, or in some cases, suspended in a well.
All pumps are better at pushing than pulling. Surface pumps must be placed no higher than 10 or 20 feet above the surface of the water source at sea level (subtract one foot per 1000 feet elevation).
Suction piping must be oversized a bit and not allow air entrapment (much like a drain line) and should be as short as possible. Pumps can push very long distances. The vertical lift and flow rates are the primary factors that determine power requirements.
Pressurization
Many conventional AC powered water systems pump from a well or other water source, into a pressure tank that stores water and stabilizes the pressure for household use. When you turn on the water in the house, an air-filled bladder in the tank forces the water into the pipes. When the pressure drops, a pressure switch turns on the pump, refilling and repressurizing the tank. This works fine because of the ability of the AC pump to deliver a volume of water larger than what is required for household use.
An AC pressure pump can work in systems with an inverter large enough to run a standard AC pump. However, this will not work with pumps operating directly from PV modules because the sun may not be shining when you need pressure and thus the pump may not keep up with household use.
There are two ways to solve this problem. A non-pressurized water tank can be located high enough above the house for gravity to supply the water pressure. This can be on a hill or a tower. Water pressure in psi = head (in feet) times 0.433. For reasonable pressure, the tank needs to be at least 40 feet above the house. If this is not possible, a battery operated pressure booster pump can fill a pressure tank as needed from a storage tank that is filled by a solar pump during the day. The Flowlight booster pump, the SHURflo 2088 pumps and the SunPumps DC centrifugal pumps can be used for this purpose.
You must use a pump that can deliver the maximum gpm required by the house, or have a pressure tank that is large enough to make up the difference between what the pressure pump can deliver and what is required, for the amount of time it is required. This is called the "drawdown volume" of the tank. Ask us about obtaining air-filled pressure tanks.
Calculation of Solar Power Needs
With all solar powered pumps, the necessary solar array can be determined by looking at the watts required for the head and flow in your situation. Solar array watts should be at least 20% higher than the power required by the pump in your situation. If you use a larger array or a tracking array, the pump will operate at its maximum output for more hours of the day, delivering more gallons per day.
If the pump runs on 24 volts, you can use pairs of 12V solar modules wired in series or 24V modules. Two solar modules with total wattage equivalent to or exceeding the wattage required by the pump must be used. If the pump uses 48 volts, you can use groups of four 12V solar modules wired in series or a group of two 24V modules whose total wattage exceeds the pump's power requirement.
