Solar Water Pumping
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. When its cloudy, they pump less water, but often you need less water when it is cloudy.
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. 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 or early morning, the pump will receive less energy and
run more slowly. 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.
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.
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.
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