The sun is the natural source of energy for an independent water supply. Solar water pumps and systems 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 water pump systems, have no moving parts, require no maintenance and last for decades. A properly designed solar water pumping system will be efficient, simple and reliable. Solar water pump systems operate on direct current, (the Shurflo 9300 solar water pump operates at 24v, the Grundfos SQflex solar water pump for wells operate as high as 300VDC).
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 solar water pump
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 submersible solar water pumps are unique, both electrically and mechanically. The most efficient solar water pumps for wells are “positive displacement” pumps. They pump a certain amount of water with each rotation. If it is cloudy or early morning, the solar water 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 water pump system that needs attention only once every 2 to 20 years depending on the model.
Solar powered water 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 water pump works slowly and efficiently all day. Often a solar water pump specifcally for wells will work fine in a well with a recovery rate too slow for a conventional AC pump.
TheSolarStore.com suggests that for solar water pumps for wells go to Submersible Pumps Category below. For booster pumps to increase pressure from cistern or tank see Surface pumps.
Can I use the sun to power a pump?
Any renewable energy source can make the electricity you need to power appliances, including pumps. Solar electric cells convert sunlight into DC electricity that can be routed directly to DC appliances, or can be stored in batteries for use when the sun is not shining, or can be inverted into AC electricity to power AC appliances.
Solar well pumping generally refers to the use of sunlight to power pumps, while the sun is shining. These are simple systems that do not incorporate batteries for storing electricity. In essence, the water tank or cistern acts as storage. If you can pump water fast enough and your cistern is big enough, then you do not need to pump during the night or during cloudy days.
Batteries are generally not necessary in remote water pumping situations, as long as your system is sized properly and you have enough water flow from the water source.
Is solar water pumping economically feasible?
The reliability and economy of solar electric power make it an excellent choice for powering remote water pumping. Cattle ranchers all over the world are enthusiastic solar pump users. Their water sources are often spread over many miles of rangeland where utility power is not accessible and where refueling and maintenance costs are high for generator use.
If your water source is more than 1/3 mile from utility power, solar is a favorable economic choice. This fact is substantiated by a number of rural electric cooperatives across the U.S. These co-ops actively promote use of solar pumps because the cost to extend new power lines is prohibitive.
Where do solar pumping systems work?
Solar panels should be located in a sunny spot where no shading occurs. Altitude is not a factor, but height off the ground will affect whether or not you are able to keep them clear of snow.
Panels should be angled optimally for solar gain, particularly during the shorter winter days. If your site is in the northern hemisphere you should point your panels to true south. The reverse is true for places in the southern hemisphere. For many locations there is quite a difference between magnetic south and true south, so you should consult a declination map before setting your mounting structure.
The solar panels should be tiled up from horizontal to get a better angle at the sun and to help shed rain and snow. For best year round power output, with the least amount of maintenance, you should face the solar panel(s) true south at a tilt angle equal to your latitude with respect to the horizontal position.
If you are able to adjust the solar panel seasonally, a good rule of thumb is:
•Latitude minus 15 degrees in the summer
•Latitude in the spring/fall
•Latitude plus 15 degrees in the winter