The term solar water pump is a little misleading as a solar water pump is a method and system consisting of several components. Obtaining water for a household or livestock with the use of solar panels, a water source and a pump system needs to carefully planned and designed. Most solar water pump systems are used in remote locations, off the grid pilgrims with a sunny climate and on large ranches specifically for watering livestock. With a solar water pump, the solar panels are installed for the pump system only. Many different sets of criteria are needed to make an informed decision as to whether a solar pump is right for any given situation.
A source of water is needed such as a pond, lake, or well. Regardless of what type of water source is available, information is needed as to how high the water must be lifted, pumped up (vertical lift), and how far the water needs to be pumped to the storage tank (horizontal transport) for pump and piping design. If the source is an open body of water such as a lake or pond, consideration must be given to insure the water is potable, clean for consumption. Wells may be a hand dug or drilled. Hand dug wells are generally excavated at a spring or seep and the opening in the ground is the reservoir, at the source end. Dug wells are typically 25 feet or less in depth. Drilled wells are usually deep wells with 100 to 250 feet deep being common, but a drilled well may be up to 500 feet deep or more. Special equipment is needed to drill wells and the site must be suitable for access for a large truck with machinery. A submersible DC pump is generally used to draw water from the well for with a solar system. The water source, or reservoir, must be adequate to supply the amount of water needed. The reservoir is the ground itself, and that reservoir is often shaped like a “V” (the cone of influence) with the point of the “V” at the bottom of the well. Depending on the soil type, either the spaces between soil particles hold water or in fractured rock aquifers, water flows through cracks in the rock layers to the well opening. Well drillers submit a well log that specifies important criteria that is needed for system design. The depth of the well, the static level (where the level of water is within the well when at rest), and the amount of water the well produces at what flow rate would be some of the information available on the well log. Large ponds and lakes are reservoirs and generally adequate unless severe drought occurs. Dug wells would need to be tested. The ability of the reservoir to produce an adequate amount of water must be firmly established.
Solar panels produce DC (Direct Current) electric whereas a household system in the US, electricity that is provided by the utility companies, is AC (alternating current) electric. The difference between a typical household water well pump and a solar pump is that the household system pumps swiftly and at a high flow rate to complete a short range cycle, using AC. A solar pump system is designed to pump water almost continuously throughout the daylight hours, at a low flow rate, using DC. As most solar power is produced between 9 am to 3 pm, on sunny days, large storage tanks are needed to hold adequate quantities of water to be used when the power source, the sun, is no longer available. It’s best to place the tanks or tanks above the point of use to allow gravity feed rather than another pump system for pressure. Pipe sizing from the pump to the storage tanks is must be designed properly, as pressure is reduced from friction. The piping must be properly sized for top performance. The piping must be buried below frost line to prevent freezing from the water source to the storage tank area.
How much water is needed per day is an important factor, and water conservation is often a critical factor. While low flow plumbing fixtures and faucets, water conserving front loading washers, various dishwashing methods, and possibly recycling some gray water, may save substantial quantities of water while a teenager taking a 45 minute shower could destroy the best planning and ideas.
After the information pertaining to the water is evaluated and established, and the pump and piping properly sized for flow and efficiency, the number and size of the solar panels needs to be determined. Pumps require a large amount of electricity and generally 1 to 4 solar panels (modules) are needed for a single water well pump. The solar panels are usually placed close to the water source to reduce electric loss from long wire installations. A platform needs to be erected for the panels to be placed. The ideal slope of the panels needs to be obtained for that particular location. Site location is also important as the solar panels should not be shaded during daylight hours.
Due to the number of complex factors in efficient function, a solar water pump system should be professionally designed. Most solar system retailers have access to a professional staff for design purposes. As the solar water pump system relies on sunlight for power, not all areas of the US are suitable for this type system. As several days of stormy or cloudy weather will mean no water, most systems are can designed for use with a temporary emergency backup energy supply. For those in areas inclined to adverse weather conditions on a regular basis, other types of solar systems may allow more versatility such as backup and battery storage systems.
Burning coal is by far the cheapest method of obtaining electricity but has proved to be a very dirty process. With energy and green technology progressing to more energy efficient and less expensive solar panels, the cost to produce electricity for the same price as burning coal is becoming closer to reality.
