Technology
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Water pumping is one of the most prevalent uses of solar in the agricultural sector. Using photovoltaic solar energy to move water for agricultural uses is a cost effective, low maintenance, reliable option where the grid is not easily accessible or reliable. There are a wide variety of pumps designed to work with solar pumping systems for a variety of pumping needs.
The first experiments and commercial applications of solar water pumping date back to the 1800s when parabolic solar collectors which produced steam to run an engine were used. Photovoltaic panels for solar water pumping are the technology of choice for agricultural purposes today. In the 1970s, uses of PV technology expanded during the oil crisis. PV prices have continued to decrease over time and solar water pumping continues to be an effective and economic application PV technology. Solar water pumping uses include water delivery to livestock where the grid is not readily available and a reliable low maintenance system is required, to pump large volumes of water or water from deep wells where human powered mechanical pumps are not adequate, to pump water from a dugout to a livestock waterer, for crop irrigation, pond management, in aquaculture and as a portable water pumping system.
Solar water pumping systems are typically designed with a PV array, pump controller and DC water pump. AC pumps can be used, however an inverter is required which reduces the efficiency and increases the cost of the system. Many pumps are commercially available that are specifically designed to work with solar water pumping systems. Surface or submersible pumps can be used. If water must be pumped when there is no sun, storage can be designed into the system in the form of an elevated water tank and or batteries. PV systems can be designed to pump small or large volumes of water from depths and distances of hundreds of meters. For greater volume or distance, more PV panels can be added. For example, "a h.p. pump supplied by three 50-watt panels can deliver water at a rate of about 1½ gpm to a location 30 m higher than the source. As a comparison, a 3 h.p. low-lift irrigation pump powered by an array of 60 panels could deliver water at a rate of about 1,000 gpm." (http://www.agr.gc.ca/pfra/water/solar_e.htm)
The solar controller either regulates the amount of electricity from the PV panel to the pump or to the batteries. The solar controller helps the pump start and reduce stalling. Trackers are sometimes used with solar water pumping systems. Trackers are pole mounting hardware for the PV panels that use electricity or a heat sensitive fluid to tilt the panels on one or two axes throughout the day to follow the sun and maximize pumping time and energy.
Modified: 02-14-2008
