Pumping water using photovoltaic panels is common in ranching country.
Direct water pumping uses the sun’s rays to lift water into water tanks from wells, dugouts, ponds, or streams, and away from the source.
This provides easy access to the water for the livestock and eliminates some problems caused when animals have to wade into their water source, such as erosion of stream banks.
Direct photovoltaic pumping systems are not limited to the role of stock watering. Pumping from wells to elevated cisterns and then using gravity to provide water pressure for the house or cabin can provide for human consumption.
Irrigation operations also benefit from direct solar pumping systems, pumping water when the sun shines, and thusly when it is needed most.
If the property has significant elevation change, direct water pumping can be used for energy storage, filling tanks that can use the water to run turbines for those dark or foggy hours encountered in off grid systems.
Considerations for installation of a photovoltaic direct pumping system take into account the distance and elevation between source and tank, friction losses in system piping caused by that distance, the amount of water required to be moved, and design intent of the system.
Lift capacity for specific pumps is provided by the manufacturer, and is calculated from the surface of the water, dugout, stream, or the draw down level in the water well.
Pressure generated by elevation change or TDH, total dynamic head, is calculated at 1 lb. per 2.3 feet of lift or 9.8 kPa / meter. To determine friction losses incurred by the piping charts are available at plumbing suppliers or online.
Power requirements are calculated from the amount of water needed on a daily basis, the total lift from source to tank, and the distance between pump and tank.
In stock watering, cow calf units and days of service are also necessary to calculate the size of the system.
Switching equipment is necessary to shut down the pump when the tank is full, or in the case of irrigation systems, when the amount of moisture required has been pumped.
Tanks size has to be large enough to provide storage for days with low solar power availability caused by cloud or fog.
Pump control units provide the switching, and linear current boosters, (LCB). LCB’s modulate the power coming photovoltaic allowing the pump to start under lower light conditions when a system without an LCB would not.
Battery backup can also be installed into the system for the more critical applications of home or stock watering.
The simplest systems consist of a water source, a floating surface pump, hoses, and photovoltaic panels.
Advanced systems would have pump controllers, charge controllers, battery backup, submersible pumps with high lift capacity, and filtering capabilities for the water before it enters the storage tank.
Direct photovoltaic pumping systems have a proven track record, can serve a number of applications, and form a viable alternative to generators or the installation of grid power.
Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta. He built his first off-grid home in 2003. His column appears every second Friday in the Advocate. Contact him at: firstname.lastname@example.org.