Solar-Powered Water Pump Maintenance, Part 2
By Kristin Lewis Hawkins
While low maintenance is a major selling point for using solar power to run the water pumps on your operation, there are still a few upkeep chores to perform and some things to keep in mind, especially if you want to guarantee the best return on your investment.
A benefit of solar pumping systems is a “set it and forget it” water source. They can be consistent and worry-free, but only with proper care and occasional maintenance.
Last month we covered maintaining the installation framework and photovoltaic (PV) unit of a solar-powered water pump system, as well as how weather and environment may affect its performance. This month we will tackle the issues a solar system owner may encounter with the pump, pipe and water.
Pump size and type
Total Dynamic Head, or TDH, is a formula used to determine the output you will need to get the amount of water you require. This includes the power needed to push water up the vertical lift portion of pipe plus friction losses from the pipe and fittings and output pressure. If a well were especially deep, the power required to lift water out of the well and through pipes to a holding tank would be greater than that of a shallow system. If your well requires drilling deeper, this could change what type of pump you will require to get the best flow.
The power required to push the water to a holding tank, possibly to the top of a tall tank, is also factored into the size of a pump. If you change the tank you use to collect water to a different size or configuration, this could affect how your pump performs.
Before installing a solar system, a well should be test pumped if it is old or was once windmilled. Older wells often produce less over time, and windmill systems can require a different setup to produce the same amount of water a solar pump would. Having a well test-pumped will also give you a good idea of the health of your well over time.
Macias recommends having a test pump performed on wells that have not been utilized in a year or more, and on wells in which you increase the gallon-per-minute withdrawal rate.
“For example, if an old existing windmill well had 2-inch drop pipe, you can assume that the well was never pumped at more than 3 gallons-per-minute,” said Macias. “If you go put a 7 gallon-per-minute pump in the well, it might make that much and it might not. By test pumping, you get the right sized pump for the well and keep your costs at efficient as possible.”
Macias also says that some solar pumps have variable speed capability that can be adjusted in the smart controller, helping to maximize the production of the well.
Pipe size
The size of the pipe used to transport water in and out of the well has a direct affect on how your system performs. Pipe that is too small for the rate of water you are pumping can be as bad as a pipe that is too large for the volume.
“When sizing your pipe, too much flow increases the friction loss, which increases the power required and means more upfront costs. Too large of a pipe reduces the fluid velocity, and if the well produces sand this can cause the sand to settle out on top of the discharge of the pump, which will cause the pump to fail prematurely,” Macias said.
When in doubt, contact a professional solar pump installer or dealer.
Decreased output
If your well is not performing like it once did, or you notice the tank is not filling up as fast or as full as it should, the first thing to check is to make sure your solar arrays are not blocked and getting inadequate sunlight. Shrubs and trees can grow up to shade a system installed near a fence or close to the ground.
Consideration of nearby vegetation and trees when you are planning where to install your system can help landowners avoid problems later. Check where the sun will be at all times of the year, not only when your arrays are installed. The sun travels around in the sky through the year, and your panels could be obscured this winter by trees that did not seem close enough to cause problems a few summers ago.
Wear and tear on your system’s working parts can cause changes in pump output or water production. The composition of your local well water can wear down or cause changes in the materials inside the pump over time. Your water may have sand that is building up in pipes or wearing away at moving parts. Hydrocarbons In the water can also cause the rubber parts in a standard helical rotor pump to swell; some companies have offered hydrocarbon-resistant pump materials to combat this problem.
Smart controllers
The newest generations of pump controllers have gone digital. They can monitor a wide array of information regarding your pump, well and tank, and automatically adjust to keep the system operating at its best.
Some controllers can be monitored and adjusted simply by using an interface that is accessed on the internet or a Smartphone app. By broadcasting via a secure network similar to your cell phone, landowners can access well information from anywhere and make adjustments, if needed.
Submersible or floating pumps
High or low temperatures can affect some pumps, so make sure the pump you are using is rated within your local water temperature range. Submersible pumps can become clogged with mud or debris, especially when water levels drop during drought or hot summers. Floating pumps should remain at the proper angle for operation and not be obscured by vegetation, debris or perching animals and turtles.
By following these few guidelines and keeping an eye out for problems, your solar system should have water tanks full for years to come. ❚
“Solar-Powered Water Pump Maintenance – Part 2” is excerpted from the June 2017 issue of The Cattleman magazine.