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Solar Water Pumping: A Do-it-yourself Example


Joe Pattie owns and operates an Angus-cross cattle farm near Lead Hill, Arkansas. Many of his pastures have small ponds or creeks to supply livestock drinking water; others are on permanently fenced ridge tops with very little access to water during the normally dry summer and fall. He started looking for a reliable remote water pumping solution for a 38-acre pasture with no direct access to water. He decided drilling a new well was the most logical solution.

Joe Pattie with solar panels
Joe Pattie with solar panels set at 24 degrees for summer water pumping and tripod for farm_energy_pulling pump in background. Photo by Leif Kindberg.

Pattie knew there were multiple options for pumping well water including mechanical pumps powered by a windmill and AC and DC electric pumps drawing power from the local electric company, a generator, or a solar system. He priced the cost of running power lines for an AC pump with his local electric CO-OP and found that this would cost about $6,000. A generator would create ongoing fuel expenses. His existing Aermotor windmill pump on another pasture required a generator with an AC pump as backup during times of insufficient wind. After researching Solar-Powered Livestock Watering Systems, he found that they pump their highest volume of water during summer days—when the cattle need water the most.

"I was interested in trying out solar pumping," says Pattie. "It sounded pretty reliable."

Design Considerations

Sizing a water pumping system is critical to delivering the gallons per minute (GPM) required to meet livestock water needs. Through conversations with local livestock specialists, Pattie concluded that 30 gallons per day per cow-calf pair during the summer and a minimum of 25 gallons per day during the winter is sufficient for his cattle. He expected to have a stocking density of 30 - 40 cow-calf pairs, which worked out to be a maximum of 1,200 gallons per day. Pattie decided to pump from 275 feet to be safe during dry years when the water table may drop. The distance from the well head to the 625-gallon watering tanks he purchased for the project is about 10 feet.

Design Considerations

Location: Lead Hill, AR
Latitude: about 36 degrees
Water needs: 1,200 gallons per day
Well diameter: 6"
Static water depth: 200 feet
Pumping depth: 275 feet
Pumping distance: 10 feet (to holding tank)
Holding tank capacity: 1,200 gallons

Most reputable dealers will use this basic information to design a solar-powered system for a farm's particular needs. In summary, dealers need to know the location or latitude of the installation, gallons per day required, the well casing diameter, the distance between the ground level and the static water level in the well, the distance and elevation gain between the wellhead and the holding tank, and the size of the holding tanks. Dealers generally do not know or provide sufficient guidance on water storage requirements for livestock.

Pattie called Panhandle Sales and Service who provided a couple pump options. He chose a Bison helical rotor DC pump based upon the dealer’s recommendation and the affordable cost of the pump. Once the pump specifications were known, the solar panels, 12 Kaneka 60 Watt panels, were purchased from Sun Electronics for their low amperage, high voltage, and a very reasonable $1.50/Watt price. The system was designed for 720W, 2.7A, and 268V when wired in series/parallel circuits. (Ask the dealer to provide a wiring diagram when you purchase the pump.)

Financials

Farm-constructed racking
Farm-constructed racking must be heavy-duty and well secured to protect the panels from wind loading. Photo by Leif Kindberg.

Pattie started looking for ways to make the solar pump system cost-effective well in advance of purchasing it. He knew the Natural Resources Conservation Service (NRCS) in Arkansas offered a cost-share incentive for stock watering through the Environmental Quality Incentives Program (EQIP). Before purchasing the system, he submitted a request to NRCS to cost-share the well drilling and pumping equipment. The project was evaluated for its cost-effectiveness in comparison to the alternative watering options and the request was approved by the NRCS District Conservationist prior to beginning the project. The cost-share covered equipment, installation costs and the cost of drilling the well.

Pattie saved on equipment costs by planning ahead. He purchased three 15-foot leads to run from the series/parallel circuits to the combiner box and cut them in half for a total of six leads. He salvaged steel and used submersible wire that he already had available around the farm. He also received a bulk order discount on the solar panels by purchasing a pallet of 25. In total, he estimates his equipment costs for one solar pumping system at $4,500 - $5,000 plus labor and well drilling costs.

"I'm going to install another pump in another pasture if the first system works well," says Pattie.

Do-it-yourself Considerations

Equipment Details

Pump: Bison Solar Pump BSP14-500
Solar panels: 12 Kaneka G-SAO60
Wiring: series/parallel circuits
Watts: 60 W (720W total)
Amps: 0.9A (2.7A total)
Volts: 67V (268V total)
Racking: Farm construction, manual adjustment, 24 (summer), 36 (spring/fall) & 48 (winter) degrees
Water line: 1" poly
Water storage: two 625 "tire" tanks with a float cutoff
Total equipment cost: about $4,500 - $5,000 plus labor and well drilling costs

Designing the system took more than two months of research, but in the end, Pattie reduced the overall costs through thorough cost analysis and by doing the work himself. He designed and built his own racking system. Some of the design elements he chose include four posts with 4-inch tube piping set in concrete 3 feet in the ground and 3-inch reinforced angle iron racking with three adjustable angles of 24 degrees for summer, 36 degrees for spring and fall, and 48 degrees for winter.

Freeze protection for the water lines was also considered. All water lines are buried underground to protect against freezing. A permanent fence will be constructed surrounding the system to protect the equipment.

Do-it-yourself requires a understanding of DC electrical, patience, and willingness to work through mistakes - which may sometimes be time-consuming and costly. Before the system could start pumping, Pattie had to return a controller box that was not operating correctly. It turned out that the controller box just needed to be reset, but this took some back-and-forth between Pattie and the dealer.

"By doing the work myself, I now understand how to maintain and fix the system when it breaks," says Pattie.

Controller (left) installed in a weatherproof box
Controller (left) installed in a weatherproof box with fabricated PVC air vents in top and bottom and the combiner box with lightning arrestor (right).
Photo by Leif Kindberg.

Conclusion

Deep wells combined with solar powered DC pumps may not be able to keep up with livestock water needs. Pattie estimates his system is pumping about 3.75 to 4.25 GPM (he times the flow with a five gallon bucket). When he disconnected one of the circuits wired in series so only eight panels (two sets of four) were connected to the pump, output dropped to about 2.5 GPM. "The dealer thought eight would be enough, but I don’t think so," says Pattie.

By placing watering tanks near the middle of the pasture and close to shade, livestock will be more likely to drink at watering tanks individually rather than as a herd. This will help balance stock water needs with daily pump flow.

If there is any question of whether the system is pumping enough water for livestock, check the water level in the tanks daily - especially after cloudy days and during hot or dry weather. Low volume solar water systems with less storage require frequent water-level checks and may require you to move cattle to nearby water for a few days. Livestock watering systems should usually be designed to store a minimum of 3 days water for cattle and up to 10 days in the most arid and remote locations.

Solar panels, combiner box, and controller
The owner checks leads between the panels, combiner box, and controller.
Photo by Leif Kindberg.

While Pattie did not design his system to store 3 days water, he lives within eyesight of the system and will check the cattle and water level in the tanks daily. He may also add storage over time or adjust the stocking rate. If this was a remote pasture that would be checked less regularly, additional storage would be required.

Overall, Pattie is satisfied with the system. "I plan to put in another one of these solar water pumps if it continues to work well," says Pattie.

For the contact information of Panhandle Sales and Service and other solar water pump equipment suppliers, visit ATTRA's Directory of Energy Alternatives, a nationwide directory of alternative energy installers and consultants.


Water Pumping: A Do-it-yourself Example
By Leif Kindberg, ATTRA Farm Energy Specialist, August 2010

Caution

The do-it-yourself installer should be cautious when designing and installing a solar water pumping system. Strings of PV panels can produce several hundred volts whenever the sun is on them. Talk to a local livestock specialist to determine the number of gallons that is appropriate for your livestock, pasture conditions and climate and build in a reserve. Choose large enough holding tanks to factor in cloudy days when solar pumps may shut down. Avoid shading panels when wired in series. Shading will cause a decrease in voltage and amperage that will affect performance. Installation is complex task that combines elements of electrical work, plumbing, and heavy construction (often including earthmoving, concrete-pouring, and welding). If you do not have experience doing this work, involve someone who does.

 

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This page was last updated on: June 13, 2016