Many cattle producers rely on direct access to surface waters, despite wanting to fence out riparian areas and protect water quality. There are many reasons for this, the cost of creating an alternative water source being the big one. This is especially true on leased land, where drilling a well can be hard to justify. In some cases, a lack of electrical service may preclude standard watering systems altogether. Thankfully, using solar power to pump water is now a reliable and affordable alternative.
For the past three years, the Augusta County office of Virginia Cooperative Extension has worked with producers in the Shenandoah Valley to build and test portable, solar-powered watering systems for pumping from surface waters. Along with partners including the Virginia Agricultural Council, our local Conservation District, and the Chesapeake Bay Foundation, we have focused on semi-permanent use, though solar can easily be adapted to a permanent setup. Through this project, we’ve found solar panels to be affordable, effective, and simple to install.
So far, we have built four solar-powered watering systems of similar design, which are constructed as portable setups that draw from surface water using submersible pumps. In each case, the pump is powered by a solar array about 3 x 5 feet in size, and 250 watts or greater, based on site criteria. Most solar panels come standard with quick-connects for wiring that runs from pump to panel.
Each system was designed to pump from a surface water source to a 1,000 gallon reservoir, through 1” diameter or greater, black plastic (HDPE) pipe laid aboveground or buried to a shallow depth. The reservoir then gravity-feeds a portable stock tank governed by a float valve. We sometimes found it helpful to place the reservoir on a wagon or trailer, which provides portability as well as built-in fall for the gravity-dependent systems. Additional considerations should be made when plumbing a gravity-fed stock tank. For example, we tried several float valves before finding a full-flow option that can quickly recharge a stock tank under low pressure situations. Valve placement proved important, as plumbing the valve through the floor of the tank and underwater kept cattle from messing with it. We used a 700-gallon stock tank to ensure plenty of water was available when the herd came to drink.
We often placed the solar panel on the wagon and ran a sensor wire to the reservoir to shut off the panel when the system was topped-off. Alternatively, we also placed the panel closer to the pump and used a pressure switch to turn off the pump when the system storage was full. The solar panel can be located in any sunny location, but it may require lengthening either the pump wire or a sensor wire, depending on the setup, with pros and cons to each option.
We moved our watering systems among farms to test them under different conditions and water sources (currently over a dozen sites). Pumping capacity averaged from 3-6 gallons/minute, depending on the site and the system used. This amounts to around 1,000-1,500 gallons/day, which is enough to meet the daily water demand for a herd of around 40-50 cow-calf pairs. We watered up to 60 cow-calf pairs, but were able to open a limited access point to the creek if a few days of cloudy weather set in. For complete self-sufficiency, many resources recommend sizing the system to store 3 days-worth of water – ours only held about 1 day of storage for a 60-cow herd.
We have pulled water from spring-fed ponds, springs, creeks, and rivers; and pumped against anywhere from 5 to 100 feet of head (pumps are capable of tackling greater elevation, but it varies by the system). In most cases, we established new watering points 300-1,000 feet from the water source, which allowed producers we worked with to fence out their riparian areas and shift grazing to upland pasture. The climate is pretty mild here, so we’ve been able to operate without worry from May-October. Some system modifications such as adding weep holes and pressure relief valves, have allowed us to extend the pumping season through November.
Initially, we had concerns about pumping from turbid water sources. While I would still recommend care in selecting a clean and protected location for the pump, the positive displacement, submersible types we’ve used have done well in pumping water that has been muddied by storms or livestock upstream. You should always select a water source that has adequate recharge to it, and you may want to consider installing a sensor to shut off the system if the water source gets too low.
How can you get started?
Solar panel and pump selection begins with calculating the daily water demand of your herd, including additional water storage for overcast days. A larger panel array than the ones we used, along with more powerful pump, would be needed to accommodate a large herd. Site considerations including solar energy available and total head (elevation gain, friction, etc.) influence the solar system sizing and pump selection for your situation. An online NRCS publication entitled “Design of Small PV Solar-Powered Water Pump Systems” is helpful for selecting solar-powered pumping systems. Solar panels and compatible pumps can be purchased from retail stores or online, as individual components or as ready-to-go kits. For our project, we purchased kits from Advanced Power Solar, and Lorentz USA. Based on the equipment we’ve priced, pump and panel systems capable of pumping up to anywhere from 4 to 6 gal/min. are running around $1,500- $3,000. With the way solar panel prices have dropped, it pays to spend some time shopping around.
While solar pumping can enable stream fencing where it hasn’t been practical before, the possibilities don’t stop there. Solar-generated watering points can open poorly used upland areas to summer grazing, allow pasture subdivision for rotational grazing, and enable stockpiling of pasture to extend the grazing season. Used in this way, solar-powered watering systems can serve as powerful tools to improve grazing management.
Semi-permanent Solar-powered Watering Options to
Enhance Grazing Management
Matt Booher, Extension Agent, Augusta County
Alston Horn, Field Technician, Chesapeake Bay Foundation
John Ignosh, Biological Systems Engineering, Virginia Tech
|Figure 1. 2015. A 270 Watt solar panel used to pump water from nearby river. In this case, water was pumped against roughly 15 feet of head to a reservoir and trough 50 feet from the river. Maximum flow under ideal conditions was 3.0 gallons/minute. The pump was a 34 volt, DC, positive displacement pump.|
Solar-powered pumps can be an option to pump water to livestock where a well and/or electricity are not available. Solar panels and pumps are widely available online, and their cost has decreased considerably in recent years. System design options vary based on management goals, site and budget constraints. However, for the systems explored through this demonstration project, plug-and-go pump and panel systems can be purchased for around $3,000, (not including plumbing) with enough capability to pump about 1,500 gallons/day under ideal conditions. Solar-powered watering systems can be installed on a semi-permanent basis where issues of land ownership dictate (e.g., they can be removed, relocated, etc.). However, the aboveground system components used in these demonstration projects are only operational during freeze-free months, and must be prepared for winter storage to prevent damage to equipment.
|Figure 2. 2016. Solar used to pump water from a small spring creek. This system was initially designed for educational purposes to highlight the primary system components, including a 380W solar array, Lorentz PS200 controller, and a Lorentz HR-07-2 submersible helical pump.|
Many considerations must be taken into account when selecting a solar-powered pumping system, including the water source and flow, and pumping distance and height. It is critical to match the pumping capabilities of the solar panel and pump with the daily water requirements of your livestock herd. Various types of pumps exist, and are broadly classified as either centrifugal or positive displacement, and each one has pros and cons under different conditions. To date, the demonstration projects have used a variety of positive displacement pumps. Proper pump selection is critical. For example, some pumps cope better than others in water containing a lot of sediment. Some pumps are designed to maintain flow rate better than others when operating near their maximum lift capacity. While others are designed to produce more flow at the expense of maximizing lift. It is best to work with potential vendors or manufacturers to figure out what is the best fit for your scenario. A pump curve provides valuable data on a pump’s ability to produce flow against a certain head. We have found that obtaining a pump curve is an important first step in properly configuring a solar-powered pumping system in order to meet the water supply needs for the site.
|Figure 4. 2017. Solar used to pump water from a spring-fed creek. In this case, a 270 Watt solar panel was used to pump against roughly 75 feet of dynamic head to a reservoir and trough 750 feet from the creek. Maximum flow under ideal conditions was about 4 gallons per minute.|
|Figure 5. In-stream water pick-up by a solar-powered pump.|
|Figure 3. 2017. Solar used to pump water from a small river. In this case, a 380 Watt photovoltaic array was used to pump against roughly 115 feet of dynamic head to a reservoir and trough 600 feet from the river.|
|Figure 8. 2017. Solar-powered positive displacement pump being used to pull water from a spring-fed creek. In this case, a 270W solar panel was used to pump against roughly 70 feet of dynamic head to a reservoir and trough 750 feet from the creek. Maximum flow under ideal conditions was about 4 gallons per minute.|
|Figure 6. Using solar to pump water from an old springhead.|
|Figure 7. Solar-powered pump suspended in river. In this case, a 270-Watt solar panel was used to pump against roughly 60 feet of head to a reservoir and trough 300 feet from the river. Maximum flow under ideal conditions was 2.5 gallons/minute. The pump was a 34 volt, DC, positive displacement pump.
“Autonomy” is a term used by the solar industry to refer to backup for when solar panels are not functioning. Since solar systems do not work at full capacity on overcast days, and not at all at night. There are two main options, store energy or store water. Systems can be designed to store excess energy in batteries; however, this can be expensive and add to system complexity. As an alternative, systems can be designed to store pumped water in reservoirs which then gravity flow to troughs. This option may often be the least expensive and a more reliable way to ensure adequate water supply when the solar panel is not producing. An intermediate bulk container (IBC), also known as a cage tank or pallet tote, can be used as a very affordable reservoir. Plumbing multiple tanks together is a simple way to multiply reservoir size quickly. Plastic polyethylene water tanks are more expensive (roughly $0.75-$1.00/gallon of capacity) but are still an option.
|Figure 9. 2017. Solar used to pump water from a spring-fed pond. In this case, a 270 Watt solar panel was used to pump against roughly 10 feet of dynamic head to a reservoir and trough 600 feet from the pond. Maximum flow under ideal conditions was 5.0 gallons/minute. The pump was a 34 volt, DC, positive displacement pump.
Float valve selection
Most people’s first instinct in valve selection is to use the cheap, automatic float valves that abound at many farm supply stores. These may work fine in situations where water is under high pressure and/or required rates of trough recharge are very low. The flow of this type of valve, however, is restricted by the small size of the internal orifice for the shutoff mechanism. When selecting a valve, pay attention to the minimum amount of pressure required for its operation. Some designs can be used even in cases of low-pressure or gravity systems. Consider using full flow valves–which do not restrict the flow coming from the pipe–to recharge the trough more quickly. For a good example of the full flow valve concept, search online for ‘jobevalves.com’ or ‘apexvalves.co.nz’. A standard, brass, bob float valve available at plumbing supply stores can work well too.
For additional information on solar-powered pumping systems design considerations, please refer to Technical Note No. 28 Design of Small Photovoltaic (PV) Solar-Powered Water Pump Systems from USDA-NRCS, for additional information on livestock watering facility design considerations, please refer to Watering Facility: Virginia Engineering Design Note 614 (DN-614) USDA, Natural Resources Conservation Service (NRCS), Virginia or, contact the Augusta County Extension Office: 540-245-5750, firstname.lastname@example.org.