ATTRA is the national sustainable agriculture information service, operated by the National Centerfor Appropriate Technology through a grant from the Rural Business-Cooperative Service, U.S.Department of Agriculture. These organizations do not recommend or endorse products,companies, or individuals. NCAT has offices in Fayetteville, Arkansas (P.O. Box 3657, Fayetteville,AR 72702), Butte, Montana, and Davis, California.

By Mike Morris and Vicki LynneNCAT Agricultural Energy SpecialistsOctober 2002

LIVESTOCK TECHNICAL NOTE

SOLAR-POWERED LIVESTOCK

WATERING SYSTEMS

Remote or off-grid power sources—includ-ing solar panels, mechanical windmills, andportable generators—can pump water forlivestock in locations where electricity frompower lines is unavailable. By encouraginganimals to move away from lakes and streams,these systems give livestock greater access toforage. They also reduce livestock pressure onstream banks—preventing nutrient loading,damage to streamside vegetation, erosion, andpollution.

Solar pumping works anywhere the sunshines, and most parts of the United States

Abstract: This publication gives an introduction to solar-powered livestock watering systems, including discussions ofcost, components, and terminology, as well as some suggestions for designing and installing these systems. The strengthsand weaknesses of solar pumping are compared to the main options for pumping in remote locations: mechanical windmillsand portable generators powered by gas, propane, or diesel fuel. The publication also includes descriptions of threesuccessful projects and a brief resource list.

have plenty of sunlight to run these systems.Solar pumping is a natural match for summergrazing applications, since it produces thegreatest volumes of water in sunny weatherand during long summer days—exactly whenanimals need water the most. With properprecautions, solar pumping systems can beused through the winter months too, eventhough shorter daylight hours will causereduced water output.

Why should you consider installing a solar-powered livestock watering system on yourfarm or ranch? These factors may affect yourdecision:

• Distance from power lines and the cost of aline extension

• Operation and maintenance cost of a solarsystem compared to the alternatives, suchas a mechanical windmill or a gasoline,propane, or diesel-powered generator

• The uncertainty of future electricity prices

• Rising costs of propane, gasoline, and dieselfuel

• Season of use—summer versus winter

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Prices increase sharply where large volumesand deep wells are involved. NCAT estimatedcosts for six demonstration solar pumpingprojects over an assumed 10-year period. Thecost of water per cow ranged from $0.03 to$0.15 per day. The cost per gallon of pumpedwater ranged from $0.002 to $0.007 per gallon.

Gas- or propane-powered generators oftenhave a lower initial cost than mechanicalwindmills or solar power. But many low-endgas-powered generators require frequentmaintenance and have a design life of onlyabout 1500 hours, making them a costly andlabor-intensive option in the long run. On theother hand, better-quality generators havemany strong points. A high-quality self-start-ing propane-powered generator operatesunattended, runs day and night, is easy toinstall, should last for many years, and isespecially well-suited for situations involvingdeep wells and high volumes of water.

Although they cost about one-third morethan comparable gas-powered generators,diesel-powered generators will usually have alower initial cost than wind- or solar-poweredsystems. In low-head and low-water-volumesituations a solar-powered system will gener-ally produce cheaper water than a diesel-powered generator. On the other hand, wherelarge volumes of water are required a diesel-powered system may produce cheaper waterthan a solar-powered system.

Mechanical windmills usually have a some-what higher initial cost than comparable solar

or generator-basedpumping systems.Installation oftenrequires specializedequipment, and somestudies have shownhigher typical mainte-nance costs for wind-mills compared tosolar-powered sys-tems. Since no fuel isrequired, the operat-ing costs for a wind-mill are typicallylower than those for agenerator-basedsystem. Windmills

Many people considering a solar waterpumping system are put off by the initialexpense. Looking at the big picture, though,gives a better idea of the actual cost. For onething, utility line extensions commonly cost$10,000 to $30,000 or more per mile. One rule ofthumb is that remote pumping (whether solar-,wind-, or generator-powered) is worth consid-ering whenever the distance from the utilitygrid exceeds about one-half mile. Where powerlines are readily available they will generallyprovide the cheapest source of power.

Looking at the big picture also meansfactoring in installation, fuel, and maintenancecosts over the life of the project. When youinclude all these factors you may find that solaris an economical choice.

How do you choose between solar power, amechanical windmill, and a gas-, propane-, ordiesel-powered generator? No two pumpingsituations are alike, but here are a few guide-lines:

Solar-powered systems have a relatively highinitial cost compared to the other remotepumping options. Solar-powered systems arealso often described as having comparativelylow operation and maintenance costs. Thismay very well be true. Keep in mind, though,that many solar components are of fairly recentdesign, so reliability data tend to be lacking. In2002, the typical cost for a small to moderate-sized solar pumpingsystem suitable forstock-watering is $2,500to $7,500, not includinginstallation cost or well-drilling. Despite thesteep initial cost, thereare site-specific situa-tions where solar-powered systems can bechosen based on eco-nomic reasons alone.The cost advantages ofsolar pumping aregenerally strongest inlow-head and low-volume situations.

Solar pumpingreplaced a gas-poweredgenerator on theTomlinsonRanch near GoldCreek, MT.

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generally last longer than most solar pumps. Ina good location—where average wind speed isabove about seven miles per hour—a wind-powered pump may produce cheaper waterthan a solar-powered pump.

All of the points just made should be takenwith a grain of salt. The technologies for andcosts of solar-, wind-, and generator-poweredpumping are continually changing. (For ex-ample, no effort is made here to evaluate wind-electric or wind/solar hybrid pumping sys-tems.) Every option has its advantages, and itbears repeating that every pumping and stock-watering situation is site-specific.

Modern solar panels are designed to withstandgolf-ball-sized hail and usually come with 20-year (or longer) warranties.

MOUNTING STRUCTURES

There are two ways to mount solar mod-ules: either on a fixed structure or on a trackingstructure. Fixed mounts are less expensive andtolerate higher winds but have to be orientedto face true south (not magnetic south). The tiltangle also needs to be adjusted. The usualrecommendation is to adjust the tilt angle tolatitude minus 15 degrees for summer use orlatitude plus 15 degrees for winter use, and setthe tilt equal to latitude for year-round opera-tion. For example, if you were located at 40degrees latitude you would set the tilt angle at25 degrees in the summer and 55 degrees in thewinter, or else leave the tilt angle at 40 degreesyear-round.

A tracking array follows the sun across thesky. A tracker will add at least $400 to $800 tothe cost of a system, but in many cases this is agood investment since trackers can increasewater volume by 25 percent or more in thesummertime, compared to a fixed array.Trackers are generally “passive,” meaning thatthey use no electricity. A liquid stored in thetracker is warmed by sunlight and flowsthrough tubing to the opposite side of thetracker. The weight of the fluid causes thetracker to tilt the panels toward the sun.

Once the panels are fastened to a mountingstructure, the system can easily be put on atrailer to make it portable. Towing the trailerfrom one pasture to another makes it possibleto follow animals through a rotation and pumpwater from the nearest well, stream, or pond.

PUMPS

In general, DC water pumps use one-thirdto one-half the energy of conventional AC(alternating current) pumps. DC pumps areclassed as either displacement or centrifugal, andcan be either submersible or surface types.

Displacement pumps use diaphragms,vanes, or pistons to seal water in a chamberand force it through a discharge outlet—similar to the way your heart pumps blood.Centrifugal pumps use a spinning impeller thatadds energy to the water and pushes it into thedischarge outlet, similar to the way water

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A typical solar-powered stock watering system includes asolar array, pump, storage tank and controller.

Before talking to a dealer, you shouldbecome acquainted with the terms and equip-ment:

SOLAR MODULES

Solar electric systems are sometimes calledphotovoltaic systems. The word “photovoltaic”is often abbreviated “PV.” Solar panels, ormodules, generate direct current (DC) electric-ity. A group of modules is called an array.

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sprays off a spinning bicycle tire. Submersiblepumps, placed down a well or sump, arehighly reliable because they are not exposed tofreezing temperatures, do not need specialprotection from the elements, and do notrequire priming. Surface pumps, located at ornear the water surface, are used primarily formoving water through a pipeline. Some surfacepumps can develop high heads and are suit-able for moving water long distances or to highelevations.

STORAGE

Batteries are usually not recommended forsolar-powered livestock watering systemsbecause they reduce the overall efficiency ofthe system and add to the maintenance andcost. Instead of storing electricity in batteries,it’s generally simpler and more economical toinstall 3 to 10 days’ worth of water storagetanks. Adding batteries to a system may makesense, however, if a continuous flow of water isneeded during nighttime and cloudy weather.

CONTROLLER OR INVERTER

The pump controller protects the pump fromharmful high or low voltage and maximizesthe amount of water pumped in less-than-ideallight conditions. An AC pump requires aninverter—an electronic component that con-verts DC electricity from the solar panels intoAC electricity to operate the pump.

OTHER EQUIPMENT

A float switch turns the pump on and offwhen filling the stock tank. It’s similar to thefloat in a toilet tank but is wired to the pumpcontroller. Low-water cut-off electrodes protectthe pump from low-water conditions in thewell.

price seems too high, you can easily get bidsfrom other dealers.

In order to size and design a system cor-rectly, the dealer will want to know:

• How much water you need

• When you need the water

• Whether your water source is a stream,pond, spring, or well

• Water available in gallons per minute(gpm)

• Well depth

• How far the water needs to be pumped,and with what elevation gain

• Water quality problems (e.g., silt or highmineral content) that may damage thepump

• How much volume is available in storagetanks and how the tanks are arranged

Based on these factors, the dealer willrecommend a system, putting together a list ofsuitable components. This is one area wherethe dealer’s experience and familiarity withsystems is essential. A dealer can also save you

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The average consumer is likely to be intimi-dated by the prospect of sizing and designing asolar pumping system, and most people needhelp from a qualified solar dealer. In general,dealers are eager to help. Many will provide ano-cost proposal based on a few simple ques-tions you can answer over the phone. If the

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BALLARD RANCH

LAVINA, MONTANA

When their old water-pumpingwindmill finally died, Jim and AdeleBallard installed a solar pumpingsystem to replace it. The new systempumps water from a 65-foot-deep wellto a pair of stock tanks holding about4000 gallons. Four 80-Watt PV moduleson a tracking rack power a submersiblepiston pump that delivers a maximumflow rate of 5.5 gpm, enough to water100 cow/calf pairs. The system pro-duces average flows of 2000 to 3000gallons per day (gpd) during the sum-mer months. Solar component costs:$5,500.

time and aggravation by providing the correct hardware: clips, screws, nuts, bolts, washers, cable(cut to correct lengths), and assorted wiring and connectors. The customer usually provides periph-eral items, such as water piping and fittings, tanks, the mounting-structure support post, concrete,and grounding materials.

Installing a solar pumping system is generally something the landowner can do. A few wordsof caution are necessary, however. Installing one of these systems is a complex task, combiningelements of electrical work, plumbing, and heavy construction (often including earthmoving,concrete-pouring, and welding). Written instructions are not always as complete as they should be.A backhoe or tractor with a front-end loader is almost a necessity for some larger projects.

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A tracking PV array replaced an old and unreliable windmill onthe Ballard Ranch near Lavina, MT.

HIRSCH RANCH

RACETRACK, MONTANA

Rick and Pam Hirsch installed asolar pumping system on a 10-foot-deep backhoe-dug well on their prop-erty to water 36 cow/calf pairs. Thepumping system uses two 64-Watt PVmodules, a passive tracking rack, and asubmersible diaphragm pumpequipped with a sand shroud and low-water cut-off electrodes to protect thepump. The system is designed toproduce flows of 2600 to 2800 gpdduring the summer months. Solarcomponent costs: $2,400.

This solar pumping system on the Hirsch Ranch near Deer Lodgeis protecting stream banks along Racetrack Creek, an importanttrout spawning stream.

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PAINTED ROBE WATERSHED GROUP, LAVINA, MONTANA

The Painted Robe Watershed Group has been developing off-stream sources of drinking waterfor cattle along Painted Robe Creek, a tributary to the Musselshell River with water quality prob-lems. The group received a trailer-mounted solar pumping system from the Montana Departmentof Environmental Quality. It was first installed on the Leo Schraudner Ranch to water 150 cattle atthe site of a 60-foot-deep well. Seven 60-Watt panels on a fixed trailer-mounted rack use an inverterto convert solar-produced DC to the AC electricity needed by the submersible centrifugal pump.Water is pumped into two 1100-gallon tanks. The system is designed to produce average flows of2880 to 4000 gpd during the summer months. Solar component costs: $10,650.

Water Pumping: the Solar Alternative

This 67-page guide, first published in 1987 bySandia National Laboratories, includes chap-ters on design considerations, system selection,cost, and economics of solar pumping systems.You can order a copy from:

National Technical Information ServiceU.S. Department of Commerce5285 Port Royal RdSpringfield, VA 22161(800)553-6847Or download an Adobe Acrobat .pdf version ofthis document from http://www.sandia.gov/pv/lib.htm

A trailer-mounted PVsystem is improving

range management andwater quality alongPainted Robe Creeknear Lavina, MT.

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Electricity When and Where You Need It: From theSun - Photovoltaics for Farms and Ranches

This 28-page guide, published in 1997 by theNational Renewable Energy Laboratory,includes chapters on pumping water, powerfor buildings, applications around the ranch,and working with the sun.

You can download an Adobe Acrobat .pdfversion of this report (#MK-411-21732) from:http://www.nrel.gov/publications/

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Solar-Powered Livestock Watering Systems, byMichael J. Buschermole and Robert T. Burns.

This 16-page guide, published by the Agricul-tural Extension Service at the University ofTennessee, includes system configurations aswell as guidelines for selecting, installing, andmaintaining solar pumping systems. You canorder a copy from:

Agricultural Extension ServiceUniversity of Tennessee301 Agricultural Engineering Building2506 Chapman DriveKnoxville, TN 37996-4531(865) 974-7266Or download an Adobe Acrobat pdf version ofthis document from http://www.utextension.utk.edu/pbfiles/pb1640.pdf

Edited by Richard EarlesFormatted by Gail Hardy

October 2002

The Montana AgSolar Project

This 86-page report, published by The NationalCenter for Appropriate Technology in Decem-ber 2000, includes case studies, research on themarket potential for solar pumping in Mon-tana, and an overview of current technology.

A downloadable Adobe Acrobat pdf version ofthis report is available from http://www.montanagreenpower.org

Solar equipment dealers and manufacturersare also a good source of information. Viewtheir websites or check the yellow pages fordealers in your area.

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The electronic version of Solar-poweredLivestock Watering Systems is located at:HTMLhttp://www.attra.ncat.org/attra-pub/solarlswater.htmlPDFhttp://www.attra.ncat.org/attra-pub/PDF/solarlswater.pdf

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