Energy Saving Tips for Irrigators

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Energy Saving Tips for Irrigators


<ul><li> 1. ATTRA Energy Saving Tips for IrrigatorsA Publication of ATTRA - National Sustainable Agriculture Information Service 1-800-346-9140 www.attra.ncat.orgBy Mike Morris andThis publication describes ways that irrigators can save energy to reduce irrigation costs. It describesVicki Lynne recommended irrigation system installations, explains how utilities charge their irrigation customersNCAT Energy for electricity and describes common causes of wasted energy, as well as common energy-saving hard-Specialists ware improvements. It also includes a do-it-yourself method to estimate the efciency of electrically 2006 NCAT powered irrigation systems. A listing of references and resources follows the narrative.ContentsIntroduction ..................... 1RecommendedInstallations ...................... 2Centrifugal Pumps ......... 2Turbine Pumps ................ 4Electrical Use andCharges .............................. 5Causes of WastedEnergy ................................ 6HardwareImprovements ................. 7Estimating SprinklerPlant Efficiency ............. 11References ...................... 13Further Resources ........ 13 NCAT photoIntroduction would when properly sized, adjusted, and maintained. (Black and Rogers, 1993) AEspecially in times of high energy costs,study in Colorado, Wyoming, Nebraska,efficient irrigation equipment is essential to and other states found that, on average,the viability of farms and ranches. Accord- about 25 percent of the electrical energying to USDAs 2003 Farm and Ranch Irriga- used for irrigation pumping was wastedtion Survey, there were 43 million pump- due to poor pump and motor efciency.irrigated acres in the United States, withenergy costs for these systems averaging (Loftis and Miles, 2004)$1.5 billion per year, or $36 per irrigatedSince 1988, NCAT has conducted energyATTRANational SustainableAgriculture Information Serviceacre. Farms spent an additional $12 perefciency audits on more than 400 irriga-is managed by the National Cen- acre, on average, to maintain and repair tion systems. In the vast majority of theseter for Appropriate Technology(NCAT) and is funded under airrigation equipment. (U.S. Department ofcases, our technicians identied at leastgrant from the United StatesAgriculture, 2003) one equipment change or repair that wouldDepartment of AgriculturesRural Business-Cooperative Ser-Most irrigation systems are not as ef - quickly pay for itself in energy savingsvice. Visit the NCAT Web site( cient as they should be. A Kansas studyalone. Very often, the irrigators who ownedhtml) for more informa-tion on our sustainablefound that, on average, irrigation systems these inefficient systems were unaware ofagriculture projects. use about 40 percent more fuel than they any problems.</li></ul><p> 2. This publicationOn the other hand, mechanical improve- describes ways to ments do not necessarily result in energy sav- save energy and ings, unless the irrigator makes management reduce irrigation changes that reduce hours of operation. (See energy costs. There Hanson, 2002) This is a key point that are basically fouris frequently misunderstood. Mechani- ways to do this:cal improvements like the ones described in Ma ke mechani-this article generally improve irrigation sys-cal improvements,tem performance, resulting in higher pressureso the irrigationand increased volumes of applied water. Thesesystem uses less improvements in turn should make it possibleenergy during each to meet crop water needs with fewer hourshour it runs.of irrigation. But if the irrigator continuesNCAT photo to run the system for the same number of M a k e m an a ge - hours, energy consumption often stays thement changes, so the system runs same or even increases.fewer hours. This publication focuses on direct energy Reduce cost per unit of energy by, for consumptionusing electricity and fuel toexample, negotiating a better rate run irrigation pumps and motors. Indirectwith the utility, switching fuels, or energy costs are at least as important fornding a lower price for diesel fuel.Related ATTRA many farm operations. Natural gas, elec- Make your own energy by installingtricity, fuel oil, and other fossil fuels are allPublicationsa wind turbine to generate electric- used in making commercial fertilizers andBiodiesel a Primerity or by making your own biodieselpesticides. In 2002, commercial fertilizersfuel, for example. (nitrogen, phosphate, and potash) accountedDrought Resistant Soil This publication focuses on mechanicalfor 29 percent of all energy consumed inDrought Resource improvements. Of course, good managementU.S. farm production. (Miranowski, 2004)GuideThe cost of these inputs has skyrocketed in is also critically important for saving energy.The Montana Irriga-The most obvious energy-saving management recent years. One of the best things farmerstors Pocket Guide strategy is to eliminate unnecessary watering,can do to reduce energy consumption andSoil Moisturemeeting only the water needs of your crops. energy-related costs is to reduce their use ofMonitoring: Low-Cost But you might also consider less obviouscommercial fertilizers and pesticides. ManyTools and Methodsoptions such as changing to less water-inten- ATTRA publications are available on thisWind-powered sive crops, timing plantings to take better topic. See, for example, the ATTRA publica-Electric Systems for advantage of natural precipitation, reducingtions Cover Crops and Green Manures, Alter-Homes, Farms, andirrigated acreage, using mulches and covernative Soil Amendments, Sustainable SoilRanches: Resources cropping to increase soil organic matter andManagement, Pursuing Conservation Tillage build the water-holding capacity of your soils, Systems for Organic Crop Production, andMeasuring andConserving or taking steps (such as planting wind breaks)Farm-Scale Composting.Irrigation Water to reduce evaporation in your elds. Equipment problems and management prob- Recommended lems tend to go hand in hand. Equipment Installations that is badly designed, inefcient, or poorly maintained reduces the irrigators degree Centrifugal Pumping of control over the way water is applied. Problems like patchy water distribution Plant Installation with and inadequate pressure make it impossi-Electric Motor ble to maintain correct soil moisture levels, Especially if you have an older system, your leading to crop stress, reduced yields, pumping plant might look like Poor in Fig- wasted water, runoff, soil erosion, and manyure 1, on the discharge side. (The term other problems. pumping plant means the pump and motorPage 2ATTRAEnergy Saving Tips for Irrigators 3. considered together.) Its a false economy to An eccentric reducer to keep airsave money by installing undersized valvesfrom becoming trapped in theand ttings. Youll only achieve greater fric-reducer tting.tion loss and higher pumping costs. The A vacuum gauge to indicate whethernext time you rebuild your pump, replacethe primer is pulling a vacuumthe ttings so that your pumping plant looksor just moving air through the Ideal in Figure 1.On the Discharge Side of PumpFigure 1. Ideal and Poor Installations A valve that is the same diameter as the mainline.IDEALDischarge pressure Concentric gauge with ball valve A non-slam check valve to pre- expansion Shut-off valveDischarge pipe larger than pump discharge size vent back spin of the pump when shutting it off. An air relief device when a Flexible joint permits some Pipe support buried mainline is used. A discharge line water veloc- Check misalignment and axial valve movement; resolves most thermal expansion problemsValve tooity of less than seven fps.POORsmall Five fps is best. An energy efficient 1,800 rpm motor with a 15 percent Sudden expansion safety factor. (Adapted from Saving Energy on Montana Farms A simple shade over the motor. and Ranches, Montana Department of Environmental Quality.)Figure 2. Recommended Pump Installations, Top and Side ViewsAn ideal installation should also have: A discharge concentric expansion, Solid foundation Gradually increasing tapered sectioninstead of an abrupt change in pipeSump volume (in gallons) at least twice maximum gpmdiameter, to minimize head loss, tur- Inletbulence, and air pockets. All joints Uniformly distributed flow A discharge valve the same diameter Cone increaserwater tightPressure placed at pumpas the mainline. outlet if required gaugeo 45 maximumFigure 2 shows what a plant should look like Straight run of at leastSupports asrequiredwhen pumping from a surface source such as 10 pipe diameters D or straightening vanesTop Viewa river or canal. The pumping plant should for testing flowalso have the following features: CheckvalveShut-offOn the Suction Side of Pump valve A well-designed and screened sumpthat keeps trash out.Primer Straightening vanes orstraight run as short as Side Viewpossible but not less than Suction line joints that are airtightGlobe isolation Vacuum6 pipe diameters D1/4 per footunder a vacuum.valve gaugeminimum upwardslope to pumpGrating, bar racks and screens at beginning of No high spots where air can collect. Smoothmaximum width section long-radius A suction line water velocity of ve elbowsfeet per second (fps) or less. Two tothree fps is best. AnchorPipe supports DMinimum waterlevel (as required) A suction entrance at least two pipe- Drainage boltsEccentric4 DMinimuminlet Inletaway from reducerminimumturbulencebell diameters from sump inlet. motor Suction bell Inlet below A suction lift (vertical distance from As close as possibleD minimum minimum water level D = pipediameterwater surface to pump impeller) lessthan 15 to 20 feet.(Adapted from Energy Efficient Pumping Standards, Utah Power &amp; Light Company.)www.attra.ncat.orgATTRAPage 3 4. Figure 3. Deep Well Turbine Pump Pump motor RECOMMENDEDSounding tube Discharge pipeaccessGrout sealCasing centered in holewith 3 spacers @ 40intervals Pumping water level Static water levelNCAT photo Drawdown less than 60% of water depth Pump housingAbout Pressure Gauges Air lineA good quality oil- or glycerin-lled pressure gauge on the dischargeside of the pump tells a lot about a systems condition. If operationalpressure remains close to the original design pressure, the pump isprobably in good working order. Pressure changes can indicate cloggedsuction screens, leaks, pump wear, worn nozzles, and other problems. Excess pumping rate;Use the gauge when lling the mainline to reduce electrical demand drawdown more than 60% of water depthand water hammer. Extend the life of the gauge by installing a ball NOT RECOMMENDEDvalve on the riser. Keep the valve closed except when referring to thegauge. With a ball valve in place, the operator can remove the gauge (Adapted from Energy Efficient Pumping Standards, Utahduring the winter. Power &amp; Light Company.) Turbine Pump Installation Control Panel for Electric Motors Refer to the left half of Figure 3 for proper The importance of a properly installed installation of a turbine pump in a well. control panel cannot be overemphasized, Many of these same principles apply to tur- both for personal safety and to protect your bine pumps in sumps. The properly con-investment in the pump and motor. structed well should also: Your control panel should: Be at least six inches in diameter larger than the outside diameter of Have a shade over it to cool the well casing when a gravel pack thermal breakers. is required. Be mounted on secure poles Have horizontal well screen slots or foundation. that continue below the pumping Have any missing knockout plugs water level. The openings should hold back at least 85 percent of the and other holes in the starting surrounding material.switch box replaced and screenedor puttied against rodents, insects, The poorly constructed well in the lower and dirt. right half of Figure 3 shows a well casing not centered in the well. Vertical slotted Have a small hole (about 3/16-inch pipe perforations are above the minimumdiameter) in the bottom of the panel water level, creating cascading water. to allow moisture to drain.Page 4 ATTRAEnergy Saving Tips for Irrigators 5. electric consumption orenergy rate. This mayremind you of the ante ina poker gamea fee toget into the energy con-suming game.2. Electric Consumption or Energy Charge. This cha rge is based on the amount of electric- ity used over time as recorded on a kilowatt- hour meter, with a rate charged for each kWh NCAT photoconsumed.Your control panel should include the 3. Electric Demand Charge. Many utili-following controls, at a minimum:ties charge larger customers an amount over and above the electric consump- Circuit breakers for overloadtion charge. The basic rationale forcurrents these demand charges is that the util- Lightning arrester ity incurs costs to maintain enough Surge protectorcapacity to serve the needs of its large customers. Electric providers gener- Phase failure relay, to protect theally calculate the demand charge inmotor from phase reversal or failure one of two ways. Each method gives anand from low voltage approximation of the customers size or A pressure switch to shut off thepower requirements.motor if pumping pressure drops toundesirable levels. a. The demand charge may be based on connected load or horsepower, with a xed rate charged per horsepowerElectrical Use and Power during each billing period. ThisBill Charges charge is usually based on name-Electricity is measured in watts or kilowattsplate horsepower. For example, if(equal to 1,000 watts). The number of wattsthe demand charge is $10 per horse-is the product of operating voltage times thepower, the demand charge for a 40-current (or amps) owing to the load. Ahorsepower system would be $400.kilowatt-hour (kWh) is an amount of energyequivalent to using one kilowatt (kW) over ab. The demand charge may be basedone-hour period. To visualize one kilowatt-on maximum wattage during thehour, it may be helpful to imagine ten 100-billing period. In this method, awatt light bulbs burning for one hour. special demand meter measures wattage for each 15-minute intervalAlthough billing procedures vary among (or some other interval) during theelectric providers and in different regions of billing period. The demand chargethe country, irrigation bills typically includewould be based on the 15-minutethree basic charges for electricity. interval with highest wattage during1. The Base Rate or Meter Charge. This isthe billing period. either a monthly or seasonal charge. For example, suppose the demand charge is Some utilities roll this charge into the $10 per kilowatt, and your demand ATTRA Page 5 6. records use of 29 kilowatts for some 15-2. The wrong pump for the system minute intervals in the billing period, 30 A pump that is oversized, undersized, or just kilowatts for other 15-minute intervals, not right for your system, will never operate and 31 kilowatts for other intervals. You efciently. While it...</p>