Water For Livestock Using Solar Generated Electricity

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Title:
Water For Livestock Using Solar Generated Electricity
Physical Description:
Fact sheet
Creator:
Williams, Charles A.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:

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Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"Publication date: March 1993."
General Note:
"EES-97"

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University of Florida Institutional Repository
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University of Florida
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All rights reserved by the submitter.
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IR00004849:00001


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FactSheetEES-97 TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/ChristineTaylorStephens,Dean March1993WaterForLivestockUsingSolarGeneratedElectricity1 CharlesA.Williams,HelenH.Whiffen,DorotaZ.Haman2TRADITIONALWATERSUPPLIESSurfacewateristheusuallivestockwatersupply sourceonFloridaranches.Sincetheearly1500s whenSpanishexplorersbroughtcattletoFlorida, creeks,sloughs,lakesandrivershaveprovidedthe waterneededforbeefproduction.Sincethe inventionofthedragline,dug-outpondshavealso beenusedquiteextensivelyasasurfacewatersupply. Thereareadvantagesanddisadvantagesto surfacewatersupplies.Oneofthemajoradvantages ofnaturalsurfacewateristhatithasnoinstallation ormaintenancecosttotherancher.Disadvantages oftenincludethedistancetothenaturalwatersupply, suchasacreek,fromthegrazingarea.Surfacewater alsocanbeunreliableduringdroughtperiods.Itmay oftenpresentahealthhazard.Cattleinfectedwith Leptospirosiscaninfectothermembersoftheherdby urinatinginthewatersupply.Inadditioncertain areasofFloridahaveanaquaticsnailwhichcarries thecattleliverflukeorganism.Anadvantageofdugoutwaterholesisthattheycanbeplacedwherethe rancherwantstheminmostofthe"flatwoods" pasturesinFlorida.However,inadditiontoahigh initialinstallationcost,theypresentthesameor biggerhealthproblemsasnaturalsurfacewater sources.Dug-outwaterholesaregenerallymuddy anduncleansincethereisnoupstreamsourceto refreshthewater. Onsomeranchesonlygroundwaterisavailable naturallyforthelivestock.Windmillsusedfor pumpinggroundwaterenjoyedabriefpopularityin Florida.Fewstillremain,havingbeenreplacedby dug-outwaterholeswherenaturalsurfacewater sourcesareabsent.Windmillsareunreliablein Floridabecauseofgenerallylowwindspeedsand occasionalseveresummerstormsorhurricanes.Calm daysmayleavecattlewithoutwaterandstrong thunderstormorhurricanewindscandestroy windmills.Inadditionwindmillsareexpensiveto purchaseandmaintain.Newenergysuppliesfor pumpinggroundwater,thatarereliableand economical,areofgreatinteresttoFloridaranchers, becauseagoodsupplyofcleanwatercaneliminate manyproblemsinlivestockproduction.ALTERNATIVEWATERSUPPLIESPerhapsthemostcompellingreasonfor rancherstoconsideralternativemethodsofsupplying livestockwateristheincreasingenvironmental concernandlegislationinvolvingsurfacewater.The SurfaceWaterImprovementandManagement (SWIM)legislationiscurrentlybeingenforcedin southFlorida.Naturalsurfacewaterhasbeenfenced 1.ThisdocumentisFactSheetEES-97,aseriesoftheFloridaEnergyExtensionService,FloridaCooperativeExtensionService,InstituteofFood andAgriculturalSciences,UniversityofFlorida.Publicationdate:March1993. 2.CharlesA.Williams,CountyExtensionDirector,OsceolaCounty;HelenH.Whiffen,AgriculturalEnergySpecialist,FloridaEnergyExtension Service/AgriculturalEngineeringDepartment;DorotaZ.Haman,AssociateProfessor,AgriculturalEngineeringDepartment,Gainesville; respectively,IFAS,UniversityofFlorida,Gainesville,Florida32611. TheFloridaEnergyExtensionServicereceivesfundingfromtheFloridaEnergyOffice,DepartmentofCommunityAffairsandisoperatedbythe UniversityofFlorida'sInstituteofFoodandAgriculturalSciencesthroughtheCooperativeExtensionService.Theinformationcontainedherein istheproductoftheFloridaEnergyExtensionServiceanddoesnotnecessarilyreflecttheviewsoftheFloridaEnergyOffice.

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WaterForLivestockUsingSolarGeneratedElectricity Page2offinsomeareaswherephosphorousloadsexceed Table1. Pumpoptionsforsolarphotovoltaicpoweredwaterpumpingsystems PUMPTYPE RATE (gal/min) TDH (ft) COMMENTS positivedisplacementrotaryvane 0.15-3.5 470 self-priming;notsubmersible;does nottoleratesandorsilt;25ftlift diaphragm 1.7-4.8 210 self-priming;canberundrywithout damage centrifugaljet 0.5-23 5-60 self-priming;motormustbekeptdry centrifugal 1-55 100 suctionliftlimitedto25feet centrifugalsubmersible 0.5-67 450 four-inchwellrequired diaphragmsubmersible 0.5-1.7 230 four-inchwellrequired jack 0.5-15 1,000 thewatermanagementdistrict'slimits. Thecostofinstallingelectricpowerlinesforthe purposeofpumpingwaterinremotepastureareasis prohibitive.Usingsolargeneratedelectricitytopump waterforlivestockcanbeacost-effectiveandreliable methodofplacingthewatersupplywhereitisneeded withoutproducingthenegativeenvironmentaleffects ofelectricitygeneratedfromcoal,oilornaturalgas.PHOTOVOLTAIC(PV): ELECTRICITYFROMSUNSHINEManyPVcellsaremadefromsilicon,thesame stuffasthesandatthebeach.APVcellhastwo sides;onesidehasextraelectrons,andtheotherside lackssufficientelectrons.WhensunshinehitsaPV cell,thesolarenergydislocateselectronsfromthe sidewithtoomany.Thesedislocatedelectrons,which haveanegativecharge,aredrawntotheothersideof thePVcellwhichisshortinelectronsandhasa positivecharge.Thissetsupaflowofelectronsin tinywiresconnectedtoeachPVcell.Electrons flowingfromallthePVcellstogethergeneratethe directcurrenteletricitywhichdrivesthemotor.The onlythingthatmovesinaPVcellistheelectrons. PVcellscanlasttwentyyearsbecausethereareno movingpartstobreakdown.EVALUATINGTHEWELLOneofthemostimportantphasesindesigninga solarwaterpumpingsystemisevaluatingthewell.If therancherisfortunateenoughtohaveunusedwells onhisproperty,theexpenseofdrillinganewwell maybeavoidedbyevaluatingthewell.Ifthewellis foundtobeusable,installingthePVpumpingsystem on-sitecanbeasimplematter. Usingcompressedair,thewelldrillercan determinewateryieldanddraw-downleveland removesomeaccumulatedtrashfromanoldwell. Thewaterwillalmostcertainlybedirtyatfirstbut canclearupafterprolongedpumpingiftheoriginal screenandcasingareintact. Anexperiencedwelldrillercanhaveagoodidea ofthewelldepthneededforagoodwatersupplyin hisworkingarea.Inmanycasesartisanpressure pusheswaterclosetothegroundlevel.Ifthisisthe caseandthewellyieldisadequate,acentrifugal pumpcanbeused.Otherwise,submersiblepositive displacementtypepumpsmustbeusedtopushthe waterupandoutofthewell(Table1). Thetheoreticalpumpinglimitforasuctionpump isapproximatelythirty-fourfeet.Thatisthelimit regardlessofthemotorsizeconnectedtothepump becausesuctionislimitedtooneatmosphereof negativepressure.Thepracticallimitfora centrifugalpumpisabouttwenty-feetbecauseofpipe friction,non-perfectseals,etc.

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WaterForLivestockUsingSolarGeneratedElectricity Page3Whenevaluatinganexistingwellforconversionto asolarpumpingsystem,thefollowingquestionsmust beanswered: Whatisthesizeofthewellcasing? Isthecasingingoodconditionwithnopinhole leaks? Howdeepisthewell? Whatisthedepthtothewatersurface? Howmuchwaterwillthewellproduce? Whatisthedraw-downlevelduringwaterflow? Isthewaterfreeofsiltandsand? Howmanygallonsofwaterwillthelivestockneed eachday?SYSTEMDESIGNPVcellsgenerateelectricityattheirmaximum rateunderclear,sunnyskies.Theydon'tgenerate electricityatnightoronextremelycloudydays. UnderpartiallycloudycentralFloridaAugustskies, PVsystemsturnoffandonascloudspassoverhead. Thecertaintyofcloudspassingoverheadandthe occasionalovercastdayarefactorsindesigningthe PVsystem. Therearetwothingswhichincreasethepower outputofaPVsystem:alargerareacoveredbyPV cells,orahighlevelofsunshinealldaylong.While thefirstiseasilycontrolledbydesign,naturealone controlshowmuchsunshinefallsonanyparticular day. ThePVarrayneedstobelargeenoughtodeliver enoughpowertoworkthepumponpartiallycloudy days,butoversizingthePVarrayaddsunnecessary expense. TheDCmotorandpumpassemblymustbesized correctlyalso.Thevoltageandamperage requirementsofthemotorneedtomatchthevoltage andamperageoutputofthePVsystem.Thismustbe checkedcarefully.Directcurrentmotorsaredesigned toworkatvaryingorreducedpowerlevelswithout overheatingasalternatingcurrentmotorsdowhen powerlevelsfluctuate.Iftheentirecapacityofthe pumpisdesiredunderfullsun,thevoltageproduced bythesolararrayshouldexceedthepumpmodel wattagespecificationsbyatleastfifteenpercent. CountyExtensionAgents,TheFloridaEnergy ExtensionService,theFloridaSolarEnergyCenter andsystemmanufacturerscanprovideassistancein systemdesign.OPERATINGEXPERIENCEThewellusedintheOsceolaCounty demonstrationwasanabandonedtwo-inchwindmill well.Thewellwasonehundredfeetdeepwithseven feettothewatersurface.Anexperiencedwelldriller gaugedthewellyieldatthirtygallonsperminutewith draw-downnotmorethaneightfeet.Withthis information,itwasdeterminedthata36DCvolt15 ampmotorandcentrifugalpumpwoulddeliverthe neededwater. ThePVarrayintheOsceloaCountysolar Table2. 1992pricesforvariouslivestockwatersupply options SYSTEM COSTS (approx.) windgenerators(windmills) $4,500 photovoltaic(270peakwatts) Panels:$2,000; Motor&Pump: $600 electricityfromautilitycompany Powerline: $10,000permile; Motor&Pump: $300 dugoutpond $3,000for0.5 acrepondpumpingdemonstrationwasalmost27squarefeet (4.2ftx6.4ft)andcostabout$2,000(Table2).The six-panelphotovoltaicarraywassizedtoproduce270 wattsofDCelectricityfrom2,700wattsofsolar radiation(fullsun)underperfectoperating conditions.Theactualpowerdeliveredtothemotor wasabout240wattsunderfullsunduetofactorssuch aslineresistanceandlengthofrunoftheelectricity. Thesystemneededaminimumof900wattsofsolar power(energyarrivingfromthesun)topumpwater intothetank.Thesystemyieldedupto10gallons perminuteunderpeaksunshine(Figure1). Waterwaspumpedintoafive-hundredgallon watertank.Thefloatswitchturnedthepumpoff whenthetankwasfull,andallowedthepumpto resumeoperationwhenthewaterlevelrecededsix inches.Thisconservedwaterandkepttheground aroundthewatertankfrombecomingmuddyasitdid whenthewindmillwasinoperation.

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WaterForLivestockUsingSolarGeneratedElectricity Page4Theherdusedforthedemonstrationconsistedof Figure1. Solarphotovoltaic(PV)poweredwaterpumping demonstrationforlivestock thirtypregnantcows.ThewatersuppliedbythePV pumpingsystemwasmorethanadequate,sothe installedfloatswitchwasusedalmostdailytoturnthe pumpoffwhenthetankwasfilled,preventingwaste.WHATABOUTCLOUDYDAYS?Justastherearedayswithoutwindtopowera windmill,therearedayswithoutsunshine.Thereare twowaysaroundthecloudydayproblem.Oneisto installapowercontroller,abatterychargeranda batterytosupplyenergytothepumpondemand. Theothersolutionistosimplystoretheenergy,i.e., thewaterabovegroundinalargewatertank,orin severalsmallertanks. Storagebatteriesincreasethecost,complexityand maintenanceofaPVpumpingsystem.Solar pumpingsystemmanufacturersrecommendusingthe abovegroundwatertankstoragemethodwhenever possible.WHATABOUTTRACKINGSYSTEMS?ThePVarrayattheOsceolaCountysolarwater pumpingdemonstrationdidnottrackthesun.Itwas pointedduesouthwithatiltangleofforty-five degreesandmountedonastationarywooden platform.OnatypicalAugustmorning,itbegan supplyingenoughelectricitytopumpwateratabout 9:30a.m.,usuallybeforethesummerdayrainclouds begandeveloping.Thewatertankwould fillinthemorningandkeepthecattle supplieduntilthenextday. SolartrackerswhichtiltthePVarray towardsthesunandfollowitsmovement duringtheday,increasetheamountof electricitygeneratedandtheamountof waterpumped.However,thisadds considerableexpenseandtherancher maypreferthelessexpensive,more dependablestationaryPVarray.CONCLUSIONSolarpumpsrequirenofuelandare lowmaintenance.Therearenomoving partsinthePVcellsandmost manufacturersguaranteethemforalong lifetime. DCpumpscanbeselectedtofitthe existingconditions.Evenifthewellwaterlevelis one-hundredfeetormoredeep,solar-powered positivedisplacementpumpscanpushittothe surface.And,ifawellproducesonlytwogallonsper minute,aPVpoweredpumpcandeliverseven hundredandtwentygallonsofwaterwithonlysix hoursofgoodsunshine. Solarenergyistherewhereyouneedit.Youdo notneedtotruckitorpumpitorpipelineittoyour pasture.Whenthesunisshiningbrightly,makingthe cattlemorethirsty,thePVsystemisalsopumping morewaterforthem.Whenitisovercastandrainy, thePVsystemwillnotpumpasmuchwater,butthe cattlewillnotneedasmuchdrinkingwaterduring cooler,cloudyweather.Therefore,usingsolar photovoltaic-generatedelectricitytopumpwaterfor livestockcanbecost-effectiveandreliable.