Saving Energy on WA Dairy Farms 1

Water Heating• Minimise the volume of water used to wash the plant and vat. Wash at the lowest temperature possible without

compromisinghygiene.• Useathermometertomonitorhotwaterinputsandoutputs.• Installawaterheaterwithcapacityforalldailywashrequirementssothatallheatingcanoccurontheoffpeaktariff.• Ifatimeofusetariffisinplace,installatimertoensurewaterisonlyheatedduringtheovernightoffpeakperiod.• Installahotwaterpreheatingdevicesuchasaheatrecoveryunitorsolarhotwaterheatersothatmostoftheheating

canoccurwithoutusingextraelectricity.• Insulatepipestoreduceheatloss.• Keepstoragetankoutofbreezewaysanddrafts.• Usethebestqualitywateravailable–highlevelsofmineralsororganicmatterreducesheatingperformance.

SolarHotWaterSystemsIn most cases producing hot water for the dairy using a solar hot water system is the best move financially andenvironmentally.Therearetwotypesofsolarhotwatersystems,flatpanelcollectorsandevacuatedtubesolarcollectors.Flatplatecollectorshavecopperpipesrunningthroughaglasscoveredcollector,oftenconnectedtoawaterstoragetankontheroof.Thewaterthermo-siphonsinandoutofthetank,heatingthewater.

Evacuatedtubesuseaglasstubewithavacuuminsideandcopperpipesrunningthroughthecentre.Thecopperpipesareconnectedtoacommonmanifoldwhichisconnectedtoaslowflowcirculationpump.Thispumpswatertoastoragetankbelow,heatingthehotwaterduringtheday.Thehotwatercanbeusedatnightorthenextdayduetotheinsulationofthetank.

Flat Plate Evacuated Tube

Less expensive ($10,550*) More expensive ($11,039**)

Operates most efficiently in the middle of the day

Can heat water to a higher temperature as they have a greater surface area exposed to the sun at any one time (40% more efficient)

More sensitive to frost causing damage to the collectors

Can be used in sub zero and overcast conditions (can extract heat out of the air on a humid day).

Risk of overheating as the water reaches its maximum temperature in the tank the pressure and temperature valve automatically activate and release some water to allow for cold water to come back in reducing the temperature build up. The number of tubes needs to be matched to the quantity of water to be heated to minimise the risk.

Heavier Lighter – some lightweight designs can be mounted on walls and even poles.

Requires a smaller roof area.

Less corrosion than flat plate systems.

Are durable and broken tubes can be easily and cheaply replaced.

Quotesobtainedfromwww.dpi.vic.gov.au/agriculture/dairy/energy-in-dairy*SolarDynamics–3x300Lstoragetankswithnointernalboost,sixflatpanelsandthreemanifoldkits.**ApricusAustralia-90evacuatedtubesandheatpipes,threemanifoldkits.

PhotocourtesyofSCEEnergySolutions

Saving Energy on WA Dairy Farms 2

BoostersInthecoolermonthsasolarhotwatersystemwillnotprovidewatersufficientlyhotenoughtocleanthemilkingmachinesoanelectricboosterisrequiredforbothflatplateandevacuatedtubesystems.Itisrecommendedthatwateriskeptbelow90°Centeringtheline(undervacuum)topreventsteamfromdamagingthevacuumpumpbutwillstillneedtobehotenoughtoachieveaneffectivecleanofthemilkingmachine.

Factorstoconsiderwheninstallingsolarhotwatersystematthedairy• Tanksizesarelimitedto315Lor440L.Costsincreasedramaticallywhenmoretanksareneeded(CowTimeresearchshows

thateachclusterrequiressevenlitresofwaterperwash.Usethistocalculatethevolumeofhotwaterrequired).• Correctinstallationandmountingiscriticaltosuccess.Theroofneedstobestrongenoughtoholdthesystem.Thecollector

shouldbemountedtofacenorthortheamountofenergythatcanbecapturedisreduced.Thetiltangleshouldbethelatitudeoftheinstallationsite.

• Thehigherthequalityofcollectorsinthesystemthehotterthewaterproduced.• Ifyourgas/electrichotwatersystemhasplentyoflifeinit,considerretrofittingcollectors,pumpandcontrollertoanexisting

storagetank.Theretrofitoptioncansavelargeamountsoninstallationbuteliminatestheneedtoreplaceanexistinghotwatercylinder.

ThermalHeatRecoverySystemsAlargeamountofwasteheatgeneratedduringmilkingcanbeharvestedandused.Sourcesincludetheplatecooler,refrigerationsystemsandsomevacuumpumps.Heatrecoverysystemsareavailablethatcapturetheheatfromthemilkrefrigerationsystemanduseittoheatwater(to50°Cto60°C).Thesystemsitsbetweenthecompressoronthemilkvatandtheaircooledcondensertoextracttheheatduringmilkcooling.Thehotrefrigerantgaseswithhighpressurefromthecompressoraretransportedtotheheatrecoverysystemwheretheheatisreleasedintothecyclingwaterinthesystem.Mostofthecommercialunitsavailablehave450Lcapacity.Thiswatercanthenfeedintothehotwatersystem.Usingwatertoremoveheatfromtherefrigerationsystemismoreefficientthanusingairsoimprovestheefficiencyandlifeofthecompressor.

Advantages Disadvantages

Free energy from the refrigeration system Capital expense ($7000-$11,000)

Can reduce milk refrigeration costs if properly designed Poorly designed systems can result in water that is too hot and reduce the overall efficiency of the refrigeration

Con prolong the life of the compressor Difficult to recover heat from the large volume of warm water generated from the plate cooler (without insulated storage)

In some cases can get water to greater than 75°C

*informationfromCowTime

WashingRegimesIs there a better way?• Checkthetemperatureofthewashwaterinthedrumasthewashcyclecommences(itshouldnotexceed85°C).

• Duringrecirculationthedrumshouldbearound20%fullasthewashwaterreturns.Ifitismorethensmallerwashquantitiesshouldbeconsidered.

• Investigatedetergentsthatworkeffectivelyatlowertemperatures.

• Useachemicalsanitiserinthefinalwashcycletoreducehotwaterdemand.

• Capturethefinalrinseforusenexttime.

Saving Energy on WA Dairy Farms 3

Cost ArecentprojectfromDPIVictoriadevelopedahypotheticalcasestudydairyfarminsouthGippslandtoestimatethecostofenergysavingtechnologies.Thecasestudyassessedthecostassociatedwithaheatrecoverysystemtoheat700litresofwaterto65°C.Thepreheatedwaterenteredtheelectrichotwaterservicetoheatto90°Covernight.Theenergysavedunderthesystemwas41kWhwhichequatedto$2905savedinthefirstyear.Thecapitalinvestmentofthesystemwas$7375plus$3000forinstallation.Thesystemwasaprofitableinvestmentwhichrecoupedtheinitialcashoutlayandwill cost less thanbusiness-as-usual in yearfive.After yearfive thesystemwouldbeacheaperalternativetoelectrichotwater.Attheendofyeartenthesystemwas$16800betteroffthanbusiness-as-usualandhadaninternalrateofreturn(IRR)of27percent.

Factorstoconsiderwheninstallingthermalheatrecoverysystems• Correctinstallationontheexistingmilkcoolingsystemtoachievetargetwatertemperatures• Thevolumeofthewatertankandvolumeusedduringandbetweenmilkings.• Theamountofmilktobecooledwilldeterminehowmuchheatcanbecaptured.• Thenetworkwatertemperature.• Typeofrefrigerantgasesandtheconfigurationoftheinstallation.• Combininganevacuated tubesolarhotwatersystemwith the thermalheatrecoverysystem.Thiscanbean

optionthatwillreducedependencyonelectricitybutthecomplexityofcombiningthedifferentsystemswillneedtobeconsidered.

Heaps of Hot WaterBobandJacquiBiddulphrealisedthatheatingupto1600Lofwater,towashtheir44standrotaryinCowaramup,formedabigpartoftheirelectricitybill.ParticipatinginWesternDairy’sEnergyAuditprogramconfirmedthatthedecisiontopurchaseanEnergyRecoverySystem(ERS)wastherightone.

The dairy already had two 800 L Wilson hot water storagetankswhichheatedupcoldwaterduringoffpeakperiods.This was complemented by the installation of two 550 LDelaval Energy recovery tanks which heat water using thewaste heat generated from the vat compressors. The ERSsystemcost$12,500(45percentwasinstallationofelectricsandplumbing)andatcurrentelectricityrates(notcountingrisingrateincreases)thepaybackperiodwillbe3years.

Bob has been very happy with the result. “We recentlymeasuredsurpluswaterfromtheheatrecoverytankanditvariesbetween60°Cand73°C.Thismeansthattheelectrichotwatersystemonlyhastoheatitanother20-30°Cbeforeitisreadyforwashingoutthemilkingmachine”Bobsaid.

AnanalysisoftheirelectricitybillsestimatesthattheBiddulphsareusingapproximately18percent fewerunitsofelectricitythanforthesameperiodlastyear,despitemilkproductionoverthatsameperiodbeingup20percent.Bobhasbeenunableto quantify the savings accurately, but he feels that the milkcoolingsystemisworkingmoreefficientlywiththecompressorshuttingoffearlier,despitethisyear’slonghotsummer.

BobandJacquihadtoyedwithvariousideasinthelastfewyears for reducingcostsassociatedwithheatingwaterbutfeltthattheheatrecoveryunitsgavethemthe‘biggestbangfortheirbuck’.TheERSalsoallowsforquickaccesstohotwater through an outlet direct from the tanks. This hasprovedhandyforwashingcalfbucketsandgeneralcleaning,andmeans thatwater isnot sourceddirectly from thehotwaterstoragetanks.

Saving Energy on WA Dairy Farms 4

Facts about Heat Pumps• Most have a volume of 340 L, however 400 L and 1000 L

tanksarealsoavailable.Twoormoretankscanbeinstalledinmanifoldtosupplylargevolumesofhotwater.

• Tanksaremadeofstainlesssteel,copperorceramiclinedsteel.• Compressormotorsareusuallysmalldrawing0.7kWto4.2

kWdependingonthemodelandsizeoftheunit.• Smaller units run off single phase and large models will

requirethreephasepower.• Of the energy required to heat the water, two thirds comes

fromtheheatintheair,andtheremainingonethirdfromthepowerusedtodrivethecompressor.

HeatPumpsAheatpumpcanreducepowerconsumptionandcostsbypreheatinglargevolumesofwaterto60°C.Asolarheatpumpworkslikearefrigeratorinreverse.Thecompressorontheheatpumptransfersheatfromthesurroundingairtowaterheldinaninsulatedtank.Thewaterfromtheheatpumpisthentransferredtothehotwaterheatersoitcanbeheatedtotherequiredtemperaturerequiredtowashthemilkingmachine.Theyarenotasubstituteforthehotwatersystem.

Savingsofapproximately40percentcanbemadewithheatpumpsToheat800Lofwaterto85°Csavingsrangedfrom$700foroffpeakhotwatersystemsto$2500wherethereisnooffpeakhotwateratthedairy(EwenReport).

Manufacturersrecommendthatheatpumpsshouldbeoperatedduringthewarmerpartofthedaywhentheywillworkmostefficientlyastheambienttemperatureis highest. They can operate at night as they do notrequire direct sunlight to work. Some heat pumpshavebeendesignedtoworkinambienttemperaturesrangingfrom-10°Cto+40°C.

CostThe Ewen Report indicates that three tanks inmanifoldwithacapacity toheat800Lofwatercostsapproximately$12,000includinginstallation.Ifthereisnooffpeakpowersupplyatthedairy,installingaheatpumptopreheatwatercansaveupto$2500eachyear.Inthisexamplethepaybackperiodwasfiveyears.