Final Year Project最后一年的项目

FinalYearProjectFinalPresentationTitle:EnergyConversionforlowvoltagesources.Supervisor:Dr.MaeveDuffyAimofProjectTheaimofthisprojectwastodevelopcircuitstodemonstratetheperformanceofbiofuelcellswhicharebeingdevelopedbytheEnergyresearchcentreinNUIGalway.TheidealendgoalwouldhavebeenwhereaMicrobialFuelCellarrangementhastheabilitytochargeamobilephonebattery.OutlineofPresentationThispresentationwilldealwiththefollowingtopics:OverviewofProjectWorkCompletedOutlookforfuturedevelopmentConclusionsQuestions1)Overviewofproject:DemonstrationCircuit:2)WorkCompleted:ThéveninEquivalentcircuit:LEDDemonstrationDemonstrationoffuelcellpoweringlowpowerdevicesStorageCapacitorKnowledgeofchargingalgorithmsDemonstrationoffuelcellpoweringaDCFanThéveninEquivalentcircuit:PowerDensitycurve:BluelinerepresentsthepowerdensityVscurrentdensity.WhitelinerepresentsVoltageVscurrentdensity.Areaacrosswhichpowerdensityismeasuredis5.4cm^2.1cm^2=0.0001m^2Thepointatwhichwehavemaximumpoweroutputisthesecondfromrightsowetakethispoint.Whenworkedoutthefollowingoutputsresult:Power~0.486milli-WattsVoltage~0.42voltsCurrent~1.215milli-AmpsInternalResistanceofFuelCell~345ohmsThéveninEquivalentcircuit:LEDDemonstration:OntestingtheLED’sfoundintheelectronicslabsitwasfoundthatthelowestpowerLEDneededaminimumof3.8milli-Ampsandaminimumof1.83voltstolight.Thismeantthevoltage¤toutputfromthefuelcellneededtobesteppedup.Thereisthreesolutionstothisproblem:Cascadeanumberoffuelcellsinparallel,thiswayincreasingthecurrentoutputandthenuseaDC-DCboostconvertertostepupthevoltage.UseanRCcircuittoboostthecurrentusingamosfetforswitchingandthenuseaDC-DCboostconvertertostepthevoltageup.UsealowpowerLED(1milli-AmpLEDcanbeobtained)Lowpowerdevicesidentified:Voltageneeded:1.5VoltsDCPowerneeded:0.0001WattsCurrentneeded:66.66micro-AmpsVoltageneeded:2.7voltsDCPowerneeded:1.4WattsCurrentneeded:0.42AmpsVoltageneeded:~3.3voltsDCPowerneeded:unknownCurrentneeded:unknownDemonstrationoffuelcellpoweringlowpowerdevices:TodemonstratethesedevicesaDC-DCboostconverterneededtobedesigned.ThiscausedproblemsasmostcommonDC-DCboostconvertersuseeitherdiodesorBJT’swhichhaveadiodebetweenthebaseandemitter.TheBJTisusedduetoitsfastswitchingspeeds.Thediodescauseaminimumof0.3voltagedrop.AstheoutputvoltagefromthefuelcellissolowalreadywecannotaffordtouseBJT’s.Demonstrationoffuelcellpoweringlowpowerdevices:UsingaboostconverterobtainedfromTexasinstrumentscalledtheTPS61200theoutputvoltagecouldbeboosted.ThisconvertergetsaroundtheproblemofusingBJT’sbyusingMOSFET’sinstead.TheTPS61200canneeds0.8voltstostartup,afterwhichitcanoperateatavoltageaslowas0.3volts.AstheTPS61200wastosmalltofitonaboardIneededtoordertheevaluationmodule.Demonstrationoffuelcellpoweringlowpowerdevices:Demonstrationoffuelcellpoweringlowpowerdevices:Demonstrationoffuelcellpoweringlowpowerdevices:Demonstrationoffuelcellpoweringlowpowerdevices:Fromusingtheformulatoworkouttheminimuminductanceneeded(Vin=L*DI/DT),Ifoundthattheminimuminductancerequiredwas2.1333micro-Henry’s.Sothe2.2micro-Henryshouldbesatisfactorytoinducttheinputcurrentfromthefuelcell.Storagecapacitor:AstheDC-DCboostconverterneededmorepoweratstartupthantheMFCcouldprovideaCapacitorneededtointegratedintothesystemtooutputenoughpower.Itwasfoundthroughusingtheequation:thattheEnergywhichcouldbeobtainedfroma0.1Faradcapacitorwouldbeenoughtogetoverthestartuppowerrequirements.3.3Faradand10FaradCapacitorswerealsoobtainedtoenablethepoweringofhighloaddevicesforlongeranddeviceswhichrequiremoreEnergythanthe0.1Faradcapacitorcanstore.Storagecapacitor:Researchofbatterychemistries,chargingalgorithms:Exampleoftypeofvoltageandcurrentusedtochargeaphone:Myphone(SonyEricsson)isalithium-polymerbatterywhichsupplies3.6voltstothephone.Andhas780milli-Amphours.Thechargerforthephonesupplies5voltsandacurrentof1Amp.Thisisprobablyimplementingachargingalgorithmknownasconstantchargewhereaconstantchargeisappliedtothebattery.Thetypeofchargingalgorithmthatcouldbeimplementedforthisprojectwouldbeeitherpulsechargingortricklecharging.DemonstrationoffuelcellpoweringaDCFan:DemonstrationoffuelcellpoweringaDCFan:3)OutlookforfuturedevelopmentContinuouspoweringoflowpowerdeviceHowmanycapacitorsareneeded.Possibleswitchingcontroldevices.HowmanyMicrobialFuelCellsareneededResearchonmoreefficientDC-DCboostconverters.FurtherResearchonbatterychargingprofiles.Therearevariouswaysinwhichacontinuouspoweringofdevicesusingthiscircuitcanbeimplemented.ObviouslyastheloadattachedtotheDC-DCboostconverterchangessotoodoestherateofcurrentdischargefromthecapacitors.Forthisreasonasystemhastobedevisedforeachspecificdevice.Anexamplechosenforthispresentationisthecontinuouspoweringofa1.5voltDCcalculatorThroughtestingithasbeenfoundthatthecalculatordrawsaconstantcurrentof9μAmpsfromoutputoftheBoostconverterandaconstantvoltageof3.3voltsisappliedacrossit.ContinuouspoweringofalowpowerdeviceContinuouspoweringofalowpowerdeviceA0.1Faradcapacitortookapproximately194secondstochargefully.Whentestedafullychargedcapacitorcouldpowerthecalculatorfor100seconds.Thismeantthatifthesystemwasgoingtobeimplementedbyallowingthecapacitorstofullychargethenthree0.1FaradCapacitorswouldhavetobeusedasthechargeratedoesnotequalthedischargerate.ThisalsomeantusingtwoextraMicrobialFuelCellsaseachcapacitorwouldneedtobechargedseparately.ContinuouspoweringofalowpowerdeviceThealternativetothisistochargethecapacitorforabout40seconds.Ifyoudothisthecalculatorcanbepoweredfornearly40secondsmeaningyouwillonlyneedtwocapacitorstocontinuouslypowerthecalculator.ThisinturnmeansthereislessMFC’sneededtochargethecapacitors.Continuouspoweringofalowpowerdevice555TimerMSP430C1101VoltageComparatorPossibleswitchingdevices:Continuouspoweringofalowpowerdevice555Timer:Advantages:Inexpensive(47cent)EasytoimplementDisadvantages:SyncissuesmayariseInflexibleHigheroperationalvoltage&inputcurrent(MoreMFC’susedtopowerit)Minimumof3milli-Amps&4.5voltsContinuouspoweringofalowpowerdeviceVoltageComparator:Advantages:Inexpensive(€1.65)EasytoimplementLowvoltageandcurrentinput(LessMFC’susedtopowerit)1.8volts&15μAmpsDisadvantages:ValueofvoltageacrosscapacitorhastobeverypreciseContinuouspoweringofalowpowerdeviceMSP430C1101:Advantages:MoreFlexibleMPcouldalsobeusedifimplementingasmartbatterychargerLowvoltageandcurrentinput(LessMFC’susedtopowerit)2.2voltsand150μAmpsDisadvantages:Expensive($49.49–Evaluationmodule&chip)MorecomplextoimplementResearchonmoreefficientDC-DCboostconverters.ThefollowinggraphshowstheefficiencyoftheDC-DCboostconverterataninputvoltageof0.8volts:ResearchonmoreefficientDC-DCboostconverters.Anexampleofthislackofefficiencywasobservedwhenpoweringthecalculator.Atthestarttherewasfrom0.9milli-AmpsbeingdrawnfromthecapacitorintotheBoostconverterwhichhad0.8voltsappliedacrosstheinput.Attheendtherewas0.3voltsappliedacrosstheDC-DCboostconverterand2.2milli-Ampsbeingdrawnfromit.Thismeanstheinputpowerwasbetween0.72milli-Wattsdownto0.66milli-Wattsyettheoutputpowerwasonly0.0297milli-Watts.Thisisequalto4.5%efficiency.FurtherResearchonbatterychargingprofiles.Asthe0.1Faradcapacitortakessolongtochargeandoutputsrelativelysolittlepoweritishardtoknowifasystemlikethesystemproposedforthecalculatorcanbealteredtotricklechargeaevena1milli-AmpshourbatterywithoutdrasticallyincreasingthenumberofMicrobialFuelCellsonavailable.ForatricklechargealgorithmusuallytherateatwhichthebatteryisChargedis15%oftherateatwhichconstantchargingAlgorithmsareimplemented.Ifimplementeditishardtoknowwhetherthecurrentbeingdrawnintothebatterywouldbeenoughtocompensatefortheidledischargeofthebatterythroughair.FurtherResearchonbatterychargingprofiles.Throughtestingofthedischargerateofa10Faradcapacitorapossiblewaytoimplementaconstantvoltage\currentchargingalgorithmwasidentified.The10FaradcapacitorpoweredanLedinserieswitha1kresistorfor5minutessupplyingtheLedwithaconstantcurrentof1.6milli-Amps.Thismeansthatiftwelve10Faradcapacitorswherechargeda1.5milli-AmpHourbatterycouldbecharged.4)Conclusion:BetterunderstandingofElectroniccircuitdesign&MFC’sLEDDemonstrationDemonstrationoffuelcellpoweringlowpowerdevicesKnowledgeofchargingalgorithms5)Questions!!