780294 ADiesel-Electric HybridBus VernonP.Roan Univ.ofFlorida CongressandExposition CoboHall,Detroit February27-March3,1978 Downloaded from SAE International by University of New South Wales, Sunday, September 16, 2018Downloaded from SAE International by University of New South Wales, Sunday, September 16, 2018780294 ADiesel-Electric HybridBus VernonP.Roan Univ.ofFlorida THEHYBRID CONCEPT FORVEHICLE PROPULSION is certainlynotnew.Therehavebeeninthepast andarestilltodaymanyexamplesoftranspor tationsystemsusinghybridpropulsion systems ofsomekind.However,inmostoftheexamples fromthepastandpresentthemainpurposein choosingthehybridsystemwasotherthenener gyefficiency. Themostrecentexamplewasasurgeofin terestinhybridvehiclesutilizing heaten ginesandvariousenergystoragesystemsinthe late60'sandearly70's.Thisinterest was primarily duetothedifficulty oftheconven tionalheat-engine; mechanical-drive systemin meetingmandatedrequirements forexhaustemis sions.Theoperation ofthesparkignitionen gineorcompression ignitionengineatacon stantspeed,nearmaximumpoweroutput,was knowntoresultingreatlyreducedexhaustem issionsforgiventotalenergyrequirements.Thusthehybridconceptrepresented apoten tialmeansofsatisfying theexhaustemission requirements usingheatenginetechnology av ailableatthatparticular time. Anotheradvantageous characteristic ofthe heatengine-hybrid systemisthatforcertain tasks,suchaspropelling avehiclethrough repeatedaccelerations atvariousspeeds,it canprovidethepowerrequirements usingan engineconsiderably smallerinhorsepower (and corresponding displacement) thanwouldother wiseberequired. Inahybridsystemofthis kind,theheatengineprovidesonlytheaverage powerrequirements, whiletheenergystoredin theformofbatteries, flywheels, etc.provides thehigherlevelsofpowerforaccelerations andtemporary topspeed. Afinalcharacteristicoftheheatengine-hybrid system,whichis veryimportant insomecases,isthatforshort periodsoftimeavehiclemaybepropellednor ABSTRACT Adiesel-electric hybridbushasbeen developedattheUniversity ofFlorida. The drivesystemisaserieshybridwithtwolead acidbatteries andadiesel-driven threephasealternator. Itwasdesigned withthe aidof acomputersimulation program, andhasundergonethreeevaluation phasessincetheinitial construction phase.Allresultstodatehave confirmed thefeasibility ofthesystemin cludingapparentsignificant advantages inthe areasofexhaustemissions andfuelconsumption. 0148-7191/78/0227-0294S02.50 Copyright©1978SocietyofAutomotive Engineers,Inc. Downloaded from SAE International by University of New South Wales, Sunday, September 16, 20182 mallywithoutoperating theheatengineatall,i.e.,thevehiclemayoperateentirely onthe storedenergy. Itwasprimarily thesereasons: theex pectedreduction inemissions, thereduction oftherequiredenginepower,andthepossibilityoftemporarily operating thevehicle inanall-electric mode,thatfirstledto thedevelopment oftheUniversity ofFlorida FloridaDepartment ofTransportation hybridelectric urbantransitvehicle. Theresearch programbeganintheFallof1973,andthe vehiclewasfirstoperational inDecemberof 1974.Todate,fourseparatestudyphases havebeencompleted andafifthisinprogress. DISCUSSION Whiletherearemanyvalidarguments forand againsttheuseofthehybridsystem,andfor parallelhybridversusserieshybrideachwith variouschoicesofprimemoversandenergy storagedevices,thoseargmentsarenotcon sideredinthispaper.Thedecision wasmade atthebeginning oftheresearchprogramto investigate thefeasibility oftheserieshy bridsystem,bydeveloping anaccuratecom putersimulation, andtoimplement theconcept intohardwareifprovedfeasible. Further, decisions weremadeatthebeginning ofthepro gramthattheheatenginewouldbediesel- fueledandthattheenergystoragewouldbe provided bylead-acidbatteries. Consequent ly,theprogrambeganwiththegeneralcon figuration predetermined andaprimarygoalof studyingfeasibility throughoptimization, andtranslating theresultsintohardware. Thisparticular serieshybridarrangement isessentially abatterypoweredelectricve hiclewithanon-board power