Assessment of BYD K11 Battery Electric Bus operation on ...evaluating the capability of the BYD K11 60-foot articulated bus for service on ABQ Ride’s BRT service branded as Albuquerque

Assessment of

BYD K11 Battery Electric Bus operation on the

Albuquerque Rapid Transit (ART) Service

Submitted by:

The Center for Transportation and the Environment

Issued: November 7, 2018 Revised: December 5, 2018

AssessmentofBYDK11BatteryElectricBusoperationontheAlbuquerqueRapidTransit(ART)ServiceAlbuquerqueRapidTransit(ART)Service

CenterforTransportation&theEnvironment Page2

Introduction

TheCityofAlbuquerque’sTransitDepartment(ABQRide)engagedtheCenterforTransportationandtheEnvironment(CTE)toconductavehicleperformanceassessmentonbusesdedicatedtoAlbuquerque’snewbusrapidtransit(BRT)service.CTEwastaskedwithevaluatingthecapabilityoftheBYDK1160-footarticulatedbusforserviceonABQRide’sBRTservicebrandedasAlbuquerqueRapidTransit(ART).Specifically,ABQRiderequestedanassessmentoffuelefficiency,dailyrange,chargingprofiles,andfuelcoststhatcanbeexpectedfromdeployingtheBYDK11busonthenewARTBRTservice.

ThisdocumentsummarizestheresultsofCTE’sscopeofwork,whichincluded:• Performancevalidationandroutemodeling,• Chargemodeling• Ratemodeling• Operationsandchargingassessment

PerformancevalidationandroutemodelingisusedtodetermineiftheselectedbusesarecapableofmeetingtheexpectedserviceforwhichABQRidepurchasedthem.Chargemodelingisusedtoestimatethechargetimerequiredforthebuses,theenergyconsumedduringcharging,andpowerdemandforcharging.Ratemodelingisusedtoestimatethecostoffuel(i.e.,electricity)neededtooperatethebuses.Theoperationsandchargingassessmentevaluatesserviceblocksandvariouschargingstrategies,includingdepotandon-routecharging,thatcouldbeusedtooperatethebusesontheblocks.Astheseassessmentsareinterrelated,theresultsarepresentedinacombinedfashion.



Field Testing

SincetheBYDbusesanddepotchargersarealreadydeliveredandcommissioned,CTEchosetocollectdataonthebusesinsimulatedserviceratherthanperformcomputersimulationsoftheservice.Basedontheobservedperformanceandpastexperienceandengineeringcalculations,CTEprojectedtheperformanceofthebusunderavarietyofoperatingconditions.

CTEstaffvisitedABQRide’sDaytonabusdepotonSeptember4–7,2018.BYDstaffalsoparticipatedinthetesting.

Theweatherconditionsduringtestingrangedfrom64to80°Fahrenheitwithmostlysunnyskies.

CTEdesignedthetestplananddirectedthetest.BYDprovidedengineeringsupportandABQRideprovidedthebusesanddrivers.Thebuseswereballastedwithwaterbarrels,asneededforspecifictests,tosimulatepassengerloads.ABQRideadded18waterbarrels,weighingapproximately8,700lbs.,whichistheequivalentof58passengerswhenusingthesame150lbs.perpassengerdefinedbyFTA.

Thetestplanutilizedthreebuses:onetooperatetheBRTroutesatcurbweight,onetooperatetheBRTrouteswithballast,andonetooperateintheparkinglottotestHVACloads.ThesetestconditionsweredesignedsothatCTEcouldprojectthebusperformanceunderconditionsotherthanthosethatprevailedonthedayofthetests.

AsummaryoftheroadtestisshowninTable1.

Bus BeginningSOC

Distance(miles)

Time(hh:mm)

EndingSOC

1706(curbweight) 84% 110.2 10:28 26%

1702(≃8700lb.ballast) 85% 109.6 10:43 24%

Table1:RoadTestSummary

Table2showstherawdatacollectedduringthetestofthestationarybusrunningtheHVACsystem.Theenergyusagemeasuredinthistest,astudyofAlbuquerque’sclimateconditions,andCTE’spriorexperiencewithotherbusesinformedCTE’sprojectionsofthebusperformanceonhotterandcolderdaysthanexperiencedduringthetesting.



Time SOC EnergyRemaining(kWh)

EnergyUsed(kWh)

ElapsedTime(min)

Temp(°F)

7:30AM 94% 506.8 0.0 30 648:00AM 94% 506.8 0.0 30 8:30AM 93% 501.4 5.4 30 9:00AM 92% 496.0 5.4 30 669:30AM 91% 490.6 5.4 30 10:00AM 91% 490.6 0.0 30 10:30AM 91% 490.6 0.0 30 11:00AM 90% 485.2 5.4 30 11:30AM 90% 485.2 0.0 30 12:00PM 89% 479.8 5.4 30 7312:30PM 87% 469.0 10.8 30 1:00PM 87% 469.0 0.0 30 1:30PM 86% 463.6 5.4 30 2:00PM 84% 452.8 10.8 30 2:30PM 84% 452.8 0.0 30 783:00PM 82% 442.1 10.8 30 803:30PM 81% 436.7 5.4 30 804:00PM 80% 431.3 5.4 30 804:30PM 79% 425.9 5.4 30 805:00PM 77% 415.1 10.8 30 805:30PM 76% 409.7 5.4 30 806:00PM 75% 404.3 5.4 30 796:20PM 74% 398.9 5.4 20 Table2:StationaryVehicleEnergyUse



Performance Validation

Acommonchallengeinanybatteryelectricbusdeploymentisthelimitedenergystorageavailableascomparedtoconventionallyfueledbuses.Albuquerque’sBYDbusesweredesignedtohaveacapacityof591kWhwhenfullychargedandBYDrecommendsusing90%ofthiscapacityforservice.Serviceenergyisdefinedastheenergyavailabletopowerthepropulsionsystem,aswellastheHVACandauxiliarysystems(lighting,doors,radios,etc.).Therefore,theserviceenergyfora591kWhbatteryis532kWh.Batterycapacitymaybelowerthanthedesigncapacityduetobatterydegradation,whichisaphenomenonthatreducesthebatterycapacitythroughuseandthepassageoftime.Ifthebatterydegrades,theavailableserviceenergywillbelower.

CTEmeasuredtheactualcapacityofbuses1702and1706bydischargingthebusesandthenfullychargingthem.Table3showstheactualbatterycapacityofthesetwobusesasmeasuredbyBYDdataloggers.Thebatteriesinthetwobusestestedhaveeithersuffereddegradationortheoriginalcapacitydidnotmeetthedesigncapacity.

Bus Capacity(kWh) ServiceEnergy(kWh)

BYDK11DesignGoal 591 532

1702Measured 551(-7%) 496

1706Measured 527(-11%) 474

CapacityUsedinCTEProjections 551 496ExpectedCapacityatEnd-of-Life(70%ofDesign) 414 373

Table3:BatteryCapacity

Charging Power TheBYDbusesuseanonboardchargerratedat200kW.

CTErecordedthechargepowerforbothbusesduringthechargetest.ThechargepowerwasrecordedfromtheindicationonthebusdashboardandisthereforeaBYDmeasurement.Thechargepowerwasfoundtovaryacrossthestateofchargerangeofthebattery.Inotherwords,thebuseswerefoundtochargeslowerorfasterdependingonthestateofcharge.

AccordingtoBYD,thechargepowerislimitedbytwomainfactors:cellvoltageandcelltemperature.Thetractionbatteryiscomprisedofhundredsofcellseachofwhichmustbemonitoredbytheintegratedbatterymanagementsystem.Itislikelythatthebatterymanagementsystemwaslimitingthechargerpowerbydesigninordertolowertheriskofdamagingthebatteries.

Astandardpracticeistoreducethechargerateathighstatesofchargeinordertokeepthecellvoltagefromclimbingbeyondthemaximumallowablecellvoltage.CTEobservedthiseffect



duringthechargeprocessofABQRide’sBYDbuses,butthechargepoweratverylowstatesofchargewasalsolimitedandthecauseisunknown.

CTEobservedlowerchargeratesthanthechargerratingacrosstheentirerangeofstatesofcharge.Onepossibilityforthereducedperformanceisthatthebatterypacksmaythermallylimitthechargeperformance.TheARTBYDbatterypacksdonothaveanytypeofactivecoolingsysteminsteadrelyingonnaturalconvectiontorejectheat.Chargetestingaftercoldsoakingthebatteriescouldtestthistheory.CTEdoesnotcurrentlyhaveenoughinformationtoknowthereasonforthechargelimitationthatcouldbeunrelatedtothermallimitations.

TherawdataCTEcollectedforeachbusisshowninTable4andTable5.Thestate-of-chargecolumn(SOC)and“time-to-full”columnswerealsorecordedfromthebusandarethereforeBYDmeasurements.

Time ElapsedTime(hh:mm) SOC Energy

(kWh)TimetoFull(hh:mm)

Power(kW)

1:38PM 0:00 4% 22.05 2:45 1:47PM 0:09 11% 60.63 2:34 2:07PM 0:29 22% 121.26 3:27 2:20PM 0:42 27% 148.82 3:14 1252:38PM 1:00 33% 181.90 2:57 1252:51PM 1:13 38% 209.46 2:42 1253:06PM 1:28 44% 242.53 2:31 1243:19PM 1:41 49% 270.09 2:18 1243:45PM 2:07 58% 319.70 1:51 1234:03PM 2:25 65% 358.28 1:35 1234:15PM 2:37 69% 380.33 1:23 1234:31PM 2:53 75% 413.40 1:07 1224:48PM 3:10 81% 446.47 0:51 1225:03PM 3:25 87% 479.54 0:36 1225:16PM 3:38 91% 501.59 0:23 1235:30PM 3:52 96% 529.15 0:09 1235:45PM 4:07 99.5% 548.44 0:02 1235:48PM 4:10 99.5% 548.44 0:03 755:53PM 4:15 100% 551.20 Table4:Bus1702ObservedChargePower



Time ElapsedTime(hh:mm) SOC Energy

(kWh)TimetoFull(hh:mm)

Power(kW)

2:06PM 0:00 5% 26.35 2:39 1872:11PM 0:05 10% 52.70 2:32 1872:22PM 0:16 16% 84.32 2:22 1852:37PM 0:31 23% 121.21 3:20 1252:50PM 0:44 27% 142.29 3:07 1253:05PM 0:59 33% 173.91 2:54 1253:20PM 1:14 39% 205.53 2:39 1253:45PM 1:39 48% 252.96 2:15 1254:01PM 1:55 54% 284.58 2:00 1254:15PM 2:09 59% 310.93 1:46 1254:31PM 2:25 65% 342.55 1:31 1244:47PM 2:41 71% 374.17 1:16 1235:02PM 2:56 77% 405.79 1:00 1235:15PM 3:09 82% 432.14 0:48 1235:29PM 3:23 87% 458.49 0:34 1235:46PM 3:40 93% 490.11 0:17 1236:00PM 3:54 97% 511.19 0:08 1256:13PM 4:07 100% 524.37 0:01 1256:16PM 4:10 100% 524.37 0:00 1236:28PM 4:22 100% 524.37 0:00 756:33PM 4:27 100% 527.00 0:00 0

Table5:Bus1706ObservedChargePower

Table6showsasummaryofthechargeperformanceforeachbus.Theaveragechargepowerduringthedurationwascalculatedusingthebeginningandendingstate-of-chargeandthebatterycapacity,eachasreportedbyBYD,toestimatetheenergyreplenished.Notethatthereissomemeasurementerrorinthetableasoneentryhaschargeperformanceovertheratedlimitofthecharger.However,CTEiscomfortablethattheaveragespresentedlaterareclosetotheactualperformance.



Duration(hh:mm)

SOCAfterDuration

EnergyReplenished*(kWh)

Power(kW)

1702(551kWh)

First30Minutes 0:29 22% 99 205UntilTop-offChargeBegins 3:38 99.5% 427 118

TotalTime 4:15 100% 529 125

1706(527kWh)

First30Minutes 0:31 23% 95 184UntilTop-offChargeBegins 3:39 99.5% 403 110

TotalTime 4:27 100% 501 113

Average

First30Minutes 0:30 22.5% 97 194UntilTop-offChargeBegins 3:38 99.5% 415 114

TotalTime 4:21 100% 515 119Table6:ChargePerformanceSummary

TheaveragechargepowerforeachbuswascalculatedbyCTEbasedonthedatarecordedfromtheBYDinstrumentpanel.TheresultsarereportedinTable7.CTE’stestingdidnotincludeon-routecharging.BYDhassuggestedthatchargeratesforashorton-routechargewouldbefasterthanmeasuredduringdepotcharging.CTErecommendsfurthertestingtoverifytheactualchargeratepossiblewithshortchargingdurationsduringvehicleoperations,simulatingon-routecharging,toensurehighcelltemperaturesduringthecharge.Highcelltemperatureswouldbeexpectedtobemoreofaconcernduringthesummermonths.

Power(kW)ChargerRatedPower 2001702ObservedAveragePower 1251706ObservedAveragePower 113BYDEstimatefor10Min.Charge 180

Table7:AverageChargePower



Capability Analysis

Assumptions for Performance Projections

Battery Capacity Aspreviouslypresented,CTEused551kWhasthebatterycapacityforitsrangeprojectionssincethiswastheobservedcapacityon1702.ThisislowerthantheBYDdesigngoalforthebatterypack.Bus1706hadalowerobservedbatterycapacity,however,BYDinformedCTEthatbus1706requiresrepairstothebatterysystem.Thecapacityof1706isexpectedtobeatleast551kWhifBYDisabletocompletetherepair.

Inadditiontocurrentlyobservedbatterycapacity,CTEalsoanalyzesbusperformancewhenthebatteryisfullydegradedtothewarrantylevel.BYDhaswarrantedtheARTbusesto70%degradation,meaningthattheywillrepairorreplacethebatterysystemtoacapacityabovethe70%degradationminimum.Notethatdegradationisaffectedbycellmanufacturingquality,chargecycles,levelofdischarge,operatingtemperature,andthepassageoftime.Eachagencywillhaveadifferentexperiencewithdegradationanditisdifficulttopredictthetimingorlevelofdegradation.

CTEalsoanalyzedtheperformanceofthebusesat590kWhthatisnearlyatthedesigngoallevelandthusrepresentsabest-casescenario.Thisanalysisisincludedasanappendixtothisdocument.

Climate Considerations Toprojectvariancesinperformancebetweendayswithdifferentclimaticconditions,CTEmeasuredtheauxiliaryloadsaspreviouslydiscussed.Auxiliaryloadsaredefinedastheelectricalloadsonthebusunrelatedtopropellingthebus.Theseloadsincludehighvoltageloadssuchasthepowersteeringsystemandaircompressorsystemaswellaslowvoltageloadslikelighting.Thelargestauxiliaryloadistheheatingandcoolingsystemsforthebuscabin.Thisisalsotheonlyloadthatvariesseasonally.

AstudyofAlbuquerque’sclimatepatternsaswellasCTE’spreviousexperiencewithbatteryelectricbusesshowsthattheairconditioningloadsonahotdayarelikelytopresentthemostdifficultloadsforthesebuses.Inotherwords,rangeislikelytobeloweronhotsummerdaysduetothefactthatmoreenergyisrequiredtocoolthebusratherthanbeingusedtomovethebusdowntheroad.WinterheatingloadsarealsoexpectedtogreaterthanauxiliaryloadsencounteredduringCTE’stesting,butnotasbadassummerairconditioningloadsandthusarenotconsideredfurther.CTEchose99°Fasastrenuoussummertemperatureforitsanalysis.AlthoughhottertemperatureswillbeexperiencedinAlbuquerque,theytendtobebalancedbycoolermorningandeveningtemperatures.

BasedoninformationprovidedbyBYDandbasedonCTE’spriorexperiencewithmodelingsimilarsystems,CTEestimatesthestrenuouscoolingloadtobe15kWascomparedto9.5kWmeasuredduringfield-testing.Asthefieldtestwasconductedonadaywithan80°Fhigh,thestrenuous-daycoolingloadwouldrequiresignificantlymorepowerfortheairconditioning.



BYD’sfeedback,utilizingloadinformationobtainedfromanotherproject’sresults,helpedtodeterminethisestimateforthecoolingloadona99°Fday.

Notes on Weight CTEfoundthedifferenceinefficiencybetweenthebusnearcurbweightandthebusloadedwithballasttosimulatepassengerloadstobewithin8%,whereasthedifferenceintemperaturebetweenthemorningandafternoonportionsofthetestresultina16%changeinefficiency.CTEisthereforeusingtheaverageofcurbweightvehicleandballastedvehicleefficiencymeasuresinitsprojections.Notethatefficiencyislikelytobemarginallylowerasweightisincreasedbeyondthetestedweight,butthatthiseffectisnotexpectedtobenearlyasdramaticaschangesinclimaticconditions.

Onefinalnoteonweight:althoughCTEdidnotseealargeefficiencydifferencebasedonweight,anecdotallytheweightedbuswasreportedtobesomewhatsluggishupthehillsthroughouttesting.Theunweightedbuswasreportedsluggishonlywhenthestateofchargedroppedappreciably.CTEdidnotfurtherinvestigatethesluggishnessbecauseitwasnotdeemedsevereandiscommontomostbatteryelectricbuseswhenheavilyloaded.

Block Analysis AsummaryofARTblocksisshowninTable8.ABQRideprovidedtheblockdata.CTE’sestimatesoftheenergyrequiredtooperatetheblockisalsoshowninthetable.Notethattheenergyrequiredismorethantheenergyavailableonthebusesevenforbuseswithoutdegradedbatteries.Theblocks,asdesigned,wouldbedifficultforanydepot-chargedbatteryelectricbustooperateduetotherangerequired.

Block TotalDistance(mi) Layovers AverageLayover(min)

EnergyRequired(kWh)Observed

Day HotterDay

1 260 19 10.2 722 8822 233 18 10.7 649 7933 212 16 9.6 589 7194 240 18 9.7 668 8165 237 18 10.7 661 8076 240 18 10.6 668 8167 236 18 10.2 656 8028 211 17 9.8 588 7189 238 17 10.6 663 81010 240 18 10.8 668 81611 236 18 10.5 656 80212 233 18 9.9 649 79313 210 15 9.6 585 71514 209 15 8.7 582 71215 206 16 10.2 573 700Average 230 17 10 639 780

Table8:ARTBlocks



Depot Charging

CTEprojectedrangesofmorestrenuousconditions(i.e.,hotterdays)basedontheconditionsobservedduringtesting.RangesforboththeobservedbatteryandthefullydegradedbatteryareshownforbothobservedandstrenuousclimateconditionsinFigure1.Theseresultsassumenoon-routecharging.Thefullydegradedbatterywillhaveshorterrangeasindicatedbytheredportionofthebars.Thegreenportionofthebarsshowstheincreaseinrangebatteriescurrentlyhaveoverthefullydegradedbatteries.

Figure1:ProjectedRangeUsingCTEEstimateofCapacity

Manytransitagenciesfindestimatesofendurancemoreusefulthanrangeestimatesforblockanddriverscheduling.Enduranceissimplyameasureofhowlongthebuscanbekeptinservicemeasuredinhours.CTE’sestimateofenduranceisshowninFigure2.

Figure2:ProjectedBusEnduranceUsingCTEEstimateofCapacity



EndurancecanalsobevisualizedasshowninFigure3,whichshowstheserviceenergyavailableforblock12asthebusoperatesthroughouttheserviceday.Block12isanaveragedifficultyblockforART,ascanbeseeninTable8basedonthedistancetraveled,aswellasthenumberandfrequencyoflayovers.Asshowninthefigure,thebusesdonothaveenoughenergytocompleteblock12underanycondition.Asbatteriesdegradetothewarrantylevel,rangeandendurancearelower.

Theavailableenergythroughoutthedayisrepresentedbyaconeshapeinthegraphwhichdepictsthevariationthatcanbeseenbasedonpassengerloadingandweatherconditions,withthetopedgeoftheconerepresentingtheavailableenergyremainingonanominaldayandthebottomedgeoftheconerepresentativeofthestrenuousday.

Figure3:VisualizationofEnduranceUsingCTEEstimateofCapacityforBlock12

Basedonouranalysis,wecanconcludethattheproposedBYDK11busesusingonlydepotchargingisinadequatefortheintendedBRTservice,ascurrentlydesigned.Thistypeofissueisnotuncommonforrange-limitedbatteryelectricbuses.Tosuccessfullydeploythesebuses,itwouldbenecessarytomodifytheservice,modifytheblockingscheduleandaddmorebuses,oraddon-routecharging.



On-Route Charging

SincetheBYDK11busesdeliveredtoABQRidehaveinsufficientrangeandendurancetooperatetheARTserviceblocks,CTEevaluatedanon-routechargingstrategy.

Thereareseveralchallengesthatmustbeaddressedwhenconsideringon-routecharging:

1. Chargingstationsshouldnotbeaccessibletothepublic.Theymustbelocatedindedicated,restrictedaccessareas.

2. Itisrecommendedtoonlyuseoverheadconductiveorin-groundinductive,automatedcharging.Plug-inchargingisnotrecommendedasitrequiresanindividualon-siteduringtheservicedaytoplug-inthebus,monitorthecharge,andun-plugthebus.Inadditiontolaborcosts,thechargecablingmaybeatrippinghazardtothepublicandliabilitytotheCity.

3. Peakdemandchargesfromtheelectricutilitycanmakeon-routechargingexpensive.

4. Theremaybeinsufficienttimetoaddenoughenergywhilechargingduringbuslayovers,particularlyifthebusisrunninglate.Or,abusthatisrunninglatewillstaybehindscheduleinordertoreceiveasufficientcharge.

CTEdidnotevaluateanydifficultiesthatAlbuquerquemayencounterinlocatingandoperatingthechargersinpublicareas,butCTEencouragesABQRidetoinvestigatethesechallengesfurtherbeforeembarkingonthisstrategy.

CTEdidevaluatethecostsofonroutechargingandtheresultscanbefoundintheratemodelingsection.

CTEalsoevaluatedtheavailablelayovertimeforchargingbothinan“on-time”scenarioanda“behindschedule”scenario(i.e.busesarerunningthreeminuteslate).NotethatARTwasdesignedusingbusrapidtransitprinciplesthataredesignedtokeepthesystemrunningontimesuchasbuslanes,trafficsignalpriority,andembarkationfromanydoor.

Assumptions CTEassumedthatchargerswouldbeinstalledatUTC,CUTC,andTRWENthataretheterminationpointsoftheroute.CTEfurtherassumedthatachargerwasavailableeachtimeabusarrivedatoneoftheselocationsforalayover.CTEassumedthatitwouldtakeacombinedtwominutestoplugandunplugthebusatthestationandsothistimewasexcludedfromtheavailablechargetime.

Foron-routecharging,thechargerateiscritical.BYDofferedtoaugmentovernight,plug-indepotchargingwithplug-inon-routecharging.Thus,CTEassumedthesameBYDplug-inchargersthatareinstalledinART’sdepot.CTEusedavariablechargeratedependentonstate-of-chargebecausethatistheperformanceCTEobservedandalsobecausethatmethodwasrecommendedbyBYD.Inadditiontothechargepowerobserved,CTEalsoanalyzedthechargepowerthatBYDsaystheycansustainduringaten-minutecharge.CTErecommendsthatthischargerateistestedandconfirmedbeforeacceptingthissolution.



Results Figure4belowshowstheupdatedcapabilitiesoftheBYDbusonBlock12whenon-routechargingisincludedinthemodelandthebusbatterycapacityisassumedto551kWh.Chargepowerislimitedto115kWabove23%state-of-chargeand180kWbelow23%state-of-charge,basedonCTE’sobservations.Withthisbatterycapacityandthesechargingcapabilities,theblockcanbecompletedundermostconditions.However,ifthebatterydegradesfurther,thesechargingcapabilitiesarenotexpectedtomeetwhatisnecessaryforthebustocompletetheblock.BecauseCTEdidnotconductroadtestsofsimulatedon-routecharging,CTEwouldrecommendconductingsuchtestsbeforeutilizingon-routechargingwiththesebuses.

Figure4:VisualizationofEnduranceUsingCTEEstimateofCapacityandChargeCapabilitiesforBlock12

Theenergyusageforon-routechargingisshowninTable9.Thesevaluesarebasedontheaverageusagebyeachblock,andsomustbescaleduptorepresentaday’susage.Theassociatedcostsarediscussedintheratemodelsectionofthisreport.



UTC CUTC TRWEN Garage

WeatherConditions

On-PeakEnergy(kWh)

Off-PeakEnergy(kWh)

On-PeakEnergy(kWh)

Off-PeakEnergy(kWh)

On-PeakEnergy(kWh)

Off-PeakEnergy(kWh)

Off-PeakEnergy(kWh)

CTE-ObservedCharging

ObservedDay 116 13 70 18 73 17 264

HotterDay 123 18 77 21 80 20 386

NumberofChargersrequiredateachstation 2 3 1 1perbus

Table9:EstimatesofAverageFacilityEnergyUsagePerBlock



Rate Model

ThetotaldailyenergydemandforeachfacilitywascalculatedusingtheTable9valuesscaledupbyfifteentotalblocks.Withthisinformationandtherateinformation,alongwiththeon-peakenergydemandbasedonthechargingrateandthemaximumnumberofvehicleschargingwithinthesamefifteen-minutewindow,thecostoffuelingcanbecalculated.Thecompletechargingsystemisassumedtobe90%efficient,meaningthat90%oftheenergypurchasedfromthegridwillendupasusableenergyinthebattery.ABQRideprovidedCTEwiththeapplicablePNMRate3Butilitytariffschedule.

Figure5showstheestimatedannualfuelcostateachchargingstationtooperatetheARTservicewithon-routecharging.CostestimatesarebasedontheperformancecharacteristicsobservedduringCTE’sroadandchargingtests.Itisimportanttonotethattheseresultsdonotaccountforthecapitalcostofthefacilitymodificationstoaddon-routechargingtotheARTservice.Thecostestimatesarecalculatedusingtheaverageoftheobservedandhotweatherscenariosforsimplicityindemonstration.Actualcostsmayvary.

Figure5:AnnualCostswithCTE-ObservedCapacityandChargeRate

Figure6showsthetotalofallchargingstationfuelcostsasaper-milecost,andcomparesthisagainstadieselbaselinewhichassumes2.55milespergallonfora60’dieselvehicle,andapriceof$2.50pergallon.



Figure6:CostsperMile



Conclusions

ABQRide’soriginaldeploymentplanfortheARTBRTservicewastooperatethedeliveredBYDK11busesonallARTblocksusingovernightdepotcharging.Atthecompletionofeachblock,thebuswouldreturntoDaytonaandrechargeinpreparationforservicethenextday.Asaresultofouranalysis,CTEconcludesthatthisplanwillnotworkwiththeBYDK11busesthatweredeliveredtoABQRide,regardlessifthebuseswereatfulldesigncapacityorattheobservedcapacity.

BYDhasproposedamodifieddeploymenttoaddon-routechargingtotheARTservice.Tobeplausible,onetothreechargingstationsarerequiredateachterminationpoint;UTC,CUTC,TRWEN,aswellastheDaytonadepot.Whilethisoperationalmodelmaywork,therearerisksthatmustbeconsidered.ThedeliveredBYDK11busesarenotequippedwithoverheadorinductivechargingsystems.Asaresult,thebusesmustbechargedon-routeusingtheplug-inchargeconnector.Thiswouldrequirethatthesestationsbemannedorthatthedriverexitthebustoplugthebusin.Plug-incharginginapublicareaisnotidealduetopotentialliabilityissuesaswellasstaffingrequirements.

Consistentchargeratesduringon-routechargecyclesarecriticaltomaintainingserviceschedules.Additionaltestingisrequiredtoconfirmchargeratesduringvariousoperationalandclimaticconditionsaspassively-cooledbatterysystemsaresubjecttogreatervariationsinchargerate.Batteries,bynature,willheatupwhentheyarechargedordischarged.Thermalmanagementsystemsmaypurposefullylimitvehicleperformanceorchargeratetoprotectthebatteries.Somethermalmanagementstrategiesincludeactiveliquid-coolingsystemsthatarebetteratmaintainingbatterytemperatureinhotclimates,thusminimizingthechancethatperformanceorchargerateisdegraded.

Finally,theanalysisshowsthattheproposedBRTserviceusingtheproposedBYDK11buseswithbothdepotandon-routechargingcannotbecompletedasbatteriesdegradetowarrantylevels.Asaresult,ABQRidewillneedtomakealterationstotheblocksorserviceovertimeifthissolutionisimplemented.

IfABQRidedeterminesthattheoriginaldeploymentplanormodifieddeploymentplanareunacceptable,thereareseveralzero-emissionstrategiesthatmaybeconsidered:

1. Modifytheblockschedule2. Highercapacitybatteryelectricbuseswithfasteron-routecharging.3. Hydrogenfuelcellelectricbuses.4. CombinationStrategy

Asummarydescriptionandconsiderationforeachoptionisprovidedbelow:

Modify the Block Schedule ShorterblocksaremoresuitabletothedeliveredBYDK11buses.However,shorterblocksmayrequiremiddaycharginginadditiontoovernightcharging.Thischargingstrategycouldincurhigherelectricitycostsduetomiddaydemandcharges.Alternatively,morebusesmaybeneededtooperatetheservicewhenshorterblockingstrategiesareemployed.



Higher capacity battery electric buses with overhead on-route charging TheARTBRTservicecanbeashowpieceforstate-of-theartzeroemissionbustechnology.Fixedrouteswithdedicatedroadwaysareidealforbatteryelectricbuses.Highercapacitybatteryelectricbuseswithliquid-cooledbatteriescanprovidegreaterrangewithlessimpactfromdegradation.Additionally,fasteroverheadconductivechargerscanprovidetherouteenergyrequiredinashortertime,andarealsolessimpactedbydegradation.

Hydrogen Fuel Cell Vehicles HydrogenfuelcellbuseswouldhavetherangeneededtooperateART’sblocks,andtheycanberefueledinminutes,similartoCNGbuses.However,thesebusesrequireasourceofhydrogenthatmustbemanufacturedon-siteordelivered.Eitheroptionisexpensivecomparedwithotherfuels.Hydrogenfuelinginfrastructureisexpensivebutcostsareeasilyleveragedoveralargerfleet.Thebusesthemselvesarealsomoreexpensivethananyotheroptionduetothelimitednumberofvehiclescurrentlyproduced.CTEexpectsthatbothfuelandbuscosttoshiftdownwardovertimeasthisoptionbecomesmorewidelydeployed.

Combination Strategies Acombinationoftheabovestrategiesisalsopossible.Forexample,abatteryelectricbusfleetcouldbesupplementedwithasmallnumberofconventionalbusestoavoidthenecessityofon-routechargingandprovidealternativestoservelongerblocks.


CenterforTransportation&theEnvironment PageA-1

Appendix: BYD-Proposed Scenario

DuringthecourseofCTE’sanalysis,BYDproposedtorestorebatteriestotheirfulldesigncapacityandreprogramtheirbatterymanagementsystemtoallowforahigherchargerateduringon-routecharging.SinceCTEdidnotobservetheseconditionsonthedeliveredBYDK11buses,wedidnotanalyzethoseconditionsaspartoftheprimaryassessment.However,wedidanalyzetheseconditionsforABQRideintheeventthatBYDisabletodeliverthesebusesinthefuture.Aswithanybusprocurement,CTErecommendstestingandvalidationofbusesandchargingequipmentpriortoacceptanceandplacementintopassengerservice.

CTErepeateditsanalysisofrangeandenduranceassumingabatterywithcapacityof590kWh.ThisanalysisassumesthatBYDwillbeabletorestorethebatterytoitsfulldesigncapacity.TheresultingrangeandendurancearepresentedinFigure7,Figure8,Figure9,andFigure10below.Itshouldbenotedthatthecapacityofthedegradedbatteryisunaffectedbythischange,asthewarranteddegradationis70%ofthedesignedcapacityregardlessofthisrepair.BYDalsocontendsthatthebatterieswillbeabletochargeatthefull180kWpowerlevelfor10-minutecharges,regardlessofthestateofchargethatthebusbeginsthechargeat.Theaffectthishasontheon-routechargingscenariocanbeseeninFigure10:VisualizationofEnduranceUsingBYD-ProposedCapacityandChargeCapabilitiesforBlock12.

Bus Capacity(kWh) ServiceEnergy(kWh)

BYDK11DesignGoal 591 532

BYDEstimatesafterRepair 590 531

DegradedBattery(70%ofDesign) 414 373Table10:BatteryCapacityforEstimateswithBYD'sProposedrepair

Figure7:ProjectedRangewithBYD'sProposedBatteryCapacityRepair



Figure8:ProjectedEndurancewithBYD'sProposedBatteryCapacityRepair

Figure6showsthatevenwiththerepairedbatteries,additionalenergyisneededtocompletetheblocksastheycurrentlystand.Thisconclusioncanbeconfirmedbycomparingtheenergyrequiredfortheblocksaslistedinthetableabovetotheserviceenergyavailableintherepairedbattery.

Figure9:VisualizationofEnduranceUsingBYD'sProposedRepairedCapacityforBlock12

Whenthebatteryhasbeenrepaired,asBYDhasproposed,andwhenBYDmakeschangesthatallowsforconsistent180kWon-routechargingovera10-minuteperiod,theresultingenduranceisshowninFigure10.Whileafewofthechargewindowsarelongerthanthis10-minutelimitandthesubsequentchangeinchargepowerafterthe10-minutelimitisexceeded



isnotincludedinthemodel,thisisnotexpectedtohaveasignificanteffectontheresultsbecausetheselower-powerchargewindowsareinfrequentandbrief.

Figure10:VisualizationofEnduranceUsingBYD-ProposedCapacityandChargeCapabilitiesforBlock12

UTC CUTC TRWEN Garage

WeatherConditions

On-PeakEnergy(kWh)

Off-PeakEnergy(kWh)

On-PeakEnergy(kWh)

Off-PeakEnergy(kWh)

On-PeakEnergy(kWh)

Off-PeakEnergy(kWh)

Off-PeakEnergy(kWh)

BYD-ProposedCharging

ObservedDay 153 19 94 24 97 24 299

HotterDay 169 19 100 25 106 24 424

Table11:EstimatesofAverageFacilityEnergyUsagePerBlockUnderBYD-ProposedScenario

Theannualcostsatthethreeon-routechargingfacilitiesareprojectedtobehigherundertheBYD-proposedchargingscenariothantheCTE-observedscenariofromFigure5,whilethecostsattheDaytonafacilityarelower.Duetothehigherchargingpoweravailablethroughoutthewholeday,moreenergyisreplacedduringtheon-routechargesthatresultinlessenergyneedingtobereplacedovernight.Sincetheincreaseddaytimeenergyusageoccursduringtheon-peakrates,thechargesatthethreeon-routefacilitiesrisedisproportionatelymorethantheDaytonafacilitychargesfallwhencomparingtheCTE-observedscenariototheBYD-proposed.However,thischangedoesnothavealargeeffectonper-milecosts,asthecostper-mileunder



thisscenarioisestimatedtobe$0.32,asopposedtothe$0.30undertheCTE-observedchargingscenario.

Figure11:AnnualCostswithBYD-ProposedCapacityandChargeRate

Whiletheseresultsmakeon-routechargingwiththesevehiclesontheseblocksmorefeasible,theyarereliantonBYD’sabilitytorealizetheclaimedimprovements.

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