Seite - 91 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 86 3. StrategicandPlanningIssuesRelatedto theUseofEVs Dueto thedifferentaspects thatdistinguishEVsfromtraditional ICEVs, theL&Tproblemsthat havebeenaddressedsofar forconventionalvehiclesneedtoberethoughtandreformulatedto take intoaccount thenewfeaturesofEVs.Unlikeconventionalvehicles,EVsmust refuel frequentlydueto theshort lengthof theirbatteries in termsof traveldistance, i.e., their limiteddrivingrange[10]. Thus, usersmustconsiderhowmanymilescanbecoveredbeforearecharge isneeded. There isnodoubt that this restricts theiruse as transport tools. Therefore, theprovisionof thenecessary recharging stations and their integration in the transport networkare important issues to address. Themain issues todetermineare: (i) thenumber andkindof refueling stations to establish; (ii) the location of thesestations;and(iii) theiroptimalcapacity.Moreover, companiesneedtoassess the impactof the introductionofEVs in theirfleet, so that theycanchoose thebest sizeandmixofvehicles touse. Hence, thefleet sizeandmix is another important issue toanalyze. The followingsubsectionsare devotedtoreviewanddescribe the influenceofsomeof theseaspects in theL&Tarena. 3.1.DifferentKindsofRechargingStations AsEVsareentering themarket, there isarisingdemandforpublic refuelingstations.Nowadays, when theEV’s batteries aredepleted there are twopossibilities: recharge themor exchange them. Chargingstationscanbedividedinto twocategories: fastchargingandslowcharging.Afast refueling station can quickly recharge an EV in less than fiveminutes [33], but this kind of charging can significantlyshortenthe lifeof thebatteries.Conversely,aslowrefuelingstationneedsa longer time torechargeanEV.AtslowrechargingstationsofLevel1or2 (110–240V),vehiclesneedtowait from 2upto8hto fullycharge theirbatteries.At rechargestationsofLevel3 (480V), chargingabattery fully takes about 20–40min. Therefore, recharge timehasbeena critical factor influencingpublic acceptanceofEVs.Amajorsolutioncouldbetoremovetheexistingbattery that isnearlydepleted and replace thebatterywith a fully chargedone, asproposedbyLi [34]. Suchamethod is called battery swapping. Themainbenefit associatedwith the swappingmodel is the speed. Thewhole operationcould take less than10min,which isonparwithconventionalvehiclesandmuchfaster thanevensomefast rechargingstations. Othernoted featuresofbattery swapstations include the following: (i) chargingdepletedbatteriescanbe left for thenightwhenthechargingcost is low; (ii) the provisionofgrid-support service inacentralizedcharginganddischargingmanner; (iii) theability for drivers toresumetheir journeys inminuteswithafull-capacitybattery; (iv) thechargingofbatteries in slow-chargingmodetoextendtheir lifetime;and(v) thesavings incostofEVsbyprovidingbatteries byoperators.AspointedoutbyYang et al. (2015) [35], abatteryswappingmodelcouldbeconsidered moreappropriate thanabatteryrechargingmodelsince the formernotonly improves theproductivity of vehicles but also lowers the charging cost. Due to thebatterydriving range limitation and the natureofbatteryswapping,distributionnetworkoptimizationwithabatteryswapping infrastructure couldbeanimportantpartofestablishinganygreenL&Tpolicy.However, companiescantakethis possibility, since thebestbatteryswappinginfrastructureownershipmodel is thecompany-owned businessmodel, which indicates that the L&T companies establish andoperate the battery swap stations for theEVsby themselves. Thisway,determining the idealbattery swapstations location strategyandvehicle routingplanforadistributionnetwork ismainlyaquestionofservice leveland operationalcost for the logisticsenterprises. All inall, themajor challengesencounteredregarding thekindofEVs rechargingstationsare summarizednext. Ontheonehand,EVconsumersexpecta short charging time just like refueling their currentvehicles. This requirementmakes fast chargingstationsmorepreferred,but thiskind ofchargingcanshortenthe lifeof thebatteries.Moreover,asclearlyexplainedin[36], implementing centralizedcharging/dischargingcontrolunderplug-inmodeisverydifficult, sinceEVuserspresenta stochasticchargingprofile. Inorder toavoiduncontrolledcharging,whichmayproduceasignificantly increaseof thepeak loadandendangerpowersystemsecurity , someincentivestrategiescouldbe proposed.Ontheotherhand,consideringtheaforementionedchallenges,analternativestrategybased 91