Autonomous Battery Swapping System and Methodologies of Electric Vehicles

energies

Review

Autonomous Battery Swapping System and Methodologies of Electric Vehicles

Feyijimi Adegbohun *, Annette von Jouanne and Kwang Y. Lee

Department of Electrical and Computer Engineering, Baylor University, Waco, TX 76798, USA; annette_vonjouanne@baylor.edu (A.v.J.); kwang_y_lee@baylor.edu (K.Y.L.) * Correspondence: jimi_adegbohun@baylor.edu; Tel.: +1-304-809-4122

Received: 18 January 2019; Accepted: 12 February 2019; Published: 19 February 2019

Abstract: The transportation industry contributes a significant amount of carbon emissions and pollutants to the environment globally. The adoption of electric vehicles (EVs) has a significant potential to not only reduce carbon emissions, but also to provide needed energy storage to contribute to the adoption of distributed renewable generation. This paper focuses on a design model and methodology for increasing EV adoption through automated swapping of battery packs at battery sharing stations (BShS) as a part of a battery sharing network (BShN), which would become integral to the smart grid. Current battery swapping methodologies are reviewed and a new practical approach is proposed considering both the technical and socio-economic impacts. The proposed BShS/BShN provides novel solutions to some of the most preeminent challenges that EV adoption faces today such as range anxiety, grid reliability, and cost. Challenges and advancements specific to this solution are also discussed.

Keywords: battery swapping station (BSS); battery sharing station (BShS); battery sharing network (BShN); battery energy storage system (BESS); battery energy control module (BECM) electric vehicle (EV); zero emission vehicle (ZEV); direct current fast charging (DCFC); universal battery pack (UBP); state of health (SOH); state of charge (SOC)

1. Introduction

Electric vehicles (EVs) have been deemed as being the future of mobility both by auto industry experts as well as major original equipment manufacturers (OEMs) globally. General Motors (GM) announced that it will release more than twenty new models by 2023; Daimler AG (Mercedes Benz parent company) announced that all of the models available will be electrified by 2022; Ford Motor Co. announced 40 electrified models by 2022; several other automakers have committed to an all-electric future [1]. In addition to the original equipment manufacturers' (OEMs') commitments to an all-electric future, government agencies across the world have also set various zero emission mandates. The California Air Resource Board (CARB), Zero Emission Vehicle (ZEV) regulation has a mandate to reduce emissions level by 40% in 2030 in comparison to the level in 1990, and 80% by 2050 through regulations and ZEV credits for automakers that produce a significant number of electrified vehicles. China's New Energy Vehicle (NEV) mandate is similar in implementation to CARB's policies, requiring 2.5% of vehicles sold to be ZEVs by 2018 and 8% by 2025. Norway and the Netherlands have also committed to 100% EVs by 2025 and 2030, respectively. According to [1], the EV market share is expected to grow from roughly 1% today to about 30% in Europe and around 15% in the U.S. by 2025, totaling 130 million by 2030 globally.

This exponential increase in EV adoption within a short period of time poses significant technical challenges; specifically, grid reliability issues as the current state/capacity of generation and power distribution grid is not designed to support the load profile of this number of EVs [2?4]. Another

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concept that poses a significant technical challenge and could also critically affect the reliability and stability of the power grid is fast DC charging of EVs. Fast charging of EVs at 50 kW and up can lead to unsustainable load spikes on the distribution grid, especially at the peak-load periods. Therefore, fast charging will require that local energy storage/generation be present at the charging stations to meet these demands, mitigate the negative impact on the grid, and reduce operational costs during the peak-load of the grid [5]. Studies have also shown that the degradation of existing Li-ion battery cells at DC fast charging (DCFC) is much faster than slower AC charging of less than 10 kW [6].

For EVs to be adopted at scale, the charging infrastructure and integration with the power grid must also evolve rapidly. It is therefore imperative that these technical issues be studied and that new methods of replenishing the energy in EVs and extending the range of EVs be developed. Today, an EV of 110 km range requires 2?3 h to charge the battery from 0% to 100% state of charge (SOC) using AC charging, or 30 min to 1 h for DCFC. While fast charging shows a great deal of promise, it still poses critical technical challenges and current technologies do not offer the convenience that traditional vehicles offer in terms of replenishment of energy within 5?10 min. An optimized battery swapping station (BSS) has been presented in [7]; however, this method is based on the assumption that consumers are willing to lease their battery as opposed to owning the battery. Several automakers and start-ups including Tesla Motors [8] and Better Place [9] have introduced a BSS similar to this model; however, consumer acceptance of not owning the battery and their original battery being tampered with during a swap has plagued the success of this model. This paper proposes a battery sharing station (BShS) and a battery sharing network (BShN) as a novel solution to mitigate the impact of the EVs' scale and improve the reliability/stability of the grid. The BShS proposed in this paper is based on some of the concepts and methods that Tesla and Better Place have implemented in their BSS, but it is focused on solving the issues of consumer acceptance, standardization of battery architecture and mitigation of grid impact by EV battery charging. The BShN topology proposed is comprised of several subsystems and components such as the connected battery energy storage system (BESS) or battery, connected battery charger, renewable energy source (RES), power electronic converters, control systems, power distribution grid, and the participating EVs. The term connected in this case, refers to the internet of things (IoT) as well as grid coupling, enabling the BESS and BShN to interact and become an aggregator providing different services to the smart grid as a whole [10]. The structural design of the BSS model is detailed in the patent in [11], and the architecture of battery placement in the vehicle is also detailed in [11]. A RES integrated with the BSS is reviewed in [12], and the interaction and power exchange between different components of the BShN and the power grid is also detailed in [12]. An optimal configuration of a BSS in terms of the number of chargers and battery packs is discussed in [13]. Converters and charger topologies for enabling grid-to-vehicle (G2V) and vehicle-to-grid (V2G) power exchanges are discussed in detail in [14].

This paper serves as a survey paper highlighting the current state-of-the-art battery swapping technologies and implementations available today. In addition, this paper presents a newly revamped model of battery swapping methodologies that resolves some of the issues that current battery swapping technologies face, highlighting technical challenges that face this newly proposed model and technological advancements in the near future. Section Section 2 presents current battery swapping technologies, using the Tesla BSS as a main point of reference. The mechanical design of the swapping station system and vehicle architecture is described. Following this, the electrical design of the vehicle system, BESS, BSS, and charging system are described in detail. Section 3 introduces a novel BShS and BShN model. The mechanical, electrical, and economic advantages over the current state-of-the-art battery swapping technology are also highlighted. Finally, the research opportunities and technical hurdles related to this novel model are presented, highlighting the important differences, the benefits, and the technological advancements needed to commercialize this proposed model.

Table 1 is a list of acronyms and abbreviations with definitions of technical terminology used in this paper.

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Table 1. Acronyms and abbreviations.

Table 1. Acronyms and abbreviations.

Acronym/Abbreviation

Description

Acronym/Abbreviation

Description

BSSBSS BShBSShS BShBNShN BESBSESS BECBMECM

BBatattetreyrySwSawpappinpginSgtaStitoantion BBatattetreyryShSahrianrginSgtaStitoantion BBatattetreyryShSahrianrginNgeNtweotrwkork BBaatttetreyryEnEenregrygSytoSrtaogreaSgyesSteymstem BBaatttetreyryEnEenregrygCyoCnotrnotlrMoloMduoledule

EVEV

ElEecletrcitcrViceVhiechleicle

UCUC

UUltrlatrcaapcaapciatocritor

DCDFCCFC

DDiriercetcCt CururernretnFtasFtaCsthaCrhgainrgging

ZEVZEV

ZZereoroEmEimssiisosnioVnehViechleicle

SOHSOH

SSttaateteoof fHHeaelathlt(hBa(BttaetrtyeLryifeLCifyecCley) cle)

SOCSOC

SSttaateteoof fCChahragreg(eBa(BttaerttyeCryapCaacpitya)city)

CACRABRB

CCaalilfiofronrinaiAa iAr RireRsoeusrocuerBcoeaBrdoard

NENVEV

NNewewEnEenrgeyrgVyehViechleicle

RESRES

RReneenwewabaleblEenEerngeyrgSyouSroceurce

G2VG2V

GGridri-dto--tVoe-Vhiechleicle

V2GV2G

VeVheihcliec-lteo--tGor-Gidrid

UBUPBP

UUninvievresrasl aBlaBttaerttyePryacPkack

IoTIoT

InItnetrenrent eotf oTfhTinhgisngs

C-rCat-erate

CChharagregeanadnDdiDscihsacrhgaerRgeatRe ate

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2. Ov2e.rOvvieewrvioefwCoufrCreunrrteBntaBttaetrtyerSywSwapapppininggSSttaattiioonn TTeecchhnnoollooggyy In thIins stheicstisoecnt,ioang, eangeernaelraolvoevrevriveiwewooffththeemmaaiinn ccoommppoonnenentstsofoaf BaSBSSisSiilsluisltlruastterda,twedit,hwthitehTtehselaTesla

BcoSmS paBcsooSnmaSepcanasotsnsae.ecnFsattissgue.udFsriytgeu.ud1Tryehi.se1TaihBsceSaoSBncSoccSnoecpnceotspnuistsautilssatdlsodefosefmcsmcreripiecpchtthiiaooannnniicocoaafflltthahanenedBdBSsSsStStr.ru.uctcuturarlaclocmopmopnoenntesnatsswaesllwaesllelaescterilceacltrical

Figure 1. Conceptual design of a battery swapping station (BSS). Figure 1. Conceptual design of a battery swapping station (BSS).

2.1. Structural Design of a BSS T2.h1e. STtersulactuBrSaSl DsheosiwgnnoifnaFBigSuSre 2 includes a vehicle platform, a vehicle lift, battery lifts, vehicle alignment

eEqneurigpiems 2e0n1Tt9,hr1oe2ll,Texersl,aelBeScStrischaolwconninneFctigiounreal2igincmluednets,abvatetheircylecopnlavtefoyromr,sahuvtethleics,leanlidft,bbaattteerryysltioftrsa,gveehraicclke4s oafn1d4 rails. aFliiggunrmee2nstheoqwuispmanenEtVrotlhleartsh, ealseactrrriicvaeldcoantnaeBctSioSnaanldiginsmreeandtsy, btoatbteeryencgonagveedyoirnsahuswttlaeps,.and battery

storage racks and rails. Figure 2 shows an EV that has arrived at a BSS and is ready to be engaged in a swap.

Figure 2. Diagram of an electric vehicle (EV) at a BSS ready to engage in a battery swap [15]. Figure 2. Diagram of an electric vehicle (EV) at a BSS ready to engage in a battery swap [15].

2.2. Mechanical Operation of BSS A compatible EV with a battery architecture designed for the BSS is needed in order to

participate in battery swapping. In addition, prior to arriving at the BSS, the EV must schedule the

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Figure 2. Diagram of an electric vehicle (EV) at a BSS ready to engage in a battery swap [15].

22.2.2. .MMeecchhaannicicaallOOppeerraatitoionnoof fBBSSSS

AAcocmompaptaibtilbelEeVEwVitwh iathbaattebraytaterrcyhitaerccthuirteecdteusriegndedesfiogrntehde BfoSrS tihs eneBedSSedisinnoereddeerdtoipnarotircdiperatteo inpabrattitceipryatsewinapbpaitntger.yInswadadpiptiionng,. pInrioardtdoitaiorrniv, pinrgioartttohearBriSvSi,ntgheatEtVhemBuSsSt,stchheedEuVlemthuestbsacthteerdyuslwe athpe abhaetatderyofstwimape taohceoadnfiorfmtimtheattoa cboanttfeirmy ptahcakt awbilaltbteerayvpaailcakblweiflol rbeswavapai.laWblheefnorthsewEaVp.aWrrhiveens tahtethEeV BaSrSr,ivitesclaimt tbhseuBpSSa, sitlicglhimt rbasmupp aassslhigohwt nraimnpFiagsusrheo2wanndintFhigsucroen2staitnudtetshtishecobnesgtintuntiensgthoef tbheegisnwnainpg. Foigf uthre 3swisatph.eFfligouwreo3f oisptehreatfiloonwoof fthoepebraattieorny oswf tahpe[b1a5t]t.ery swap [15].

TThheevevheihcilceleisipsopsoitsioitnioendecdorcroercrtelyctilny tihne tXhediXrecdtiiroenctaionnd tahnedvtehheicvleephoicwleerpioswtuerniesdtuofrfnfeodr soaffeftoy.r Nsaefxett,yt.hNe evxeth, itchle visehraicisleediswraiitshedthwe ivthehtihcelevleifhticalse slhifot wasnshinowFinguinreF4ig, uwrehe4r,ewtherleifthbeolaifrtdbso, ainrdtsh,iisn ctahsies, ceansgea, egnegtahgeejathcke jpaackdspaodnstohne tvheehvicelheictoleptoropvriodveidsuepspuoprpto. rOt.nOcnectehtehveevheihcliecleisisliflitfetded, h, hoorirzizoonntatal l ddoooorrssuunnddeerrnneeaatthh ththeevveehhiciclele aarreeooppeenneeddtotoaalllolowwaaccceessstotoththeebbaattteteryryththaat tsististsuunnddeernrneeaaththththee vveehhiciclele. .NNeexxtt,,tthheebbaattteerryylilfifttisisrraaisiseedduunnttililitittotouucchheessththeeuunnddeerrssidideeooffththeebbaatteterryyppaacckkininoordrdeerrtoto ssuuppppoorrttititfoforrreremmoovvaal.l.OOnncceeththeelilfitftisisccoorrreecctltylypplalacceedduunnddeerrnneeaatthhtthheebbaattteerryysseeccuurreellyy, ,ththeefafasstetenneerr reremmoovvaallccaannbbeegginin. .NNeexxt,t,aabbaatteterryyccoonnvveeyyoorrsshhuuttlteleisisbbrorouugghhttuunnddeerrnneeaaththththeebbaatteterryylilfitftaasssshhoowwnn ininFFigiguurere55. .TThheeuusseeddbbaattteerryy, ,nnoowwoonnththeebbaattteterryylilfitf,t,isislolowweerreeddoonntotoththeebbaattteterryyccoonnvveeyyoorrsshhuutttllee;; ththeeuusesded//ddeeppleleteteddbbatattetreyryisirserpelpaclaecdebdybayfraesfhreoshneofnroemfrothme bthatetebrayttrearcyk rsahcokwsnhionwFnigiunreF6ig. uTrhee6f.reTshhe bfartetsehrybiastttehreynirsatihseedn urapisuenddueprnuenatdherthneeavtehhtihclee.vTehhieclbea. tTtehreybisatatgerayinispoagsiatiinonpeodsiatniodnseedcuanreddsbeycutrheed bbayttetrhyelibfatst,tethrye flaifsttse,ntehres afarseteenngerasgeadreanendgdaogoerds aclnodseddo. oNros wcl,othseedv.eNhiocwle,isthreeavdeyhtioclebeislorweaedreydtaonbde ploowweerreeddbaancdkpoonwtoergeedt bbaacckk oonn ttohegerot abdacwkiothnathfeulrloyardepwleitnhisahfeudllbyarteteprlyenpiaschke.d battery pack.

Figure 3. Battery swapping procedure flow chart [15].

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Figure 3. Battery swapping procedure flow chart [15]. Figure 3. Battery swapping procedure flow chart [15].

Figure 3. Battery swapping procedure flow chart [15].

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Figure 4. EV raised with the vehicle lift in preparation for a swap [15]. Figure 4. EV raised with the vehicle lift in preparation for a swap [15].

FFiigguurree44.. EEVV rraaiisseedd wwiitthh tthheevveehhiicclleelliiffttiinnpprreeppaarraattiioonnffoorraasswwaapp[[1155]]..

Figure 5. Battery lift lowering the depleted battery from the EV [15]. Figure 5. Battery lift lowering the depleted battery from the EV [15]. Figure 5. Battery lift lowering the depleted battery from the EV [15].

Figure 5. Battery lift lowering the depleted battery from the EV [15].

FFiigguurree 66.. FFuullllyy cchhaarrggeedd bbaatttteerryy ppaacckkss oonn aa rraacckk rreeaaddyy ffoorr bbaatttteerryy sswwaappss [[1155]].. 2.3. Electrical DFeisgiugrne o6f. BFuSlSly charged battery packs on a rack ready for battery swaps [15].

2.3. Electrical Design of BSS In today's implementation, the BSS is heavily dependent on the distribution grid and represents

2.n3.eEwlehctigrihcapl oDweseirgFnciogounfrsBeuS6mS. pFutilolynclhoaardgsedfobratttheerydpisatcrkibs uontioanrascyksrteeamdyofpoerrbaatottresr.yTswheapesle[c1t5r]i.cal components of the BSS are mainly composed of a distribution transformer, AC/DC chargers, battery packs, and a b2a.3tt.eErlyecetnriecraglyDceosnigtrnool fmBoSdSule (BECM). Figure 7 is a block diagram of the electrical relationship between the components of the BSS.

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