Impact of the electricity mix and use prole in the life-cycle
assessmentof electric vehiclesRicardo Fariaa,n, Pedro Marquesb,
Pedro Mouraa,nn, Fausto Freireb, Joaquim Delgadoa,Anbal T. de
AlmeidaaaInstitute of Systems and Robotics, Department of
Electrical and Computer Engineering, University of Coimbra,
3030-290, PortugalbADAI-LAETA, Department of Mechanical
Engineering, University of Coimbra, 3030-290 Coimbra, Portugala rti
cle in foArticle history:Received 30 November 2012Received in
revised form6 March 2013Accepted 15 March 2013Available online 16
April 2013Keywords:Battery electric vehiclesPlug-in hybrid electric
vehiclesLife-cycle assessmentGreenhouse gas emissionsWell-to-wheel
balancesTotal costs of
ownershipabstractThispaperpresentsanenvironmentalandaneconomicLife-CycleAssessment(LCA)forconventionalandelectric
vehicle technologies, focusing mainly onthe primary energy source
andthe vehicleoperationphase Greenhouse Gas (GHG) emissions.
Adetailedanalysis of the electricity mix wasperformed, based on the
contribution of each type of primary energy source and their
variation alonga year. Three mixes were considered, with different
life cycle GHG intensity: one mainly based in fossilsources, a
second one with a large contribution from nuclear and a third one
with a signicant share ofrenewableenergysources.
TheconventionalvehicletechnologyisrepresentedbygasolineanddieselInternational
Combustion Engine Vehicles (ICEVs), while the electric technology
is represented by Plug-in Hybrid Electric Vehicles (PHEVs) and
Battery Electric Vehicles (BEVs). Real world tests were
performedforrepresentativecompact andsub-compact EVs. Theuseproleof
thevehiclewasbasedondataacquired by a real time data acquisition
system installed in the vehicles. The results show that a mix witha
large contribution from Renewable Energy Sources (RESs) does not
always translate directly into lowGHG emissions for EVs due to the
high variability of these sources. The driving prole under
differentscenarios was also analyzed, showing that an aggressive
style can increase the energy consumption by47%. The tests also
showed that the use of climate control can increase the energy
consumption between24 and 60%. Compared with other technologies,
EVs can be more sustainable from an environmental andeconomic
perspective; however, three main factors are required: improvement
of battery technology, aneco-driving attitude and an environmental
friendly electricity mix.& 2013 Elsevier Ltd. All rights
reserved.Contents1. Introduction. . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . 2722. Life-cycle model and
system boundary. . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . 2722.1. Vehicle
characteristics and assumptions . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . 2732.2. Use phase and
main factors that contribute to EVs energy consumption. . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 2752.3. Energy sources: emissions assessment . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . 2782.3.1. Crude oil extraction and rening. . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2782.3.2. Electricity mix. . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
278Contents lists available at SciVerse ScienceDirectjournal
homepage: www.elsevier.com/locate/rserRenewable and Sustainable
Energy Reviews1364-0321/$ - see front matter& 2013 Elsevier
Ltd. All rights
reserved.http://dx.doi.org/10.1016/j.rser.2013.03.063Abbreviations:
AC, AlternateCurrent;AFV, AlternativeFuel Vehicle;BEV,
BatteryElectricVehicle;BMS, BatteryManagementSystem;CNG,
CompressedNatural Gas;DOD, Depth of Discharge; ESS, Energy Storage
System; EC, European Commission; EU, European Union; EV, Electric
Vehicle; FC, Fuel Cell; FCEV, Fuel Cell Electric Vehicle;FTP-75,
Federal Test Procedure 75; GWP, Global Warming Potential; GHG,
Greenhouse Gas; HEV, Hybrid Electric Vehicle; HFCV, Hydrogen Fuel
Cell Vehicle; ICE, InternalCombustion Engine; ICEV, Internal
Combustion Engine Vehicle; IMU, Inertial Measurement Unit; IEA,
International Energy Agency; LCA, Life-Cycle Assessment;
LNG,Liqueed Natural Gas; LPG, Liqueed Petroleum Gas; MFI,
Maintenance, Fuel, Insurance; MRT, Maintenance, Repair, Insurance
and Taxes; NEDC, New European Drive Cycle;PEM, Power Electronics
Module; PHEV, Plug-in Hybrid Electric Vehicle; PM, Particulate
Matter; PT, Powertrain; RES, Renewable Energy Source; SFTP,
Supplemental FederalTest Procedures; SOC, State of Charge; TCO,
Total Cost of Ownership; TTW, Tank-to-Wheel; WTT, Well-to-Tank;
WTW, Well-to-WheelnPrincipal corresponding author. Tel.: +351 965
513 899.nnCorresponding author. Tel.: +351 239 796 250.E-mail
addresses: [email protected] (R. Faria), [email protected] (P.
Marques), [email protected] (P. Moura), [email protected] (F.
Freire),[email protected] (J. Delgado),
[email protected] (A.T. de Almeida).Renewable and Sustainable
Energy Reviews 24 (2013) 2712872.3.3. Contribution of the RESs to
the reduction of GHG emissions over the next decade in the European
Union (EU) . . . . . . . . . . . 2783. Life-cycle GHG emissions. .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . 2793.0.4. Impact of
the vehicle charging prole on the overall GHG emissions. . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . 2803.0.5. Impact of the vehicle driving
prole on the overall GHG emissions. . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . 2804. Life-cycle ownership costs . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . 2825. Conclusion . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . 283Acknowledgments. . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
286References . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . 2861. IntroductionClimate change ismore
than ever a driving force ondifferentaspects of today's society.
People are becoming increasingly awareof the real impacts of this
change and want to play an active partin the mitigation of this
issue. The search for more energy
efcientandenvironmentallyfriendlyproductscanalsotranslateintoareduction
of the energy bill.The transport sector is a major contributor of
carbondioxideemissions and EVs are becoming more relevant on the
future of thetransport system, for the Governments around the
world, due to theirpotential to reduce GHG emissions and increase
energy security [1].Withaccess toa more accessiblemobility, the
demandfor newvehicles is rising rapidly and vehicle numbers are
estimated to morethandoublebefore2050,
withhighestgrowthratesindevelopingcountries [24]. In the absence of
new legislation or policies that mayaffect the energy market, the
transport energy use and associated GHGemissions, are projected to
increase by 46% in 2035, compared to 2005values, accounting for 82%
of the total increase in liquid fuelconsumption, while the use of
liquid fuels for electric power genera-tiondeclines [5]. Tolimit
theriseof theglobal longtermmeantemperature by 2 1C, a 5085%
reduction of GHG emissions, comparedto 2000 levels, has been
proposed [6].To meet the increasing demand for transport and at the
sametime reduce GHG emissions and improve air quality, the
paradigmof personal transportationhastochange.
Thischangeembracesalternativevehicleandfuel technologyaswell
asmarterinfra-structure, through the electrication of the
powertrain, usingbatteriesor fuel cells, andtheuseof
alternativefuels, suchasbiofuels, natural gas and hydrogen
[79].AlternativeFuel Vehicles (AFVs), suchas
thosepoweredbyCompressedNaturalGas(CNG),
LiqueedNaturalGas(LNG)andLiqueedPetroleumGas(LPG)arealsootherviablelow-carbonalternatives.These
are in hand with conventionalICE vehiclesintermsofenvironmental
impacts, associatedwiththeproductionanddisposal. Theadditional
impactsduringtheproductionanddisposal phase come from the
additional material required for thegasreservoir. Intermsof
investment, thesevehiclesare510%more expensive than the
conventional vehicles but present loweroperatingcosts,
duetothelower cost of thefuel. Duringtheoperation phase, these
vehicles have lower GHG emissions whencompared with conventional
ICEVs, with a signicant reduction inparticle emissions [1012].
However, some studies also shown
anincreaseinNOxandCOdependingonthedrivingcycle[1315].AkeyaspectthatshouldalsobetakenintoaccountistheGHGupstream
emissions, which vary with the fuel production processand
geographic location, which could offset the GHG
savings.HydrogenFuel Cell Vehicles (HFCVs) aresimilar toBEVs
interms of havingahighefciencypowertrain. Akeydifferencebetween
both technologies is the upstream GHG emissions asso-ciated with
the generation and delivery of the energy carrier [16].Two key
aspects that affect the viability of HFCVs are related withthe
hydrogen storage and production [17]. In [18,19]
severalhydrogenproductionandstoragetechnologiesarestudiedfroma
Well-to-Tank (WTT) perspective. Despite some of
themcontributetolower Well-to-Wheel (WTW) GHGemissions,
theaddedcostassociatedwithdoesnotenablethemassicationofthe
technology. Due to the energy intensive process of
producinghydrogenbyhydrolysis, aHFCVwill requireuptothreetimesmore
energy and will emit three time more GHG than a BEV [11].However,
the use of HFCVs ina scenariowhere electricity
isobtainedfromRESscouldhaveadvantagesoverBEVstoachievea higher
autonomy.ImprovementsinconventionalInternalCombustionEngine(ICE)technology
can reduce petroleum demand, however efciency alonecannot reduce
GHG emissions to levels 80% below 1990 for the lightvehicleseet.
The cost and availability of low GHG fuels will imposelimits to
their use. To achieve signicant reductions in GHG emissionsthe
future transport systems will require optimized combinations
ofadvanced fuels and vehicle technologies
[11].Powertrainelectricationisseenhasthesolutiontoamoresustainable
transport system that can contribute to a reduction ofGHG emissions
and the import of crude oil, due to a much higherefciency,from
2830% of an ICEV to 7485% of an EV, and zerotailpipe emissions
[20], however due to a higher initial cost
whencomparedwithconventional technology, takingseveral
yearstooffset the investment, their penetration on the market is
expectedbe slow [21].The presence of an energy storage device
allows the EVs to be usedas a exible load and to support large
scale renewable energygenerationthroughsmart
rechargingmethodologies, however themassive electrication of the
vehicles may bring additional problemsto the electric grid if not
correctly managed [22,23]. Despite the use ofelectricity as the
energy source for EVs and zero tailpipe emissions, it isfundamental
toassessthesevehiclesintermsofeconomic,
energyconsumptionandGHGemissions,
takingintoaccountnotonlythevehicle LCA but also the electricity
generation [24].The contribution of EVs to reduce GHG emissions
must be assessedby using a cradle-to-grave perspective for the
vehicles and WTW forenergy carries. In this context, a comparative
LCA can be performed forICEVs and EVs. This type of assessment
allows a detailed comparisonbetween several vehicle technologies
and the identication of
oppor-tunitiesoftechnologicaldevelopmentandimprovementinthelife-cycle
phase of a vehicle. In this LCA, the vehicle technology analyzedwas
the conventional motorization, represented by both gasoline
anddiesel ICEVs, andelectricvehicletechnologyrepresentedbyPHEVsand
BEVs. Fuel Cell Electric Vehicles (FCEVs) were not considered
inthisstudyduetohighcostandtechnical issueswiththistypeoftechnology
that still need to be addressed, such as hydrogen capture,storage
and distribution, limiting their widespread adoption
[7,25,26].Since the EVs environmental impact is directly related to
the electricitygeneration mix, several scenarios from the European
Union (EU) wereconsidered based on the renewable, nuclear and
fossil fuel share.2. Life-cycle model and system boundaryThe model
andrespective system boundaries for each vehicletechnology (ICEV,
PHEV and BEV) are presented on Fig. 1. A globalR. Faria et al. /
Renewable and Sustainable Energy Reviews 24 (2013) 271287
272perspectiveisconsideredoverthevehicleslife-cycleandtheirkeycomponents,
suchasthebattery, aswelltheelectricity generation.The manufacturing
phase was considered common to all vehicles andcalculated based on
the vehicle weight. An additional burden, due tothe use of a
battery, was added to the EVs based on battery weight.Several LCA
studies show that the most critical phase in termsof GHG emissions
is typically the operation phase, whether it be aconventional
orelectricvehicle[27]. Theexceptionisfor BEVscharged with
electricity in a mix with low GHG emissions, wherethe production
phase is the most critical. Gasoline and diesel ICEVshave the
higher emissions during the operation phase followed byPHEVs and
BEVs while the emissions during the production phaseare similar to
all vehicle technologies, excluding the batteryproduction.
Duringthevehicleproduction, thebatteryusedinPHEVs and BEVs is the
most critical component in terms of GHGemissions,
contributingwith3050%of total emissions, mainlydue to the materials
and quantities required for the batteryproduction [2830,27].During
the vehicle use phase, for the BEV and for the PHEV thevehicle
Tank-to-Wheel (TTW) efciency was taken into account aswell real
worlddrivingproles. GHGemissionsassociatedwiththe infrastructure
for crude oil processing, transport and distribu-tionaswell
forelectricitygenerationwerealsoconsidered. Theproductionand end of
life phases for the considered vehicletechnologywerebasedon[31],
whilethebatteryLCAinventorywas based on [29,32]. The LCA database
for the consideredvehicleswascreatedusingtheEcoinventdataset[33].
ThisLCAintends to provide a comparison between EVs and ICEVs over
theirentire life-cycle and also assess the impact due to the use
prole ofthevehicleandenergysource. Thistypeof
analyzeallowstheidentifyof themost critical aspects intermsof
emissions andwhere actions can be taken in order to reduce
them.2.1. Vehicle characteristics and
assumptionsThevehicletechnologyaddressedwereICEVs,
PHEVsandBEVs.ICEVs (both diesel and gasoline) were used as a
baseline for the impactassessment of theother
vehicletechnologyconsidered. Basedonmarketrelevance,
theICEVisrepresentedbytheVolkswagenGolf(best seller in the European
market), both for the gasoline and dieselversion, the PHEV and BEV
are represented by the Chevrolet Volt andby the Nissan Leaf
respectively. Since subcompact vehicles arebecoming more popular in
a urban environment, two electric vehiclesthat t in this category
were also considered, represented by the SmartED and Peugeot iOn
(also sold in Europe re-branded as the
Mitsubishii-MiEVandCitronC-Zero). SincetheSmart
EDtsinadifferentcategorywhencomparedwiththeothervehiclesconsidered,
bothdiesel and gasoline versions were included to be used as a
comparisonbase. The vehicle main characteristics are listed on
Table 1, based onmanufacturer data and average cost in the European
market [34].Fuel Extraction andRefiningMaintenanceBattery
RecyclingBattery DisposalVehicle Use Phase End of LifeICEV and PHEV
specific motorization processesBEV and PHEV specific motorization
processesElectricityGenerationBattery ProductionVehicle
ProductionFig. 1. Model and system boundaries for the three vehicle
technologies.Table 1Characteristics of the vehicles considered for
each category.Characteristics ICEV PHEV BEVVW Golf 1.6 TDI VW Golf
1.4 TSI Smart CDI Smart Chevrolet Volt Nissan Leaf Smart ED Peugeot
iOnEmissions gCO2=km 118 144 98 86 0(ED) 160(GD) 91(MD) Fuel
consumption (l/100 km) 4.2 6.2 3.3 4.2 -(ED) 6.9(GD) 3.9(MD)
Electricity consumption (Wh/km) 140 140 110 120Combustion engine
(cc) 1600 1400 800 1000 1400 Electric motor (kW) 111 80 30
47Battery capacity (kW h) 16 24 16.5 16Battery weight (kg) 197 300
140 200Battery type Li-Ion Li-Ion Li-Ion Li-IonRange (km) 700+ 700+
500+ 500+ 580 (80ED + 500ER) 160 135 120Curb weight (kg) 1240 1290
770 750 1715 1521 870 1080Note: For the PHEV were considered three
driving scenarios: only gasoline drive (GD), only electric drive
(ED) and mixed drive (MD). The fuel consumption is given for
thevehicle running with the battery depleted.R. Faria et al. /
Renewable and Sustainable Energy Reviews 24 (2013) 271287
273Tocorrectlyassess the impact of vehicle interms of GHGemissions
during the use phase, the energy losses in a vehicle needto be
characterized. For ICEVs these losses are translated directlyto
fuel consumption, however since BEVs and PHEVs requireenergy from
the grid to charge the batteries, the additional lossesin the
transmission and distribution system must be accounted for,usually
around 910%[3537]. Forinstance, tochargea 16 kW hbattery connected
to a power grid with an efciency of 90% it willrequire a generation
of 17.6 kW h.InaEVs, energylosses occur
intheenergystoragesystem(usuallyabattery), at
thedrivetrain(thegroupof mechanicalcomponents responsible to
transmit the power from the motor tothewheels topropel thevehicle)
andinthepower electronicmodule(responsibleforthemotorcontrol,
regenerativebrakingand charging)
[38,39].Theenergystoragesystemcanbeconstitutedbybatteries,supercapacitorsor
bythecombinationof them. Nowadays, thebattery is the main component
of the Energy Storage System (ESS)dueto alower costwhencompared
withother storage technol-ogies [4043]. Lithium-Ion batteries are
the most common in EVsduetoaspecic energyupto400
Wh/kgandahighspecicpower (up to 10 kW/kg) when compared with
lead-acid batteries,whichhaveaspecicenergydensitybetween20and30
Wh/kgandaspecicpowerupto400 W/kg[44].
ThebatteriesusedinEVshaveanenergy capacityintherangeof1085 kW
handanefciencyofabout70%95%[45]. Internalresistance, typicallyinthe
range of milliohms, which increases both with cycling and age,is
one parameter that contributes tothe batteryefciencybycausing a
voltage drop under load and by reducing the maximumoutput current
affecting the charge/discharge rate [4648].Battery life and
capacity are key aspects for the wide adoptionofelectricvehicles.
To estimatethepotential savingsin terms
ofGHGemissionsandalsotheTotal CostofOwnership(TCO)ofavehicle it is
fundamental to estimate the life of a battery under realworld
operation. The battery state of health is greatly inuencedby the
load and environmental conditions [49,50]. Depending onthe
lithium-ion cell chemistry, both high and low State of
Charge(SOC)contributeto thedeteriorationofthebattery performanceand
lifetime. Overcharge, over-discharge, high Depth of Discharge(DOD)s
and high temperatures also inuence the fast decay of thebattery
life and low temperatures can also have a negative impact,mainly
during the charging phase [46,51].Modern electric vehicles employ
Battery Management System(BMS) that monitor the battery state of
health and avoid workingpointsthatcontributetoacceleratedaging,
forinstancebycon-trollingthebatterypacktemperatureusingactiveheatingandcooling
systems, as well as by avoiding the battery overcharge
andover-discharge. Depth of discharge is also managed by limiting
theamount of energy that can be drawn (from a 24 kW h pack, only20
kW h or less are used). It is expected, that the battery, managedby
the BMS, working within specied boundaries will last, with ahigh
degree of probability, the life time of a vehicle. The user canalso
contribute to the mitigationofthe aging effectsby
avoidingcompletebattery
charge/dischargecyclesandbyminimizingtheload applied to the battery
due to fast accelerations, by adoptingan eco-driving prole.The
powertrain includes the Internal ICE and/or electric
motor,transmission, drive shaft, differential and drive wheels. In
the caseof diesel ICEs, the efciency is around 3035% in the ideal
speedrange, decliningoutsidethisrange,
whilegasolineICEshaveanefciency of 1825%, meaning that around 80%
of available energyis lost as heat.In EVs, the most common types of
electric motors are perma-nent magnet motors andinductionmotors
withanefciency,depending on the type of motor, that can go from 85%
up to 95%from a wide speed range [52].In the drivetrain,
responsible by the transmission of themechanical energy generated
by the engine to the road, the energylosses occur in the
differential andnal drive. In an ICEV, the
oilpumpisresponsiblefor3040%of total powerloss,
theclutchcontributeswithadditional 2025%andgearmeshing,
bearings,bushings and drag on the gears caused by the gear oil
areresponsiblefortheadditional losses. Inthecaseofrearandall-wheel
drive vehicles the power losses in the differential tend to
belarger due to a 901 turn in the torque path and are usually
610%,while losses from the drive shaft are 0.51% of total losses
[53,36].The total losses in the drivetrain account around 58%.One
characteristic of electric motors is the ability to supply
themaximumamount of torqueoveraverylargerangeof speeds,eliminating
the need for gear shifting in EVs and giving the vehicleasmoother
accelerationandbraking. Themechanical power isWall SocketL2 Slow
Charger (95-97%)DC Fast Charger
(91-94%)Battery(90-95%)Inverter(90-98%)ElectricMotor(85-96%)Drivetrain(87-93%)DrivingCharging
Elec. Gen. Reg.
BrakeGenerationTransmission(98-99%)Distribution(91-93%)Wall
SocketFig. 2. Range of efciency of the different components in the
energy path of an EV.Table 2WTW systemefciency for the electric
powertrain, consideringthe power lossesalongtheelectricitypath,
usingaDCfastcharger(DC)andastandard240VACcharger (L2), with
Lithium-Ion batteries as energy storage. It should be noted thatfor
the overall system efciency the battery efciency was accounted
twice due tothe charge and discharge cycles.System components
Global system efciency (%)Minimum MaximumTransmission 98
99Distribution 91 93L2 Charger (L2) 95 97DC Fast Charge (DC) 91
94Battery 90 95Inverter 90 98Electric Motor 85 96Drivetrain 87
93WTT (w/L2) 76.2 84.8WTT (w/DC) 73.0 82.2TTW 59.9 83.1R. Faria et
al. / Renewable and Sustainable Energy Reviews 24 (2013) 271287
274delivered directly, or through a simple gear reduction step to
themain-shaft of the transmission, so the only loss sources
arewindage, frictionanddrag, resultingintotalat-the-wheellossesas
low as 1.5% to 2%. The Power Electronics Module (PEM) controlsthe
energyow from the battery to the motor and vice versa. Themain
component is an inverter with an efciency of 90-98%. Othercomponent
tobetakenintoaccount, bothforPHEVsandBEVsefciency,
isthechargertypicallywith9197%efciency. Fig. 2shows the
conversionpathof energy,
fromgenerationtothewheels.Table2summarizestheefciencyof
eachsystemalongtheenergy path to power an EV. WTT and TTWefciency
wascalculated using (1) and (2).WTT trans: dist: charger batt:1TTW
batt: inv: electricMotor trans:22.2. Use phase and main factors
that contribute to EVs energyconsumptionThe phase during the
vehicle life-cycle that dominates theoverall GHG emissions is
generally the use phase, regardless of thetypeof vehicle,
beingthegasolineICEVtheonewithahigherenvironmental impact,
according to several LCA studies
[28,54,55],thereforeitscharacterizationwithahighdegreeof
accuracyisdesirable. Usually the emissions from motor vehicles are
based inspecicdrivecyclesapprovedbyGovernmental entities, suchasNew
European Drive Cycle (NEDC) in Europe or FTP-75 in USA, toassess
vehicle fuel consumption, performance and emissions [56].These type
of cycles are important since they compare and check ifa specic
vehicle meet Government requirements. However theydo not take into
account some factors that contribute heavily to avehicle energy
consumption, such as the path elevation prole andthe driving prole.
Fig. 3. Data acquisition system installed on the EVs
[55].0.000.050.100.150.200.250.300.350.40010000200003000040000500000
10 20 30 40 50 60 70 80 90 100 110 120 130 140Energy Consumption
[kWh/km]Power [W]Speed [km/h]Leaf [kW] Volt [kW] Smart [kW] iOn
[kW]Leaf_er [kW] Volt_er [kW] Smart_er [kW] iOn_er [kW]Leaf
[kWh/km] Volt [kWh/km] iOn [kWh/km] Smart
[kWh/km]0.000.100.200.300.400.500.600.700.800.901.00010000200003000040000500000
10 20 30 40 50 60 70 80 90 100 110Energy Consumption [kWh/km]Power
[W]Speed [km/h]Leaf [kW] Volt [kW] Smart [kW] iOn [kW]Leaf_er [kW]
Volt_er [kW] Smart_er [kW] iOn_er [kW]Leaf [kWh/km] Volt [kWh/km]
iOn [kWh/km] Smart [kWh/km]Fig. 4. Power and energy consumption for
the Nissan Leaf, Smart ED and Chevrolet Volt for a 01 (top) and
7.21 (bottom) slope. Some data points from experimental runs
areidentied with the subscript_er with an error of less than 5%
when compared with the mathematical model from Eq. (7).R. Faria et
al. / Renewable and Sustainable Energy Reviews 24 (2013) 271287
275Inthecaseof EVs, sincetheyareequippedwithanelectricmotor that
can work as a generator, they can recharge the
batterywhengoingdownhillorduringthebrakingphase, reducingtheoverall
energy consumption, aspect that is not taken in to accountin drive
cycles suitable for ICEVs.In order to assess the energy
consumption, and associated GHGemissions, a data acquisition system
was developed and installedin the EVs considered in the study. The
system was constituted bya6degreesof freedomXSensMTI-gInertial
MeasurementUnit(IMU), with a three axis accelerometer, gyroscope,
magnetometer,GPS and barometric sensor for instantaneous velocity
and positionmeasurements; a Fluke i410 current clamp and a Metex
M3640Dmultimeter for instantaneous power measurements,
bothcon-nected to a computer, through RS-232 for data logging up to
10 Hz(Fig. 3).Using this data acquisition system it is possible to
correlate
theenergyconsumptionwiththeroadproleandwiththedrivingprole.
Thissystemalsoallowsthebreakdownof theinstanta-neouspower
consumptionintothepowerrequiredtoovercometheforces
actuatingonthevehicle. Amoving vehicle, atagivenspeed, requires
power toovercomethefollowingforces:
aero-dynamicdrag,rollingresistance,
gravitywhenascendingaslope0200400600800100012000%10%20%30%40%50%60%70%80%90%100%Jan
Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecgCO2e/kWhPolish
Electricity Mix: Share and GHG Emissions by source for 2011Coal CHP
Fuel Gas Hidro Wind
gCO2e/kWh01002003004005006000%10%20%30%40%50%60%70%80%90%100%Jan
Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecgCO2e/kWhPortuguese
Electricity Mix : Share and GHG Emissions by source for 2011Coal
CHP Fuel Gas Hydro Wind PV
gCO2e/kWh0204060801001201401600%10%20%30%40%50%60%70%80%90%100%Jan
Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecgCO2e/kWhFrench
Electricity Mix: Share and GHG Emissions by source for 2011Nuclear
Coal Fuel Gas Hydro Wind gCO2e/kWhFig. 5. Electricity mixes share
and associated GHG emissions.R. Faria et al. / Renewable and
Sustainable Energy Reviews 24 (2013) 271287 276and vehicle inertia
when accelerating given by Eqs. (3), (4), (5) and(6)
respectively:Pdrag 12 Cd A vvwind33Proll m g v Crr cos 4Pslope m g
v sin 5Pacc m a v 6where Crr is the rolling coefcient, Cd is the
drag coefcient, isthe air density, m is the vehicle mass, A is the
vehicle frontal
area,vandvwindcorrespondtothevehicleandwindvelocityrespec-tively, a
is the vehicle acceleration, g is the gravity acceleration and is
the terrain slope, in degrees.Eq. (7) representsthetotal
powerrequiredtoovercometheforces acting over the vehicle
considering the motor and transmis-sion efciency and the auxiliary
power, denoted by Paux, requiredfor the control equipment, radio,
lights etc.Ptotal Pacc Pslope Pdrag Pfrictionmotor trans Paux7On
Fig.4 the comparison between the EVs in terms of powerand energy
consumption in for aat road prole is presented. Dueto a lighter
weight, the Smart ED is vehicle with the lower
energyconsumptionfollowedbytheNissanLeaf andbytheChevroletVolt,
howeverat higherspeedstheChevrolet volt requireslesspower and
consequently less energy due to a better
aerodynamiccoefcient(Cd)whencomparedwiththeNissanLeaf (0.28and0.29
respectively).0200400600800100012000 1 2 3 4 5 6 7 8 9 10 11 12 13
14 15 16 17 18 19 20 21 22 23gCO2e/kWhPolish Electricity Mix: GHG
Emissions variation during a dayJan Feb Mar Apr May Jun Jul Aug Sep
Oct Nov Dec01002003004005006007000 1 2 3 4 5 6 7 8 9 10 11 12 13 14
15 16 17 18 19 20 21 22 23gCO2e/kWhPortuguese Electricity Mix: GHG
Emissions variation during a dayJan Feb Mar Apr May Jun Jul Aug Sep
Oct Nov Dec0204060801001201401601800 1 2 3 4 5 6 7 8 9 10 11 12 13
14 15 16 17 18 19 20 21 22 23gCO2e/kWhFrench Electricity Mix: GHG
Emissions variation during a dayJan Feb Mar Apr May Jun Jul Aug Sep
Oct Nov DecFig. 6. Average GHG emissions variation during the day,
over a year, for the considered mixes.R. Faria et al. / Renewable
and Sustainable Energy Reviews 24 (2013) 271287 2772.3. Energy
sources: emissions assessment2.3.1. Crude oil extraction and
reningIn Europe, transport is responsible for almost 20% of the
GHGemissions, with 930 MTCO2e in 2010 according the Eurostat
latestdata, with passenger cars contributing with almost 12%.
EUtransportemissionscurrentlycontributewith3.5%of
theglobalCO2emissions. Relative CO2emissions fromtransport
havedecreased over the past years, from 2005 to 2010 they
decreased3.4% despite the increase of 5% in the motorization rate
during thesame period, due to a proposed a legislative framework to
reduceGHG emissions from the transport sector [57,58].The
International Energy Agency (IEA) predicts that the crudeoil
consumptionwill increase27%until 2030, from83 MMbbl/d(million
barrels of oil per day), in 2009, to 102 MMbbl/d, in
2030.Crudeoilextraction, transportandrening, accountsinaverage,for
about 18% of WTW of GHG emissions [59]. The quanticationof the WTW
emissions is divided intove components associatedwiththe
petroleumproduction: (i) extraction, (ii) aring andventing, (iii)
fugitive emissions, (iv) crude oil transport and(v)
rening.InEuropethecrudeoil comes fromalargenumber of oilelds around
the world and each of themhas specic GHGemissions,
dependingonthetype. Thecarbonintensityofcrudeoil rangesfrom4to50
gCO2e=MJ (gramsof CO2-equivalent permegajoule), with an average of
1372 gCO2e=MJ [59]. Extraction ofcrudeoil fromtar sands,
averyenergyintensiveprocess, con-tributingtohighGHGemissions
andtheIEAprojects that 8%(8.9 MMbbl/d) of the world crude oil will
come from this source in2035 [60].Additional emissionsfromfuel
combustioninmotorvehiclesare about 73 g CO2e=MJ 152 gCO2e=km, for
gasoline with34.8 MJ/l andaconsumptionof 6 l/100 kmand127
gCO2e=km,for diesel with 38.4 MJ/l and a consumption of 4.5 l/100
km). life-cycleemissionsfordiesel andgasolineduetofuel
burningarearound 3200 gCO2e=l and 2900 gCO2e=l respectively.2.3.2.
Electricity mixGenerallytheusephasedominatestheoverallimpacts,
how-ever, for an electricity mix with a large contribution from
RES,
theproductionphaseofaBEVistheonethatdominatestheoverallenvironmental
impact [29,61]. To assess correctly the impact of aBEV the
electricity mix used to charge the vehicle must be knownwith a good
degree of certainty.The primary energy source used for electricity
generationcontributes directly to the overall GHG emissions of the
generationmix, which in turn affect the use phase GHG emissions of
an EV.Emissions associated with fuel production are more or
lessconstantovertime, mainlyaffectedfromwherethecrudeoil
isextracted, andcouldbeconsideredoveralargegeographicareaunlike
electricity generation that depends directly from the
shareandtypeofpowerplantsonthesystemandcouldvarysigni-cantlyfromcountrytocountry.
Other keyaspect totakeintoconsideration, is that theshareof
eachtypeof energysourcecontributing to the overall electricity mix
varies daily and is alsodependent on the season [62].Most studies
consider an average electricity mix over a year fora given
geographic region that can lead to results, in terms of
GHGemissions during a vehicle life-cycle, that do not reect the
reality,sincetheemissionsassociatedtodifferent
chargingperiodsarenot constant during the day. One objective of the
presented studyis to assess the impact of the electricity mix and
the EV chargingproleintheoverall life-cycleemissions.
Toassessmoreaccu-ratelythecontributionfromelectricitygenerationtotheoverallLCA,
aWTTanalyzeswas performedconsideringthefollowingmixes found in
Europe:
A mix with high GHG emissions represented by Poland.
AmixwithverylowGHGemissionsrepresentedbyFrance.item A mix with
large contributionfrom RESs represented byPortugal.On Fig. 5 and on
Fig. 6 it is easily noticeable that the mix
variesconsiderablyovertheyearandalsoduringtheday,
duetotheintermittence and share of RESs for the overall electricity
genera-tion. This variation is very noticeable in mixes with a
largecontributionfromRESsorNuclear, suchasPortugal andFrance,where
a drop in the contribution from RESs must be
compensatedbyusingfossil poweredplants, leadingtohigher overall
GHGemissions [63]. In a mix mainly ruled by fossil fuel powered
powerplants, the associated GHG emissions are fairly constant over
theyear and over the day. This type of mix has the higher
associatedemissions with an average value of 979 gCO2e=kW h over
the year,while the Portuguese and French mix had an average value
of 376and 103 gCO2e=kW h respectively. It should be noted that for
thecaseofPolandduetoahighshareoffossilfuelpoweredpowerplants and
low variation in the electricity mix during the year, thedata for a
typical month was considered for all
year.TheGHGemissionswerecalculatedtakingintoaccount thestandard
emissions from Table 3 [64].2.3.3. Contribution of the RESs to the
reduction of GHG emissionsover the next decade in the European
Union (EU)TheEuropeanCommission(EC) is
committedtoreducetheGHGemissionsto8095%bellow1990levelsby2050andtheinvestment
in RESs is seen as a key factor for the decarbonizationobjective
whileatthesametimereducingthedependencefromfossil fuel sources and
ensuring security of energy supply. Accord-ing to the National
Renewable Energy Action Plans, in a referencescenario, is estimated
that the RESs in EU will contribute with 25%in 2015 and 31% in
2020. In an increased energy efciencyscenario, the
contributionfromRES is expectedtobe 26%in2015and34%in2020[65].
Projectionsestimatethat REScon-tribution will increase to 902 TW h,
a 32% growth, by 2015 and to1216 TW hby 2020, a 87%growth, fromthe
2010 652 TW h.Between2010and2020, theRESs withthehighest
growthinterms of installed capacity will be solar, with a 250%
growth, andwind, with a 151% growth. In 2020, hydro and wind will
continueto be the sources with the highest share, both in terms of
installedcapacity and electricity generation, with 495 TW h and 370
TW hrespectively. This increase in the share of RESs in the
totalelectricity generation, to 3040% in 2020, will lead to a
reductionintheelectricitymixemissions of 1466 gCO2=kW
hfromthe312364 gCO2=kW hin2009. Additional measures topromoteenergy
efciency will lead to additional reductions. Due to this factTable
3Typical lifecycle GHG intensity by type of generator
[64].Technology Emissions (gCO2e/kW h) ObservationsCoal 1050
Without scrubbingCoal 960 With scrubbingWind 910Hydroelectric 13
Run of riverHydroelectric 10 ReservoirBiomass 1441Solar PV 32
Polycrystalline siliconeNuclear 66Natural gas 443Diesel oil 778CHP
354R. Faria et al. / Renewable and Sustainable Energy Reviews 24
(2013) 271287 278the EV is the only vehicle that gets cleaner, due
to an increasinglycleaner energy source, during its life-cycle.3.
Life-cycle GHG emissionsFig. 7presents thelife-cycleGHGemissions
for eachvehicletechnology. The emissions for the EVs were
calculated based on
theWTWefciencyandontheaverageelectricitymixemissionsfor2011 (979
gCO2e=kW hfor the Polish mix, 376 gCO2e=kW hfor thePortuguese mix
and 103 gCO2e=kW h for the French mix). The resultsshow that the
overall emissions from EVs are highly dependent onthe electricity
mix. The Chevrolet Volt shows higher GHG emissionsthan conventional
Internal Combustion Engine (ICE) technology. Theadditionalweight of
PHEVs due to the two engines has a
negativeimpactsincemoreenergyisrequiredtomovethevehicle. Ontheother
hand, the Smart ED shows the lower GHG emissions since it isthe
lighter of the EVs analyzed. As expected, charging an EV with
anelectricity mixwith lower GHG emissions reduces
signicantlytheoverall life-cycle emissions. In this case, the PHEV
Chevrolet Volt canhave overall emissions similar to a sub-compact
conventional vehicle,the Smart diesel, despite their signicant
weight difference.Fig. 8 presents the share of the life-cycle
emissions by vehiclecategory, for each vehicle technology and
electricitymix. For theInternal CombustionEngine(ICE) conventional
technology, thedominant phase is by far the operation phase,
accounting for 8590% of the global emissions, mainly associated to
fuel combustion.ForEVs, thebattery productionaccountsfor alarge
share oftheemissions, almost the same as vehicle production, due
tothehighly energy intensive processes required to obtain the
materialsusedinthe batteryproduction. The emissions
fromoperationphase are highly dependent on the electricity mix. In
a mix heavilydependent on fossil energy sources, such as the Polish
mix, the usephase account for 7080% of the overall emissions. For
anelectricitymixwithlower GHGemissions, suchas theFrenchmix where
the generation is mainly from nuclear, the productionphase is the
most signicant to the overall emissions, accountingfor around
7075%.GHG emissions from maintenance and vehicle disposal
repre-sent less than 10% of the overall emissions. Despite EVs
having lessmaintenancecomparedtoconventionalvehicles,
theshareasso-ciatedwithmaintenancewill behigher
sincetheyhaveloweremissions. Additional emissions for thedisposal
of thebatteryshouldalsobetakenintoaccount. However,
itshouldbenotedthat batteries still retainsomecapacityat
theend-of-life, and,thus,
canbereusedonotherapplicationssuchasstaticenergystorage, where the
requirements are moreexible thus extendingtheir useful
life.050100150200250gCO2e/km050100150200250gCO2e/kmFig. 7. GHG
intensity per km traveled and by electricity mix considered (top:
compact vehicles; bottom subcompact vehicles) category. Note: In
the case of the ChevroletVolt, the FE denominates the full electric
mode.R. Faria et al. / Renewable and Sustainable Energy Reviews 24
(2013) 271287 2793.0.4. Impact of the vehicle charging prole on the
overall
GHGemissionsAsstatedbeforetheemissionsassociatedwiththeelectricitymixvarysignicantlyduringtheyearandevenduringtheday.These
variations are associated with the intermittent nature of
therenewable resources. In this case, some conventional
powerplants,powered by fossil fuel, must be in standby increasing
theoverallemissionsassociatedtoelectricitygeneration.
InAutumnandWinterthecontributionfromRESsissignicantduetotherainyandwindynatureof
theseseasons. However duetothevariations of theweather conditions
betweenyears this is notalways veried.Other
aspectthatinuencestheoverall emissionsfor agivenvehicle is when the
vehicle is charged on a daily basis. This is morerelevant for
electricity mixes with a large share of RESs. For
mixeswithalargecontributionfromfossilornuclearsources, suchasPoland
or France respectively, the emissions fromelectricitygeneration are
more stable. However, in the case where
RESrepresentsalargeshareoftheelectricitymixthisisnotalwaystrueduetodifferentlevelsofrenewablegenerationavailableateach
hour. Since coal and gas fueled power plants require asignicant
start up time, that can go up to 8 h, they must be keptat a minimum
level of operation independently of theconsumption.
ThisaspectisvisiblewherewascleanertochargeanEVduringthedayratheratnightforseveralmonthsforthePortuguese
electricity mix during 2011 (Fig. 10). For a mix were
themainshareof RESishydroandwindsuchasPortugal, duringwinter
months, charging at night will emit approximately less
2050%whencomparedwithachargeduringtheday. Forsummermonths, this
situationis not always true, as for somemonthscharging during the
day will emit approximately less 423% whencompared with a night
charge.For mixes witha large contributionfromfossil or
nuclearpower, theemissions
variationduringthedayfromelectricitygenerationarenotusuallysignicant(Figs.
9and11), exceptinwinter months, meaning that charging at night or
during the daywillnothaveamajorimpactontheoverallemissions.
Howeverthe best time to charge an EVis at night, since the
energyconsumedbytheEVwillcontributetoaatterloadproleandalsotomaximizetheamountof
timethatpowerplantsremaincloser to their nominal capacity.3.0.5.
Impact of the vehicle driving prole on the overall
GHGemissionsToassesstheimpactofthedrivingproleseveralrealworlddriving
cycles were performed in two predenedroutes,
one0%10%20%30%40%50%60%70%80%90%100%0%10%20%30%40%50%60%70%80%90%100%Fig.
8.
ConventionalandelectricvehicletechnologiesGHGemissionsbyshareandby
electricitymix considered,
dividedintocompact(top)andsubcompact(bottom)category. Note: In the
case of the Chevrolet Volt, the FE denominates Full Electric
mode.R. Faria et al. / Renewable and Sustainable Energy Reviews 24
(2013) 271287 280urban and other suburban, under different driving
conditions(aggressive,
normalandECO)andwithdifferentsettingsfortheclimate control (A/C
OFF, A/C in cooling mode and A/C inheating mode).The aggressive
driving prolediffersfrom
thenormaldrivingprolemainlyintheaccelerationandbrakingphase,
wheretheaggressive has fast accelerations and sudden braking to
maximizethe energy consumption. The ECO driving prole is
characterizedby slow accelerations, lower top speed and the braking
is mainlyduetotheregenerativebraking, tominimizetheoverall
energyconsumption. For the driving cycles, the climate control was
set inmanual modeat 21 1Cwiththefanat mediumspeed,
bothforcoolingandheating, beingthebaselinewiththeclimatecontrolOFF.
The use of a manual setting for climate control allows a
betterunderstandingabout howit canaffect theoverall
energycon-sumptionandassociatedemissions.
Fig.12showstheelevationprole for the urban and extra urban routes
used to assess the EVenergy consumption.The data was captured using
the data acquisition system fromFig. 3. OnTable 4some results of
the runs performedunderdifferent conditions and with different
settings for climate controlarepresented. Inthissection, all
thepresentedresultsrefertotrials performed with a Nissan Leaf. The
remaining EVs consideredalongthepaperwill
haveasimilarresultsbutreferredtotheirspecic energyconsumptionfor
thepresentedscenarios, byaweighting
factor.0,0020,0040,0060,0080,00100,00120,00Jan Feb Mar Apr May Jun
Jul Aug Sep Oct Nov DecgCO2e/kmVolt FE (00:00-08:00)
Leaf(00:00-08:00) iOn(00:00-08:00) Smart ED(00:00-08:00)Volt FE
(10:00-17:00) Leaf (10:00-17:00) iOn (10:00-17:00) Smart ED
(10:00-17:00)Volt FE (19:00-00:00) Leaf (19:00-00:00)
iOn(19:00-00:00) Smart ED (19:00-00:00)Fig. 10.
GHGemissionsassociatedtotheoperationphase, fortheconsideredEVs,
basedonthetimeofdaywhenthevehicleischarged,
consideringthePortugueseelectricity mix for 2011. Only the
emissions during the specied charging intervals were accounted for,
emissions during 2 h in the morning and in the afternoon, when
thevehicle is being used for commuting, were not
accounted.80,00100,00120,00140,00160,00180,00200,00Jan Feb Mar Apr
May Jun Jul Aug Sep Oct Nov DecgCO2e/kmVolt FE (00:00-08:00)
Leaf(00:00-08:00) iOn(00:00-08:00) Smart ED(00:00-08:00)Volt FE
(10:00-17:00) Leaf (10:00-17:00) iOn (10:00-17:00) Smart ED
(10:00-17:00)Volt FE (19:00-00:00) Leaf (19:00-00:00)
iOn(19:00-00:00) Smart ED (19:00-00:00)Fig. 9. GHG emissions
associated to the operation phase, for the considered EVs, based on
the time of day when the vehicle is charged, considering the Polish
electricity mixfor 2011. Only the emissions during the specied
charging intervals were accounted for, emissions during 2 h in the
morning and in the afternoon, when the vehicle is beingused for
commuting, were not accounted.R. Faria et al. / Renewable and
Sustainable Energy Reviews 24 (2013) 271287 281Table 5 summarizes
the average energy consumption andestimated range for the
considered scenarios while Table 6, basedontheenergyconsumption,
showstheassociatedemissionsbyscenarioandelectricitymix. As
expected, aneconomicdrivingprole is more efcient than an aggressive
one, which can reducethe driving range by 90 km due to the
increased energy consump-tion in 47%. The use of climate control
also has a signicant
impact,increasingtheenergyconsumptionin24%incoolingmodeand61% in
heating mode for the ECO driving prole.In Fig. 13 is possible to
compare the impacts, per km traveled,duetodifferent
drivingproleandtheuseof climatecontrolagainstabaselinescenario,
fortheconsideredelectricitymixes.For an electricitymix with low
GHGemissions the way an EV
isusedwillnotaffectthelife-cycleemissionsinasignicantway.HoweverforanmixwithhighGHGemissionsthisisnolongervalid.
AstheelectricitymixassociatedGHGemissionsincrease,more relevant
will be the impact of the use prole of the EV. Fig.
14correlatesthevehicleenergyconsumption(inWh/km), directlyrelated
with the emissions per km traveled (in gCO2e=km), and
theelectricitymixlife-cycleemissions (ingCO2e=kW h) ontheEVoverall
life-cycle GHG emissions.4. Life-cycle ownership costsFrom a
consumer stand point a key aspect of EVs is how muchwill a given
technology cost during its life-cycle. To evaluate it, aneconomic
assessmentfor each vehicle technology duringthe fulllife-cycle was
performed, intending to estimate the cross point intime which a
given vehicle technology takes advantage overanother. For the
economic analysis the purchase, operation,depreciation and capital
cost was considered based on EU marketand manufacturer data.The
operational cost, per year, was calculated based on a totaldriven
distance of 20 000 km and the average fuel and electricityprices
inEUin2012(1:42for diesel, 1:51for gasolineand0:17=kW h for
electricity) [66]. It should be noted that in certaincountries the
electricitycost varies withthe hour of
theday.5,0010,0015,0020,0025,0030,00Jan Feb Mar Apr May Jun Jul Aug
Sep Oct Nov DecgCO2e/kmVolt FE (00:00-08:00) Leaf(00:00-08:00)
iOn(00:00-08:00) Smart ED(00:00-08:00)Volt FE (10:00-17:00) Leaf
(10:00-17:00) iOn (10:00-17:00) Smart ED (10:00-17:00)Volt FE
(19:00-00:00) Leaf (19:00-00:00) iOn(19:00-00:00) Smart ED
(19:00-00:00)Fig. 11. GHG emissions associated to the operation
phase, for the considered EVs, based on the time of day when the
vehicle is charged, considering the French electricitymix for 2011.
Only the emissions during the specied charging intervals were
accounted for, emissions during 2 h in the morning and in the
afternoon, when the vehicle isbeing used for commuting, were not
accounted.Fig. 12. Urban (top) and extra urban (bottom) elevation
prole for the two routes considered in this study to assess the
driving prole impact in the overall EV energyconsumption.R. Faria
et al. / Renewable and Sustainable Energy Reviews 24 (2013) 271287
282In Portugal during the day (08:00 h22:00 h) the electricity
costs0:14=kW h while at night (22:00 h08:00 h) it costs 0:08=kW
h,which translates to a 43% reduction in the electricity cost per
yearonly by charging the EV at night. Other operational costs such
asmaintenance and insurance were also considered for each
vehiclebased on market and manufacturer data. An ination and
interestrate of 2.5%/year and 5%/year,respectively,were also
considered.Theusescenarioconsideredfor thePHEVwas
80%inelectricmode, for commute during the week, and 20% in extended
rangemode for longer trips. Table 7 summarizes the costs associated
toeach vehicle used to calculate their annual operational
costs.Fig. 15shows that EVs havelower costs
thanconventionalvehicles,
duetoasimplermaintenanceandtheequivalentelec-tricity cost required
to travel a given distance is much lower thangasoline and diesel.
The PHEV has a higher maintenance cost duetothecombustionengine,
howeverlowerthanICEVs. Themaincostsduringthelifetimeof
EVsaretheinitial investment andassociatedinterest,
accountingaround7080%of thetotal life-cycle costs, while for
conventional vehicles they only account upto 50%.From Fig. 16 it is
possible to estimate the break even point foreach EVs when compared
with a conventional vehicle. Due to thehigher initial cost of an EV
the turn around time could be up to theentirelife-cycleof
thevehicle(910years), despitetheirloweroperational cost. This is
even worst for the PHEV since it has twotypes of drivetrains, a
conventional and an electrical one, making itthe most expensive
version of all of them. As expected, thecheapest EV is the Smart
ED, because of its lower initial cost, butit should be noted that
this vehicle is in a different category fromthe rest in terms of
capacity.5. ConclusionWith vehicle emissions becoming stricter over
the next decadeduetogovernmental requirements tomitigateglobal
warmingandlocal pollution,
aswellastherequirementstoimprovefueleconomy, manufacturers are
continuously improving ICE technol-ogy and are also developing new
technologies such as BEV, HybridElectricVehicle(HEV), PHEVandHFCV.
Themarket viabilityofBEV and PHEV is highly dependent on the TCO
and how the costsaredistributedalongthevehiclelifetime.
Forthesevehicles, themajor cost is the acquisition cost in contrast
with the lower costsof ICE vehicles, leading to a slow market
penetration.For diesel, gasoline LPG and CNG vehicles, better
control overfuel injection, spark timing and a better fuel/air
mixture could leadto additional reduction in emissions, by
adjusting the fuel burningparameters depending on the vehicle
conditions. Advanced gaso-lineanddiesel vehicles, withstop-star
capabilities, downsizedTable 4ResultsfortheNissanLeaf real
worlddrivingcycles, forurbanandextraurbanroutes, under different
driving proles and climate control settings.Type Length(km)Energy
consumption(Wh/km)Speed (km/h)ACOFFAC ONCool.AC
ONHeat.Max./MedianDrivingproleUrban 16 155.4 177.7 213.4 86/43
AggressiveUrban 16 126.6 148.1 182.3 86/47 NormalUrban 16 95.5
122.2 164.8 61/42 ECOUrban 17 135.1 153.7 183.2 96/58 NormalUrban
17 103.9 128.5 167.8 82/45 ECOUrban 16 114.9 135.6 168.6 71/42
ECOExtraUrban16 157.2 172.7 197.4 115/63 AggressiveExtraUrban16
143.0 157.3 180.1 100/67 NormalExtraUrban16 138.1 154.5 180.6 85/70
NormalExtraUrban16 132.8 148.3 173.0 100/77 ECOExtraUrban16 129.3
145.0 170.0 100/60 ECOTable 5Energy consumption and estimated range
for the Nissan Leaf based on the drivingprole and climate control
settings based on data acquired from several runs in aurban and
suburban environment.Driving style AC OFF AC ON Cool. AC ON
Heat.Wh/km km Wh/km km Wh/km kmAggressive 155.4 129 177.7 113 213.4
94Normal 131.0 153 151.0 132 182.8 109ECO 104.7 191 129.0 155 167.1
120Table 6EstimatedGHGemissionsfortheNissanLeaf, perkmtraveled
fortheoperation,basedonthe driving prole andclimate control
settings, for the consideredelectricity mixes. The emissions
considered, for each mix, were the average valuesfor 2011 (979
gCO2e=kW h for the Polish mix, 103 gCO2e=kW h for the French mixand
376 gCO2e=kW h for the Portuguese mix).DrivingstyleAC OFF AC ON
Cool. AC ON
Heat.PLMixPTMixFRMixPLMixPTMixFRMixPLMixPTMixFRMixAggressive 177 68
19 202 78 21 243 93 26Normal 149 57 16 172 66 18 208 80 22ECO 119
46 13 147 56 15 190 73
200,0050,00100,00150,00200,00250,00300,00350,00Nissan Leaf PT2011
Mix Nissan Leaf FR2011 Mix Nissan Leaf PL2011 MixgCO2e/kmFig. 13.
Impact of the operation phase on the Nissan Leaf on the overall
life-cycle emissions per km traveled, by electricity mix. The
baseline scenario is based on the rangefor a full charge provided
by the manufacturer (122 gCO2e=kW h for the Portuguese mix, 83
gCO2e=kW h for the French mix and 210 gCO2e=kW h for the Polish
mix).R. Faria et al. / Renewable and Sustainable Energy Reviews 24
(2013) 271287 283turbo-charged engines and with some level of
hybridization due tothe use of an electric motor coupled with small
lithium-ion batterieswill contribute to additional reduction of
vehicles emissions withoutgreatly increasing the cost of ICE
vehicles. The use of alternative fuels,such as bio-diesel, ethanol
and hydrogen, may also lead to lower lifecycle environmental
impacts, due to the improvements not only invehicle technology but
also in the fuel production cycle.Thereductionof
vehicleweightbyusinglightermaterialsisanotherstrategytoreduceenergyconsumptionandGHGemis-sions
which can be implemented independently of the powertraintechnology.
Abreakthroughincarbon-ber cost wouldbeveryvaluable, mainly for body
parts.The future of the transport systemwill pass through
theincreasingelectricationof thepowertrainsinceEVs aremoreefcient,
canbecleanerthanICEVsandsignicantlyreducethedependence from fossil
fuels. Although the payback period
couldtakeupto912yearsduetothehigherinitial costofaBEVorPHEV, the
long term EV ownership costs is lower when
comparedwithaconventional vehiclefromthesamecategory. Improve-ments
in lithium-ion batteries and super-capacitor technology byusing
advanced materials will increase their lifetime and
efciencycontributing to a longer life cycle andoptimizing the
batteryproduction will reduce their cost, making EVs more
affordable. Thesecond life of EVs batteries, for use in grid
storage for instance, willalsocontribute, toacertainextent,
toreduceoverall environ-mental impacts associated to EVs.Also,
theelectricitypriceisalsomorestablewhencomparedwith gasoline or
diesel, and with the constant increase in the
costofcrudeoilthepaybackperiodofanEVmaybereducedinthefuture. With
improvements in the battery technology, the cost ofthe EVs will
likely decrease, due to the reduction of massproduction costs and
increased efciency, making the EV aincreasingly attractive choice
from the consumer stand point.For all vehicle technologies
analyzed, the operation phase is theone that most contribute to the
GHG emissions over the life-cycleof a vehicle, contributing with
8590% for a conventionalvehicle while for an EV this is highly
dependent on the electricitymix. For a mix dominated by fossil
sources, the operation phase ofan EVwill be dominant representing
more than 75% of thevehiclelife-cycleemissions. For amixwithaheavy
contributionfromnuclear or renewableenergysourcethedominant
phasewill be the vehicle andbatteryproduction, withat least 50%of
the life-cycle emissions, largely dependent on the batterycapacity.
Otherrelevantaspect isthatanelectricitymixwithalarge contribution
fromRESs can have signicant
emissions,duringspecicperiods(hoursordays). Theintermittentnatureof
renewable sources requires fossil power to be in standby to
takeover thegenerationinthecaseof
failurefromtherenewablesources.Duringtheoperationphasebesidesthedirectimpactof
theelectricity mix in the overall emissions of EVs, the way the
vehicleisoperatedisakey aspect. A veryaggressivedrivingstyle,
with10337697950100150200250300350105125129131151155167178183213gCO2e/kWhgCO2e/kmWh/kmFig.
14. Variation of life-cycle GHG emissions, per km traveled (based
on electricity mix and energy consumption for the Nissan Leaf). The
emissions per km traveled takeinto account the emissions associated
with vehicle production.Table
7Economicperformanceforthevehiclesconsideredperyear.
Theconsideredcostsweretheinvestmentandownershipcostsperyear(whichincludefuel/electricity,maintenance,
repair and taxes). All the calculations were based on a driving
distance of 20,000 km/year and the average fuel and electricity
prices for 2011 in EU (1:42=l fordiesel, 1:51=l for gasoline and
0:17=kW h for electricity).Costs ICEV PHEV BEVGolf 1.6 TDI Golf 1.4
TSI Smart CDI Smart Volt ED Volt GD Volt MD Nissan Leaf Smart ED
Peugeot iOnInvestment 22,200 20,300 12,600 9800 42,000 35,000
19,000 30,000Insurance =year 350 350 350 350 350 350 350 350Battery
leasing =year 720 Fuel =year 1192.8 1872.4 937.2 1268.4 1932.8 386
Electricity =year 552.5 442 425 340 368Maintenance =year 420 380
330 300 335 303 240 280Operational cost =year 1962.8 2602.4 1617.2
1918.4 1237.5 2617.8 1513.6 1078 1650 998.3Note: For the PHEV were
considered three scenarios: electric drive (ED) powered only by the
battery; gasoline drive (GD) powered only by the ICE and mixed
drive (MD)powered 80% of the time by battery and the remaining 20%
by the ICE.R. Faria et al. / Renewable and Sustainable Energy
Reviews 24 (2013) 271287 284fast accelerations andhighspeed, is
directlytranslatedintoareducedrange per charge and therefore
translated into moreemissions due to a higher energy consumption.
By increasing theconsumer awareness to a more efcient driving style
it is possibletoachieve, onlybyitself, signicant impact
inthereductionofGHG emissions.During the production phase the
impacts can bereduced by using recycled materials and replacing
certain alloys bycomposite
materials.0100002000030000400005000060000700008000090000Golf 1.6
TDI Golf 1.4 TSI Smart CDI Smart Leaf Smart ED iOn Volt ED Volt GD
Volt MDLife Cycle Costs []050010001500200025003000Golf 1.6 TDI Golf
1.4 TSI Smart CDI Smart Leaf Smart ED iOn Volt ED Volt GD Volt
MDAnnual Cost of Operation []Fuel/Electricity Maintenace and
Insurance Battery LeasingInvestment Interest OperationFig. 15.
Total life-cycle costs (top) for the considered vehicles and annual
operation cost (bottom). It should be noted that the annual
ownership cost does not take intoaccount the ination rate, however
it is considered in the life-cycle
costs.10000150002000025000300003500040000450005000055000600006500070000750001
2 3 4 5 6 7 8 9 10Cost []YearGolf 1.6 TDI Golf 1.4 TSI Volt GD
Smart Smart CDILeaf Volt ED Volt MD Smart ED iOnFig. 16. Cumulative
costs of ownership for the considered vehicles during their
life-cycle. Only the costs directly associated with the use of the
vehicle were considered,depreciation and interests were not taken
into account.R. Faria et al. / Renewable and Sustainable Energy
Reviews 24 (2013) 271287 285AcknowledgmentsThis work was supported
by Foundation for Science and
Technol-ogy(FCT)undertheprojectsMIT/MCA/0066/2009(EconomicandEnvironmentalSustainabilityofElectricVehicleSystems),
MIT/SET/0014/2009(Capturing Uncertainty inBiofuels for
Transportation.Resolving Environmental Performance and Enabling
Improved Use)and PTDC/SEN-TRA/117251/2010 (Extended well-to-wheels
assess-ment of biodiesel for heavytransport vehicles). This
researchisframed under the Energy for Sustainability Initiative of
the Universityof Coimbra and was supported by the FCT, through the
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