Real Drive Well-To-Wheel Energy Analysis of Conventional And

energies

Article Real Drive Well-to-Wheel Energy Analysis of † Conventional and Electriﬁed Car Powertrains

Fabio Orecchini, Adriano Santiangeli * and Fabrizio Zuccari

Center for Automotive Research and Evolution (CARe), Department of Sustainability Engineering (DIS), Guglielmo Marconi University, via Plinio 44, 00193 Rome, Italy; [email protected] (F.O.); [email protected] (F.Z.) * Correspondence: [email protected] This paper is an extended version of our paper published in AIP Conference Proceedings 2191, 020158 (2019); † https://doi.org/10.1063/1.5138891; 74 ATI National Conference.

Received: 30 July 2020; Accepted: 8 September 2020; Published: 14 September 2020

Abstract: Reducing fuel consumption and global emissions in the automotive sector has been a main focus of vehicle technology development for long time. The most eﬀective goal to achieve the overall sustainability objectives is to reduce the need for non-renewable and fossil resources. Five vehicles, two conventional ICE, two hybrid-electric, and one pure electric powertrain, are considered. Non-renewable primary energy consumption and CO2 emissions are calculated for each powertrain considered. All data—including calculated values—are based on the experimental measure of fuel consumption taken in real driving conditions. The data were recorded in an experimental campaign in Rome, Italy on urban, extra-urban streets, and highway on a total of 5400 km and 197 h of road acquisitions. The analysis shows signiﬁcant reductions in non-renewable fossil fuel consumption and CO2 emissions of hybrid-electric powertrains compared to conventional ones (petrol and diesel engines). Furthermore, a supplementary and very interesting comparison analysis was made between the values of energy consumptions measured during the tests in real driving conditions and the values deriving from the NEDC and WLTP homologation cycles.

Keywords: battery electric vehicle; full hybrid-electric vehicle; WTW analysis; non-renewable primary energy balance; real drive; NEDC; WLTP

1. Introduction The EU commitment to greenhouse gas emissions reduction accounts for 80–95% by 2050 compared to 1990, with a mid-term target of 40% at 2030, and a reduction in the non-emission trading sectors (including transport) of 30% in line with the Paris Climate Agreement. To achieve the stated objectives, very strong innovations are needed in mobility, as:

Higher efficiency of vehicles; • Optimized use of road space; • Diffusion of alternative fuels; • Low emission fuel production; • Low, ultra-low, and zero emission powertrain technologies; • Mobility and transportation intelligent management systems [1]. • Road traffic, representing the main form of transport, is a major source of pollution in Europe: According to the latest data, it produces about 71% of total greenhouse gas emissions (GHG)—out of which two thirds are generated by cars [2].

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Solutions to reduce fuel consumption and emissions include both fuel and traction systems: The use of cleaner traditional fuels has been a reality in the European refinery and distribution system for several years now, with biofuels mixed to fossil fuels, proportionally reducing climate emissions of conventional vehicles [3]. Bio-methane, in particular, has a high potential to achieve a significant decrease in consumption of fossil resources and overall environmental impact [3,4]. Consequently, hybrid traction systems are expected to become more and more electrically based, passing from micro, mild, and full hybrid, to plug-in hybrid (PHEV) [5,6]. The electric traction can in this way enter the habits of car customers without introducing in the short term the absolute need for a dedicated charging or fueling infrastructure, as for full electric powertrains like BEV (charging points) and FCEV (hydrogen stations). So far, very few research data are available on the real time acquisition of values indicating the fuel consumption and the energy flows of hybrid systems. This work, an update of a previous work [7], exclusively bases its analysis and calculation on experimental real time driving data and uses a well-defined procedural guideline called “Truth Test Protocol” [8]. The truth test protocol (TTP) is based on a statistical analysis of the energy behavioral data recorded in real drive conditions. The TTP was firstly applied to the energy analysis of full hybrid vehicles with the particular and adjunctive aim to fully evaluate the mileage and time driven in ZEV conditions. It has been designed for a much wider applicability and can be successfully used to assess the energy performance of all types of car powertrain. In this paper the TTP shows to be effective to analyze conventional ICE vehicle (petrol and diesel), BEV, as well as the HEV. The consumption of non-renewable primary energy and GHG emissions are calculated and compared considering experimental real time driving data of the following cars:

Conventional ICE powertrain • Toyota Yaris (petrol) # Toyota Auris (diesel) Hybrid-electric# powertrain • Toyota Yaris Hybrid # Toyota Prius Electric# powertrain • Nissan Leaf (BEV) # 2. Well-to-Wheel (WTW) Analysis The WTW analysis is based on the scheme of Figure1. The vehicle consumption is measured in real drive conditions [8,9]. According to the consumption of the energy vector used, the consumption of non-renewable primary energy consumption (TTW NRPEC) and GHG emission (TTW GHG) are calculated. The WTT analysis is referenced to EU-JRC (European Union Joint Research Center) published information [10]. Energies 2020, 13, 4788 3 of 21 Energies 2020, 13, x FOR PEER REVIEW 3 of 22

FigureFigure 1. 1. WellWell-to-wheel-to-wheel (WTW (WTW)) analysis analysis scheme. scheme. 2.1. Tank-to-Wheel (TTW) Analysis 2.1. Tank-To-Wheel (TTW) Analysis The procedure used to test the energy performance of different powertrains has shown full The procedure used to test the energy performance of different powertrains has shown full applicability and solid reliability [5,6]. applicability and solid reliability [5,6]. The test path, planned in metropolitan area of Rome, Italy, is designed to be in line with average The test path, planned in metropolitan area of Rome, Italy, is designed to be in line with average per capita daily driving profile in Italy (length, time, road type distribution), as reported by the ISFORT per capita daily driving profile in Italy (length, time, road type distribution), as reported by the mobility reports 2017 [11], 2018 [12], and 2019 [13], generally considered as a reference in Italy for this ISFORT mobility reports 2017 [11], 2018 [12], and 2019 [13], generally considered as a reference in kind of data. Italy for this kind of data. The test drives were made on five cars available on the market, equipped with a different The test drives were made on five cars available on the market, equipped with a different electrification level of powertrain and characterized as shown in Table1. electrification level of powertrain and characterized as shown in Table 1.

Table 1. Main speciﬁcations of vehicle tested. Table 1. Main specifications of vehicle tested. Characteristic Yaris Petrol Auris Diesel Yaris Hybrid Prius Leaf Characteristic Yaris Petrol Auris Diesel Yaris Hybrid Prius Leaf PowertrainPowertrain ICE ICE Petrol ICE ICE Diesel Diesel Full Full Hybrid Hybrid Full Full Hybrid Hybrid BEV BEV Maximum power (kW) 82 82 74 90 80 MaximumMass (kg)power (kW) 154582 82 1320 74 1565 90 1790 80 1600 Mass (kg) 1545 1320 1565 1790 1600

AsAs can can be seen inin TableTable1 the1 the vehicles vehicles have have been been selected selected with with quite quite similar similar specifications specifications in terms in termsof power of power and mass. and mass. TheThe powertrains powertrains have have a a range range of of electrification electrification level level,, from from 0 0 to to 1. 1. L Levelevel 0 0 is is assigned assigned to to the the two two vehiclesvehicles with with conventional conventional ICE ICE and and no no electric electric aid aid to to the the traction, traction, level level 1 1is is given given to to the the BEV, BEV, and and the the twotwo hybrids hybrids have have an an electrification electrification level level between between 0 0 and and 1. 1. ConsideringConsidering hybrid hybrid vehicles, vehicles, the the hybridization hybridization ratio ratio is considered is considered as an as electrification an electrification level. level.The hybridizationThe hybridization ratio ratiois the is ratio the ratiobetween between the power the power of the of electric the electric motor motor and andthe thesum sum of the of thepower power of theof theelectric electric motor motor and and the the engine, engine, and and is widely is widely used used in inliterature, literature, [14 [14–17–17]. ].The The Toyota Toyota Yaris Yaris hybrid hybrid hashas a a level level of of electrification electrification higher higher than than the the Toyota Toyota Prius. Prius. Nevertheless, Nevertheless, the the experimental experimental analysis analysis on on thethe behavior behavior of of vehicles vehicles in real drive conditions,conditions, withwith particularparticular regard regard to to the the ZEV ZEV mode mode operation operation of ofthe the two two vehicles vehicles [9 ],[9 has], has shown shown the the Prius Prius operates operates in in ZEV ZEV much much more more frequently frequently than than the the Yaris. Yaris. Two test paths have been designed and used for the experimental activity: Urban and extra-urban/highway. The urban test path has high (Figure 2) and low (Figure 3) traffic density sections. The two urban sections are located in the so-called “green traffic area” and “railway ring area” (green and purple areas, respectively, in Figure 4) of Rome, regularly used as a reference for road traffic restrictions.

Energies 2020, 13, x FOR PEER REVIEW 4 of 22 Energies 2020, 13, x FOR PEER REVIEW 4 of 22 The extra-urban/highway test path is shown in Figure 5 [9]. The test paths have been assembled Energies 2020, 13, 4788 4 of 21 consideringThe extra the-u rban/averagehighway per capita test path daily is travel show nin in Italy, Figure as 5reported [9]. The testby the paths ISFORT have beenmobility assembled report [considering14]. In the test the paths average four per sections capita have daily been travel identified: in Italy, as reported by the ISFORT mobility report [14]. TwoIn the test test paths four have sections been designedhave been andidentified: used for the experimental activity: Urban and  Urban with high traffic density; extra-urban/highway. The urban test path has high (Figure2) and low (Figure3) tra ffic density  Urban with lowhigh traffic traffic density; density ; sections. The two urban sections are located in the so-called “green traffic area” and “railway ring  ExtraUrban-urban; with low traffic density; area” (green and purple areas, respectively, in Figure4) of Rome, regularly used as a reference for road  Highway.Extra-urban; tra ffiHighway.c restrictions.

Figure 2. Urban with high traffic density section. Figure 2. Urban with high traffic traﬃc density s section.ection.

Figure 3. UrbanUrban with low traffic traﬃc density s section.ection. Figure 3. Urban with low traffic density section.

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Figure 4. Map of Rome (highlighted in green: LEZ LEZ—low—low e emissionmission z zone;one; b bluelue line: T Testest drive path).

The extra-urban/highway test path is shown in Figure5[ 9]. The test paths have been assembled considering the average per capita daily travel in Italy, as reported by the ISFORT mobility report [14]. In the test paths four sections have been identiﬁed:

Urban with high traffic density; • Urban with low traffic density; • Extra-urban; • Highway. • The test conditions were designed considering all the main variables affecting the energy performance, like driving attitude, circulation intensity, and auxiliaries energy request [18–22]. The tests were conducted on the routes described above according to our test protocol [8] which includes:

Compliance with speed limits; • Drivers clustered by gender and age (to take into account different driving styles); • Three tests in three different time slots for each driver (10:00–13:30–15:00); • Tests carried out on standard traffic days, i.e., not on holidays, or holiday periods (Christmas, • Easter, July–August); Auxiliaries (for example air conditioning) turned off; • Eco-mode (when selectable). •

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Figure 5. ExtraExtra-urban—highway-urban—highway s sections.ections.

TheAs the test objective conditions of thewere study designed was not considering to analyze allthe the energy main result variables on a specific affecting driving the energy cycle, performance,but in generally like meaningful driving attitude, conditions, circulation a large intensity number, of and tests auxiliaries has been energy made on request the same [18– path22]. with comparableThe tests tra wereffic conditions conducted (considering on the routes time, described day of above the week) according and the to testsour test were protocol analyzed [8] mainlywhich includes:considering the average speed. The energy performance is assessed exclusively referring to real time measured values, and related  Compliance with speed limits; calculations; consumption and/or efficiency models of the vehicles analyzed have not been used.  Drivers clustered by gender and age (to take into account different driving styles); Figure6 illustrates the energy consumption (MJ /km) of the tested vehicles found in the experimental  Three tests in three different time slots for each driver (10:00–13:30–15:00); acquisition campaign in the test run in the different sections it is divided into. The Leaf BEV had the  Tests carried out on standard traffic days, i.e., not on holidays, or holiday periods (Christmas, lowest energy consumption thanks to the greater efficiency of the traction system: 114% compared Easter, July–August); − to Full HEV Prius, 193% compared to Full HEV Yaris, 376% compared to Yaris ICE petrol, and  Auxiliaries (for− example air conditioning) turned off;− 330% compared to Auris ICE Diesel. Lower consumption occurred in urban with high traffic density − Eco-mode (when selectable). sections (0.47 MJ/km) and remained substantially unchanged for urban with low traffic intensity sectionsAs the (0.52 objective MJ/km, of+8.5%) the study and extra-urbanwas not to analy sectionsze the (0.46 energy MJ/km, result2.1%), on a andspecific increased driving significantly cycle, but − in thegenerally highway meaningful sections (0.71conditions, MJ/km, a+ large50%). number Consumption of tests of has the been two made Full HEV on the vehicles same (Priuspath with and Yaris)comparable showed traffic completely conditions similar (considering trends; the time, lower day consumption of the week) of the and Prius the was tests due were to the analy greaterzed mainlyefficiency considering thanks to the higheraverage braking speed. energy recovery capacity of the Prius [9]. The energy performance is assessed exclusively referring to real time measured values, and related calculations; consumption and/or efficiency models of the vehicles analyzed have not been used. Figure 6 illustrates the energy consumption (MJ/km) of the tested vehicles found in the experimental acquisition campaign in the test run in the different sections it is divided into. The Leaf BEV had the lowest energy consumption thanks to the greater efficiency of the traction system: −114% compared to Full HEV Prius, −193% compared to Full HEV Yaris, −376% compared to Yaris ICE petrol, and −330% compared to Auris ICE Diesel. Lower consumption occurred in urban with high traffic density sections (0.47 MJ/km) and remained substantially unchanged for urban with low

Energies 2020, 13, x FOR PEER REVIEW 7 of 22 traffic intensity sections (0.52 MJ/km, +8.5%) and extra-urban sections (0.46 MJ/km, −2.1%), and increased significantly in the highway sections (0.71 MJ/km, +50%). Consumption of the two Full HEV vehicles (Prius and Yaris) showed completely similar trends; the lower consumption of the Prius was due to the greater efficiency thanks to the higher braking energy recovery capacity of the Prius [9]. Compared to conventional ICE vehicles, the two full HEVs had low energy consumption in urban with high traffic density sections (1.13 MJ/km Prius and 1.63 MJ/km Yaris); these consumptions decreased passing to urban with low traffic density sections (1.08 MJ/km, −4%, Prius and 1.49 MJ/km, −9%, Yaris) and presented a minimum in the extra-urban stretches (1.02 MJ/km, −10%, Prius and 1.38 MJ/km, −15%, Yaris) thanks to the greater contribution of regenerative braking which increased the efficiency of the hybrid traction system. The energy consumption of full HEVs Energies 2020, 13, 4788 7 of 21 vehicles increased in the highway sections (1.40 MJ/km, +23%, Prius, and 1.86 MJ/km, +14%, Yaris) where they were similar to those of conventional ICE vehicles.

Figure 6. Energy consumption of vehicle tested in the test path (MJ/km). Figure 6. Energy consumption of vehicle tested in the test path (MJ/km).

TheCompared two conventional to conventional ICE vehicles ICE vehicles, had high the twoenergy full consumption HEVs had low in urbanenergy areas consumption with high in trafficurban density with high (3.47 tra MJ/kmffic density Yaris sections petrol and (1.13 3.11 MJ MJ/km/km Prius Auris and Diesel) 1.63 MJ due/km to Yaris); the low these efficiency consumptions of the thermaldecreased engine passing at low to urban engine with speeds; low tratheseffic densityconsumptions sections decrease (1.08 MJd/ km,significantly4%, Prius passing and 1.49 to MJurban/km, − sections9%, Yaris) with andlow traffic presented density a minimum (2.42 MJ/km, in the −35% extra-urban Yaris petrol, stretches and 2.16 (1.02 MJ/km, MJ/km, −31%,10%, Auris Prius Diesel) and − − and1.38 extra MJ/km,-urban15%, sections Yaris) thanks(2.30 MJ/km, to the greater−39% Yaris contribution petrol, ofand regenerative 1.96 MJ/km, braking −37%, which Auris increased Diesel). − Turningthe efficiency to the of the motorway hybrid traction sections, system. the consumption The energy consumption of the Yaris of full decrease HEVsd vehicles compared increased to the in extrathe highway-urban sections sections (1.86 (1.40 MJ/km, MJ/km, −+123%,9%), Prius,while andthose 1.86 of MJAuris/km, Diesel+14%, remain Yaris)ed where almost they con werestant similar but slightlyto those increasing of conventional (2.09 MJ/km, ICE vehicles. +6%). ForThe the two car conventional models fueled ICE vehicles by fossil had fuels, high the energy mileage consumption (ML (g/km in) urban) was areas obtained with from high tra dataffic acquisition,density (3.47 while MJ/km for Yaris the petrol electric and vehicle 3.11 MJ the/km valueAuris Diesel) measured due wa to thes the low need efficiency of electricity of the thermal (EC (MJ/kmengine) at). low engine speeds; these consumptions decreased significantly passing to urban sections withConsumption low traffic density was calculated (2.42 MJ/km, from35% data Yaris acquired petrol, by and the 2.16 vehicle MJ/km, control31%, unit Auris via Diesel) the OBD and − − interfaceextra-urban with sections a PC with (2.30 suitable MJ/km, software39% Yaris for petrol, reading and 1.96and MJstoring/km, the37%, selected Auris Diesel). data. In Turning vehicles to − − poweredthe motorway by fossil sections, fuel, the the data consumption stored wa ofs the the flow Yaris rate decreased (g/s) of comparedfuel, while to for the the extra-urban electric vehicle sections it wa(1.86s the MJ electrical/km, 19%), power while (voltage those and of Auriscurrent) Diesel supplied remained by the almost traction constant battery butpack. slightly increasing − (2.09From MJ/km, the+ mileage6%). the energy consumption was calculated considering the low heating value (LHV)For (MJ/kg): the car models fueled by fossil fuels, the mileage (ML (g/km)) was obtained from data acquisition, while for the electric vehicle the value measured was the need of electricity (EC (MJ/km)).

Consumption was calculated from data acquired by the vehicle control unit via the OBD interface with a PC with suitable software for reading and storing the selected data. In vehicles powered by fossil fuel, the data stored was the ﬂow rate (g/s) of fuel, while for the electric vehicle it was the electrical power (voltage and current) supplied by the traction battery pack. From the mileage the energy consumption was calculated considering the low heating value (LHV) (MJ/kg): EC = ML HLV (1) · Starting from energy consumption, TTW NRPEC and the TTW GHG (Figure1) were obtained considering a non-renewable primary energy consumption factor fNR and GHG emission factor fGHG (g/MJ) identiﬁed considering national standard parameters [23]. Energies 2020, 13, x FOR PEER REVIEW 8 of 22

EC = ML ∙ HLV (1) Energies 2020, 13, 4788 8 of 21 Starting from energy consumption, TTW NRPEC and the TTW GHG (Figure 1) were obtained considering a non-renewable primary energy consumption factor fNR and GHG emission factor fGHG (g/MJ) identified considering national standard parameters [23]. TTW = EC f (2) NRPEC · NR TTWNRPEC = EC ∙ fNR (2) TTWGHG = EC fGHG (3) TTWGHG = EC·∙ fGHG (3) Table2 shows the values of the low heating value, non-renewable primary energy consumption factor,Table and 2 GHG shows emission the values factor of the for thelow energyheating vectors value, usednon-r [enewable23]. primary energy consumption factor, and GHG emission factor for the energy vectors used [23]. Table 2. Low heating value (LHV), non-renewable primary energy consumption factor (fNR), and Tablegreenhouse 2. Low gas heating (GHG) v emissionalue (LHV), factor non (fGHG)-renewable of the p energyrimary vectorsenergy used.consumption factor (fNR), and greenhouse gas (GHG) emission factor (fGHG) of the energy vectors used. Energy Vectors LHV [MJ/kg] fNR fGHG [g/MJ] EnergyPetrol Vectors 42.817LHV [MJ/kg] 1fNR fGHG 73.335[g/MJ] GasolinePetrol 42.87742.817 11 73.335 73.583 ElectricityGasoline n.a.42.877 01 73.583 0 Electricity n.a. 0 0 2.2. Well-to-Tank (WTT) Analysis 2.2. WellAs- alreadyto-Tank mentioned,(WTT) Analysis the WTT analysis reference is based on EU-JRC published values [10]. For theAs electricalready vehicle, mentioned, several the charging WTT analysis systems reference have been is based taken intoon EU account-JRC published [24]: values [10]. For the electric vehicle, several charging systems have been taken into account [24]: 50 kW (maximum power output of mostly diffused quick charge stations); •  5043 kW (“fast(maximum AC” powerpower outputoutput onof Europeanmostly diffused standard); quick charge stations); •  4322 kW (three-phase(“fast AC” power power output for AC on on-board European charger); standard); •  2216 kW (contractual(three-phase powerpower forfor theAC main on-board electric charger) distributor; in Italy); •  163 kW kW (standard (contractual residential power for power the main in Italy). electric distributor in Italy); • 3 kW (standard residential power in Italy). Figure7 shows the charger e fficiency, battery efficiency, and overall charging efficiency of the differentFigure charging 7 shows systems. the charger efficiency, battery efficiency, and overall charging efficiency of the different charging systems.

FigureFigure 7. 7. ChargerCharger efficiency, efficiency, battery battery efficiency efficiency,, and overall charging eefficiency.fficiency.

Figure8 shows the well-to-tank analysis of electricity [ 10], considering the listed charging systems. The electricity production box considers the average eﬃciency of a power plant in EU EnergiesEnergies 20 202020, ,1 133, ,x x FOR FOR PEER PEER REVIEW REVIEW 99 of of 22 22 Energies 2020, 13, 4788 9 of 21

FigureFigure 88 showsshows thethe wwellell--ttoo--ttankank analysis analysis of of electricity electricity [ [1010]], , consideringconsidering the the listed listed charging charging countries,systems.systems. The including The electricity electricity fuel extraction, production production transportation, box box considers considers and the the pumping average average losses. ef efficiencyficiency The transport, of of a a power power transformation, plant plant in in EU EU andcountries,countries, distribution including including box consider fuel fuel extraction, extraction, transport and transportation transportation distribution, ,losses andand and pumping pumping transformation losses. losses. e The Theﬃciency transport, transport, at the lowtransformationtransformation voltage. The, ,and and vehicle distribution distribution battery chargebox box consider consider box considers transport transport the and and overall distribution distribution eﬃciency losses losses of the and and charging transformation transformation systems analyzedefficiencyefficiency (Figure atat thethe 7 lowlow). voltage.voltage. TheThe vvehicleehicle batterybattery chargecharge boxbox considersconsiders thethe overalloverall efficiencyefficiency ofof thethe chargingcharging systems systems analy analyzzeded ( (FigureFigure 7 7).).

Figure 8. FigureFigure 8. 8. WellWell-to-tank Well-to-to-t-anktank analysis analysis of of electricity electricity considering considering several several charging charging devices.devices. devices. Figure9 shows the well-to-tank analysis for the fossil fuels; petrol (a) and diesel (b). FigureFigure 9 9 shows shows the the w wellell--ttoo--ttankank analysis analysis for for the the fossil fossil fuels; fuels; p petroletrol (a) (a) and and d dieseliesel (b). (b).

FigureFigure 9. 9. WellWell-to-tank Well-to-to-t-anktank analysis analysis of of fossil fossil fuels,fuels fuels, , petrol petrol (( aa(a)) ) andand and dieseld dieseliesel (( bb(b).).). 3. Result Analysis 3.3. Result Result Analysis Analysis The main results of the WTW analysis, obtained on the basis of what is set out in the previous TheThe main main results results of of the the WTW WTW analysis, analysis, obtained obtained on on the the basis basis of of what what is is set set out out in in the the previous previous Sections 2.1 and 2.2, are shown below. SectionSectionss 2.1 2.1 and and 2.2 2.2, ,are are shown shown below. below. Figure 10 shows the primary non-renewable energy consumption of the vehicle analyzed in FigureFigure 1010 showsshows thethe primary primary non non--renewablerenewable energy energy consumption consumption of of the the vehicle vehicle analyanalyzzeded inin urban roads with high traffic density (a), urban low traffic intensity (b), extra-urban (c), and highway. urbanurban roads roads with with high high traffic traffic density density (a), (a), urban urban low low traffic traffic intensity intensity (b), (b), extra extra--urbanurban (c) (c), , andand Referring to the Nissan Leaf, different charging systems are specifically assessed: 3 (CH_3), 16 (CH_16), highway.highway. Referring Referring to to the the Nissan Nissan Leaf, Leaf, different different charging charging systems systems are are specifically specifically assessed: assessed: 3 3 22 (CH_22), 43 (CH_43), and 50 kW (CH_50). (CH_3),(CH_3), 16 16 (CH_16), (CH_16), 22 22 (CH_22), (CH_22), 43 43 (CH_43) (CH_43), ,and and 50 50 kW kW (CH_50). (CH_50). Figure 10 clearly shows that through the powertrain electrification it is possible to reach an important consumption decrease of non-renewable primary energy in real drive conditions. The reduction was higher in urban traffic conditions, with better results with stronger circulation (the lower the average speed, the higher the fuel save). The two cars equipped with conventional powertrain, compared with the two hybrids, had in urban traffic-intensive sections a non-renewable primary energy consumption 2.5 times larger. The difference in consumption of primary energy decreased as the average speed increases. The conventional cars, compared with the two hybrids, showed a non-renewable primary energy consumption 1.8 times higher in low traffic density and extra-urban sections, and 1.2 times higher on the highway section. The hybrid model Toyota Prius recorded the lowest consumption of non-renewable primary energy of the whole test campaign. The overall efficiency of the powertrain showed the highest value, mainly due to the excellent performance of the energy recovery system during deceleration phases [9].

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Figure 10. Non-renewable energy consumption of the vehicle analyzed in urban roads with high traffic densityFigure ( 10.a), urbanNon-renewable low traffi c energy intensity consumption (b), extra-urban of the (c vehicle), and motorway analyzed ( ind). urban roads with high traffic density (a), urban low traffic intensity (b), extra-urban (c), and motorway (d). The electric Nissan Leaf recorded a lower overall consumption value than conventional cars (exceptFigure on the 10 highway), clearly shows but still that slightly through higher the powertrain in most conditions electrification than hybrid it is possible cars. to reach an importantIn detail, consumption the WTW non-renewabledecrease of non primary-renewable energy primary need energy of the in Nissan real drive Leaf conditions. is the following: The reduction was higher in urban traffic conditions, with better results with stronger circulationUrban with (the high lower tra theffi c average density: speed,61% compared the higher to the conventional fuel save). vehicles The twoand cars 3% equipped compared with to • − − conventionalfull hybrid powertrain, vehicles; compared with the two hybrids, had in urban traffic-intensive sections a non-Urbanrenewable with primarylow traffi energyc density: consumption37% compared 2.5 times to conventional larger. The cars difference and +12% in consumption compared to full of • − primaryhybrid energy cars; decreased as the average speed increases. The conventional cars, compared with the two Extra-urban:hybrids, showed39% a comparednon-renewable to conventional primary energy cars andconsumption+8% compared 1.8 times to full higher hybrid in low cars; traffic • − densityHighway: and extra+1%-urban compared sections, to conventionaland 1.2 times carshigher and on+ the19% highway compared section. to full hybrid cars. • The hybrid model Toyota Prius recorded the lowest consumption of non-renewable primary energyGHG of emissionsthe whole testare campaign.directly proportional The overall to efficiency fossil fuel of the consumption. powertrain showThe electriced the highest vehicle, consideringvalue, mainly the due European to the excellent production performance system for of electricity,the energy showedrecovery in system all conditions during deceleration lower GHG emissionsphases [9]. than both conventional and hybrid cars. InThe detail, electric the Nissan GHG emission Leaf record analysised a oflower the Nissanoverall Leafconsumption is the following value than (Figure conventional 11): cars (except on the highway), but still slightly higher in most conditions than hybrid cars. Urban with high traffic density: 76% compared to conventional cars and 65% compared to full • In detail, the WTW non-renewable− primary energy need of the Nissan Leaf− is the following: hybrid cars;  UrbanUrban with with lowhigh tra trafficffic density: density: −61%61% comparedcompared toto conventionalconventional carsvehicles and and42% −3% compared compared to fullto • − − hybridfull hybrid cars; vehicles;  Extra-urban:Urban with low62% traffic compared density: to − conventional37% compared cars to conventional and 47% compared cars and to+12% full compared hybrid cars; to full • hybrid cars; − − Highway: 37% compared to conventional cars and 30% compared to full hybrid cars. • Extra-urban:− −39% compared to conventional cars and− +8% compared to full hybrid cars;  Highway: +1% compared to conventional cars and +19% compared to full hybrid cars.

Energies 2020, 13, x FOR PEER REVIEW 11 of 22

GHG emissions are directly proportional to fossil fuel consumption. The electric vehicle, considering the European production system for electricity, showed in all conditions lower GHG emissions than both conventional and hybrid cars. In detail, the GHG emission analysis of the Nissan Leaf is the following (Figure 11):  Urban with high traffic density: −76% compared to conventional cars and −65% compared to full hybrid cars;  Urban with low traffic density: −61% compared to conventional cars and −42% compared to full hybrid cars;  Extra-urban: −62% compared to conventional cars and −47% compared to full hybrid cars;  Highway: −37% compared to conventional cars and −30% compared to full hybrid cars. The GHG emissions of an electric vehicles are the emissions caused by the production of the electricity by the European power generation system. Figure 12 shows the GHG emission Energies 2020, 13, 4788 11 of 21 accounting, referring to electricity production from different energy resources (EU average values) [25].

Figure 11. GHG emission of the vehicle analy analyzedzed in urban roads with high traffic traﬃc density ( a), urban low traffic traﬃc intensity (b), extra-urbanextra-urban (c),), and motorway ((d).).

The GHG emissions of an electric vehicles are the emissions caused by the production of the electricity by the European power generation system. Figure 12 shows the GHG emission accounting, referringEnergies 2020 to, 1 electricity3, x FOR PEER production REVIEW from diﬀerent energy resources (EU average values) [25]. 12 of 22

Figure 12. GHG emissions for the electricity production for didifferentﬀerent sources.sources.

Referring to GHG emission accounting reported in Figures 12 and 13 shows the GHG emission of the Nissan Leaf referred to the different primary sources.

Figure 13. GHG emission of BEV for electricity produced by several energy sources.

3.1. Energy Vectors Cost Table 3 shows the comparison between the energy vector cost of the five vehicles considering the four sections of the path considered we have, calculated considering average prices (including taxes) of petrol, gasoline [26], and electricity [27] in Italy in 2019:  Petrol: 1.574 €/L;  Diesel: 1.479 €/L;

Energies 2020, 13, x FOR PEER REVIEW 12 of 22

Energies 2020, 13, 4788 12 of 21 Figure 12. GHG emissions for the electricity production for different sources. Referring to GHG emission accounting reported in Figures 12 and 13 shows the GHG emission of Referring to GHG emission accounting reported in Figures 12 and 13 shows the GHG emission the Nissan Leaf referred to the diﬀerent primary sources. of the Nissan Leaf referred to the different primary sources.

Figure 13. GHGGHG emission emission of BEV for electricity produced by several energy sources.

3.1. Energy Vectors Cost Table3 3 shows shows the the comparison comparison between between the the energy energy vector vector cost cost of theof the ﬁve five vehicles vehicles considering considering the thefour four sections sections of the of paththe path considered considered we have, we have, calculated calculated considering considering average average prices prices (including (including taxes) taxes)of petrol, of pe gasolinetrol, gasoline [26], and [26 electricity], and electricity [27] in [ Italy27] in in Italy 2019: in 2019: Petrol: 1.574 €/L; • Petrol: 1.574 €/L;  Diesel: 1.479 €/L; • Diesel: 1.479 €/L; Electricity: 20.67 c€/kWh. • Table 3. Energy vectors cost (c€/km).

Characteristic Yaris Petrol Auris Diesel Yaris Hybrid Prius Leaf Urban with high traﬃc density 18.46 12.85 8.03 5.60 3.52 Urban with low traﬃc density 11.96 8.92 7.33 5.35 3.82 Extra-urban 11.34 8.11 6.80 5.05 3.45 Highway 9.20 8.62 9.19 6.91 5.28

Despite the higher energy cost of electricity (about 74 €/GJ) compared to petrol (about 49 €/GJ) and gasoline (about 41 €/GJ), the unit cost (€/km) of the energy vector per BEV was the lowest thanks to the high efficiency of these vehicles [28]. For BEV, the unit costs of the energy vector increased passing from urban with high traffic density sections (3.52 €/km) to highway sections (5.28 €/km); for conventional ICE vehicles (Otto cycle and Diesel cycle) the trend was opposite and the unit costs of the energy vector decreased passing from urban with high traffic density sections (18.96 €/km Yaris petrol and 12.85 €/km Auris Diesel) to the highway sections (9.20 €/km Yaris petrol and 8.62 €/km Auris Diesel). The difference in unit costs between petrol and diesel was due in part to the lower costs of diesel compared to petrol and in part to the greater efficiency of the diesel vehicle. Hybrid vehicles, on the other hand, had a minimum of unit costs in extra-urban stretches. Energies 2020, 13, 4788 13 of 21

Compared to the unit costs of the BEV energy vector, in the urban areas with high traffic densities the unit cost of the traditional petrol vehicle was more than 5 times higher and that of the diesel vehicle almost 4 times, due to the low efficiency of the traditional ICE vehicles and the high efficiency of the BEV in these sections. Hybrid vehicles have high efficiency in urban high traffic density sections and the difference in unit costs compared to BEV is limited (about 2 times).

3.2. Comparison between Tests Result and Homologation Energy Consumption This paragraph will compare the WWT energy consumption found in the tests in real conditions of use with those declared by the car manufacturers on the basis of the NEDC and WLTP homologation cycles. Table4 illustrates the consumption values declared by the car manufacturers based on the NEDC and WLTP procedure of the 5 vehicles tested: For the Leaf (BEV) and Auris Diesel, being registered before the entry into force of the approval procedure based on WLTP, the consumption data on this cycle are not available.

Table 4. Energy consumption in NEDC and WLTP homologation tests (MJ/km).

NEDC WLTP Leaf 0.54 n.a. Prius 1.13 1.47 Yaris Hybrid 1.21 1.53 Yaris Petrol 1.62 1.94 Auris Diesel 1.43 n.a.

3.2.1. Comparison between Tests Result and NEDC Homologation Energy Consumption Energies 2020, 13, x FOR PEER REVIEW 14 of 22 Figure 14 illustrates the NEDC homologation cycle. As is known, the NEDC cycle is composed of the ECE cycle (urban driving cycle—UDC) repeated four times and the EUDC cycle.

Figure 14. NEDC cycle. Figure 14. NEDC cycle. Figure9 shows the lengths of the urban and extra-urban section of the NEDC. ToFigure compare 9 shows the the speciﬁc lengths energy of the consumption urban and extra (MJ/km)-urban obtained section in of the the testsNEDC. in real conditions of use andTo compare those declared the specific by the energy car manufacturer consumption on (MJ/km the basis) obtained of the in NEDC the tests cycle, in thereal tests’conditions speciﬁc of use and those declared by the car manufacturer on the basis of the NEDC cycle, the tests’ specific energy consumption was calculated as the weighted average of the consumption detected in the four sections in which the test path was divided (Section 2.1). The weights were calculated by associating the urban with high traffic density and urban with low traffic intensity sections to the ECE cycle and the extra-urban and highway sections to the EUDC cycle according to the distances shown in Table 5, as illustrated in Figure 15.

Table 5. NEDC distance.

Distance (m) Distance (%) 4 ECE 3978 36.4 EUDC 6955 63.6 Total 10,933 100.0

Energies 2020, 13, 4788 14 of 21 energy consumption was calculated as the weighted average of the consumption detected in the four sections in which the test path was divided (Section 2.1). The weights were calculated by associating the urban with high traﬃc density and urban with low traﬃc intensity sections to the ECE cycle and the extra-urban and highway sections to the EUDC cycle according to the distances shown in Table5, as illustrated in Figure 15.

Table 5. NEDC distance.

Distance (m) Distance (%) 4 ECE 3978 36.4 EUDC 6955 63.6 Energies 2020, 13, x FOR PEER REVIEWTotal 10,933 100.0 15 of 22

Figure 15. Scheme of calculation of energy consumption in the tests to compare with energy consumption Figure 15. Scheme of calculation of energy consumption in the tests to compare with energy in NEDC (4 ECE, EUDC). consumption in NEDC (4 ECE, EUDC). Based on the above, the specific consumption obtained in the tests under real conditions of use of the fiveBased vehicles on the analyzed above, isthe calculated specific consumption as follows: obtained in the tests under real conditions of use of the five vehicles analyzed is calculated as follows: ECUHTD + ECULTD ECEU + ECH ECT,NEDC = 0.364 + 0.636 (4) 퐸퐶푈퐻푇퐷2+ 퐸퐶푈퐿푇퐷 · 퐸퐶퐸푈2+ 퐸퐶퐻 · 퐸퐶 = ∙ 0.364 + ∙ 0.636 (4) 푇,푁퐸퐷퐶 2 2 Figure 16 shows the comparison between the specific energy consumption obtained in the tests and thoseFigure declared 16 shows by thethe carcomparison manufacturers between based the onspecific the NEDC energy cycle. consumption obtained in the tests andFrom those Figure declared 16 itby can the be car seen manufacturers that the higher based specific on the energy NEDC consumption cycle. in the tests compared to the NEDC cycle varies significantly for the different powertrains: In fact, for the BEV vehicle, the energy consumption in the tests was lower ( 12.3%) compared to the NEDC cycle (this could be due to very − low speeds in the urban with high traffic density section); for the full HEV Prius the consumption in tests was slightly higher (+3.7%) than in the NEDC cycle; while for the full HEV Yaris the increase in consumption in tests was more relevant (+24.3%). For both conventional ICE vehicles the difference was very high, +33.7% for the Yaris petrol and +36.4% for the Auris Diesel. It is interesting to make some considerations regarding the different values of the deviations between the energy consumptions in the tests and those in the NEDC cycle for the two full HEV vehicles; Figure 17 shows that the two hybrid cars are in ZEV mode a very large part of the driving

Figure 16. Comparison between test and NECD energy consumption.

Energies 2020, 13, x FOR PEER REVIEW 15 of 22

Figure 15. Scheme of calculation of energy consumption in the tests to compare with energy consumption in NEDC (4 ECE, EUDC).

Based on the above, the specific consumption obtained in the tests under real conditions of use of the five vehicles analyzed is calculated as follows: Energies 2020, 13, 4788 15 of 21

퐸퐶푈퐻푇퐷 + 퐸퐶푈퐿푇퐷 퐸퐶퐸푈 + 퐸퐶퐻 퐸퐶 = ∙ 0.364 + ∙ 0.636 (4) 푇,푁퐸퐷퐶 2 2 time (70% of the driving time for the Toyota Yaris Hybrid and 79.4% of the driving time for the Toyota Prius)Figure in congested16 shows tratheﬃ comparisonc conditions; between when the the average specific speed energy analyzed consumption increased obtained to 30 km in /theh, the tests ZEV anddriving those declared time to 56% by the for Toyotacar manufacturers Yaris Hybrid based and 70.1%on the forNEDC Toyota cycle. Prius.

Energies 2020, 13, x FOR PEER REVIEW 16 of 22

From Figure 16 it can be seen that the higher specific energy consumption in the tests compared to the NEDC cycle varies significantly for the different powertrains: In fact, for the BEV vehicle, the energy consumption in the tests was lower (−12.3%) compared to the NEDC cycle (this could be due to very low speeds in the urban with high traffic density section); for the full HEV Prius the consumption in tests was slightly higher (+3.7%) than in the NEDC cycle; while for the full HEV Yaris the increase in consumption in tests was more relevant (+24.3%). For both conventional ICE vehicles the difference was very high, +33.7% for the Yaris petrol and +36.4% for the Auris Diesel. It is interesting to make some considerations regarding the different values of the deviations between the energy consumptions in the tests and those in the NEDC cycle for the two full HEV vehicles; Figure 17 shows that the two hybrid cars are in ZEV mode a very large part of the driving time (70% of the driving time for the Toyota Yaris Hybrid and 79.4% of the driving time for the Toyota Prius) in congested traffic conditions; when the average speed analyzed increased to 30 km/h, the ZEV driving time to 56% for Toyota Yaris Hybrid and 70.1% for Toyota Prius. At higher average speeds (around 60 km/h) the driving time in ZEV mode was dramatically decreased to 23% for the Toyota Yaris Hybrid. The Toyota Prius in the ZEV mode kept over 50% of the driving time even at 60 km/h, showing again that its higherFigureFigure electrification 16. 16.ComparisonComparison of thebetween between powertrain test test and and allow NECD NECDed energy for energy a consumption.high consumption.er efficiency [9].

Figure 17. ZEV value of HEV vs. average speed.

AtHence, higher it average can be speeds said that (around the 60full km HEV/h) the Prius driving had timea substantially in ZEV mode greater was dramatically degree of decreased“electrification to 23%” than for thethe Toyota full HEV Yaris Yaris. Hybrid. From the above it is evident that the increase in energy consumptionThe Toyota in tests Prius in in real the conditions ZEV mode of kept use over compared 50% of to the those driving in the time NEDC even cycle at 60 decrease km/h, showingd with againincreasing that itsdegrees higher of electriﬁcation electricity in ofthe the powertrain. powertrain allowed for a higher eﬃciency [9].

3.2.2. Comparison between Test Result and WLTP Homologation Procedure Energy Consumption The official indication of emission and fuel consumption levels of cars is provided by the worldwide harmonized light vehicles test cycles (WLTC) developed by the UN ECE GRPE (Working Party on Pollution and Energy) group in the more general framework of worldwide harmonized light vehicles test procedures (WLTP). The acronyms WLTP and WLTC are not interchangeably: WLTP procedures define a larger number of procedures, are finalized to type approve a vehicle and are applied in addition to the WLTC test cycles.

Energies 2020, 13, 4788 16 of 21

Hence, it can be said that the full HEV Prius had a substantially greater degree of “electriﬁcation” than the full HEV Yaris. From the above it is evident that the increase in energy consumption in tests in real conditions of use compared to those in the NEDC cycle decreased with increasing degrees of electricity in the powertrain.

3.2.2. Comparison between Test Result and WLTP Homologation Procedure Energy Consumption The official indication of emission and fuel consumption levels of cars is provided by the worldwide harmonized light vehicles test cycles (WLTC) developed by the UN ECE GRPE (Working Party on Pollution and Energy) group in the more general framework of worldwide harmonized light vehicles test procedures (WLTP). The acronyms WLTP and WLTC are not interchangeably: WLTP procedures define a larger number of procedures, are finalized to type approve a vehicle and are applied in addition to the WLTC test cycles. The transition from the previous NEDC-based procedure for type approval testing of light-duty vehicles to WLTP has occurred over 2017–2019. Also in Japan, the WLTP has been introduced for vehicle certification. The WLTP procedures include several WLTC test cycles for different vehicle categories based on power-to-mass (PMR) ratio defined as the ratio between rated power (W) and the curb mass (kg) (not including the driver) and on the maximum speed (vmax) of the vehicle as declared by the car manufacturer (Table6).

Table 6. WLTC test cycles.

Category PMR (W/kg) Vmax (km/h) Speed Phase Sequence Class 3b PMR > 34 Vmax 120 Low 3 + Medium 3-2 + High 3-2 + Extra-high 3 ≤ Class 3b PMR > 34 Vmax > 120 Low 3 + Medium 3-1 + High 3-1 + Extra-high 3 Class 2 22 < PMR 34 - Low 2 + Medium 2 + High 2 + Extra-high 2 ≤ Class 1 PMR 22 - Low 1 + Medium 1 + Low 1 ≤

Table7 illustrates the definition of the WLTP procedure class of the five vehicles analyzed based on their specifications. Table7 shows that all vehicles are in the WLTP procedure 3b class.

Table 7. Class in WLTP classiﬁcation of vehicle tested.

Power (W) Mass (kg) PMR (W/kg) Vmax (km/h) WLTP Class Leaf 80,000 1600 50.0 >120 3b Prius 90,000 1790 50.3 >120 3b Yaris Hybrid 74,000 1565 47.3 >120 3b Yaris Petrol 82,000 1545 53.1 >120 3b Auris Diesel 82,000 1320 62.1 >120 3b

Figure 18 illustrates the NEDC homologation cycle. As is known, the NEDC cycle is composed of the ECE cycle (urban driving cycle—UDC) repeated four times and the EUDC cycle. As is shown in Figure 18, the WLTP procedure class 3b cycle is composed of four sections: Low, medium, high, and extra-high. Similarly to what is stated in Section 3.2.1, to compare the specific energy consumption (MJ/km) obtained in the tests in real conditions of use and those declared by the car manufacturer on the basis of the WLTP procedure, the tests’ specific energy consumption was calculated as the weighted average of the consumption detected in the four sections in which the test path was divided (Section 2.1). The weights were calculated by associating the urban with the high traffic density to low section, the urban with the low traffic intensity sections to medium section, extra-urban to high section, and highway to extra-high section according to the distances shown in Table8, as illustrated in Figure 19. Energies 2020, 13, x FOR PEER REVIEW 17 of 22

The transition from the previous NEDC-based procedure for type approval testing of light-duty vehicles to WLTP has occurred over 2017–2019. Also in Japan, the WLTP has been introduced for vehicle certification. The WLTP procedures include several WLTC test cycles for different vehicle categories based on power-to-mass (PMR) ratio defined as the ratio between rated power (W) and the curb mass (kg) (not including the driver) and on the maximum speed (vmax) of the vehicle as declared by the car manufacturer (Table 6).

Table 6. WLTC test cycles.

Category PMR (W/kg) Vmax (km/h) Speed Phase Sequence Class 3b PMR > 34 Vmax ≤ 120 Low 3 + Medium 3-2 + High 3-2 + Extra-high 3 Class 3b PMR > 34 Vmax > 120 Low 3 + Medium 3-1 + High 3-1 + Extra-high 3 Class 2 22 < PMR ≤ 34 - Low 2 + Medium 2 + High 2 + Extra-high 2 Class 1 PMR ≤ 22 - Low 1 + Medium 1 + Low 1

Table 7 illustrates the definition of the WLTP procedure class of the five vehicles analyzed based on their specifications. Table 7 shows that all vehicles are in the WLTP procedure 3b class.

Table 7. Class in WLTP classification of vehicle tested.

Figure 18 illustrates the NEDC homologation cycle. As is known, the NEDC cycle is composed of the ECE cycle (urban driving cycle—UDC) repeated four times and the EUDC cycle. As is shown inEnergies Figure2020 18, 13, ,the 4788 WLTP procedure class 3b cycle is composed of four sections: Low, medium, 17high of 21, and extra-high.

Energies 2020, 13, x FOR PEER REVIEW 18 of 22

Similarly to what is stated in Section 3.2.1, to compare the specific energy consumption (MJ/km) obtained in the tests in real conditions of use and those declared by the car manufacturer on the basis of the WLTP procedure, the tests’ specific energy consumption was calculated as the weighted average of the consumption detected in the four sections in which the test path was divided (Section 2.1). The weights were calculated by associating the urban with the high traffic density to low section, the urban with the low traffic intensity sections to medium section, extra-urban to high section, and highway to extra-high section according to the distances shown in Table 8, as illustrated in Figure 19.

Table 8. WLTP procedure distance.

Distance (m) Distance (%) Low 3095 13.3 Medium 4756 20.4 High 7162 30.8 Extra-high 8254 35.5

Total 23,267 100.0 Figure 18. WLTC cycle for class 3b vehicles. Figure 18. WLTC cycle for class 3b vehicles.

Figure 19. Scheme of calculation of energy consumption in the tests to compare with energy consumption in WLTP procedure (ECT, WLTP). Figure 19. Scheme of calculation of energy consumption in the tests to compare with energy consumption in WLTP procedureTable (ECT, 8. WLTP).WLTP procedure distance.

Distance (m) Distance (%) Based on the above, the specific consumption obtained in the tests under real conditions of use of the five vehicles analyzed is calculatedLow as follows: 3095 13.3 Medium 4756 20.4 High 7162 30.8 퐸퐶 = 퐸퐶 ∙ 0.133 + 퐸퐶 ∙ 0.204 + 퐸퐶 ∙ 0.308 + 퐸퐶 ∙ 0.355 (5) 푇,푊퐿푇푃 Extra-high푈퐻푇퐷 푈퐿푇퐷 8254 35.5퐸푈 퐻 Total 23,267 100.0 As already mentioned, for the Leaf (BEV) and Auris (ICE Diesel) vehicles, the energy consumption for WTLP procedure was not available as it was registered before the entry into force of the legislation that provided for approval with the WLTP procedure. Figure 20 shows the comparison between the specific energy consumption obtained in the tests and those declared by the car manufacturers based on the WLTP procedure. In this case the difference between the energy consumption in the tests and in the homologation procedure was lower compared to the NEDC, but also in this case the increase in energy

Energies 2020, 13, 4788 18 of 21

Based on the above, the speciﬁc consumption obtained in the tests under real conditions of use of the ﬁve vehicles analyzed is calculated as follows:

ECT WLTP = ECUHTD 0.133 + ECULTD 0.204 + ECEU 0.308 + ECH 0.355 (5) , · · · · As already mentioned, for the Leaf (BEV) and Auris (ICE Diesel) vehicles, the energy consumption for WTLP procedure was not available as it was registered before the entry into force of the legislation Energies 2020, 13, x FOR PEER REVIEW 19 of 22 that provided for approval with the WLTP procedure. Figure 20 shows the comparison between the speciﬁcconsumption energy in consumption the tests compared obtained to homologation in the tests and consumption those declared decreased by the car with manufacturers the increase basedin the onelectrification the WLTP procedure.degree of the vehicle.

Figure 20. Comparison between test and WLTP procedure energy consumption.consumption.

In thisfact, case for the the full diff erenceHEV Prius between the consumptions the energy consumption in the tests in were the testslower and than in the homologation procedureones (−24.1%), was lowerthose of compared the full HEV to the Yaris NEDC, were but substa also inntially this case the thesame increase (+4.7%), in and energy those consumption of the ICE inpetrol the testsYaris compared were substantially to homologation higher (+17.8%). consumption decreased with the increase in the electrification degree of the vehicle. 4. ConclusionsIn fact, for the full HEV Prius the consumptions in the tests were lower than the homologation ones ( 24.1%), those of the full HEV Yaris were substantially the same (+4.7%), and those of the ICE The− results of the experimental tests in real driving conditions of conventional (petrol and petroldiesel), Yaris hybrid-electric, were substantially and full higher electric (+ 17.8%).models clearly show the electrification of the powertrain is an effective way for primary non-renewable energy consumption and GHG emission reduction. The 4. Conclusions real drive achievable reductions, in comparison with conventional ICE-only cars, were significant in urbanThe conditions results of (both the experimental low and high tests traffic in real density) driving and conditions were less of conventionalsignificant in (petrol extra-urban and diesel), and hybrid-electric,highway driving and conditions. full electric models clearly show the electrification of the powertrain is an effective way forIn the primary transition non-renewable time towards energy pure consumptionelectric vehicles, and hybrid GHG emissionsystems can reduction. be considered The real a drivegood achievabletransitory solution reductions, for inthe comparison reduction of with primary conventional non-renewable ICE-only energy cars, were consumption significant and in urbanGHG conditionsemission without (both low any and need high for tra ffisupplementaryc density) and char wereging/refueling less significant infrastructure in extra-urban [29]. and The highway most drivingelectrified conditions. of the two hybrid cars analyzed, the Toyota Prius, showed a very high percentage of drivingIn thetime transition in electric time mode towards and a purevery high electric capacity vehicles, for hybridregenerative systems braking can be [9]. considered a good transitoryThe efficiency solution for of the reductionNissan Leaf of primary(BEV) measured non-renewable in real energydrive conditions consumption was and very GHG high emission with an withoutaverage anyenergy need need for supplementary for 0.470 MJ/km charging (electricity)/refueling compared infrastructure to the [energy29]. The need most for electrified 2.456 MJ/km of the (fuel) for conventional ICE vehicles. The non-renewable primary energy consumption and GHG emissions of the BEV depended on the production, transport, transformation, and distribution method of electricity (the charging system does not have a very relevant weight on the total efficiency). A possible adjunctive advantage can be given by energy traceability that could allow us to know the actual production source of the renewable electricity made available at the charging point [30]. From the comparison of the consumptions detected in the tests in real conditions of use and those of homologation for the five vehicles analyzed, it emerged that with the WLTP procedure the differences were less than the NEDC and, in both cases, the differences varied significantly for the

Energies 2020, 13, 4788 19 of 21 two hybrid cars analyzed, the Toyota Prius, showed a very high percentage of driving time in electric mode and a very high capacity for regenerative braking [9]. The efficiency of the Nissan Leaf (BEV) measured in real drive conditions was very high with an average energy need for 0.470 MJ/km (electricity) compared to the energy need for 2.456 MJ/km (fuel) for conventional ICE vehicles. The non-renewable primary energy consumption and GHG emissions of the BEV depended on the production, transport, transformation, and distribution method of electricity (the charging system does not have a very relevant weight on the total efficiency). A possible adjunctive advantage can be given by energy traceability that could allow us to know the actual production source of the renewable electricity made available at the charging point [30]. From the comparison of the consumptions detected in the tests in real conditions of use and those of homologation for the five vehicles analyzed, it emerged that with the WLTP procedure the differences were less than the NEDC and, in both cases, the differences varied significantly for the various powertrains analyzed (conventional ICE Diesel and petrol, HEV, and BEV) based on the degree of electrification of the vehicle.

Author Contributions: F.O., A.S. and F.Z. contributed equally to the development of the study, and to the editing and review of the article. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Conﬂicts of Interest: The authors declare no conﬂict of interest.

Nomenclature

BEV Battery electric vehicle EC WTT energy consumption ECT, NEDC Energy consumption in the tests to compare with energy consumption in NEDC ECT, WLTP Energy consumption in the tests to compare with energy consumption in WLTP ECE Urban driving cycle (UDC) EUDC Extra-urban driving cycle FCEV Fuel cell electric vehicle fGHG GHG emission factor fNR Non-renewable primary energy consumption factor GHG Greenhouse gasses GHGEM Greenhouse gasses emission HEV Hybrid-electric vehicle ICE Internal combustion engine LHV Low heating low value ML Mileage NEDC New European driving cycle NRPEC Non-renewable primary energy consumption PHEV Plug-in hybrid-electric vehicle PMR Power-to-mass ratio TTW Tank-to-wheel TTWGHG Tank-to-wheel GHG emission TTWNRPEC Tank-to-wheel non-renewable primary energy consumption WTT Well-to-tank WTW Well-to-wheel WLTC Worldwide harmonized light vehicles test cycle WLTP Worldwide harmonized light vehicles test procedure ZEV Percentage of operating time in ZEV mode with respect to total time Energies 2020, 13, 4788 20 of 21

References

1. European Commission, Directorate-General for Internal Market, Industry, Entrepreneurship and SMEs, Industrial Transformation and Advanced Value Chains, Automotive and Mobility Industries. GEAR 2030: Ensuring that Europe Has the Most Competitive, Innovative and Sustainable Automotive Industry of the 2030s and beyond. The Report of the High Level Group on the Competitiveness and Sustainable Growth of the Automotive Industry in the European Union. October 2017. Available online: https://ec.europa.eu/ docsroom/documents/26081/attachments/1/translations/en/renditions/native (accessed on 20 April 2020). 2. European Commission. Collegare i cittadini e le imprese dell’Europa;Office for Official Publications of the European Union: Luxembourg, 2014; ISBN 978-92-79-42785-5. Available online: https://elearning.unite.it/ pluginfile.php/58636/mod_resource/content/1/transport_it.pdf (accessed on 20 April 2020). [CrossRef] 3. Ministry of the Environment and the Protection of the Territory and the Sea, Ministry of Economic Development, Ministry of Infrastructure and Transport. RSE (Energy System Research) Elements for a Roadmap for Sustainable Mobility: General Framework and Focus on Road Transport; Alkes, E., Milanese, S.G., Eds.; Italy, Arti Grafiche Fiorin SPA: San Giuliano Milanese (MI), Italy, 2017. 4. Zuccari, F.; Santiangeli, A.; Dell’Era, A.; D’orazio, A.; Fiori, C.; Orecchini, F. Use of Bio-methane for Auto Motive Application: Primary Energy Balance and Well to Wheel Analysis. Energy Procedia 2015, 81, 255–271. [CrossRef] 5. Orecchini, F.; Santiangeli, A. Automakers’ Powertrain Options for Hybrid and Electric Vehicles. In Electric and Hybrid Vehicles—Power Sources, Models, Sustainability, Infrastructure and the Market; Pistoia, G., Ed.; Elsevier: Amsterdam, The Netherlands, 2010; pp. 579–636. ISBN 978-0-444-53565-8. [CrossRef] 6. Orecchini, F.; Santiangeli, A.; Zuccari, F. Technological analysis of solutions and development strategies proposed by the major automakers. In Electrical and Hybrid Propulsion Systems: From Source on Board to Mechanical Engineering; Brusaglino, G., Pede, G., Vitale, E., Eds.; ENEA: Rome, Italy, 2009; ISBN 978-88-8286-205-3. 7. Zuccari, F.; Orecchini, F.; Santiangeli, A.; Suppa, T.; Ortenzi, F.; Genovese, A.; Pede, G. Well to wheel analysis and comparison between conventional, hybrid and electric powertrain in real conditions of use. In Proceedings of the AIP Conference 2191, Modena, Italy, 11–13 September 2019; p. 020158. [CrossRef] 8. Orecchini, F.; Santiangeli, A.; Zuccari, F. Hybrid-electric system truth test: Energy analysis of Toyota Prius IV in real urban drive conditions. Sustain. Energy Technol. Assess. 2020, 37, 100573. [CrossRef] 9. Orecchini, F.; Santiangeli, A.; Zuccari, F.; Ortenzi, F.; Genovese, A.; Spazzafumo, G.; Nardone, L. Energy consumption of a last generation full hybrid vehicle compared with a conventional vehicle in real drive conditions. Energy Procedia 2018, 148, 289–296. [CrossRef] 10. Edwards, R.; Hass, H.; Larivé, J.F.; Lonza, L.; Maas, H.; Rickeard, D. Well-to-Wheels Analysis of Future Automotive Fuels and Powertrains in the European Context; Publications Office of the European Union: Luxembourg, 2014; ISBN 978-92-79-33888-5 (pdf), ISSN 1831-9424 (online). [CrossRef] 11. ISFORT. 14th Mobility Report in Italy. Available online: http://www.appa.provincia.tn.it/binary/pat_appa_ restyle/agenda_eventi_ambientali/Rapporto_completo_2016.1495695839.pdf (accessed on 22 April 2020). 12. ISFORT. 15th Mobility Report in Italy. Available online: https://www.isfort.it/wp-content/uploads/2019/09/ Rapporto_Mobilita_2018.pdf (accessed on 22 April 2020). 13. ISFORT. 16th Mobility Report in Italy. Available online: https://www.isfort.it/wp-content/uploads/2019/12/ 16_Rapporto_Audimob.pdf (accessed on 22 April 2020). 14. Bolvashenkov, I.; Herzog, H.G. System Approach to a Choice of Optimum Factor of Hybridization of the Electric Hybrid Vehicle. In Proceedings of the Electric Vehicle Symposium and Exhibition (EVS), Yokohama, Japan, 23–28 October 2006; pp. 1–12. 15. Capata, R. Urban and Extra-Urban Hybrid Vehicles: A Technological Review. Energies 2018, 11, 2924. [CrossRef] 16. Larminie, J.; Lowry, J. Electric Vehicle Technology Explained, 2nd ed.; WILEY: Hoboken, NJ, USA, 2012; ISBN 978-1-119-94273-3. 17. Sutula, R.A.; Heitner, K.L.; Rogers, S.A.; Duong, T.Q.; Kirk, R.S.; Battaglia, V.; Henriksen, G.; McLarnon, F.; Kumar, B.J.; Schonefeld, C. Recent Accomplishment of the Electric and Hybrid Vehicle Storage R&D Programs at the U.S. Department of Energy: A Status Report; AIP: College Park, MD, USA, 2000. Energies 2020, 13, 4788 21 of 21

18. Ortenzi, F.; Costagliola, M.A. A New Method to Calculate Instantaneous Vehicle Emissions Using OBD Data; SAE Technical Papers: Pittsburgh, PA, USA, 2010; ISSN 0148-7191, e-ISSN 2688-3627. [CrossRef] 19. Adriano, S.; Chiara, F.; Fabrizio, Z.; Alessandro, D.; Fabio, O.; Annalisa, D. Experimental Analysis of the Auxiliaries Consumption in the Energy Balance of a Pre-series Plug-in Hybrid-electric Vehicle. Energy Procedia 2014, 45, 779–788. [CrossRef] 20. Alessandrini, A.; Filippi, F.; Orecchini, F.; Ortenzi, F. A New Method for Collecting Vehicle Behavior in Daily Use for Energy and Environmental Analysis. J. Automob. Eng. 2006, 220, 1527–1537. [CrossRef] 21. Orecchini, F.; Alessandrini, A. A driving cycle for electric driven vehicles in Rome. J. Automob. Eng. 2003, 217, 781–789. 22. Alessandrini, A.; Filippi, F.; Ortenzi, F.; Orecchini, F. Driver inﬂuence in hybrid vehicle economic appraisal. World Electr. Veh. J. 2010, 4, 774–781. [CrossRef] 23. Tabella Parametri standard nazionali: Coeﬃcienti utilizzati per l’inventario delle emissioni

di CO2 nell’inventario nazionale UNFCCC (media dei valori 2015–2017). Available online: https://www.minambiente.it/sites/default/files/archivio/allegati/emission_trading/tabella_coefficienti_ standard_nazionali_11022019.pdf (accessed on 24 April 2020). 24. Genovese, A.; Ortenzi, F.; Villante, C. On the energy efficiency of quick DC vehicle battery charging. World Electr. Veh. J. 2015, 7, 570–576, ISSN 2032-6653. [CrossRef] 25. Woo, J.; Choi, H.; Ahn, J. Well-to-wheel analysis of greenhouse gas emissions for electric vehicles based on electricity generation mix: A global perspective. Transp. Res. Part D Transp. Environ. 2017, 51, 340–350. [CrossRef] 26. Italian Ministry of Economic Development Web Site. Available online: https://dgsaie.mise.gov.it/prezzi_ carburanti_mensili.php (accessed on 4 May 2020). 27. ARERA. Italian Regulatory Authority for Energy Networks and the Environment. Available online: https: //www.arera.it/it/dati/eep35.htm (accessed on 4 May 2020). 28. Orecchini, F.; Santiangeli, A.; Dell’Era, A. EVs and HEVs Using Lithium-Ion Batteries. In EVs and HEVs Using Lithium-Ion Batteries; Elsevier: Amsterdam, The Netherlands, 2014; pp. 205–248, Hardcover ISBN 9780444595133, eBook ISBN 9780444595164. [CrossRef] 29. Orecchini, F.; Santiangeli, A.; Valitutti, V. Sustainability Science: Sustainable Energy for Mobility and Its Use in Policy Making. Sustainability 2011, 3, 1855–1865. [CrossRef] 30. Orecchini, F.; Santiangeli, A.; Zuccari, F.; Dell’Era, A. The Concept of Energy Traceability: Application to EV Electricity Charging by Res. Energy Procedia 2015, 82, 637–644, ISSN 1876-6102. [CrossRef]

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