Powertrain of heavy electric vehicles:: Analysis of the production chain and impact on environment and industry

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IN

DEGREE PROJECT MECHANICAL ENGINEERING, SECOND CYCLE, 30 CREDITS

STOCKHOLM SWEDEN 2018,

Powertrain of heavy electric vehicles: Analysis of the

production chain and impact on environment and industry

SVENJA GELPKE

KTH ROYAL INSTITUTE OF TECHNOLOGY

SCHOOL OF INDUSTRIAL ENGINEERING AND MANAGEMENT

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Master of Science Thesis

KTH School of Industrial Engineering and Management Energy Technology TRITA-ITM-EX208:204

SE-100 44 STOCKHOLM Svenja Gelpke

Master of Science in Sustainable Energy Engineering

Transformation of Energy Systems: Policy and Management Examiner: Dr. Anders Malmquist, KTH

Supervisor: Dr.-Ing. Jannik Henser, PMH Application Lab

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Sammanfattning

Elektrifiering av bilar och mindre transportfordon pågår och flottaaktier ökar men diskussionen om elektrifiering av långdistanstransport är relativt ny. Elektriska lastbilar som använder fossila bränslen och som produceras med förnybara energikällor är lovande, särskilt i länder med en ren elmix. I Sverige befinner sig två av de största trucktillverkarna som spelar en viktig roll i landets socioekonomi med mer än 100 000 jobb inom bilindustrin och bidrar cirka 14% av landets exportintäkter. Skiftet till elektriska fordon kan kraftigt påverka nationalekonomin. En ny drivlina design med elektrisk motor och batterier som ersätter traditionella motorer, växellådor och differentialer lovar betydande förändringar av tillverkningen och produktionskedjorna av tunga fordon. Nya processer och nya material kräver nya kompetenser. En litteraturstudie av produktionsteknik och konventionell tillverkning utfördes för att undersöka nuvarande skillnader. Processer inom elektrisk drivlinetillverkning skiljer sig betydligt från konventionella produktionsprocesser och en överföring av nuvarande produktionsteknologier är endast i liten skala möjlig. Nya produktionslinjer kräver ytterligare investeringar som utvärderades utifrån en marknadsundersökning för specifika scenariefall.

Litiumjon (Li-ion) batterier kräver investeringar av cirka 225 miljoner euro, härefter hänvisad till som maskininvesteringar. Utrustning för produktion av en induktionsmotor (IM) i massskala, ökar inköpskostnad för maskiner med ytterligare 15 miljoner euro. Nya drivline konstruktioner hotar därmed den nuvarande försörjningskedjan hos originalutrustningstillverkare (OEM) som har viktiga och värdeskapande kompetenser i produktionen av komplexa växellådor och motorer.

Produktionen av battericeller, batteripack och storskalig elmotorer är inte lika etablerade i Europa som i Asien. Detta möjliggör en relativt enkel tillgång för bilindustrin i Europa för nya spelare. Tidig positionering och leveranskedjans anpassningar är därför avgörande för OEM:er att behålla dess marknadsandel. Förutom påverkan på den svenska fordonsindustrin, visar det betydlig påverkning av miljön och samhället av tillverkningen av elmotorer för tunga fordon. Dessa konsekvenser har analyserats genom att utföra en livscykelanalys (LCA) och ytterligare litteraturforskning för att utvärdera råmaterialproduktionen och kopplade effekter på lokalsamhället. Speciellt så behöver batteriproduktionen råmaterial som kobolt och grafit vilket bidrar till politisk instabilitet i producerande länder samt dåliga arbetsförhållanden, vilket resulterar i konfliktpotential. Båda materialen klassificeras därför som kritiska och potentiella mineraler av EU. Användningen av dessa råvaror i länder där de utvinns och bearbetas bidrar financiering till lokala konflikter. LCA påpekade en negativ inverkan på miljön som orsakades av produktionen av batteripaket och elmotorer.

Miljöpåverkan orsakas primärt av utvinning av råmaterial och bearbetning av ingående material som behövs för tillverkning av drivlinor.

Speciellt gruvdrift visar en stor negativ inverkan orsakad av fossila energikällor i tillverkarländerna. Att byta produktion till länder med en ren energimix, som Sverige, kan därför bidra till att minska de negativa effekterna på miljön. Eftersom råvaror distribueras globalt och endast få länder har tillgång till dessa resurser, kan utbudet av ren energi i dessa länder förbättra miljöbalansen. Effekten av batteriproduktionen visar sig vara den största negativa faktorn som påverkar hållbarheten. Därför är andra elektriska fordonskoncept som inte behöver batterier för strömförsörjningen värda att undersöka. Att tillhandahålla konstant elkraft genom överliggande elektriska linjer eller bränsleceller är alternativ som bör vara i fokus för framtidlig forskning.

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Abstract

Electrification of cars and smaller transport vehicles has been ongoing and fleet shares are increasing.

The discussion to electrify long-distance transport is however relatively new. Electric trucks using fossil- free fuels produced with renewable energy sources is promising, especially in countries with a clean electricity mix. Sweden is hosting two of the biggest truck manufacturers, which play an important role in the socio-economy of the country. Providing more than 100,000 jobs in the automotive sector and contributing around 14% to the export revenues, that sector plays an important role within the Swedish industry. The shift from conventional to electric trucks could therefore heavily influence the national economy. A new powertrain design, where electric motor and batteries replace the engine, gearbox and differentials, is linked to a significant change in the heavy vehicle manufacture and production chains. New processes using materials, differing from established ones in the powertrain sector, require new competences from employees. A literature study on production technologies of conventional and electric powertrain manufacturing was performed to assess the differences between them. Processes used for electric powertrain manufacturing differ considerably from conventional production processes and a transfer of current production technologies is only in a small scale possible.

New production lines will require additional investments, which were assessed based on a market study for specific scenario cases. To establish a battery pack production on a mass scale referring to prismatic Lithium-ion (Li-ion) battery cells, makes 225 Mio. € necessary, hereby only referring to machine investment. Equipment for an induction motor (IM) production on a mass scale, adds another 15 Mio. € to machine purchase cost. The shift in powertrain design is additionally threatening the current supply chain of original equipment manufacturers (OEMs), having the key competence and main value creation in the manufacture of complex gearboxes and engines. Battery cell and pack production and large-scale electric motor production are not as established in Europe as they are in Asia. This enables a relatively easy access to the automotive industry in Europe for new players. Early positioning and supply chain adaptations are therefore crucial for OEMs to keep their relevant market share.

Next to influences on the Swedish automotive industry, the manufacturing of electric powertrains for heavy vehicles, shows an impact on the environment and society. Those impacts were analysed by performing an Lifecycle assessment (LCA) and an additional literature research to evaluate the raw material production and linked influences on the local society. Especially the battery production requires critical raw materials like cobalt and graphite. This refers to political instability in producing countries as well as poor working conditions, which result in a conflict potential. Both materials are therefore classified as critical and potential conflict minerals by the EU. Buying these materials as supply for battery pack production, consequently helps financing conflicts in areas where the raw material is extracted and processed.

The LCA pointed out a negative effect on the environment caused by the production of the battery pack and electric motor. The environmental impact is mainly caused by raw material extraction and processing of input materials needed in powertrain manufacturing. Especially mining shows a big negative impact, mainly caused by fossil energy sources in the producing countries. Shifting the production to countries with a clean energy mix, like Sweden, could therefore help to decrease the negative impact on the environment. Since raw materials are distributed globally and only few countries have access to those resources, the supply of clean energy in those countries could improve the environmental balance as well and should therefore be promoted. The impact of battery production was found to be the biggest negative factor affecting sustainability. Therefore, other electric truck concepts that do not need batteries for the power supply, are worth investigation.

Providing constant power through overhead electric lines or usage of fuel cells are promising alternatives and should be in focus for future research.

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Table of Contents

Table of Abbreviations

°C Degree Celsius (unit)

A-B-S-copolymer Acrylonitrile-butadiene-styrene copolymer

AC Alternating current

APOS Allocation at the point of substitution

BMS Battery management system

CMC Carboxymethyl cellulose

CO2 Carbon dioxide

CO2,equ. Carbon dioxide equivalent

DC Direct current

E Egalitarian

EU European Union

FABRIC Feasibility analysis and development of on-road charging solutions for future electric vehicle

GHG Greenhouse gas emissions

GWP Global warming potential

H Hierarchist

HP Horse powers

I Individualist

ICE Internal combustion engine

IEA International Energy Agency

IGBT Insulated-gate bipolar transistors

IM Induction motor

KFB Swedish Transport and Communications Research Board

kt Kilotons (unit)

kW Kilowatt (unit)

kWh Kilowatt hours (unit)

LCA Life cycle assessment

Li-air Lithium-air

Li-ion Lithium-ionen

LiPF6 Lithium hexafluorophosphate

Li-S Lithium-sulfur

Ni-Cd Nickel-cadmium

Ni-MH Nickel-metal hydride

NMP N-methyl-2-pyrrolidone

OECD Organisation for Economic Co-operation and Development OEM Original equipment manufacturer

Pb-acid Lead acid

PET Polyethylene terephthalate

PM Permanent Magnet

PP Polypropylene

PVDF Polyvinylfluoride

PWB-boards Printed wiring boards

RPM Revolutions per minute

SEA Swedish Energy Agency

SEI Stockholm Economy Institute

SEK Swedish Krona

tkm Tonne-kilometer (unit)

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II

TWh Terrawatt hours (unit)

UN United Nations

UV Ultra violet

ZEBRA Zero Emission Battery Research Activities

Zn-air Zinc-air

μm Micro meter (unit)

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List of Figures

Figure 1 Methodology overview ...3

Figure 2 Comparison of GHG efficiency for different freight transportation modes in 2005 [12] ...5

Figure 3 Swedish road freight CO2 emission and climate efficiency between 1990-2015 [10]...6

Figure 4 Fuel use development within the Swedish transport sector between 1995-2015 [2] ...6

Figure 5 Biofuel use within the Swedish transport sector between 1995-2015 [3] ...6

Figure 6 Comparison of different powertrain components depending on the vehicle type [29] ... 10

Figure 7 Component transformation from conventional to electric trucks [29] ... 11

Figure 8 Comparison of different types of electric motors [1, 6] ... 12

Figure 9 Timeline of battery developments used in electric vehicles according to [4] ... 14

Figure 10 Comparison of battery cell types for Li-ion batteries [5] ... 15

Figure 11 Comparison of current Li-Ion and beyond Li-Ion batteries [45] ... 16

Figure 12 Production chain and parts IM [1] ... 19

Figure 13 Production steps IM components ... 19

Figure 14 Winding technologies ... 22

Figure 15 Value chain of battery packs based on [1] ... 25

Figure 16 ReCiPe structure [66] ... 32

Figure 17 LCA explorer in SimaPro... 33

Figure 18 Methodology overview ... 34

Figure 19 Weight distribution battery pack ... 35

Figure 20 Material share induction motor ... 38

Figure 21 Material input battery pack production ... 39

Figure 22 Battery pack material input ... 40

Figure 23 Energy input battery pack production ... 41

Figure 24 Global warming potential ... 42

Figure 25 Comparison of the GWP of used materials ... 43

Figure 26 Overview on in- and output of the electric motor production ... 43

Figure 27 Material usage and GWP potential ... 44

Figure 28 Comparison between battery and electric motor ... 45

Figure 29 Machining share in powertrain production [29] ... 49

Figure 30 Potential employee development in Europe [89] ... 50

Figure 31 Competency development based on [19, 89] ... 51

Figure 32 Potential material usage development per vehicle, based on [89]... 52

Figure 33 Estimated machine investment cost for an electric motor mass production line [44] ... 53

Figure 34 Estimated machine investment cost for a Li-ion battery pack mass production ... 54

Figure 35 Impact summary ... 55 Figure 36 Tree diagram CO2 equ. generation battery pack production ... VI Figure 37 Tree diagram CO2 equ. generation during electric motor production... VI

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List of Tables

Table 1 Summary of numbers on Freight transport and Swedish transport vehicles [12-16] ...4

Table 2 Comparison of different battery types suitable for usage in electric vehicles [4] ... 14

Table 3 Comparison of available all-electric trucks [53-58] ... 18

Table 4 Battery pack properties [69] and own calculations ... 35

Table 5 Mass balance anode ... 36

Table 6 Mass balance cathode ... 36

Table 7 Cell assembly and formation mass balance ... 37

Table 8 Battery pack material balance ... 37

Table 9 Material distribution induction motor ... 38

Table 10 Comparison of results with literature ... 46

Table 11 Comparison with literature ... 47 Table 12 Summary of vehicle statistics in Sweden from 2014-2016 [14] ... VI Table 13 Detailed overview battery cell materials and mass balance ... VII Table 14 Energy demand battery cell production ... VII Table 15 Overview of machine invest battery production [43, 61, 62] ... VII Table 16 Overview of investment cost for electric motor mass production [43, 44] ... VI

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1 Introduction

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1. Introduction

Efforts in all sectors are required to reach the goals of the Paris agreement aiming to keep the temperature increase below the critical 2 degree Celsius (°C) limit. Currently, the power generation sector causes the biggest share of emissions in Organisation for Economic Co-operation and Development (OECD) countries. Following is the transport sector with almost a third of annual emissions [7]. The European Union (EU) is committed to acting as pioneer initiating the required change towards a more sustainable and renewable future. These ambitions are reflected in the Swedish policies and the country is having a leading role when it comes to carbon reduced power generation. More than 90% of the energy supply in 2014 were provided with carbon free technologies, of which 63% were from renewable sources [8]. The transport sector however, used only 19% of renewable sources the same year. Even though this share is steadily growing since 2005, the potential for carbon-free sources is still immense [9]. With the introduction of electric vehicles, the transition towards a more sustainable transport sector started, but currently mainly refers to passenger cars.

Heavy vehicles used for freight transport are not yet significantly affected by that system transformation. Since emissions caused by road freight accounted for 12% of the total greenhouse gas emissions in Sweden in 2014, improvements are required to reach the climate targets. Sweden’s government pursues the goal to achieve those being zero by 2045, furthermore, aiming to make the transport sector independent from fuels with fossil origin by 2030. Besides bio fuels, electrification of transport including freights, is seen as a crucial solution to reach those ambitious goals [10].

Introducing heavy electric vehicles, the manufacturing of freight vehicles will change, due to a different vehicle design. This will affect companies in the vehicle manufacturing sector and their product portfolio. From the manufacturer’s point of view, special interest lies in components varying between electric powered vehicles and conventional ones. Differences hereby mainly occur within the powertrain. This will cause changes in current vehicle production processes and pose new challenges to the manufacturers. Since Sweden hosts important and globally acting heavy vehicle manufacturers as well as sub-system manufacturers, the production of freight vehicles has an impact not only on companies, but the Swedish industry in general. Therefore, more knowledge on heavy electric vehicles and their powertrain production is required to understand future challenges and develop adequate corporate strategies.

1.1. Objectives

The aim of the thesis is to analyse of the role heavy electric vehicles are currently playing in the transport sector and how they could support transport system transformation integrating more sustainable energy sources. Next to that, possible impacts caused by the introduction of new production chains in line with a changed powertrain design will be outlined. Focus hereby, is the impact on the environment, social sustainability and impacts on the industry. Electric powertrain components differing from conventional ones and the related manufacturing process is outlined. By shifting the production away from conventional fuel-powered heavy vehicles to electric ones, manufacturers will face the necessity to adapt their production processes and their product portfolio. To assess the resulting challenges, an evaluation of the influence on employees, used materials and required new competencies will be included. The goal to reduce greenhouse gas emissions by electrification of road freight transport requires the inclusion of an environmental perspective. Therefore, the project contains a first impact assessment of the electric powertrain manufacturing on emission generation.

To summarize findings and enable an overview of the different aspects of the thesis, an impact matrix is added. Hereby, the different factors that were found to influence the mentioned areas, are evaluated and summarized.

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1.2. Methodology

In order to get an overview of the field of electrification of vehicles, a literature study is performed.

Particular interest lies in the question which role heavy electric vehicles could play within the transport sector in the future. Hereby, the future potential of electric trucks to contribute to a decrease of emissions is pointed out by using literature to analyze the impact of electrification on the transport sector. Literature is further used to outline the link between transport and greenhouse gas (GHG) emissions, putting the focus on freight transport. This shall provide information to the positive effect, electrification of heavy vehicles might have and enable and assessment of the pay-off. In literature outlined alternative vehicle concepts will be presented and an analysis of heavy electric vehicles suitable for road transport is performed, which bases on the performed literature study. This information is further used to determine the scenario that should be investigated within the project.

Literature is used to identify the powertrain composition. Specific parts differing compared to conventional vehicles are identified by comparing both vehicle concepts presented in the literature.

The production chain of these divergent parts is illustrated using information from literature published on the topic of current production technologies. The investment costs are evaluated based on a market study for a chosen scenario.

By analyzing results from previously performed studies, evaluating the change in powertrain manufacturing, a shift of competences, used materials and processes are further investigated.

Sustainability factors referring to social and economical aspects are analysed and results from literature linked to the chosen scenario in this study. Environmental impacts are investigated performing an LCA for two demonstrators: A battery pack made of prismatic Li-ion cells and an IM.

Both are modelled using the LCA software SimaPro. The production process of the battery pack and the electric motor are illustrated referring to data generated from literature, an open source battery calculation tool (BatPaC) and additional assumptions. Results from calculations in the software show generated emission, which are analysed to detect materials and processes contributing the most to overall emissions. The LCA software provides detailed tree diagrams of the simulated production process referring to the generated emissions, which are used to track emission drivers. The results are then compared to previous performed studies from other authors. By evaluating those results, the range in which values from literature are spread is detected and results from the performed LCA put in context to already existing studies. The methodology of the LCA itself, is displayed in detail in chapter 5.1.

Studies from different institutes and companies evaluating possible future trends in powertrain manufacturing are analysed and results linked to the Swedish heavy vehicle manufacturing sector, if possible. The content will then be discussed based on findings from literature and results developed in this study to identify future challenges occurring due to transport sector transformation. Based on the discussion, challenges are identified and an outlook on required activities presented. Figure 1 summarizes the methodology and the scope of the thesis as explained previously. The left column indicates the areas of focus within this study: Sustainability, production technologies and economy.

Each category was assessed using several indicators, which are presented in the middle. Methods used for that assessment are displayed in the right columns, differencing between an LCA, a literature study and a market analysis.

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1 Introduction

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Figure 1 Methodology overview

1.1. Limitations

The scope of this thesis refers to electric vehicle production on a mass scale, hereby focusing on the components contained in the powertrain. Other components (e.g. chassis and interiors), as well as other production stages (e.g. vehicle design and vehicle assembly), are not considered. This is also valid for other product life stages like the use phase and end-of-life treatment. For the evaluation of an electric powertrain production chain, a demonstrator was chosen for each the electric motor and the battery pack. In the case of the electric motor, an induction motor with 220 kilowatt (kW) was selected.

A lithium-ion battery pack with prismatic cells providing 220 kilo watthours (kWh) was selected as a demonstrator for the battery. Other available and suitable concepts, as well as advantages and disadvantages of the different technologies, are described and assessed in section 3.1. This section further describes the reasons for choosing specific technologies as demonstrators. The investigation of other motor or battery technologies, as well as a comparison to the chosen demonstrators, is of interest for potential future studies.

Limitations referring to the lifecycle assessment are illustrated in chapter 5.1.2. This section additionally contains information on chosen input materials and whether they were considered in the production chain or assumed to be purchased by material suppliers. None of the input materials uses recycled materials. The functional unit of the LCA is global warming potential (GWP) in carbon dioxide equivalent (CO2,equ.) per piece.

The economic assessment was performed referring to the introduction of a production line with high production volumes (mass production). Hereby, investments were only assessed for a specific production scenario, which is further described in section 6.4. The financial assessment was performed for machine investments, not including additional cost factors like production line planning, machine installation, buildings and working environment safety measures. The costs per part were not developed during this study but are of interest for future work.

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2. Road freight transport

This chapter provides background knowledge on the transport sector in Sweden and a comparison to the situation in the EU. Hereby, the focus is on freight transport using heavy vehicle trucks and its role within the transport sector. In the following, the sector’s influence on emission generation is analysed and the connection to different fuel types explained. The share of specific fuels and historical development is explained, focusing on Sweden. To understand the impact of vehicle manufacturing and the role truck manufacturing is playing within the sector, the importance in Swedish industry is illustrated, paying attention to GDP and export contribution as well as number of employees. The end of this chapter deals with current trends in road freight transport and projects investigating alternative fuel concepts, focusing on electric solutions. This sections bases on a literature study.

Within the transport sector, a division into two main categories is possible: Passenger and freight transport. Generally, means of transport are additionally divided into road vehicles, rail vehicles, airplanes and ships [11]. Sub-categories are broad, however, the popularity of road over rail vehicles for freight transport is empirical. Referring to European countries that are part of the OECD, numbers from the 2005 report Transport, Energy and CO2, show that dominance. The total covered ton kilometer (tkm) on the road using trucks amounted to 1,500 billion tkm that year. This equates to roughly 5 times the amount of covered rail tkm [12]. The countries in which this relation is the other way round and good transportation is mainly performed on rails, are only those, where long distances have to be managed like China, North America and Russia. The energy intensity, which refers to the amount of energy required per tkm, also depends on the method of transportation. Focusing again on OECD countries in 2005, the required energy for road transportation averaged in around 0.9 kWh/tkm [12]. Depending on the vehicle of choice, the energy intensity varies, but is generally highest for light commercial vehicles. The bigger the truck size gets, the less the energy intensity is.

However, with approximately 0.11 kWh/tkm, rail transportation is significantly more efficient than any type of road transport [12].

In Sweden, 65% of the freight transport took place on roads in 2006 [12]. Transport analysis, a Swedish government agency for transport policy analysis, annually publishes current numbers on transport and traffic [13]. The most actual data refers to 2016 and provides an overview of the Swedish road freight transport. In that year, the total number of registered trucks reached 582,042, from which over 60%

were used for professional freight traffic within Sweden [13, 14]. This usage resulted in roughly 43,000 million tkm [15]. According to United Nations (UN) statistics on transport, the number of trucks with a load capacity over 3,500 kg, in the following referred to as heavy trucks, slightly increased from 67,313 in 2014 to 68,749 in 2016. Most of these vehicles were fueled with diesel (around 97%). Petrol and alternative fuels were almost equally used for the remaining vehicles [14]. For a better overview, Table 1 sums up the above mentioned data.

Table 1 Summary of numbers on Freight transport and Swedish transport vehicles [12-16]

European OECD countries Road Rail

Freight transport in 2005 Ca. 1,500 billion tkm Ca. 300 billion tkm

Energy intensity 0.9 kWh/tkm 0.11 kWh/tkm

Sweden

Share freight transport 65% 35%

2014 2016

Registered trucks 567,275 582,042

-Heavy trucks (>3,500 kg payload) 67,313 68,749

Freight transport Ca. 42,000 million tkm Ca. 43,000 million tkm

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2 Road freight transport

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2.1. Emissions

Globally, the transport sector creates more than half of the oil demand, accounting roughly for 8,000 million liters per day. Between 2000 and 2015, the transport sector’s oil needs caused most of the increase in oil demand globally, being responsible for 80% of the growth during that period [11].

Combustion of oil products during vehicle operation causes immense carbon dioxide (CO2) emissions and in 2015, 22% (=7.8 Gt) of global emissions related to energy, were caused by the transport sector [11]. Even though, passenger transport emits the bigger share, freight transport still is responsible for 7% and shows an equally high oil demand as the industry sector. Since the passenger transport gained most of the attention for emission reduction measures, the oil demand and consequently CO2

emissions within freight transport, still rise [11].

Figure 2 depicts the specific GHG emissions range for the year 2005 for different modes of freight transport. The light blue line presents the world average and the dark blue bar discrepancies for different countries according to the IEA Mobility Model [12].

Figure 2 Comparison of GHG efficiency for different freight transportation modes in 2005 [12]

Road freight is responsible for most of the transport sector’s emissions on ground. When it comes to the GHG efficiency, shipping and rail transport are favorable. Consequently, the potential to decrease the emissions per transported freight on the road remains high. The emission origin within the road freight sector depicted in numbers on freight mobility by IEA [12], shows the impact of heavy trucks on emissions. With a share of around 70%, those vehicles are responsible for the biggest share of GHG emissions of freight transport. Light trucks in comparison, have a share of around 20% and the remaining 10% of emissions are caused by medium sized trucks.

The picture in Sweden is similar to the average global situation. Here, the transport on the road emitted 33% of total national GHG emissions in 2014. The share of road freight transport is hereby responsible for 12%. Those numbers cannot be compared to the above stated global shares, since the reference years and frame conditions differ. The tendency however, is similar [10].

Figure 3 illustrates the annual change in CO2 emissions from road freight transport in Sweden by depicting the total emission in kilotons (kt) between 1990 and 2015. Starting in 2000, the efficiency of transport measured in emissions per tonne-kilometer (tkm) for the transported goods is added.

Starting with 4,000 kt CO2 emissions in 1990, Sweden’s freight transport caused steadily increasing annual emissions [2]. Reaching the peak in 2008 and 2010 with almost 6,000 kt CO2, total annual emissions decrease since then. Since the climate efficiency is not visibly improving, it is most likely that these reductions are linked to increasing usage of biofuels [2]. The drop in emissions in 2009 is likely to be explained with the global drop in transported freight during that year [17].

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Figure 3 Swedish road freight CO2 emission and climate efficiency between 1990-2015 [10]

2.2. Fuels

The fuel usage within the Swedish transport sector is depicted in Figure 4. The graph shows the share development for fuels between 1995 and 2015 for domestic transport in Sweden and provides the total fuel use per year in Terrawatt hours (TWh). The total consumption varies between the years.

Starting in the nineties, the total amount showed a slow but steady increase and reached the peak 92.8 TWh in 2007. This growth was followed by a flat decreasing trend until 2013 with 85 TWh of supplied fuels in that year. 2014 and 2015 requested with 85.3 and 87.2 TWh again more fuels [2].

Focusing on the share of renewable fuels and electricity, a rising trend is visible. With the start of the new century in 2000, the share of bioethanol grew steadily until 2009, where the amount was almost constant around 2.3 TWh. After that, a slight decrease was visible until 2015. Biogas used for transportation only plays a minor role and contributed between 0.1 and 1.1 TWh. Since the introduction in 2001, the share almost constantly increased by 0.1 TWh annually. Most important within the biofuels used in domestic transport is biodiesel. Even though that share was quite low between 2001-2006, it showed a rapid growth in the following years and a rising amount of biodiesel covered Swedish fuel demand. Usage of electricity for transport purposes stayed relatively constant over the years and varied between 2.4 and 3 TWh annually [3].

0 10 20 30 40 50 60 70 80 90 100

TWh

Petrol Diesel Light fuel oil

Aviation fuel Natural gas Biofuels Electricity

0 2 4 6 8 10 12 14

TWh

Bioethanol Biodiesel Biogas

Figure 4 Fuel use development within the Swedish transport sector between 1995-2015 [2]

Figure 5 Biofuel use within the Swedish transport sector between 1995-2015 [3]

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7 So far, no obvious impact of electricity as fuel is visible. Reasons for that might be the challenges in infrastructure and vehicle development as well as required change in behavior that accompany the transformation from conventionally fueled vehicles to electric ones [10].

The UN database provides a detailed overview on vehicle statistics categorized by fuel and vehicle type for Sweden between 2014-2016 [14]. Exact and complete numbers are displayed in Table 12 placed in the Appendix. The biggest share of vehicles in the reviewed categories “Motor coaches, busses and trolley busses”, “Light good road vehicles” and “Lorries (>3,500 kg load capacity)” were fueled with diesel. Light good vehicles used petrol (10-12%) and alternative fuels (ca. 2%) to some extent. The amount of electric vehicles was however with less than 0.1% insignificant [14]. The share of other fuels than diesel, differs for trucks. Here, using petrol as fuel applies to roughly 1% of the vehicles. The same share is visible for alternative fuels. Electric vehicles are not a part and until 2016 none existed in the mentioned vehicle class [14].

2.3. Importance in industry

In 2007, the share of the Swedish automotive industry accounted for 2% of the total industry and almost 10% within the manufacturing sector in the country. In comparison to other OECD countries, Sweden belongs to the countries showing high impact of the automotive sector [18]. Between 1980 and 2015, the number of produced trucks from the two Swedish manufacturers, Scania and Volvo, together increased from around 50,000 in 1980 to 275,000 in 2015. Until 2000, this production was almost evenly distributed between the two companies, but Volvo raised its share and started to produce 75% of the annual vehicle production after that [19]. The common production of heavy vehicles from Volvo and Scania, corresponded to an European market share of 28% in 2007 and 10%

of the world’s production, therefore illustrating the importance in Swedish economy [20]. Companies contributing to the vehicle industry are spread over the whole county, whereby most of them are located in Västra Gotland and the Stockholm area [19].

The Swedish automotive industry plays an important role in national exports. In 2016, 14% of exported goods were products from that industry sector, representing the largest share within the export industries [19]. Compared to other OECD countries, with most current data referring to 2007, Sweden lies midfield with an export share of 10% of total national industry. Leading countries that year were Japan, Slovakia, Hungary and Germany [18]. According to the Swedish Economy Institute (SEI), 60% of the products from the motor-vehicle industry are exported. Latest numbers of the SEI refer to 2005 and state that 15% of exported goods were from the vehicle sector, which was worth 125 billion Swedish Krona (SEK).

In 2015, the total number of people employed in the automotive sector in Sweden was 101,596.

Hereby, 29% of the employees were working with light and heavy vehicles, 37% with heavy vehicles only, 25% with light vehicles only and 9% with construction equipment. Since 2011, the total number of employees in the automotive industry in Sweden stayed quite constant at around 100,000 people.

Most of them are contributing to complete vehicle production, which is followed by people working with body and chassis as well as details and materials. Generally, the number of employees per specific sub-group changed little over the years.

2.4. Current trends

Due to the large impact on emissions, the future of the transport sector might hold different changes and new trends. The development of road freight activity, linked energy consumption and emissions, is influenced by three main factors: (1) systematic improvements (2) vehicle efficiency (3) alternative fuels/vehicles. Systematic improvements refer to the general road freight system and the road activity.

Idea behind systematic improvements is decreasing road activity required to deliver goods, consequently delivering the same amount of goods with less transport activity (tkm).

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8 Improving truck efficiency results in less consumed energy per truck. Using alternative fuels brings a change in vehicles and power train design and includes a shift from conventional fossil-fuel based fuels like diesel or gasoline to biofuels, natural gas, hydrogen, methanol or electricity [11]. A combination of different concepts is also possible and hybrid vehicles using conventional fuels as well as electricity already exist on the market.

The development of hybrid heavy vehicles is more advanced within alternative fuel concepts. Swedish vehicle manufacturers started in 2006/2007 to develop hybrid vehicle solutions and design new products using hybrid technologies. Since hybrid vehicles help improving fuel efficiency, rising fuel prices justified the product development and introduction especially for the heavy vehicle manufacturing industry [20, 21].Volvo already started in 2008 to sell hybrid electric city busses and refuse collection trucks. Scania did not participate right away in the market and took until 2016 to first sell hybrid electric vehicles [19].

Technical principles for electrified trucks are similar to solutions available for cars. However, the bigger size and higher weight of the vehicle, pose additional challenges for the usage of batteries. Long distances to be covered and long charging times, additionally challenge the transformation from conventional fueled trucks to electric ones [10]. With powertrain-to-wheel efficiency of 85%, electric trucks reach way higher efficiencies than regular trucks. Trucks using engines, show efficiencies between 44-46%. The installation of electric motors is more flexible as well, and those can be either placed in the drivetrain or directly in the wheel hubs [11]. However, completely electrified heavy vehicles still remain in the pilot phase. Medium trucks in urban applications left that stage already and entered the early development phase. The EU partly funds demonstration projects operating electric freight vehicles and collect data. The FREVUE program for example assists stakeholders to set up demonstration projects and currently over 70 electric freight vehicles are operated under the frame of FREVUE [11]. Next to the approach of electrifying vehicles by equipping them with batteries, concepts focusing on constant electricity supply exist. In Sweden, several research projects are currently performed to investigate such electric road systems using overhead electric lines or rails for electricity supply. The technology itself is not new, but gained attention again when electrification was included in discussions to promote sustainable transport. Scania and Siemens are investigating the feasibility of these overhead electric cables for powering trucks in the region Gävleborg on a test track with a length of 2 km [11]. Volvo and Alstom focus a different approach, the in-road conductive technology and are part of the European project Feasibility analysis and development of on-road charging solutions for future electric vehicles (FABRIC) [10]. Test sites are situated in France, Italy and Sweden. The Swedish test track’s length is 435m and is located in Hällered close to Göteborg [22]. Generally, electrification gains importance in the Swedish automotive sector and the number of companies involved in electric vehicles raised from 27 in 2007 to 32 in 2015 [19].

2.5. Challenges

The electrification of heavy vehicles poses as well challenges. Using batteries in vehicles, makes a suitable charging infrastructure necessary. Covering a region requires quite a dense charging network due to the limited range of electric vehicles, which lies around 120 km currently [23]. The charging then, is not time efficient and cannot be compared to refueling conventional cars. Depending on the charging system, several hours for battery recharge are required. Speed charging is possible, reaching 80% of the capacity within 20-30 minutes, but those stations present very high installation and establishment cost [23]. To mechanically replace empty batteries with charged ones is possible within a couple of minutes. This however, causes the need for batteries in a standard battery format and location in the vehicle [23].

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9 Another drawback is the limited battery life span. Current technologies enable around 1,500 charge- discharge cycles allowing a vehicle operation between 4 and 5 years [23]. Other studies promise a lifecycle of between 10 and 15 years [24], showing the insecurity regarding the lifetime of the battery pack. However, at some point, the battery replacement is necessary, which not only causes additional cost but also increases the use of recourses and makes adequate recycling technologies necessary.

Batteries contain a high share of metals requiring mining for exploitation. Recourses, production and reserves are often located in specific regions only. Political instability or geopolitical issues can affect the availability of raw materials. Supply and price of raw materials required in battery production therefore depend on the situation in the resource regions. Additionally, increased used of energy technologies like batteries for energy storage and transport, have an impact on the demand for raw materials. Future availability of these materials (e.g. nickel, copper, lithium) therefore might be limited [25, 26]. This aspect is further discussed in chapter 6.3.2.

Assessment of the impact on the environment caused by the production and use of electric trucks, requires additional source-to-wheel efficiency and emission analysis. This approach is holistic and considers not only the raw material production stage and use phase, but as well the energy transport, generation and distribution [27]. A first assessment of specific part manufacturing required in heavy electric vehicles is performed in chapter 5.1

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10

3. Heavy electric vehicles

This chapter focuses on the heavy electric vehicle design and a comparison to the powertrain of conventional heavy trucks. First, different powertrain concepts for different vehicle types will be displayed based on a previous literature study to evaluate state-of-the Art technologies and possible future developments. Second, replacement, modification and addition of vehicle components caused by propulsion transformation will be discussed. The focus will then be put on electric trucks and their powertrain parts. The structure, operating principle and the state-of-the-art of electric motor, battery and gearbox are illustrated. The chapter ends with an overview of the market availability of all-electric truck solutions that were obtained by a literature study and press releases.

In comparison to conventional vehicles, electric trucks that do not use oil-based fuels, differ in the powertrain design. In general, common parts of conventional vehicles (e.g. tank, pump and engine) are replaced with other components fulfilling the same function (e.g. battery, charger and electric motor). Roughly 70% of all the components contained in the electric truck, cannot be found in a conventional vehicle [28]. One distinct difference is the number of moving parts. Electric vehicles possess only the motor falling into that category, conventional vehicles consist of various components that include or constitute moving parts. Principal component differences relate to the powertrain design [28]. Figure 6 compares the powertrain components of conventional and electric trucks and provides an overview of modification and replacement of specific parts.

Figure 6 Comparison of different powertrain components depending on the vehicle type [29]

Generally, conventional powertrains for trucks are well-established in the vehicle industry and the theoretical working principle is adequately described in literature [30-34]. Main components are engine, transmission, drive shafts, differentials and final drive unit. In trucks, the engine is located in front of the vehicle before the gearbox. Both are connected to the axles, located in the back of the vehicle and connected to the rear wheels. Displayed in Figure 6, the gearbox is presented on the left side and the engine, which is a diesel engine in this case, as well as the axles, on the right side of the displayed truck. Used fuels in engines are oil-based and besides diesel and gasoline, gas can be used.

Biofuels can be added to some extent as well. To use 100% biofuels in the engine, adaptations are required [35]. Hybrid powertrains contain additionally to the conventional parts (engine and transmission), electric components, such as an electric motor, power electronics and a high voltage energy storage [34]. Referring to Figure 6, hybrid vehicles would use all displayed components. They therefore represent a blend of electric and conventional vehicles. Those vehicles are generally fueled with conventional or bio-based fuels together with electricity. Depending on the fuel being used, different motor types are required [23]. Electric vehicles contain only the before mentioned electric parts and exclude most of the conventional parts. Specific components like gearbox and axles are

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3 Heavy electric vehicles

11 optional and depend on the powertrain design. This will be explained further in the sections dedicated to these components. Electric vehicles are fueled with electricity only. The placement of the motor is hereby flexible and can be placed central, on wheel hubs or rear axles. The number of motors depends on that and ranges generally between one and four [36]. Figure 6 refers to a conventional central placement of the electric motor in the front of the vehicle. The placement of battery packs can vary as well. Common however, is to place them in between the wheels, close to the road as shown in Figure 6, to provide additional stability to the vehicle [29].As mentioned above the powertrain design differs from conventional to hybrid and electric vehicles. Since the focus of this study lays on all-electric trucks, only the changes in the conventional powertrain in relation to the electric one, will be displayed in the following and are summed up in Figure 7. The figure additionally provides information on whether the vehicle manufacturer or supplier is affected from those changes.

Figure 7 Component transformation from conventional to electric trucks [29]

The left column in Figure 7 refers to components that are no longer required in electric trucks. The engine, entirely provided by the vehicle manufacturer, falls into this category. Since electric trucks generally do not contain a complex gearbox but fixed gears instead, no additional clutch is required, which partly affects manufacturers. Tank, and injection systems are replaced with the battery and adequate battery management. Since no exhaust gases are produced while driving, the exhaust system is redundant. The loss of these components affects entirely the supplier. Some components are still required in electric vehicles but need to be modified in order to be suitable. Those components are displayed in the middle column of Figure 7. As mentioned before, the powertrain design has to be adapted, which requires modifications in the manufacturer’s as well as the supplier’s production process. This is the case for the adaptation of the brake system and wheel suspension. To keep the current degree of added value, the vehicle manufacturers have to get involved in battery production and management as well as partly the electric motor [29]. Those parts represent additional components, electric vehicles require and are displayed in the right column in Figure 7. Since the share of electric components increases, power electronics have to be introduced. A characteristic of an electric motor is reduced vibration harshness, which leads to the necessity to add artificial vehicle sound using a sound module to ensure proper perception for pedestrians. The transformation of competences within truck manufacturing is confronting current manufacturing companies and their suppliers.

The decision on potential outsourcing of manufacturing of parts is an ongoing process. The question on future changes in the manufacturing environment due to the introduction of electric truck production, will be further analysed in chapter 6.

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12

3.1. Electrical powertrain components

As described above, specific parts contained in the powertrain of an electric vehicle differ from vehicle parts used in conventional vehicles. In comparison to conventional vehicles, the degree of freedom to design the powertrain is increased and more flexible [1]. The next sections describe the electric motor, battery and gearbox further. Section 3.1.4 summarizes additional required components. State-of-the- art technology for all components is depicted and the working principle explained.

3.1.1. Electric motor

Generally, three different types of electric motors are suitable for utilization in electric vehicles.

Permanent magnet (PM), induction (IM) and switched reluctance motors. The choice depends on the characteristic performance factors like torque and power density, speed range, efficiency, reliability, robustness and costs that suit best the specific demand. The following Figure 8 illustrates the basic components of the three different electric motors.

On the left side, Figure 8 depicts the components of the PM and IM, which both are variants of alternating current (AC) motors. Currently, they are most common in electric vehicle applications. Both consist of a stationery stator located on the outside with coils producing a magnetic field when supplied with AC. The other basic part is the rotor, which is situated inside the stator. The rotor is attached to a shaft providing the motor’s output and generating a second magnetic field [37]. As Figure 8 depicts, in IM, both the rotor and stator have windings, in PM motors on the other side, only the stator has windings since no additional magnetic field has to be generated. In both cases, the rotor acts as electromagnet and aligns according to magnetism when rotatable inserted into the magnetic field of the stator. Difference between those two motor types, is the placement of magnets in the rotor of the PM motor, generating the magnetic field. When adjusting, the rotor performs half a revolution.

To initiate a stable rotation, the direction of current supplied to the coil requires a change to change the poles and cause continuous movement [38]. PM motors are a sub-group of synchronous motors and induction motors belong to the group of asynchronous motors. Those types differ in the synchrony of the rotating shaft and the supply current’s frequency. In synchronous motors, those are synchronous and do not exhibit slip, which refers to a difference between actual operational and synchronous speed at the same frequency. For induction motors, it is the opposite [37]. Advantages of induction motors include, next to simplicity, robustness and wide speed range that the counter- electromotive forces at high speeds adapt automatically to the supply voltage level. This is not the case for PM motors. A disadvantage compared to PM motors, is the lower efficiency caused by inherent thermal losses in the rotor, resulting in bigger motor size. PM motors distinguish themselves in high efficiency, high torque and high power density. The speed range on the other hand is limited and at high speeds, since counter-electromotive force causes challenges for the inverter, which has to withstand the generated voltages. In case of short-circuit fault, this might cause additional and severe problems [23].

Figure 8 Comparison of different types of electric motors [1, 6]

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13 Switched reluctance motors use direct current (DC) in comparison to the PM and IM. This motor type is presented separately in the right side of Figure 8. Unlike AC motors, no coils or magnets are contained in the rotor. Instead, such motors consist of a rotor and a stator with teeth acting as magnetic poles. These parts are made of ferromagnetic material and the stator teeth are surrounded by coils carrying the DC currents. The number of stator teeth and rotor teeth are different, since an equal number would cause stationary lock-in positions [1].

Figure 8 shows a switched reluctance motor, containing six stator and four rotor teeth, placed oppositely to each other. By applying power to the stator, occurring magnetic flux result in a force aligning the rotor pole with the nearest stator tooth. Opposite teeth form a coil pair and are switched on and off in cycles in order to create a steady movement. In comparison to AC motors, electronic position sensors are used for the required pole switch, offering dynamic control. Since no slip occurs, the rotor position can be defined exactly, which is also possible in PM motors [39, 40]. Compared to AC electric motors, the switched reluctance motor is not yet commercialized in a big scale and remains in developmental stage. Purchase cost might therefore be significantly higher. Another drawback is the high noise generation. Other than that, various benefits are present: simplicity in structure and control, rugged construction and high speed operation [23]. The efficiency of switched reluctance motors is comparable to PM motors and higher than in IM [41].

There are different solutions available regarding the placement of the motor within the powertrain.

To place them centrally like the engine in conventional vehicles is one of them. However, the electric powertrain is more flexible regarding the component array. Electric motors can be installed directly on the axles, wheels or wheel hubs as well. The number of motors is then increasing from one to four per driving axle of the vehicle, yet with lower power rating [1].

3.1.2. Battery

In all-electric vehicles, included batteries provide the required energy for the electric motor by transforming chemical into electrical energy. Accumulators like Lithium (Li)-ion batteries reverses this chemical reaction, enabling recharging. The battery technology underwent several phases of development and therefore, commonly used battery types changed over time. Figure 9 provides an overview of the development and illustrates promising new technologies, likely to emerge in commercial scale in the future. Each battery type differs in characteristic features, which are further explained in Table 2. The energy density of principally used technologies increased over the time. Lead acid (Pb-acid) batteries equipped the first generation of electric vehicles, using lead electrodes and acid for electricity generation. They were the first generation of commercial available batteries and are located in the left of Figure 9. With 35 Wh/kg, the energy density is comparatively low and consequently these batteries are heavy, requiring more mass to provide the desired amount of electricity. During the last decade, nickel-based batteries were introduced and replaced Pb-acid batteries due to their higher energy density. Nickel-cadmium (Ni-Cd) reach 50-80 Wh/kg and Nickel- metal hydride (Ni-MH) 70-95 Wh/kg. Long charging times and a high self-discharge, limit their suitability for electric vehicle application. Around the same time, Zero Emission Battery Research Activities (ZEBRA) batteries using sodium-nickel chloride were introduced. Even though, the energy density is again higher than in Pb-acid batteries, the high operating temperature between 245 °C -350

°C poses a challenge for thermal management and utilization in electric vehicles. State-of-the-art today, are Li-based batteries with an energy density of up to 250 Wh/kg. Most of the current electric vehicle technologies uses this kind of batteries due to their convenient characteristics. Nickel-based and ZEBRA batteries are state-of-the-art technologies and therefore positioned in the middle of Figure 9 representing present times.

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14 Lithium-Sulfur (Li-S), Zinc-air (Zn-air) and Lithium-air (Li-air) batteries exceed the properties of Li-based batteries, but are still in their development phase. In order to become the new standard for electric vehicles, those have to be improved and current drawbacks like low lifecycle and high self-discharge rate have to be overcome. Those are placed in the right of Figure 9 representing future technologies.

Table 2 Comparison of different battery types suitable for usage in electric vehicles [4]

Li-ion batteries contain a high specific energy content and are therefore suitable for the usage in electric vehicles. Within this battery group, the distinction between cylindrical, prismatic and pouch cells is made [5]. Generally, Li-ion batteries consist of two electrodes (cathode and anode) and a separator, isolating them. In between is an ionic conductive electrolyte. Materials used as current collector influence the efficiency and cost of the batteries [42]. Figure 10 presents prismatic, cylindrical and pouch cells. For better visibility common parts are displayed in the same color for all three cell types. Hereby, the cathode is dark grey, the anode is displayed in blue and the separator in green. This is only indicated in the first picture referring to prismatic cells, but it is valid for all three types. Anode, cathode and separator foils are stacked (prismatic and pouch) or wound (prismatic and cylindrical) and placed into the housing. The material for the housing depends on the battery cell type. For prismatic cells either plastic or metallic materials are used. Cylindrical cells only use metallic housing and the pouch cell housing consists of soft bags. The negative and positive tabs are placed on the upper side of the prismatic cell, displayed on the left in Figure 10. Those cells provide a good packing density and efficient space use within the module. The size of individual cells is hereby flexible and can individually be adapted to specific purposes. The energy density per module is medium, which is caused by the oval shape the cathode, anode and separator have after they were wound. Due to a conducive volume to surface ratio, the heat controllability and dissipation is good [43].

1 The number of life cycles refers to the amount of cycles a battery can perform, before the nominal capacity decreases to less than 80% of the initial capacity [42]

Battery type Energy density

[Wh/kg]

Power density

[W/kg] Life cycle¹ Self discharge [%/month]

Lead acid (Pb-acid) 35 180 1,000 <5

Nickel-cadmium (Ni-Cd) 50-80 200 2,000 10

Nickel-metal hydride (Ni-MH) 70-95 200-300 <3,000 20

ZEBRA 90-120 155 >1,200 <5

Lithium-ion (Li-ion) 118-250 200-430 2,000 <5

Zinc-air (Zn-air) 460 80-140 200 <5

Lithium-sulfur (Li-S) 350-650 - 300 8-15

Lithium-air (Li-air) 1300-2000 - 100 <5

Figure 9 Timeline of battery developments used in electric vehicles according to [4]

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15 The structure of the cylindrical battery cell is depicted in the middle of Figure 10. In comparison to prismatic cells, the tabs are located on top (positive tab) and bottom (negative tab) of the cell. In between the housing and the positive tab, a synthetic ring is placed for isolation. The cylindrical cell type is linked to strong production experiences and well developed. In comparison to the other battery cells a lower energy density per module. This is due to inefficient space usage. When stacking the cylindrical cells to modules, space in-between the individual cells are inevitable. On the other side, this additional space improves the heat dissipation in the module. Per cell, the heat controllability is however poor. This characteristic additionally leads to limited flexibility in cell size [43].The third battery cell type, the pouch cell is presented in the right of Figure 10. In comparison to the prismatic and cylindrical cells, this type has the best energy density per module with around 730 Wh/l [43]. Space usage and packing efficiency are efficient and comparable with prismatic cell.

This is equally true regarding the placement of the tabs. Negative and positive tabs are located, as in prismatic cells, next to each other on top of the cell. Drawback of this energy efficient cell type is the stability of the cell. The tightness related to liquid or gas release from the cell, is low, as well as stiffness and mechanical stability. In addition, the stacking process is difficult. Life time is expected to be more than 10-15 years for all cell types [24]. Comparing all three battery cell types, the prismatic cell shows the best overall performance and therefore the focus in the following lies on those cells.

Battery packs used in electric vehicles consist of combined battery modules, formed by stacking of individual battery cells. Connecting the individual cells parallel, achieves higher current levels and connecting them in series leads to higher voltage [44]. The battery is a crucial part in electric vehicles and a determining characteristic feature for those. Prismatic battery cells enable space-saving assembly and are therefore mainly used in electric vehicles. The requirements for heavy electric vehicles are even more challenging, since a high payload is requested. That directly affects the battery size and therefore the vehicle’s range per charge. Sripad and Viswanathan published a paper in 2017 dealing with those challenges focusing on performance metrics required for practical electric trucks [45]. Figure 11 is from that publication and is summarizing their findings. The graphic puts battery type and size, pay load and transport range into relation and provides an overview of the interlinkages. The authors hereby compare current Li-ion technology, as described above and theoretical beyond Li-ion battery concepts. When talking about beyond Li-ion batteries, the authors refer to a Li-metal coupled system with advanced cathodes. Examples are Li-Sulphur or Li-Air. Values used in their calculation refer to optimistic numbers that are not yet available. They refer to a mean specific energy of 500 Wh/kg at the cell level. Current trucks and battery size using Li-ion batteries, are displayed in the upper half of Figure 11. The battery used in the truck is displayed in red, located in the front of the truck. The payload illustrated in black, is covering the space of the trailer. Hereby, Figure 11 shows three different transport ranges, using 480 km, 965 km and 1,450 km covered. The weight of the whole truck plus

Figure 10 Comparison of battery cell types for Li-ion batteries [5]

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16 trailer is kept under the US American legal limit of 36,000 kg. In Europe, the Directive (EU) 2015/719, regulates truck dimensions and weights. Paragraph 10 refers to the weight limit of 44,000 kg for trucks with three axles and 42,000 kg for two-axle vehicles. Comparing this to the US American regulations, the limits are higher. It is visible that the battery size increases with longer covered ranges and therefore the payload decreases due to the legal weight limits.

Figure 11 Comparison of current Li-Ion and beyond Li-Ion batteries [45]

Visible is the potential of beyond Lithium-ion (Li-ion), referring to new battery technologies than used today. Their use in freight trucks is displayed in the bottom half of Figure 11. As for the Li-ion batteries, the battery is illustrated in red and the remaining payload in black. Comparing the battery size of Li- ion equipped trucks with those using beyond Li-ion technologies, it follows that they could provide the same distance range with significantly lower battery size. This could increase valuable payload sizes, becoming essential for long transport ranges over 1,000 km. The shift in battery technology could increase the available freight weight from 4,000 kg to 15,000 kg, enabling the competitiveness of heavy electric vehicles for freight transportation with conventional trucks. However, it is important to bear EU regulations in mind that regulate truck driving time by limitations for the drivers. Regulation number 561/2006 limits the driving time to 9 hours per day. An exception can be made twice a week increasing the driving hours to 10 per day. Assuming driving speeds of around 90 km/h, the total distance reaches 810 km and 900 km in exceptional cases. Further, the drivers are obliged to take a break of 45 minutes after 4.5 hours of driving. This mandatory break would enable recharging of the batteries and together with the regulations on upper driving limits question the necessity to cover distances above 1,000 km [46].

3.1.3. Gearbox

The function of the gearbox is to transform torque and rotational speed between motor and wheels.

Referring to conventional vehicles, only a specific number of rotations per minute is feasible for the engine, which makes the gearbox necessary. It transmits the incoming rotation using the desired ratio to the output shaft and therefore transfers incoming rotation into lower or higher output rotational speed [47]. Gearbox transmission technologies are categorized according to their number of transmission stages: single-stage, two-stage and multi-stage. This refers to the number of gear pairs.

Generally, this includes the transmission from one shaft to another [48]. Conventional vehicles require coaxial transmission and therefore need multi-stage transmission. This is different for electric vehicles.

In comparison to engines, electric motors can supply constant power within a large rotational speed range and supply sufficient rotational speed from standstill. This characteristic makes the gearbox and