Abstract

Background:          The growing number of electric vehicles gives rise to a whole new reverse supply chain. Once the electric vehicle batteries reach their end-of-life, societal and governmental pressure forces automotive manufacturers to set up a network for disposing the hazardous batteries. Although, the volumes of returned batteries remain low, volumes will increase in upcoming years. Current networks and processes related to the return flow of electric vehicle batteries are not well established, nor well defined. Thus, creating an urgency to develop efficient collection networks.   Purpose:                  The purpose of this study is to investigate how reverse logistics networks are currently set up and to provide an overview of how the different actors and processes are connected. In addition, this thesis aims to identify challenges encountered by logistics providers and recyclers. By doing so, we hope to contribute to the research gap of which factors that constitutes a bottleneck for further development of the reverse logistics chain of electric vehicle batteries.   Method:                  The thesis conducts an interview study and is qualitative in nature. Semi-structured interviews generated empirical data, which was analysed through cross-case analysis incorporating a thematic analysis. Through this analysis we were able to achieve new theoretical understandings in connection to institutional theory.   Conclusion:             Through empirical findings a detailed framework of the reverse logistics chain of EVBs is portrayed. Furthermore, different challenges span over the processes illustrated in the framework. This presents an overview which is not found in current literature and extends current research on this topic.

Abstract

This thesis deals with the interaction of batteries and power electronic converters in automotive applications. Even if the additional heating caused by (unwanted) alternating currents is disregarded, there has been a concern that alternating currents can be harmful for batteries. For that reason, alternating currents can be filtered using capacitors and/or by sophisticated hardware. In this work, the concern whether alternating currents are harmful to batteries is studied particular focus on large, lithium-ion cells for use in automotive applications.First, the harmonic content in the battery current of two, commercial hybrid-electric busses were measured and analysed. The most prominent harmonic had a peak magnitude higher than 10% of the maximum direct current level (160 A) arising at frequencies below 150 Hz. The maximum amplitude detected of a harmonic caused by the voltage source converter’s switching action was around 10 A and occurred at a frequency of 2 kHz. An experimental setup with alternating current capability for evaluating large lithium-ion cells has been designed and built. Twelve lithium-ion cells were cycled at a rate if 1 C during approximately 2000 cycles (corresponding to approximately one year). The cells were cycled with an superimposed alternating current of 1 Hz, 100 Hz, or 1 kHz while the rest of the cells were cycled with direct current (only), injected with alternating current (only), or no current at all (calendar aging). No negative effects caused by the alternating current was identified in terms of capacity fade and power fade for the tested lithium-ion cells. A comparison between sinusoidal current-ripple charging and conventional constant-current constant-voltage charging was also carried out. Three lithium-ion cells were cycled (ten times) with different ac currents superimposed during charge. The results were analyzed statistically and no significant improvements in terms of charging time or charging efficiency were observed in any of the charging tests using an superimposed ac current. The injection of alternating currents into batteries for heating purposes has also been studied and a control method for battery heating using an ac current was proposed. The proposed controller is applicable regardless of the LIB’s subsequent impedance nature (capacitive, inductive or resistive). Further, a design process for the generation of magnified alternating currents in dc-dc converters was presented. By matching the switching frequency with the frequency where the LCL filter and the battery resonate, the current flowing in the semiconductors and the switching frequency could be reduced. In a small experimental setup using a single lithium-ion cell, using an LCL-resonant circuit and a full bridges witch arrangement, magnifications of up to 15.7 were reached. This allowed for a loss reduction in the semiconductors of up to 75%, when compared to an equivalent dc-dc converter enabled to produce anon-magnified ac current.  "p"QC 20190517

Abstract

The quest towards increasing the energy density of traction battery technologies has led to the emergence and diversification of battery materials. The lithium sulfur battery (LSB) is in this regard a promising material for batteries due to its specific energy. However, due to its low volumetric energy density, the LSB faces challenges in mobility applications such as electric vehicles but also other transportation modes. To understand the potential environmental implication of LSB batteries, a comparative Life Cycle Assessment (LCA) was performed. For this study, electrodes for both an NMC111 with an anode graphite and a LSB battery cell with a lithium metal foil as anode were manufactured. Data from disassembly experiments performed on a real battery system for a mid-size passenger vehicle were used to build the required life cycle inventory. The energy consumption during the use phase was calculated using a simulative approach. A set of thirteen impact categories was evaluated and characterized with the ReCiPe methodology. The results of the LCA in this study allow identification of the main sources of environmental problems as well as possible strategies to improve the environmental impact of LSB batteries. In this regard, the high requirements of N-Methyl-2-pyrrolidone (NMP) for the processing of the sulfur cathode and the thickness of the lithium foil were identified as the most important drivers. We make recommendations for necessary further research in order to broaden the understanding concerning the potential environmental implication of the implementation of LSB batteries for mobility applications. Document type: Article

Abstract

In the majority of applications using lithium-ion batteries, batteries are exposed to some harmonic content apart from the main charging/discharging current. The understanding of the effects that alternating currents have on batteries requires specific characterization methods and accurate measurement equipment. The lack of commercial battery testers with high alternating current capability simultaneously to the ability of operating at frequencies above 200 Hz, led to the design of the presented experimental setup. Additionally, the experimental setup expands the state-of-the-art of lithium-ion batteries testers by incorporating relevant lithium-ion battery cell characterization routines, namely hybrid pulse power current, incremental capacity analysis and galvanic intermittent titration technique. In this paper the hardware and the measurement capabilities of the experimental setup are presented. Moreover, the measurements errors due to the setup&rsquo s instruments were analysed to ensure lithium-ion batteries cell characterization quality. Finally, this paper presents preliminary results of capacity fade tests where 28 Ah cells were cycled with and without the injection of 21 A alternating at 1 kHz. Up to 300 cycles, no significant fade in cell capacity may be measured, meaning that alternating currents may not be as harmful for lithium-ion batteries as considered so far. Document type: Article

Abstract

The increasing number of vehicles in Colombian cities have resulted in alarmingly low quality of air, further resulting in increasing health issues. One potential solution to this issue could be a shift from ICEVs (internal combustion engine vehicles) to EVs (electric vehicles). However, EVs in Colombia are still very expensive, an issue that needs to be addressed in order for the EV market to increase enough to be able address the issue of low air quality in cities. One way of overcoming these cost barriers could be through implementation of a market for SLB (second life batteries), meaning that a battery retired from usage in EVs would be remanufactured, resold and reused in another application. Through SLB, the owner cost of EVs could potentially be decreased. SLB could also help improve the case for nondispatchable renewable energy sources by providing low cost BESS (battery energy storage solutions). Thus, SLB has the potential to facilitate sustainable transition within both the transport and the energy sector. This thesis aims to assess the potential of SLB in Colombia. This is done through a literature review where the current state of SLB is investigated, several interviews with potential stakeholders for a SLB market in Colombia, and a techno-economic assessment of four potential BESS applications in Colombia. The literature review provides with current knowledge and state of SLB in general. The interviews provide important insight to potential stakeholders’ view on SLB for the specific case of Colombia. The techno-economic assessment includes a sensitivity analysis aiming to provide insights in which factors, such as e.g. battery purchasing price or charging cost, that that gives rise to the largest impact on feasibility of SLB. Findings from the interviews shows a strong collective commitment from the interviewees to working towards cleaner air, resulting in high engagement and collaborative efforts between stakeholders for the SLB case. The main issue highlighted by stakeholders regards technoeconomic uncertainties of SLB. Findings from the techno-economic assessment indicates that SLB is viable for larger applications such as BESS at solar farms, but not for smaller applications such as backup power in residential buildings. However, SLB is not deemed to be a game changer for either application, and there are still many uncertainties regarding both technological and economic aspects that needs to be further investigated. The sensitivity analysis shows that the factors resulting in the highest impact on feasibility of SLB is battery SOH (state of health) at the beginning of SLB usage, and battery and repurposing cost. It will be hard to address both of these factors simultaneously due to a higher SOH would render higher battery prices, and vice versa. The findings from the thesis shows that SLB can facilitate sustainable transition within both the transport and energy sectors but is not to be considered a game changer for these sectors. However, even though SLB’s contribution to sustainable transition is not revolutionary, it is still necessary from a sustainability perspective. Given the environmental footprint of EV batteries and the amount of hazardous waste retired EV batteries will give rise to, circular economy must be pursued. Det ökande antalet fordon i colombianska städer har resulterat i oroväckande låg luftkvalitet, vilket ytterligare resulterat i ökande hälsoproblem. En potentiell lösning på det problemet kan vara en övergång från ICEVs (förbränningsmotorfordon) till EV (elfordon). EVs i Colombia är fortfarande väldigt dyra, en fråga som måste adresseras för att EV-marknaden ska kunna öka tillräckligt för att kunna ge en inverkan på problemet med låg luftkvalitet i städer. Ett sätt att övervinna dessa kostnadshinder skulle kunna vara genom att implementera en marknad för SLB (second life-batterier), vilket innebär att ett batteri som bedömts inte längre uppfylla kraven för användning i EVs, och därmed byts ut, skulle kunna byggas om, säljas vidare och återanvändas i andra applikationer. Genom SLB kan ägarkostnaderna för EVs potentiellt sänkas. SLB skulle också kunna användas för att tillhandahålla billigare BESS (batterilagringslösningar) hos icke-reglerbara förnyelsebara kraftverk, såsom solkraftverk. Således har SLB potentialen att underlätta för hållbara förändringar inom både transportsektorn och energisektorn. Den här uppsatsen ämnar att utvärdera SLBs potential i Colombia. Detta görs genom en litteraturöversikt där det nuvarande tillståndet av SLBs undersöks, flera intervjuer med potentiella intressenter för en SLB-marknad i Colombia, och en tekno-ekonomisk bedömning av fyra potentiella BESS-applikationer i Colombia. Litteraturöversikten samlar aktuell kunskap och status inom SLB i allmänhet. Intervjuerna ger viktig insikt om potentiella intressenters syn på SLB för det specifika fallet i Colombia. Den tekno-ekonomiska bedömningen inkluderar en känslighetsanalys som syftar till att ge insikter i vilka faktorer, som t.ex. batteriets inköpspris eller laddningskostnad, som ger upphov till den största effekten på SLBs genomförbarhet. Resultat från intervjuerna visar ett starkt kollektivt engagemang från de intervjuade att arbeta mot renare luft, vilket resulterar i högt engagemang och samarbete mellan intressenterna. Det största problemet med SLB från intressenternas synpunkt berör tekno-ekonomiska osäkerheter. Resultat från den tekno-ekonomiska bedömningen indikerar att SLB är ekonomiskt försvarbart för större applikationer som BESS vid solkraftverk, men inte för mindre applikationer som t.ex. för reservenergi i bostadshus. SLB anses dock inte vara ett genombrott för användning vid någon av applikationerna, och det finns fortfarande många osäkerheter när det gäller både tekniska och ekonomiska aspekter som måste undersökas ytterligare. Känslighetsanalysen visar att de faktorer som resulterar i den högsta påverkan på genomförbarheten av SLB är batteriets SOH (hälsotillstånd) i början av SLB-användning och kostnaden för batteri och ombyggnad av batterier. Det kommer dock att vara svårt att hantera båda dessa faktorer samtidigt på grund av att högre SOH skulle ge högre batteripriser, och vice versa. Resultaten från uppsatsen visar att SLB kan underlätta för hållbara förändringar inom både transport- och energisektorerna, men att det inte ska betraktas som något fantastiskt genombrott för dessa sektorer. Även fast SLBs bidrag till hållbara förändringar är inte revolutionerande, är det fortfarande en nödvändig faktor ur ett hållbarhetsperspektiv. Med tanke på miljöavtrycket för EV-batterier och mängden av farligt avfall som EV-batterier kommer att ge upphov till då de inte längre är önskvärda, måste cirkulär ekonomi bedrivas i största möjliga mån.

Abstract

The battery is a key component of electric vehicles. To reach the needed voltage and capacity, single Lithium-Ion cells are assembled into modules, then assembled into the pack. Their disassembly, which unlocks both remanufacturing or recycling and which nowadays is made mainly manually, has high electric hazards. Decision tools have not yet been developed to minimize these risks. This work presents a mathematical model to determine the disassembly sequence with the minimal exposure of the operator to hazardous voltages. The model considers the mechanical and electrical architecture of the battery and the tasks needed to reach the desired disassembly level.

Abstract

Formula SAE (FSAE) vehicle systems are very complex. Understanding how subsystems effect the overall vehicle is essential for making design trade-offs. FSAE is a competitive environment. Teams need to have reliable and high performing vehicles to do well in competition. The Virginia Tech (VT) FSAE team has produced a prototype electric powertrain (EPT) vehicle, VTM16e, and will take their first EPT vehicle, VTM17e, to competition in 2017. The use of model-based design (MBD) for an EPT FSAE vehicle is investigated through this thesis. The goal of the research is to build the framework of a full vehicle simulation to take knowledge gained from the VTM16e prototype vehicle, and apply it to the VTM17e competition vehicle. A top-down, bottom-up approach is taken to build a full vehicle model of an EPT FSAE vehicle. A full vehicle simulation is built with subsystems to establish an overall structure and subsystem interactions. Individual subsystems are then focused on for testing and validation. Breaking the vehicle down into subsystems allows the overall model to be incrementally improved. The battery subsystem is focused on in this thesis. Extensive testing is performed on the batteries to characterize their performance. Computer models are generated from empirical data through parameter estimation techniques. Validation of the battery models is performed and the resulting model is incorporated into the overall vehicle model. Performance limits of the vehicle are determined through model exploration, and design modifications to increase the reliability and performance for the VTM17e vehicle are proposed. Master of Science

Abstract

International audience; This paper describes the analysis of recorded data parameters from electrical battery ageing during electric vehicle use. These data allow traditional battery ageing investigation based on resulting capacity fade and resistance raise. The measured variables are examined in order to explain the battery ageing obtained during the experiment. Such study enables us to identify the main ageing factors. Then, detailed statistical dependency explorations present results on battery ageing phenomena. All studies are done on real data collected from Lithium-ion battery; thereby results demonstrate and quantify a relationship between variables and battery ageing mechanisms.

Abstract

Battery thermal management is essential to efficienct and safe operation of Li-ion batteries, particularly in challenging applications such as fast charging. This work proposes a thermal management control framework based on MPC. The novelty of this approach resides in the focus on incorporating disturbance prediction into the control decision. Simulations show that this methodology allows for (1) lower peak and mean battery temperatures during fast charging for a similarly sized battery thermal management system; or (2) battery thermal management system downsizing for similar thermal performance.