Cycle life of lithium ion batteries after flash cryogenic freezing

Growing global sales of electric vehicles (EVs) are raising concerns about the reverse logistics challenge of transporting damaged, defective and waste lithium ion battery (LIB) packs. The European Union Battery Directive stipulates that 50% of LIBs must be recycled and EV manufacturers are responsible for collection, treatment and recycling. The International Carriage of Dangerous Goods by Road requirement to transport damaged or defective LIB packs in approved explosion proof steel containers imposes expensive certification. Further, the physical weight and volume of LIB packaging increases transport costs of damaged or defective packs as part of a complete recycling or repurposing strategy. Cryogenic flash freezing (CFF) removes the possibility of thermal runaway in LIBs even in extreme abuse conditions. Meaning damaged or defective LIBs may be transported safely whilst cryogenically frozen. Herein, LIBs are cycled until 20% capacity fade to establish that CFF does not affect electrical performance (energy capacity and impedance) during ageing. This is demonstrated on two different cell chemistries and form factors. The potential to remanufacture or reuse cells/modules subjected to CFF supports circular economy principles through extending useful life and reducing raw material usage. Thereby improving the environmental sustainability of transitioning from internal combustion engines to EVs

Accelerated internal resistance measurements of lithium-ion cells to support future end-of-life strategies for electric vehicles

Industrial and academic communities have embarked on investigating the sustainability of vehicles that contain embedded electrochemical energy storage systems. Circular economy strategies for electric vehicle (EV) or hybrid electric vehicle (HEV) battery systems are underpinned by implicit assumptions about the state of health (SOH) of the battery. The internal resistance of battery systems is the essential property for determining available power, energy efficiency, and heat generation. Consequently, precise measurement is crucial to estimate the SOH; however, the international standards and best practice guides that exist to define the measurements include long preconditioning and rest times that make the test duration prohibitive. The aim of this research is to critically evaluate whether test duration times for internal resistance measurements can be reduced to values that may facilitate further end-of-life (EOL) options. Results reveal a newly developed technique using pulse-multisines is two to four times faster to perform when compared to the standard protocol whilst maintaining accuracy for battery electric vehicle (BEV) and HEV cells, respectively. This novel method allows different stakeholders to rank the relative importance of test accuracy verses experimental test time when categorising used Li-ion cells for different EOL applications. View Full-Tex

Certifying a synthetic environment for CAV validation and verification

A key element supporting the introduction of Level 4/5 Connected and Autonomous Vehicles (CAVs) will be the ability to independently certify that such systems are safe, reliable and secure. Not only must system developers and service providers have methodologies for demonstrating that consumer products are safe, but the public must also have confidence in these vehicles and systems. While testing and development of CAVs has begun across many countries in Europe and globally, a certification approach is required to underpin widespread adoption of CAVs. Among the options for delivering certification cost-effectively and faster, is the use of synthetic environments, including CAV simulators. Conducting validation of vehicles in simulators enables the creation of an almost limitless number of testing scenarios that are flexible, repeatable and safe. Compared to real-world testing, simulated validation using simulators will enable vehicles to be tested rapidly and against a challenging set of conditions that would be difficult and costly to replicate in real life. This paper will examine the conditions required for creating such a testing environment, as well as prerequisites for developing a methodology for a simulator to be independently certified as an appropriate means of evaluating the safety of CAVs. This paper presents the identification and analysis of twelve existing standards for CAV testing as a pre-requisite for creating a simulator certification methodology

Design and analysis of adaptively modulated optical orthogonal frequency division multiple access multiband passive optical networks

The aim of this thesis is to explore innovative technical solutions of utilising Optical Orthogonal Frequency Division Multiplexing (OOFDM) in intensity modulation and direct detection (IMDD) based future access networks to provide multi-service capability with a minimum 1 Gb/s per user. This thesis extensively investigates and analyses the feasibility and performance of adaptively modulated optical orthogonal frequency division multiplexing multiple access passive optical networks (AMOOFDMA PONs) upstream transmission systems by numerically simulating AMOOFDMA PONs using experimentally determined parameters. OOFDM transceivers incorporating reflective semiconductor optical amplifiers (RSOAs) and distributed feedback (DFB) lasers are utilised in the transceivers and intensity modulation and direct detection (IMDD) transmission systems are also employed to achieve a low complexity, high speed and large bandwidth PON as a solution for next generation access networks. Numerical simulations has also being undertaken to improve overall AMOOFDMA PON performance and power budget by incorporating optical band-pass filters (OBPFs) at the output of optical network units (ONUs). A major challenge of making PONs spectrally efficient has been addressed in this thesis by investigating the AMOOFDMA PON with ONUs on a single upstream wavelength. The performance of the single upstream wavelength AMOOFDMA PON is compared to the multiple wavelength AMOOFDMA PON. Another major challenge in AMOOFDMA PONs namely improving system capacity has also been addressed by implementing multiband transmission in an AMOOFDMA PON. Results show that for a multiple upstream OOFDMA IMDD PON system over 25 km single mode fibre (SMF) can achieve an aggregated data rate of 11.25 Gb/s and the minimum wavelength spacing between ONUs are independent of the number of ONUs. Results also show that a single upstream wavelength AMOOFDMA IMDD PON with multiband incorporated at the ONUs can achieve a aggregated line rate of 21.25 Gb/s over 25 km SMF

Comparison of growth performance of Nile tilapia (Oreochromis niloticus) fingerlings fed different inclusion levels of black soldier fly (Hermetia illucens) pre-pupae meal diets and its effect on the physical characteristics of the feed

Thesis (MSc)--Stellenbosch University, 2018.ENGLISH ABSTRACT: The nutritional composition of fish and the health benefit associated with the consumption thereof makes it a valuable food and feed source for both humans and animals. However, with the increasing size of the world’s population and the demand for fish and other fishery products, an increased amount of pressure is being placed on wild catch fisheries. As a result, the latter are becoming stagnant, or declining, in many regions around the world. Aquaculture has, to some extent, been able to relieve the pressure placed on wild catch fisheries. Yet, a major downfall is that it still relies on wild caught fish to be used as a protein source for many aquaculture fish species. Various alternative protein sources has been investigated for use in aquaculture feeds to replace conventional and unsustainable protein sources, such as fishmeal. Among the various alternative animal protein sources, the use of insects are gaining popularity as a promising and sustainable solution. Insects are a natural food source for many fish species and have relatively balanced amino- and fatty acid profiles, while it is also highly effective in integrated waste management (IWM) systems. The objective of the study was to investigate the effects of different inclusion levels of black soldier fly (BSF) (Hermetia illucens) pre-pupae meal in the diets of Nile tilapia (Oreochromis niloticus) fingerlings (n = 630) on the growth performance, fillet yield and feed quality. Six diets were compared: BSF0 (0 %; the control diet), BSF5 (5 %), BSF10 (10 %), BSF15.6 (15.6 %), BSF20 (20 %) and BSF25 (25 %; the summit diet). There were no significant differences in the final average body weight, feed intake, average daily gain (ADG) and conditioning factor (CF) between the different treatments. There was no significant difference for the feed conversion ratio (FCR) of BSF0 (1.35) and BSF5 (1.50), however FCR was lower (P≤0.05) for BSF10 (1.63) relative to BSF0, and worsened with increasing inclusion levels. The FCR was not significantly different between BSF10 and BSF15.6 (1.79), but BSF10 did have a significantly lower FCR than BSF20 (1.97) and BSF25 (1.91), whilst the latter two did not differ (P>0.05) from each other. During the preparation of the experimental feed, the inclusion of a binder was required in BSF20 and BSF25 in order to prevent complete crumbling with the extrusion process. The use of a binder changed the hardness and floating characteristics of diets BSF20 and BSF25, which may have had an influence on differences in FCR. There was no significant difference observed for specific growth rate (SGR) between BSF0 (2.05), BSF5 (1.91) and BSF10 (1.73), or between diets BSF10 through to BSF25 (1.62). Treatment BSF10 was thus not significantly different from any treatment diets. Treatment BSF0 was the only diet with a SGR significantly higher than BSF15 (1.68), BSF20 (1.60) and BSF25 (1.62). The protein efficiency ratio (PER) of BSF0 (2.02) and BSF5 (1.82) did not differ significantly from each other. The PER of BSF0 differed significantly from BSF10 (1.68), BSF15.6 (1.55), BSF20 (1.40) and BSF25 (1.43). The difference could be linked to the increasing lipid content of the feeds which is known to adverse effect the digestibility of the feeds. The carcass yield was not significantly different between any of the treatments, where all the yields (percentage body weight) ranged from 81.63 g (BSF20) to 83.5 g (BSF0). The fillet yield did show some variation, but the results are not very accurate (R2=0.094) due to the methodology of filleting. Furthermore, no significant differences were observed for the proximate composition (moisture, crude protein, lipid and ash) of the fillets. The inclusion level of the BSF pre-pupae meal showed a statistically significant influence on the unit density, sinking velocity, water uptake and leaching rate of the pellets. However, the effect of binder used in BSF20 and BSF25 may have had an influence on these results. All unit densities differed significantly from each other, increasing with higher BSF pre-pupae inclusion levels. The control (BSF0) and BSF5 had a sinking velocity of 0 (floating pellets), while the feed only started sinking with inclusion levels of 10 % BSF pre-pupae meal (BSF10, 4.44 cm/s). Faster sinking velocities were observed with increasing inclusion levels of BSF pre-pupae meal. Water uptake was generally higher in BSF0 compared to other treatments for all the timeframes, except for the shortest submersion time (5 min), where BSF15.6 (288.60 %) had a significantly higher water uptake than all the other diets. Due to the disintegration of the pellets over time, the water uptake was expressed as a percentage of feed remaining rather than initial quantity used. The feed remaining was used to determine disintegration rate. Factors such as lipid content and interactions between ingredients may have indirectly influenced feed quality parameters. The study did not generate enough evidence to verify the claim that BSF pre-pupae meal can be used as a viable alternative protein source to conventional sources in Nile tilapia feeds, due to variability in water stability and inclusion of a binder that were not accounted for. However, it was found that inclusion levels of up to 25 % can be used without any effect on the body composition, and up to 5 % without compromising the growth parameters. Therefore, it is recommended to use an inclusion level of 5 % BSF pre-pupae meal to maintain the growth performance. For future studies, it is suggested to use defatted BSF pre-pupae meal for potentially higher inclusion levels of the meal for comparative growth results relative to conventional protein sources – as the higher lipid content may adversely affect the binding ability and the feed quality.AFRIKAANSE OPSOMMING: Die voedingswaarde van vis en die gesondheidsvoordele wat met die verbruik daarvan gepaard gaan, maak dit 'n waardevolle voedsel- en voedingsbron vir beide mens en dier. Alhoewel, met die toename in die wêreld se bevolking en die vraag na vis en ander visseryprodukte word daar toenemend druk op wildvang vissery geplaas. Gevolglik stagneer of verminder wildvang vissery in baie streke regoor die wêreld. Akwakultuur het tot 'n mate die druk op wildvang vissery ligter gemaak. 'n Groot tekortkoming is egter dat akwakultuur nogsteeds staatmaak op die gebruik van wilde vis as 'n proteïenbron vir baie akwakultuurvisse. Navorsing word voordurend gedoen op die gebruik van verskeie alternatiewe proteïenbronne in akwakultuurvoere om konvensionele en nie-volhoubare proteïenbronne, soos vismeel, te vervang. Die gebruik van insekte as 'n belowende en volhoubare oplossing raak egter meer gewild in vergelyking met verskeie ander alternatiewe dierlike proteïenbronne. Insekte is uiteraard 'n natuurlike voedselbron vir baie visspesies en het 'n gebalanseerde amino- en vetsuurprofiel, terwyl dit ook hoogs effektief is in geïntegreerde afvalbestuurstelsels. Die doel van die studie was om die effek van verskillende Swart Soldaat Vlieg (SSV) (Hermetia illucens) pre-papie meel insluitingsvlakke in die diëte van Nyl tilapia (Oreochromis niloticus) vingervissies (n = 630) op die groeiprestasie, filet opbrengs en voergehalte te ondersoek. Ses diëte is met mekaar vergelyk: SSV0 (0 %; die kontrole dieet), SSV5 (5 %), SSV10 (10 %), SSV15.6 (15.6 %), SSV20 (20 %) en SSV25 (25 %; die toppunt dieet). Daar was geen betekenisvolle verskille in die finale gemiddelde liggaamsgewig, voerinname, gemiddelde daaglikse toename en kondisioneringsfaktor tussen die verskillende behandelings nie. Daar was geen beduidende verskil vir die voer omskakeling verhouding (VOV) van SSV0 (1.35) en SSV5 (1.50) nie, maar die VOV was laer (P≤0.05) vir SSV10 (1.63) relatief tot SSV0, en het versleg met die toename in insluitingsvlak. Die VOV het nie betekenisvol tussen SSV10 en SSV15.6 (1.79) verskil nie, maar SSV10 het 'n beduidende laer VOV as SSV20 (1.97) en SSV25 (1.91) gehad, terwyl die laaste twee nie van mekaar verskil (P>0.05) het nie. Tydens die voorbereiding van die eksperimentele voer is die insluiting van 'n bindmiddel benodig in BSF20 en BSF25 om te verhoed dat die ekstrusieproses volledig verkrummel. Die gebruik van bindmiddel het egter die hardheid en drywende eienskappe van diëte BSF20 en BSF25 verander, wat die verskille van FCR beïnvloed het. Daar was geen betekenisvolle verskille waargeneem vir die spesifieke groeikoers tussen SSV0 (2.05), SSV5 (1.91) en SSV10 (173) nie, of tussen diëte SSV10 tot SSV25 (1.62) nie. Behandeling SSV10 was dus nie betekenisvol anders as enige ander behandelingsdieet nie. SSV0 was die engiste dieet wat ‘n spesifieke groeikoers beduidend hoër as SSV15 (1.68), SSV20 (1.60) en SSV25 (1.62) gehad het. Die proteïen doeltreffendheid verhouding van SSV0 (2.02) en SSV5 (1.82) het nie betekenisvol van mekaar verskil nie. Die proteïen doeltreffendheid verhouding van SSV0 het betekenisvol van SSV10 (1.68), SSV15.6 (1.55), SSV20 (1.40) en SSV25 (1.43) verskil. Hierdie verskil kan egter aan die toenemende lipiedinhoud van die voer gekoppel word, aangesien dit bekend is dat die lipiedinhoud die verteerbaarheid van die voer nadelig kan beïnvloed. Die karkasopbrengs het nie betekenisvol tussen enige van die behandelings verskil nie, waar al die opbrengste (persentasie liggaamsgewig) van 81.63 g (SSV20) tot 83.5 g (SSV0) gewissel het. Die opbrengs van die filet het 'n mate van variasie getoon, maar die resultate is nie baie akkuraat nie (R2=0.094), moontlik as gevolg van metodologie van filetering. Daar is verder geen betekenisvolle verskille vir die proksimale samestelling (vog, ruwe proteïen, lipied en as) waargeneem nie. Die insluitingsvlakke van SSV pre-papie meel het 'n statistiese betekenisvolle invloed op die eenheidsdigtheid, sinksnelheid, wateropname en uitlogsyfer van die voer gehad. Die effek van die bindmiddel wat in BSF20 en BSF25 gebruik word, kon egter die resultate beïnvloed het. Al die eenheidsdigthede het betekenisvol van mekaar verskil, waar digtheid met elke hoër insluitingsvlak van SSV pre-papie toegeneem het. Die kontrole (SSV0) en SSV5 het ‘n sinksnelheid van 0 (drywende korrels) gehad. Die voer het egter eers begin sink met insluitingsvlakke vanaf 10 % SSV pre-papie meel (SSV10, 4.44 cm/s). Vinniger sinkingsnelhede was waargeneem met toenemende insluiting vlakke. Wateropname was oor die algemeen hoër in SSV0 in vergelyking met ander behandelings van al die tye, behalwe vir die kortste onderdompelingstyd (5 min), waar SSV15.6 (288.60 %) ‘n betekenisvolle hoër wateropname as al die ander diëte gehad het. As gevolg van die disintegrasie van korrels met die verloop van tyd, was die wateropname uitgedruk as 'n persentasie van die oorblywende voer eerder as die aanvanklike hoeveelheid wat gebruik is. Die oorblywende voer was gebruik om die desintegrasietempo te bepaal. Faktore soos die lipiedinhoud en interaksies tussen bestanddele kon indirek die voergehalteparameters beïnvloed het. Die studie het nie genoeg bewyse gelewer om die eis te verifieer dat SSV pre-papie meel as 'n lewensvatbare alternatiewe proteïenbron gebruik kan word vir konvensionele bronne in Nyl tilapia voer nie,as gevolg van veranderlikheid in waterstabiliteit en insluiting van 'n bindmiddel wat nie in ag geneem is nie. Daar is egter gevind dat insluitingsvlakke van tot 25% gebruik kan word sonder enige effek op die liggaamsamestelling en tot 5 % sonder om die groeiparameters in gedrang te bring. Daarom kan die aanbeveling gemaak word om 'n insluiting vlak van 5 % SSV pre-papie meel te gebruik om die groeiprestasie te handhaaf. Vir toekomstige studies word dit aanbeveel om ontvette SSV pre-papie meel te gebruik vir moontlike hoër insluitingvlakke van die meel vir vergelykbare groeiverslae relatief tot konvensionele proteïenbronne – aangesien die hoër lipiedinhoud die bindingsvermoë en gehalte van die voer nadelig kan beïnvloed

The experimental evaluation of lithium ion batteries after flash cryogenic freezing

The reverse logistic challenge of transporting waste automotive lithium ion battery (LIB) packs is an escalating concern as the world-wide sale of electric vehicles (EVs) continues to rise. Under the European Union (EU) Battery Directive, EV manufacturers are classified as battery producers and are responsible for the collection, treatment and recycling of waste or damaged vehicle batteries. The European agreement concerning the International Carriage of Dangerous Goods by Road (ADR) stipulates that damaged or defective LIB packs must be transported in approved explosion proof steel containers. This necessitates costly testing in order to meet ADR requirements. Furthermore, the extra size and weight of this packaging adds further prohibitive expense to the transportation of damaged or defective LIB. In this study, cryogenically frozen cells are shown to be unable to release any energy even in extreme abuse conditions. This is demonstrated on two different cell chemistries and form factors. Experiments have shown that the possibility of thermal runaway is completely removed and therefore it is argued that LIBs may be transported safely whilst cryogenically frozen. Moreover, flash freezing is shown to have little effect on the electrical performance (energy capacity and impedance) even after five repetitive cryogenic cycles. Thus, facilitating the potential reuse and remanufacture of individual LIB cells from a complete damaged pack, prolonging the useful life, reducing the consumption of raw materials, and improving environmental sustainability of EV introduction

Investigation of pre-conditioning strategies that enable state-of-health improvement for a remanufactured Li-ion battery in automotive circular economy applications

Implementing and optimizing the sustainability of vehicles that contain embedded electrochemical energy storage have recently been afforded more attention in research due to legislative requirements and cited benefits from circular economy activities. The State-of-Health (SoH) for a traction battery system that prematurely failed can be restored through circular economy activities such as remanufacturing. To enable these circular economy activities, the ability to introduce a new or graded cell or module into a series string to replace the weakest cell or module in a battery module or pack is vital. However, very little is understood about the optimal strategy that will lead to maximizing the lifetime of the most aged cell or module in the new string and predict the expected lifetime of the repaired or remanufactured battery system. The aim of this research is to assess whether aged lithium-ion cells in series, with some of the aged cells replaced with new cells, have an optimized pre-conditioning strategy to ensure the weakest cell’s life is prolonged. Three modules with six 18650 cells in series have been evaluated to determine the optimal replacement strategy for an energy storage unit albeit cell or module in series for in-use life extension activities. Results highlight that it is possible to significantly reduce the degradation of the weakest cell in a repaired string of series cells. Reduction of circa 4% in aging of the weakest cells is reached with bottom pre-conditioning, while an increase in degradation of the new cell is only 2.5% relative to the worst case scenario. Additionally, the authors show that the energy capacity of the string pre-conditioned at the top reduces the most during cycling of the three strings. Based on these experimental results, an optimal pre-conditioning strategy for circular economy activities for electric vehicle traction battery systems is proposed

Realistic LiDAR with noise model for real-time testing of automated vehicles in a virtual environment final

The global Connected and Autonomous Mobility industry is growing at a rapid pace. To ensure the successful adoption of connected automated mobility solutions, their safety, reliability and hence the public acceptance are paramount. It is widely known that in order to demonstrate that L3+ automated systems are safer with respect to human drivers, upwards of several millions of miles need to be driven. The only way to efficiently achieve this amount of tests in a timely manner is by using simulations and high fidelity virtual environments. Two key components of being able to test an automated system in a synthetic environment are validated sensor models and noise models for each sensor technology. In fact, the sensors are the element feeding information into the system in order to enable it to safely plan the trajectory and navigate. In this paper, we propose an innovative real-time LiDAR sensor model based on beam propagation and a probabilistic rain model, taking into account raindrop distribution and size. The model can seamlessly run in real-time, synchronised with the visual rendering, in immersive driving simulators, such as the WMG 3xD simulator. The models are developed using Unreal engine, therefore demonstrating that gaming technology can be merged with the Automated Vehicles (AVs) simulation toolchain for the creation and visualization of high fidelity scenarios and for AV accurate testing. This work can be extended to add more sensors and more noise factors or cyberattacks in real-time simulations

Testing of commercial electric vehicle battery modules for circular economy application

Increasingly international academic and industrial communities desire to better understand, implement and improve the sustainability of vehicles that contain embedded electrochemical energy storage. Underpinning a number of studies that evaluate different circular economy strategies for the electric vehicle (EV) battery system are implicit assumptions about the retained capacity or State-of-Health (SoH) of the battery. International standards and best-practice guides exist that address the performance evaluation of both EV and HEV battery systems. However, a common theme in performance testing is that the test duration can be excessive and last for a number of hours. The aim of this research is to assess whether energy capacity and internal resistance measurements of Li-ion based modules can be optimized, reducing the test duration to a value that may facilitate further End-of-Life (EoL) options. Experimental results for a Porsche Panamera Hybrid module and a Tesla Model S P85 module that highlight a reduction of the duration of a commercial battery module characterization test by circa 70%. This reduction is accompanied by levels of measurement accuracy for retained energy capacity in the order of 1% for module test temperatures equal to 25°C. Improvement of 85% is achieved for resistance testing while still retaining levels of measurement accuracy in the order of 2% for module temperatures equal to 25°C. Based on these experimental results, a quick characterization test sequence is proposed and within a robust system test framework would allow different organizations to prioritize the relative importance of test accuracy versus experimental test time when grading used Li-ion modules