This study explores whether the requirements of the Energy Storage System (ESS) in electrified automotive powertrains can be more effectively met by Hybridised Energy Storage Systems (HESS) than by batteries alone, and aims to quantify the benefits. Given their complementary characteristics, this study focuses upon combinations of Lithium-ion Batteries (LIBs) and Supercapacitors (SCs). In order to develop a comprehensive understanding of HESS operation and capabilities, a literature review is conducted and experiments and modelling tools are designed to address knowledge gaps. The electrochemical and thermal performance of SCs and LIBs is examined in detail, and the amassed knowledge is used to generate modelling tools. Following a review of HESS topologies, a model of a passive HESS is developed through combination of the SC and LIB models. The developed models are validated using experimental data for automotive drive-cycles. The degradation of a HESS is assessed using experimental analysis. The main findings of this study are split into three chapters: Supercapacitors This chapter explores the electrochemical and thermal characteristics of SCs and demonstrates how they vary with the operating conditions relevant for latter comparison with LIBs. Particular focus has been placed upon the attributes of SCs which affect their performance in a HESS, namely capacity and resistance variation with operating conditions, heat generation during operation, low temperature performance and performance degradation following extended use. An understanding of these factors is used to develop a model capable of predicting SC performance over an array of operating conditions, enabling latter combination with a lithium ion battery model to predict HESS behaviour in both cell-level and high voltage systems. An emphasis was placed upon the development of a high fidelity thermal model as the academic literature provided a limited understanding of thermal management and the effect of thermal gradients within SCs. The development of a high fidelity thermal model led to novel findings with respect to heat generation with SCs during operation. Lithium-ion Batteries An understanding of the performance and characteristics of LIBs relative to SCs is necessary for the development of an understanding of a HESS. This chapter briefly explains why LIBs are the dominant form of energy storage in electrified passenger vehicles, and subsequently discusses how LIBs function. The relationship between each component within the LIB and its performance is reviewed, and common internal design trade-offs such as material selection and thicknesses are explained. LIB performance variation as a function of operating conditions is subsequently presented and described analytically. This knowledge is used to generate a model to predict battery performance over a range of operating conditions, with a particular focus placed upon performance over an automotive drive-cycle. The developed model enables estimation of internal temperature during use. The causes of long term performance degradation are examined and a summary of degradation methods and their causes is provided. Hybridised Energy Storage Systems This chapter investigates whether it is possible to combine supercapacitors suitable for a micro hybrid electric vehicle (mHEV) with high-energy batteries suitable for use in a battery electric vehicle (BEV) to create a Hybridised Energy Storage System (HESS) suitable for use in a hybrid electric vehicle (HEV). A passive HESS topology is investigated due to its low cost and complexity and therefore high reliability. A low cost HESS is found to be capable of meeting the electrical demands of a HEV during a drive cycle. The operating principles of HESSs are discussed and factors limiting system performance are explored. The performance of the HESS is found to be significantly less temperature dependent than battery-only systems, however the heat generated suggests a requirement for thermal management. A correctly sized HESS is shown to generate less heat than a specialised HPB ESS. The HESS degrades at a similar rate to a specialised HPB. In a HESS, battery resistance rises faster than supercapacitor resistance; as a result, the supercapacitor provides a greater current contribution over time, therefore the energy throughput, temperature rise and rate of degradation of the batteries is reduced.

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The use of tilting bodies on railway vehicles is becoming increasingly widespread: a number of well-established services using tilt technology already exist around the world, and will appear again in the UK over the next year or so. The motivation for tilting railway vehicles is that they give a cost-effective means of achieving a substantial reduction in journey time by increasing the vehicle speed during curves. Early tilt controller designs were based upon local vehicle measurements, however at that time this approach did not prove very successful. Nowadays most European manufacturers use the so called ‘precedence' control scheme, utilising measurements from precedent vehicles to achieve ‘precedence' information. However, achieving a satisfactory local tilt control strategy is still an important research target because of the system simplifications and more straightforward failure detection. The thesis describes a comprehensive study of tilt control, and its aim is to employ advanced control techniques - based upon practical sensors - with the particular objective of identifying effective strategies which can be applied to each vehicle independently, i.e. without using precedence control. The sensors employed for control design are in particular mounted on the vehicle passenger coach. Most of the work has been undertaken using Matlab, and this has included a proper assessment of the ride quality issues.

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Roads constructed on expansive clays may be adversely affected by the behaviour of the clay. Expansive clays suffer volume change due to changes in moisture content which causes heaving, cracking and the break up of the road pavement. Stabilisation of these types of soil is necessary to suppress swelling and increase the strength of the soil and thus partially decrease the thickness of road pavement layers. The use of by-product materials for stabilisation has environmental and economic benefits. Ground granulated blastfurnace slag (GGBS), a by-product material in Egypt, and lime are used in the current work to stabilise samples of a clay soil similar to a typical Egyptian clay soil. This test soil comprises 80% River Aire soil and 20% calcium montmorillonite. The main objectives of this research were to investigate the effect of GGBS, with and without lime, on the engineering behaviour (plasticity characteristics, compaction, unconfined compressive strength (UCS) and swelling potential) of the test soil and to identify the reaction products of the stabilised materials to determine the mechanisms by which changes in engineering properties are obtained. In order to achieve these objectives, extensive laboratory investigations were carried out. Various mixes (up to 10% GGBS by dry weight of the test soil and up to 30% replacement by hydrated lime) were prepared and cured under two representative conditions {20°C with 90-100% relative humidity (CCI) and 35° C with 50-60% relative humidity (CC2)} for up to 12 months. Compaction and plasticity were measured soon after mixing, the swelling potential and UCS were measured after longer curing periods. Four analytical techniques {X ray diffraction, scanning electron microscopy, differential thermal analysis and nuclear magnetic resonance (NMR)} were used to identify the reaction products of the clay fraction of the test soil mixed with various amount of GGBS and lime. This pure clay test soil was used to ease identification of the reaction products. The investigations showed that generally the engineering properties (UCS, swelling, plasticity) improved with the addition of GGBS and with increasing curing period and temperature. The addition of lime resulted in a dramatic improvement within the test ranges covered in the programme. The maximum dry density, MDD, decreased and the optimum moisture content, OMC, increased with increasing GGBS and lime content. The major changes in the UCS and swelling behaviour are due to the formation of new cementitious materials. The analytical investigation confirmed two major reactions when GGBS and lime were added to the pure clay soil, hydration of GGBS activated by lime to produce calcium aluminosilicate hydrate gel (C-A-S-H) and hydrotalcite type phase, and the clay-lime reaction to produce calcium silicate hydrate (C-S-H), (C-A-H) and (C-A-S-H). The NMR test results revealed that the aluminosilicate chain length (EL), the aluminium: silicate (Al/Si) ratio and the amount of Si in the formed C-S-H significantly increased with an increase in the curing temperature and period, which indicates a more stable and well crystalline C-S-H. The results indicate that the use of GGBS alone, or preferably with lime, could have a significant effect on the behaviour of potentially swelling clays. Recommendations for further studies include a study of the effect of cyclic loading on the test soil. Also, site trials should be carried out to assess the suitability of using these materials in the field.