No description available.

In order to meet the 2050 targets of an 80% reduction in greenhouse gas emissions, electrification of transport is required. Of the zero-emission technologies relating to automotive applications hydrogen fuel cells, lithium-ion batteries and supercapacitors have received the greatest attention. This thesis presents work on the development and implementation of lithium-ion battery, proton exchange membrane fuel cell and supercapacitor models with the aim of developing the tools and techniques required in assessing their feasibility in automotive applications. Experimental validation of each of these devices is provided with insight given into the physical performance limitations of each device. Analysis is then presented on overall powertrain configurations with a focus on the performance of passive hybridisation as a means of reducing the cost of a vehicle powertrain whilst retaining the advantages of hybridisation. Four main chapters of content relating to work on: lithium-ion batteries, proton exchange membrane fuel cell, supercapacitors and vehicle system level analysis is presented with distinct conclusions and novel work presented in each chapter. Lithium-ion batteries The mathematical framework on the development of a psuedo 2D thermally-coupled electrochemical battery model is presented. This was parameterised using a genetic algorithm based technique against pulsed discharge test data for a 4.8 Ah lithium-polymer cell. This physics-based model was used to develop a means of tracking stoichiometric drift of battery electrodes using a simulated slow rate cyclic voltammetry technique as well as the development of a novel differential thermal voltammetry technique for the extraction of the same information as slow rate cyclic voltammetry but at a much faster rate. The differential voltammetry technique was then used to infer stoichiometric drift in a battery. The lithium-ion battery model was also used to investigate the scale up effects from single cell to large automotive scale packs. It was found that interconnect resistances in highly parallel packs can cause significant load inhomogeneities due to the increased overpotential caused by the interconnects which can be on the same order as the battery impedance. Cells near to the pack load points were found to experience the highest loads, with highly transient load conditions amplifying the effect. Proton exchange membrane fuel cells The mathematical framework for the development of a proton exchange membrane fuel cell model which accounted for transient thermal, mass balance and water management effects and the associated balance-of-plant system was presented. This was validated against experimental data from an in-house developed 9.5 kW 75 cell fuel cell system. Inhomogeneities in the reactant delivery, and thus performance of cells, in large automotive stacks were investigated with a focus on localised flooding leading to failure through pin-hole formation. It was shown that low pressure systems suffer from the increased risk of ooding, with location of the cell relative to the inlet/ outlets of the reactants being a critical parameter. Flooding was then shown to lead to catastrophic failure of the fuel cell stack through pin-hole formation which lead to a cascading potential instability and decay due to the bipolar coupling of the cells and anode side hydrogen cross over, respectively.

The remarkable characteristics of Ti02 are widely used, from everyday life applications (pigments, food/cosmetics additives) to more specialised systems, including photovoltaics and structural composites. Use in polymers is substantial (25% of all Ti02 produced), but most applications and research focus on commercial powders. A new generation of Ti02 nanoparticles has emerged, based on very small, single-crystals, with well-defined morphology and phase. A limited number of papers report the use of this new nanoscale Ti02 in polymer nanocomposites, and indicate improved properties. Although the synthesis of anisotropic nanoparticles (e. g. nanorods) has been well-reported, use in polymer nanocomposites remains largely unreported. This thesis broadly covers three topics: (1) synthesis of Ti02 nanorods using different sol-gel routes in presence of structure directing agents, (2) modification of the nanorod surface chemistry in order to control dispersion and surface properties and (3) fabrication of titania nanorod-polymer composites. Singlecrystal anatase nanorods were produced with variable aspect ratio (3-12), depending on the specific structure directing agent (SDA) used during synthesis. Due to organic functionalisation at the nanorod surface, nanorods could be well dispersed in chloroform. A new procedure, based on the self-cleaning ability of Ti02 under UV, was developed for removal of organics from the nanorod surface, without compromising the nanorod morphology, crystallinity or dispersibility. This powerful tool can be used to change the surface character of the nanorods to generate aqueous TNR dispersions. Stable dispersions were achieved using quaternary ammonium hydroxides to modify the surface electrostatically and sterically. Once dispersed individually, the surface can be further modified by sol-gel chemistry. Composite work involved blending both organic and water-soluble polymers with nanorod dispersions in chloroform and water, respectively, to produce composite films of exceptional optical transparency, even for nanorod loadings up to 30 wt%. The films possess very strong, wavelength-tuneable UV absorbance, which could be used in UV filters and optical limiting. The presence of SDAs or dispersants at the nanorodpolymer interface hinders strong adhesion, as evidenced by marginally lower tensile strength and thermal stability of the nanocomposites. The photo-stability of the nanorod composites is comparable to that of the pure polymer and better than that of composites with commercial equiaxed TiO2 nanoparticles.

Organic solar cells have shown promising results as a cheap alternative to inorganic photovoltaic devices. However, they still exhibit low power conversion efficiencies mainly ascribed to short exciton diffusion lengths as well as poor charge transport properties in organic semiconductors. These problems could be solved by controlling the structure of the active layer, which is made of an electron donor and an electron acceptor. Ideally this active layer would show (i) an increased donor/acceptor interface, (ii) a nanostructure that would reduce the distance an exciton needs to diffuse to reach an interface and dissociate and (iii) continuity of each of the donor and acceptor phases in order to provide a continuous pathway to the electrodes for the free charge carriers. However, the formation of such a structure is challenging. In this thesis, a templating strategy using colloidal crystals - 3D ordered nanosphere arrays - has been developed to create an active layer structure aimed at overcoming these issues. Porous donor films and donor/acceptor thin films were grown. The resulting nanocomposites consist of an interpenetrating interconnected donor/acceptor network with a large donor/acceptor interfacial area. Results obtained for films made of copper (II) phthalocyanine tetrasulfonic acid tetrasodium salt (tsCuPc) as the donor material and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor material are presented. The synthesis of monodisperse colloidal polystyrene spheres, the fabrication of colloidal crystals using these spheres and their characterisation by scanning electron microscopy (SEM) and reflectance spectroscopy are first discussed. Then, the growth of tsCuPc porous films and tsCuPc/PCBM nanocomposites is presented and results of material characterisation carried out by Raman spectroscopy and X-Ray diffraction are shown. SEM and pseudo-tomography experiments performed using focused ion beam microscopy provide information on the film 3D nanostructure and network interconnection and confirm that the targeted nanostructure has been fabricated.

The use of nanostructured electrodes in supercapacitor design have the potential to in- crease both the specific capacitance, via the superionic effect, and the surface electrode interfacial area optimising the energy stored in such a device. When this increase in specific capacitance was first rationalised the electrodes that formed the supercapacitor were assumed to be ideally metallic. Accordingly, interionic interactions between coun- terions are exponentially screened by metallic electrons. This allows a denser packing of counter charge than what one would usually assume possible, which in turn leads to an increased specific capacitance. This was named the superionic effect. Modern nanoporous electrodes are predominantly made of carbon materials and are not ideally metallic. To test the applicability of the superionic state to an electrode constructed of non-ideal ma- terials we study Coulomb interaction of charges in cylindrical and slit pores that allow finite electric field penetration into the pore walls. In both geometries the screening is found to be subtly different than in metallic nanopores, but still strong enough to sup- port realization of the superionic state in such pores. Furthermore, the screening is found to be strong enough to neglect long range interactions between ions packed into these pores. Motivated by this we develop several nearest neighbour lattice models of charge storage for electrodes consisting of many similar cylindrical pores wetted with an ionic liquid. Finally, we present a theoretical study of structural deformation that has been seen to occur in carbon electrodes containing pores that are comparable in size to the size of a charging ion. Our model shows qualitative agreement with the features of the experimentally observed expansion caused by variation of electrode potential.

In response to the challenge of proposed reductions to greenhouse gas emissions outlined in international agreements such as the Kyoto Protocol, countries are considering supplying a significant share of their future energy requirements from renewable energy sources. Wind power, both on and offshore, is the principal commercially available and scaleable renewable energy technology. It is expected to remain the dominant technology in the medium-term future by delivering the majority of the required growth in renewable energy. The unique characteristics of wind power generation raise issues for its integration into the existing power systems. This thesis explores three specific issues, namely, wind generation’s limited capacity value, its remoteness from demand centres and the appropriateness of the regulatory framework governing its integration. The first issue was addressed by examining how the presence of flexible generation sources like hydro power affects the capacity value of wind in an assessment of overall system generation capacity. Wind capacity credit is interpreted from a planning perspective, and also as a component of the economic value of wind. The results illustrate that hydro power can compensate the variability of wind generation thereby augmenting its capacity value. The second issue required the development of a transmission planning methodology to evaluate the sufficiency of transmission network capacity to accommodate wind generation and to manage security of supply. The methodology was used to assess, over the long term investment horizon, the requirement for additional transmission network capacity driven by wind generation. The assessment found that wind generation drives less transmission network capacity than conventional generation and that wind and conventional generation should share the same transmission network capacity. Finally, the thesis looked into the establishment of regulatory framework that could recognise the realistic contribution of wind generation characteristics to transmission security and capture this contribution within the network pricing structure. The current 4 transmission security standards were reviewed to evaluate whether they are capable of recognising the different operation characteristics and output of wind generation. Standards for assessing transmission adequacy were found to lead to under-investment in capacity for importing areas and over-investment in exporting areas. Consequently, a set of ‘contribution factors’ capturing the interaction between wind and system characteristics were derived to augment the standards. At the same time, a modification of the present TNUoS charging mechanism in order to discriminate between generation technology types and to devise cost-reflective pricing regimes is proposed. This is particularly important when transmission investment is driven by reliability, as in exporting areas the cost reflective charges for wind were uniformly found to be lower than the charges for conventional generators.

Microbial Fuel Cells (MFCs) are biological electrical generators or batteries that have shown to be able to energise electronic devices solely from the breakdown of organic matter found in wastewater. The generated power from a single unit is currently insufficient to run standard electronics hence alternative strategies are needed for stepping-up their performance to functional levels. This line of work deals with MFC miniaturisation; their proliferation into large stacks; power improvement by using new electrode components and finally a novel method of energy harvesting that will enhance the operation of a self-sustainable robotic platform. A new-design small-MFC design was developed using 3D printing technology that outperformed a pre-existing MFC of the same volume (6.25 mL) highlighting the importance of reactor configuration and material selection. Furthermore, improvements were made by the use of a cathode electrode that facilitates a higher rate of oxygen reduction reaction (ORR) due to the high surface area carbon nanoparticles coated on the outer layer. Consequently, a 24-MFC stack was built to simulate a small-scale wastewater treatment system. The MFC units were connected in various arrangements, both fluidically as a series of cascades and electrically in-parallel or in-series, for identifying the best possible configuration for organic content reduction and power output. Results suggest that in-parallel connections allow for higher waste removal and the addition of extra units in a cascade is a possible way to ensure that the organic content of the feedstock is always reduced to below the set or permitted levels for environmental discharge. Finally, a new method of fault-proof energy harvesting in stacks was devised and developed to produce a unique energy autonomous energy harvester without any voltage boosting and efficiencies above 90%. This thesis concludes with the transferability of the above findings to a robotic test platform which demonstrates energy autonomous behaviour and highlights the synergy between the bacterial engine and the mechatronics.

This thesis seeks to advance the design tools for electrical generators. It aims to undertake an electrical generator’s design, using the Finite Element method within a defined time frame. The thesis looks at the history of generator design systems and outlines the parameters a designer must predict. These parameters are then duly calculated using various finite element methods. The thesis introduces a Pseudo Rotating Superposition system, which allows large quantities of data to be found from single static finite element simulations. Initially the system is used to predict machine saturation curves, and it is later expanded to predict the transient performance of generators. The full load performance of generators is found using a novel multivariable clustered optimisation routine. An extension using a rotating finite element solver, with pseudo rotating superposition, is then demonstrated. This creates a method which allows voltage harmonics to be quickly, accurately and validly predicted. Finally a study of iron loss is undertaken and using the above method it is shown that iron loss can be validly calculated using the quicker Radial/Tangential reference frame, rather than a slower Major/Minor frame. A collection of 48 manufactured machines are used throughout as a test group for the created methods. Results from design calculations are compared to both factory test results and to the predictions from an existing customised in house design software tool. The methods within this thesis are shown to be over 35% more accurate in the majority of cases. The whole suite of methods created can automatically calculate results for any given machine in less than 1 hour. The computer macros described in this thesis and the comparison with existing design methods and test were all made by the Author.

Recent years have witnessed an enormous interest in developing solar cells by utilising different materials to increase their efficiency. This interest was motivated by the rapid world demand on cheap and clean energy sources, where the main source of world’s power is the fossil fuels. The current photovoltaics technology can not meet the solar power market due to the very low efficiency provided. The philosophy of this thesis is to find an efficient alternative by designing an efficient nanoantenna for receiving the solar radiation and coupling it to an integrated rectifier for AC to DC conversion. This thesis presents the design and optimisation of different types of nanoantennas with a performance comparison to find the optimum solution for this application. The figure of merit in choosing the best design was the captured electric field in the feed gap of the nanoantenna and the area under curve, which is essential in calculating the harvested energy. In addition, this thesis investigates the use of nanoarray instead of single elements. The aims is to increase the captured electric field at the gap of the array where all the elements will contribute in increasing the field in one common gap. Feeding lines will be employed to drive the captured fields from the centre of each single element towards the common gap. Another reason behind using nanoarrays is to reduce the number of rectifiers by using one rectifier per array instead of one rectifier per single element, and hence increase the total efficiency. Futhermore, a simple analysis on dipole nanoantenna using method of moments (MoM) is presented in this thesis. The results obtained from this method is compared with those found from finite element method (FEM) simulations and an acceptable agreement is achieved. To calculate the total conversion efficiency of solar rectennas, it is important to compute the rectification efficiency of the metal/insulator/metal (MIM) diode along with the coupling efficiency between the antenna and the diode. To this end, quantum mechanics was used to calculate the characteristics of the MIM diode. The results show that bowtie nanoantennas are the best candidate for this application in either the single and array form since they have wider bandwidth and larger area under curve. Additionally, the analysis using MoM gives the designer better understanding on how the system works and exhibits lower complexity and reduced computational requirements.

This research has assessed the environmental, economic and social sustainability of electricity generation in Turkey to contribute towards a better understanding of the overall sustainability impacts of the electricity sector and of possible future scenarios. The assessment of environmental sustainability has been carried out using life cycle assessment; capital, annualised and levelised costs have been used for the economic sustainability and various social indicators along the life cycle of the technologies have been estimated for the social assessment. Multi-criteria decision analysis has been carried out to integrate the three dimensions of sustainability for current electricity generation and future scenarios as well as to help with decision-making. The sustainability assessment of current electricity generation considers all the options present in the Turkish electricity mix: coal (lignite, hard coal), gas, hydro (large and small scale reservoir, run-of-river), onshore wind and geothermal. Each technology has been assessed and compared using 20 sustainability indicators, addressing 11 environmental, three economic and six social aspects. The findings suggest that trade-offs are needed, as each technology is better for some sustainability indicators but worse for others. For example, coal has the highest environmental impacts, except for ozone depletion for which gas is the worst option; gas is the cheapest in terms of capital costs but it provides the lowest direct employment and has the highest levelised costs. Geothermal is the best option for six environmental impacts but has the highest capital cost. Large reservoir has the lowest depletion of elements and fossil resources as well as acidification. Moreover, large reservoir is the cheapest option in terms of levelised costs and the best option for worker injuries and fatalities but provides the lowest life cycle employment. The results for the current electricity sector show that electricity generation in Turkey is responsible for around 111 million tonnes of CO2 eq. emissions annually. Total capital costs of the current electricity sector of Turkey are estimated at US$69 billion, with hydropower, coal and gas plants contributing together to 96%. Total annualised costs are equal to US$26 billion per year, of which fuel costs contribute nearly 64%. The levelised costs for the Turkish electricity generation are estimated at 123 US$/MWh. The social assessment results indicate that the electricity sector in Turkey provided 57,000 jobs. A total of 3670 worker injuries and 15 fatalities are also estimated related to the electricity sector annually. A range of future electricity generation scenarios has been developed for the year 2050 considering different mixes, carbon emission targets and generation options, including fossil-fuel technologies with and without carbon capture and storage, nuclear and a range of renewable options. Overall, business-as-usual scenarios are the least sustainable options to meet the country’s electricity demand in the future. Despite the fact that these scenarios have the lowest costs, their poor environmental and social performances make them the worst options. Increasing the contribution from renewables and nuclear power translates to a better sustainability performance. The scenario with the highest penetration of these options (C-3) is found to be the most sustainable option in this work. Although the most renewable intensive scenario (C-4) scores as the second best option overall, it performs poorly for the economic categories. The trade-offs between the different sustainability indicators highlighted by the results of this research illustrate that assessments of a range of environmental, economic and social impacts from different electricity technologies and scenarios should be considered when planning sustainability strategies for the electricity sector.