The performance of Solid Oxide Fuel Cell (SOFC) electrodes is determined both by their porous microstructure and the intrinsic properties of their component materials. This thesis details the development of two characterisation tools for analysis of mass and charge transport processes in SOFC electrode materials. Firstly, a new approach to isotopic exchange is described, which allows the oxygen self-diffusion (D*) and effective surface exchange (k*) to be measured in ambient atmospheres. This is significant as many similar studies in the literature are limited to investigations in pure, dry oxygen, or other proxy environments, which are not representative of realistic SOFC operating conditions. A finite difference simulation was created to generate profiles that were used to extract material parameters from this 'back-exchange' data. The technique was then validated by comparison of the results from two experiments in pure, dry oxygen (both single step and back-exchange), which demonstrated good agreement with values of D* and k* in the literature, for the common SOFC cathode material La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428). A third experiment found the surface exchange coefficient to increase by a factor of 5 when exchanged under ambient conditions compared with pure, dry oxygen. Secondly, following an introduction to the tortuosity factor, X-ray tomography was used to 3D image micro-tubular (MT) samples ( c. 1 mm diameter) at three key length-scales. A zirconia based MT-Solid Oxide Electrolyser Cell (SOEC) was imaged at the whole cell level, both before and after 300 hours operation at 750°C . Current collector contact was found to be poor even before operation, but afterwards the paste was seen to agglomerate into metallic silver and no longer span the gap to the current collector wire, which further degraded contact. A ceria based MT-SOFC with a hierarchical microstructure was then imaged at both the micro- and nanoscale. The geometry data was used to determine that the tortuosity factor of this radial system was significantly higher when measured at either length-scale in isolation, than when considered together in a multi length-scale model.

The electricity supply industry has been facing significant challenges in terms of meeting the projected demand for energy, environmental issues, security, reliability and integration of renewable energy. Currently, most of the power grids are based on many decades old vertical hierarchical infrastructures where the electric power flows in one direction from the power generators to the consumer side and the grid monitoring information is handled only at the operation side. It is generally believed that a fundamental evolution in electric power generation and supply system is required to make the grids more reliable, secure and efficient. This is generally recognised as the development of smart grids. Demand management is the key to the operational efficiency and reliability of smart grids. Facilitated by the two-way information flow and various optimization mechanisms, operators benefit from real time dynamic load monitoring and control while consumers benefit from optimised use of energy. In this thesis, various mathematical optimization techniques and game theoretic frameworks have been proposed for demand management in order to achieve efficient home energy consumption scheduling and optimal electric vehicle (EV) charging. A consumption scheduling technique is proposed to minimise the peak consumption load. The proposed technique is able to schedule the optimal operation time for appliances according to the power consumption patterns of the individual appliances. A game theoretic consumption optimization framework is proposed to manage the scheduling of appliances of multiple residential consumers in a decentralised manner, with the aim of achieving minimum cost of energy for consumers. The optimization incorporates integration of locally generated and stored renewable energy in order to minimise dependency on conventional energy. In addition to the appliance scheduling, a mean field game theoretic optimization framework is proposed for electric vehicles to manage their charging. In particular, the optimization considers a charging station where a large number of EVs are charged simultaneously during a flexible period of time. The proposed technique provides the EVs an optimal charging strategy in order to minimise the cost of charging. The performances of all these new proposed techniques have been demonstrated using Matlab based simulation studies.

This thesis reports upon investigations undertaken into the electrical performance of high power subsea transmission cables and is specifically focused upon their harmonic behaviour, an understanding of which is fundamental for developing accurate computer based models to evaluate the performance of existing or new offshore generation schemes. A comprehensive literature search has been undertaken in the areas of offshore generation, offshore power transmission schemes and harmonic performance of subsea cable systems. Subsea cable configurations, types and anatomy are presented to give an appreciation of the arrangement of subsea power cables. Mathematical equations and computer based algorithms have been developed to model subsea transmission system behaviour where the electrical parameters derived from natural physical phenomena such as skin effects, proximity effects and mutual couplings are included. Proximity effect is examined to determine the consequences of whether it needs to be considered for each subsea cable arrangement. Bonding solutions for subsea transmission are investigated to study the effect they have on resonance frequency and harmonic response for different cable lengths. The resulting analysis for various cable arrangements explains how geometric arrangements affect the harmonic impedance and harmonic resonance. The harmonic distortion in HVAC offshore transmission systems is also studied to demonstrate the importance of considering all power components in a subsea power transmission system for harmonic evaluation. In addition, the harmonic distortions of the VSC- HVDC link and associated harmonic power loss are examined. The effects of switching frequency, smoothing capacitor bank size, cable materials and transmission method on harmonic performances of the VSC-HVDC system with varying cable lengths is discussed and therefore subsea power cable harmonic behaviour interacted with subsea transmission systems is investigated. The novel contribution of this work is claimed to be in the development of superior models of subsea cables, transmission schemes and associated performance studies, which should lead to significant improvements over existing models and their results.

Proton exchange membrane fuel cells (PEMFCs) are promising candidates as power sources due to their high energy conversion efficiency, power density and low pollutants emission. Water management is of vital importance to achieve maximum performance and durability from PEMFCs. The main object of this work was to develop a mathematic model to better understand the water transport in PEMFCs under practical conditions. The aim is to enhance the output power of fuel cells by establishing effective water removal and distribution strategies. A single-phase flow, along the channel, isothermal model of a PEMFC is developed and validated against experimental data. Reactant flow and diffusion are simulated using the Navier-Stokes equation and Maxwell-Stefan equation, respectively. Water transport through the membrane is described by the combinational mechanism in which electro-osmotic drag, back diffusion and hydraulic permeation are all included. Agglomerate assumption is applied for the catalyst layer structure. This model is used to study the effects of the catalyst layer properties on cell performance. The model indicates that the rapid decrease in current density at lower cell voltage is due to an increased oxygen diffusion resistance through the ionomer film. A two-phase flow, across the channel, isothermal model is developed. The water phase transfers between water vapour, dissolved water and liquid water are taken into account and liquid water formation and transport are introduced. Liquid water occupies the secondary pores of the cathode catalyst layer to form a liquid water film on the outer boundary of the ionomer film. This model is used to study the influence of catalyst layer parameters and operating conditions on the cell performance. The model provides useful guidance for optimisation of the ionomer volume fraction in the cathode catalyst layer and the relative humidity of the cathode gas inlet. A two-phase flow, across the channel, non-isothermal model is developed. The model considered the non-uniform temperature distribution within the fuel cell. The modelling results show that heat accumulates within the cathode catalyst layer under the channel. Higher operating temperatures improved the fuel cell performance by increasing the kinetic rate, reducing the liquid water saturation on the cathode and increasing the water carrying capacity of the anode gas. Applying higher temperature on the anode and enlarging the width ratio of the channel/rib could improve the cell performance. A multi-variable optimisation of the cathode catalyst layer composition is represented by a surrogate modelling. Five design parameters, platinum loading, platinum mass ratio, ionomer volume fraction, catalyst layer thickness and agglomerate radius, are optimised by a multiple surrogate model and their sensitivities are analysed by a Monte Carlo method based approach. Two optimisation strategies, maximising the current density at a fixed cell voltage and within a specific range, are implemented for the optima prediction. At higher current densities, cell performance is improved by reducing the ionomer volume fraction and increasing the catalyst layer porosity. The one-dimensional, isothermal, time dependent and steady state models for the anode of a direct methanol fuel cell (DMFC) are developed. The two models are based on the dual-site mechanism, in which the coverage of intermediate species of methanol, OH and CO on the surface of platinum and ruthenium are included. Both the effect of operating conditions and electrode parameters are investigated. The distributions of methanol concentration and overpotential inside the electrode are represented and the current densities predicted by the intrinsic and macro kinetics are compared. From the analysis of the different models developed in this thesis, the main results can be summarised as: (1) Mass transport resistance resulted from the oxygen diffusion through the ionomer film surrounding the agglomerate is the main reason for the rapid fall of current density at lower cell voltage. (2) Ionomer swelling has a significant effect on fuel cell performance because it resulted in a decrease in the porosity and an increase in the ionomer film thickness, leading to an increase in the oxygen transport resistance. (3) Catalyst layer composition has a vital impact on the utilisation of the platinum catalyst and cell performance. (4) Heat accumulates within the cathode catalyst layer under the channel. Applying higher temperatures on the anode optimises the temperature distribution within the MEA and improves the cell performance. (5) Cell performance is improved by enlarging the width ratio of channel/rib. However, the improvement is limited by the sluggish oxygen reduction reaction. (6) For the methanol oxidation reaction in a Pt-Ru anode, the intrinsic current density is determined by the coverage ratios of the intermediate species. The structure and property of the electrode also play an important role in determining the anode performance of a DMFC.

Real-Time Thermal Rating (RTTR) is a technology that allows the rating of electrical conductors to be estimated using real-time, local weather conditions. In many cases this leads to an increased rating with respect to conventional approaches. It also identifies some instances in which the conventional, static, rating is greater than the true rating, and is therefore potentially unsafe. The work in this thesis comprises methodologies to improve the planning and implementation of RTTR. Techniques commonly employed in the wind energy industry have been modified for use with RTTR. Computational wind simulations were employed to allow the identification of determining conductor spans, to inform network designers of the rating potential of different conductor routes, to estimate the additional wind energy that could be accommodated through the enhanced line rating and to allow informed placement of the monitoring equipment required to implement RTTR. Furthermore, the wind simulation data were also used to allow more accurate estimation of conductor ratings during operation. Probabilistic methods have been devised to estimate the level of additional load that could be accommodated through RTTR, and quantify the risk in doing so. Finally, a method has been developed to calculate the benefit RTTR can provide to system wide reliability. State sampling and sequential Monte Carlo simulations were used to evaluate the probabilistic functions associated with the ratings, the load and failures on both the existing network and the RTTR system itself. These methods combine to address fundamental barriers to the wide scale adoption and implementation of RTTR. The majority of existing research has focussed on improving technical solutions, which are of little benefit if it is not possible to quantify the benefits of RTTR before it is implemented. This work allows quantification not only of those benefits, but of the associated risks and uncertainties as well.

Information and communication technology has been identified as a key enabler to develop a resilient, low carbon, and secure future energy system, by creating a smart grid. Starting with the premise that technology can be used to effectively match demand to generation, we address three main questions; (i) can algorithms be used to coordinate demand? (ii) can policy influence market driven demand side solutions? and (iii) how does technology influence consumer behaviour? We find that demand management algorithms are sensitive to assumptions regarding consumer flexibility. Taking this into account, we develop a novel method to simultaneously evaluate demand response business cases within a regulatory context. We find that the value proposition for providing demand response services is weak and thus requires policy based incentives and support. The analysis of a smart home project indicates that in home display devices have a half-life of 17 weeks and this is not significantly affected by engagement campaigns. Participating in community led workshops (based on energy consumption) increases in home display device activity, however this is a very short term effect. We also find evidence that in home display devices are likely to be used after changes in energy consumption are made by the householder and not prior to behaviour change. When using the Theory of Planned Behaviour (TPB), energy saving groups (low, medium, and high) were found to have different values of subjective norm, perceived behaviour control, and intention. This is the first study to objectively measure behaviour change (in terms of energy saved and in home display usage) and compare it with self-reported values of the TPB within a smart home context.

The serious energy supply problems along with the conventional resources depletion and the environmental conscience regarding global warming and climate change, have urged the need for a complete change in the energy production, supply and consumption patterns. Therefore, the switch towards renewable energy resources including solar, biomass, wind, hydro-power in addition to the development of energy efficient technologies are two key factors to attain a secure and reliable energy sector and to mitigate the global warming problem. Tri-generation is one of the most promising technologies allowing the efficient simultaneous production of heat, coolth and power with potential technical, economic and environmental benefits. [n this work, an innovative micro-scale hybrid solar-biomass tri-generation system was theoretically and experimentally investigated to provide cooling, heating and power generation in buildings. The proposed tri-generation system consists of an organic Rankinebased combined heat and power unit, a liquid desiccant dehumidification unit and a dew point evaporative cooling unit. To offset recent problems associated with small-scale ORC expanders including high cost, excessive fluid leakage and low isentropic efficiency, a novel compact and low-cost moditied scroll expander was employed in the organic Rankine unit for heat and power generation. In addition, an efficient and compact liquid-desiccant unit coupled with a dew point evaporative cooler was utilized to provide the additional cooling capacity through air dehumidification and cooling. Moreover, a novel hollow fibre-based core was proposed in this thesis to provide thermal comfort and humidity control lIsing a ho))ow fibre contactor with mUltiple bundles of micro-porous ho))ow fibres. The proposed core was developed and tested as a cooling core and dehumidification core in the Built Environment Laboratory. An extensive theoretical and experimental investigation of the micro-scale tri-generation system was carried out to model, design, develop and test the system different sub-units under various operational conditions. It was shown that using a heat input of about 19.6 kW, the micro-scale tri-generation system is capable of providing about 9.6 kW heating, 6.5 kW cooling and about 0.5 kW electric power. The overall efficiency of the combined cooling, heating and power system is about 84.4%.

Energy storage is a solution to the problem of renewable energy intermittency. The vanadium redox flow battery (VRFB) is one such energy storage technology, allowing energy to be stored electrochemically in vanadium electrolytes until required. The advantages of VRFBs include independently scalable energy and power characteristics, high reliability and long life time. The broad aim of this work was to investigate the main problems VRFBs currently present: 1. temperature stability of the vanadium electrolyte, and 2. chemical stability and vanadium cation permeability issues of the ion permeable separator membrane. It was determined that the concentrations of vanadium and sulfuric acid in the electrolyte have a greater impact on thermal stability than the presence of additives. Decreasing the sulfuric acid concentration, improves cold temperature stability of the vanadium electrolyte without impeding stability at elevated temperature.

Alcohol electrooxidation reactions in alkaline media are of great significance in fuel cell development. In this thesis, catalysts with high activity and stability performance are designed and relevant mechanisms are preliminarily proposed for alcohol electrooxidation reactions. Relevant characterisations of Pd-based electrocatalysts were achieved to study the morphology and composition such as SEM, TEM, EDS and XRD. Tetrahexahedral (THH) Pd nanocrystals (NCs) were directly electrodeposited on the glassy carbon (GC) electrode via a square-wave programme. The synthesized THH Pd NCs exhibit higher activity than bulk Pd for alcohol (ethanol, methanol and ethylene glycol) electrooxidation reaction. The kinetics data were obtained by Arrhenius plots and compared between bulk Pd and THH Pd NCs. Bi adatoms were modified on THH Pd NCs for ethanol electrooxidation reaction (EOR) in alkaline medium at various temperatures and under other conditions that practical fuel cells operate. The general kinetics data of EOR on Bi-decorated and bare THH Pd NCs have also I been obtained, from the activation energy calculated based on Arrhenius plots, and compared. Pd-ATO Ti mesh with high activity and cyclic stability was tested for EOR in alkaline media. The morphology and crystalline structure of Pd-ATO Ti mesh were investigated by SEM and XRD. PdMn02- C with high activity performance was explored for methanol electrooxiation (MOR) in alkaline media. Pd-Mn02-C was obtained by hydrothermal method and its morphology was investigated by TEM. Our work has explored novel catalysts for alcohol electrooxidation in alkaline media and investigated kinetics data in order to infer reaction mechanism. It is hoped that all these work could have a little help for fuel cell development.

State-of-the-art Density Functional Theory calculations are employed in the investigation of a number of processes occurring at the anode and cathode of Alkaline Fuel Cells for a variety of electrocatalyst materials. In the case of the methanol oxidation reaction, at the anode, the investigation is carried out with a view to quantitatively resolving the nature of the surface adsorbate on Pt(211) and is executed in combination with a cluster-continuum model approach, the principal adsorbate is found to be a methanol-OH complex. At the cathode, the oxygen reduction reaction is studied for the purpose of obtaining complete mechanistic understanding in the free energy landscape, thereby enabling the elucidation of the potential-determining step and, furthermore, the theoretical prediction of the onset potential. The oxygen reduction reaction is thus studied upon a range of cobalt oxide surfaces, and for a variety of Pt-WC catalysts, in addition to pure Pt(111}. The results obtained show good agreement with experiment, where appropriate. Furthermore, they highlight the need for detailed mechanistic studies in order to predict and explain experimental results since simplified, single-descriptor, approaches may sometimes result in misleading predictions.