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Computer based numerical prediction of wave-body interactions has become a powerful design tool and is widely used in the offshore industry. Its application to wave energy conversion is more recent. The present work investigates the modelling of three configurations of sloped wave energy converters of increasing complexity using the boundary element method package WAMIT. These configurations are all related to the concept of the Sloped IPS buoy wave energy device. In order to understand and assess the validity of numerical modelling for the specific cases considered, a two stage procedure is adopted. The first stage is to check that the results obtained from WAMIT are consistent with its underlying theory. These results are then compared with the corresponding experimental data. The experimental equipment and methodology are described. This includes discussion of wave tanks, models, and measuring techniques. The three configurations of wave energy converter investigated are the following: (a) a single degree of freedom system whose power take-off is referenced to the sea bed; (b) a free floating device with no power take-off; and (c) a free floating device fitted wit a power take-off mechanism that uses water inertia for its reference.

The requirement for decentralised power generation in the rural electrification of developing countries is vast, and extensive hydrological resources for small-hydro power have been identified. Despite this, the utilisation of small-scale hydro is extremely slow, and the market is not fully developed. This study reviews the marketplace for small-scale hydro in the industrialised, newly-industrialised, less-developed and third-world countries. The extent, characteristics, and timescales of small-hydro development are used to estimate the market for varying levels of power generation technology. Existing power plant and practices as applied to rural electrification programmes are examined and suggestions are made to improve the cost effectiveness of the generating plant. The economic effects which increase the cost of energy produced at smaller sites are considered and a pre-feasibility cost model is proposed. Existing design methods for Pelton turbines are appraised. A new method of designing and estimating the performamce of multi-jet machines has been developed in a comprehensive software package, which is described and evaluated. A test facility designed and constructed during the study is described, and the results obtained by testing a small Pelton turbine are presented. Conclusions are drawn at the end of each chapter and these are ultimately summarised in an overview of the effective market and the means by which Pelton turbine technology may be applied more widely. The market sectors which will benefit by the availability of the design software are identified, together with further work required to integrate the design ability into manufacture.

Since January 2001 it has been necessary for equipment connected to the low voltage public distribution network in Europe and Japan to comply with IEC 61000-3-2. The regulation IEC 61000-3-2 specifies the level of current that can be drawn for particular harmonics. Much equipment today is fitted with a Switch Mode Power Supply (SMPS) at its input to interface between the line voltage and internal low voltage electronics. This SMPS must not only convert the line voltage, but also ensure that the input current to the device meets the IEC regulations. To meet these regulations two methods are normally used, passive filtering using a large filter inductor or a boost converter cascaded with the main DC/DC SMPS converter with isolation. To try and reduce component count, cost and increase efficiency many new single-stage Power Factor Correction (PFC) topologies have been proposed. In a single-stage topology the output voltage regulation and meeting IEC 61000-3-2 are combined into a single power stage. Unfortunately very little is known about the behaviour or performance of these single-stage topologies. In this thesis two of the more promising single-stage topologies, the bi-forward and CS S²PFC converters are investigated further. A new topology using a low frequency switch (LFSPFC) is introduced. The topologies are analysed investigating input current shape and harmonic content, voltage variation on bulk capacitance and component stresses. Simulation in PSpice is used to confirm circuit operation. Four 150W output power experimental circuits were built: bi-forward converter, CS S2PFC converter, passive filtering cascaded with a forward converter and a boost pre-regulator cascaded with a forward converter. The converters operate from universal input voltage and have outputs at 5V and 12V. A 100W test circuit was built for the LFSPFC operating from 230V input voltage and with an output of 5V. Experimental results are presented showing circuit behaviour and performance of the bi-forward, CS S²PFC and LFSPFC converters. The bi-forward and CS S²PFC converters are compared to the passive filter and boost converter cascaded with a forward converter. It is demonstrated that neither of these single-stage topologies is at present a viable replacement for either present method, but the LFSPFC could be a lighter weight and less bulky alternative to passive filtering.

The fabrication and sintering of yttria-stabilised zirconia with varying yttria concentrations was carried out based on both wet and dry processing routes, utilising conventional single step and two-step sintering techniques. Results show that homogeneous, defect-free, high green density microstructures are essential in producing fully dense sintered samples of a desired grain size. Characterisation on morphology using HRTEM suggests that although there were no indications of impurities or secondary phases in the studies samples, there were signs of yttria segregation present in 3 mol.% YSZ, sintered at 1600°C. This was explained to be due to the increased amount of cubic phase with increased sintering temperature. High yttria ion concentration regions that form within grains undergo phase transformation from tetragonal to cubic, allowing the cubic phase regions to be partitioned. However, the transformation was not detectable based on the techniques used in this study. The activation energies obtained from AC impedance spectroscopy demonstrated reduced activation energy at higher temperature. This suggests the presence of two different oxygen diffusion mechanisms within the material. These results are backed up by DC 4-probe ionic conductivity measurements. Reduced activation energy reported in nanostructured YSZ was reported to be due to large oxygen-ion vacancies. This phenomenon was also reported at lower yttria concentrations, due to the oxygen vacancies experiencing a binding energy to the dopant atoms caused by a combination of an electrostatic attraction and repulsive lattice relaxation energy. Overall, the conductivity results based on AC impedance and DC 4-probe showed that the finer grain structured 3 mol.% YSZ at ~100 nm exhibited slightly enhanced conductivity. On the other hand, 8 mol.% YSZ displayed a clear increase in conductivity with increasing grain size based on an intrinsic grain boundary blocking effect. High temperature thermal aging carried out on 3 mol.% YSZ at ~100 nm and ~500 nm was believed to have caused polarisation loss, a time dependent phenomenon.

Formerly, to meet increases in electricity demand or to replace obsolete stations, the decision to build a new power station of a particular fuel type was not based wholly on economic grounds. Often political pressure (e.g. using coal to keep mines open), national strategy (e.g. building of nuclear reactors) or government policy (e.g. introduction of hydro generation in Scotland to counter population drift) dominated the expansion planning process. With the advent of the availability of inexpensive computing power, planning based solely on economics, with calculations that are mathematically complex, repetitive and time consuming, can be applied more readily to such decision making. In addition, a wider range of factors can be taken into account. Sensitivity analysis and comparative assessments can be made easily, allowing the Planning Engineer to consider more options and to arrive at decisions with more confidence. Occasionally, however, the preferred options indicated by such planning (termed least-cost expansion planning) may be overruled through influence of externalities such as those mentioned above, e.g. political pressure. Thus, although least-cost expansion planning software will never replace totally the human involvement in the process, such software has the considerable advantage that it can be used to rank a range of options in order of economic cost. The Planner can then quantify in economic terms the effects of overriding indicated minimum-cost options by making decisions on the basis of some other grounds, e.g. governmental policy. This thesis examines the factors and techniques which are used in least-cost expansion planning. Their integration into a decision support system is described and suitable software is developed. Using realistic data a typical run of this software demonstrates ranking of minimum-cost candidates that successfully meet expected future electricity demands and planning criteria set before a run is executed. The merits of using the software in a practical application are then discussed.

In response to the challenge of climate change and potential energy supply insecurity, the UK Government published a White Paper outlining objectives for a long term energy strategy. The Electricity Supply Industry (ESI) must address these energy policy goals of reducing environmental impact while maintaining security of supply and affordability. The lower electricity prices currently experienced in the ESI are a result of investment in natural gas generation and it is expected that this investment trend will continue. However, once the domestic North Sea resource is exhausted the UK will become dependent on imports. Here there is a conflict between low cost energy and security of supply. This study tests the thesis that energy storage and carbon dioxide (CO₂) abatement in methanol is feasible as a means of meeting the energy policy objectives. Sequestering CO₂ emitted from fossil fuel power stations will allow them to continue to generate electricity. This could maintain the diversity and therefore security in the fuel mix of the ESI. Using intermittent renewable energy to electrolyse water and produce hydrogen offers an energy storage solution that could counter and alleviate the problems of intermittency on the network. Analysis of the methanol production process, in terms of the economic requirements, abatement capability and the necessary conditions for its feasibility are set out. To establish the necessary economic and regulatory setting for the methanol process to be feasible an optimal fuel allocation model was constructed. Taking into account CO₂ emissions, security of supply, cost of electricity and economic instruments the model is used to determine how the ESI could achieve the energy policy goals. Results of the feasibility study conclude on how the methanol process can be used to help the ESI meet the energy strategy objectives and describe the necessary economic and regulatory measures required.

In airborne applications, the size and weight of equipment are critical parameters. The power supply for an airborne radar needs to have a high output power density while operating with a high efficiency. Conventional Travelling Wave Tube (TWT) radars require a high voltage power supply for operation and is prone to arcing. As the radar is a crucial piece of equipment, its power supply must be designed to withstand such operation. The Phase Shifted Pulse Width Modulation Zero Voltage Switching Full Bridge Converter has been the subject of many papers due to its ability to provide high output powers with high efficiency. As the output inductive/capacitive filters used by the present low voltage, high current, phase shifted converters are unsuitable for high output voltage applications, it is replaced with a capacitive filter, altering the basic operation of the converter. In this thesis the theory and design implementation of the Phase Shifted Bridge with Capacitive Filter (PSBCF) is described. Two auxiliary circuits developed for the conventional phase shifted bridge are analysed and implemented in the new PSBCF. Detailed cycle-by-cycle transient simulations on PSPICE are used to study the converters' behaviour and these are verified with experimental results. An averaged model of the PSBCF running in PSPICE is described and verified using the cycle-by-cycle transient simulations. Finally, the features and limitations of the PSBCF converter and the use of the auxiliary circuits are discussed and evaluated against each other and against the currently used airborne TWT radar power converter to demonstrate that this technology is a viable replacement.

The need for an economic alternative to the traditional speed governor for micro hydro applications is discussed and the Electronic Load Governor (ELG) is identified as the solution. The international market for the ELG is seen to vary in accordance with the development and traditions of those countries with micro hydro resources. Technical and economic design parameters for a novel, prototype ELG are developed in relation to previous work in the field. The need for a reliable unit based on digital electronic circuits and capable to three phase balancing is identified. The significance of the 'droop' is introduced, along with the concepts of 'deadband', 'wait delay' and the 'coefficient of stability'. A technique for prediction of the droop, and hence the deadband, using the turbine runaway speed is presented. The predictions are confirmed as a result of empirical tests. The voltage-speed characteristics are also determined empirically. A mathematical expression is derived which represents the frequency variation with time of the system, when subjected to a load rejection, and controlled by the ELG. The transfer function of the control system is derived as far as is practicable given the non-linear nature of the ELG control action. A computer model is developed which predicts the frequency transient for any Pelton installation under the control of the ELG. The mode is modified to predict the performance of the ELG subject to proportional-derivative control actions.