This thesis begins with an investigation into the optical performances of the Crossed Compound Parabolic Concentrator (CCPC) for photovoltaic application and introduces the novel concept of a Translucent Integrated Concentrated Photovoltaic (TICPV). The use of solar concentrators in BIPV enables a reduction in the cost of generating photovoltaic electricity lending to yet another field of research known as Building Integrated Concentrated Photovoltaics (BICPV). The potential of BICPV as the most promising technologies for future electricity supply is examined by the design, optimisation and testing of the main component of the TICPV, a novel static nonimaging transparent 3-D concentrator coined the Square Elliptical Hyperboloid (SEH), for the use in building fenestrations. The SEH concentrator was designed and optimised via ray-tracing technique. A preliminary investigation into the optical efficiencies of 160 SEH concentrators of varying geometries was conducted and from this 20 concentrators were chosen and studied in more detail using the developed optical model with the aim of obtaining an optimised SEH concentrator out of these 20. The optimisation process proved to be far from straightforward, however, after careful consideration, five SEH concentrators with the best optical performances, each with different heights, were chosen. These concentrators were fabricated and used to assemble five separate TICPV modules. Subsequent to carrying out the simulation, the five optimised TICPV modules were examined in different environments (indoor and outdoor). The results of the indoor test, where the TICPV modules are exposed to direct radiation from a solar simulator, provided clear validation of the optical model; the results of the outdoor test added further to the validation and confirmed the power output of the TICPV modules when exposed to both direct and diffuse radiations. The TICPV modules are developed in a way such that they collect sunlight during most of the hours throughout the day, allowing the generation of electrical power whilst maintaining the level of transparency of the fenestration. It was found that the TICPV modules are capable of saving more than 60% of the solar cells used in conventional flat PV systems. The designed TICPV modules simultaneously provide solar energy generation and optimised day lighting. The TICPV module designed in this thesis provides a viable solution to coping with the increasing energy demands and will create a new age of energy efficient buildings reducing the carbon footprint of both existing buildings and buildings of the future.

This thesis presents a detailed investigation of the design optimisation and performance analysis of a dielectric concentrator for building façade integration at high latitudes (>55°). Considering the seasonal variation of the sun’s position at these latitudes, a concentrating photovoltaic (CPV) system with stationary concentrators of large acceptance angle and low concentration ratio is a suitable alternative to conventional flat plate photovoltaic (PV) modules. A well designed dielectric asymmetric compound parabolic concentrator (ACPC) is a suitable choice to achieve optimum range of acceptance angles and concentration ratio for building façade integration in the Edinburgh and higher latitudes. A theoretical study of the optical performance shows that a truncated dielectric ACPC with acceptance half-angles of 0o and 55o (termed as DiACPC-55) is the optimum design, when compared to the dielectric ACPC designs with acceptance half angles of (0o and 66o) and (0o and 77o) in Edinburgh and higher latitudes. An increase in the range of acceptance angles is achieved by truncating the concentrator profile. Ray tracing simulations show the DiACPC-55 exhibits the widest range of acceptance angles compared to the other designs. The maximum optical efficiency of the DiACPC-55 is found to be 83%. In addition it is found to have a better intensity distribution at the receiver and a higher total annual energy collection, compared to the other designs. Thermal modelling of a CPV system with the DiACPC-55 concentrator shows that the solar cell and rear plate temperature can reach up to 41.6oC for 1000 W/m2 irradiance, when operating with an average ambient temperature of 10oC. The maximum power ratio of the CPV module (fabricated using the DiACPC-55 concentrator) to a similar non-concentrating counterpart is found to be 2.32, when characterised in an indoor controlled environment using a solar simulator. An average electrical conversion efficiency of 9.5% is measured for the entire range of acceptance angles. The optical loss analysis shows that incident light can escape from the parabolic sides and concentrator-encapsulation interface. The outdoor characterisation of the CPV module with the DiACPC-55 concentrator shows that a maximum power ratio of 2.22 can be achieved on a sunny day. In comparison, a maximum power ratio of 1.9 is observed on a rainy day. These results reveal that the designed dielectric concentrator is capable of collecting 68% of the diffuse radiation. The maximum electrical conversion efficiency of the CPV module in outdoor condition is found to be 9.4%. Module degradation due to the delamination of the solar cell is observed in the long term investigation study, which reduces the module efficiency to 8.6% on a clear sunny day. The fabricated CPV system with the DiACPC-55 concentrator is found to be £190.3/m2 cheaper than similar sized conventional glass-glass laminated modules. Therefore the cost of the CPV module is found to be £0.53/Wp cheaper than the conventional glass-glass laminated modules for building facade integration at high latitudes.

The thesis investigates the modelling, analysis, design and control of 4th -order LCLC resonant power converters. Both voltage-output and current-output variants, are considered. Key research outcomes are the derivation of new frequency- and time-domain models of the converters, based on normalised component ratios, and including the effects that parasitic elements have on circuit behaviour, and a detailed account of multi-resonant characteristics; extensions to the use of cyclicmode modelling methods for application to LCLC converters, to provide rapid steady-state analysis, thereby facilitating the use of the derived methodologies as part of an interactive design tool; the formulation of analytical methods to predict the electrical stresses on tank components-an important consideration when designing resonant converters, as they are often higher than for hard-switched converter counterparts; the characterisation of both continuous and discontinuous modes of operation and the boundary conditions that separate them; and a substantial treatment of the modelling, analysis and design of LCLC converters that can provide multiple regulated outputs by the integrated control of both excitation frequency and pulse-width-modulation. The proposed methodologies are employed, for validation purposes, in the realisation of two proof-of concept demonstrator converters. The first, to satisfy the requirements for delivering 65V (rms) to an electrode-less, SW, fluorescent lamp, to improve energy efficiency and lifetime, and operating at a nominal frequency of 2.65 MHz, is used to demonstrate capacitively-coupled operation through the lamp tube, thereby mitigating the normally detrimental effects of excitation via the electrodes. The second prototype considers the realization of an LCLC resonant power supply that can provide multiple regulated outputs without the need for post-regulation circuitry. The two outputs of the supply are independently, closed-loop regulated, to provide asymmetrical output voltage distributions, using a combination of frequency- and duty-control. Although, an analysis of the supply shows that the behaviour is extremely complex, due, in particular, to the highly non-linear interaction between the mUltiple outputs and parasitic inductances, and rectifier, an analysis to provide optimum performance characteristics, is proposed. Moreover, a PICIFPGA-based digital controller is developed that allows control of the transient performance of both outputs under start-up and steady-state conditions.

This thesis describes research into a specific area of Industrial Scientific and Medical (ISM) band applications that employ a central control panel to send broadcast information to the units in a system. One example of this is fire safety systems. The focus is on how battery life, reliability and usability of such a system may be improved through different mechanisms. The case study application is a system of radio controlled fire door holders. Following a review of the current literature and a look at the considerations of designing a wireless network, a comparison is made of two radio transceivers, each of which operates in a different frequency band. Testing is performed with both, and a choice made as to which to use in system implementations and further research. Results from the first system implementation quantify communications and circuitry improvements that increase battery life through improved receiver sensitivity and communications resilience. The second system implements a narrowband system, as well as improving unit displays for information output and system troubleshooting. Results from it show a further increase in receiver sensitivity and techniques developed to improve timing to reduce on-time, so reducing power consumption further. The third implementation employs frequency hopping techniques along with further advances in timing. Enhanced display manager techniques add to the usability of the system. Beyond this, more recent chip technology is used with algorithmic changes in small test units to assess how further improvements can be made in terms of battery life. A ten-fold improvement in battery life compared to the original implementation is shown to be possible when comparing the narrowband and wideband systems. Further improvements are described employing the latest chip technology.

The work in this thesis mainly focuses on the preparation and optimization of materials for intermediate temperature fuel cells (ITFCs) with the aim of achieving high fuel cell performance as well as good stability. The fuel cell fabrication was also studied in order to develop a cost-effective fabrication process. Methods such as solid state reaction, combustion and carbonate co-precipitation were adopted for the synthesis of the materials. The densification temperature of Ce0.8Gd0.05Y0.15O1.9 (GYDC) electrolyte was greatly reduced by the carbonate co-precipitation synthesis and subsequently a simple one-step co-press-sintering fabrication process was developed. LiNO3 as sintering additive further reduced the densification temperature of GYDC and up to 96% relative density was achieved at 800 °C. Lithiated NiO was employed as cathode for IT-SOFCs and demonstrated good electrocatalytic activity. In addition, lithiated NiO was also investigated as both anode and cathode for IT-SOFCs and its stability was studied. Oxide-carbonate composites have demonstrated very high ionic conductivity as the melting of carbonates greatly enhanced the mobility of ions in materials. High power densities up to 670 mW cm-2 at 550 °C were achieved for the composite electrolytebased ITFCs. However, the traditional lithiated NiO cathode can gradually dissolve into the carbonate melt and scanning electron microscopy studies found obvious morphology change nearby the cathode/electrolyte interface which may be due to the dissolution of nickel ions. Perovskite oxide Sm0.5Sr0.5Fe0.8Cu0.2O3-δ (SSFCu) has been demonstrated to be a compatible and stable cathode for the composite electrolyte based ITFCs, as a stable current output of about 0.4 A cm-2 was observed under a constant voltage of 0.7 V during a cell test lasting 100 h. Instead of GYDC, BaCe0.5Zr0.3Y0.16Zn0.04O3-δ (BCZYZn) was also employed as substrate material for the carbonate composite electrolyte and SrFe0.7Mn0.2Mo0.1O3-δ (SFMMo) was developed and used as cathode.

Through the judicious and efficient use of energy in both domestic and commercial products, the rate at which the world's fossil fuels and mineral resources are depleted, can be minimised, thereby securing energy reserves for the future. This thesis considers a number energy saving roles the power systems engineer can contribute, with specific emphasis on the impact of improving DC-DC power converters for providing significant energy savings. It is shown that by increasing the efficiency of such converters, through the greater use of switched-mode supplies, huge reductions in the production of green house gases can be obtained. Moreover, resonant converters, a specific subset of switched-mode supply, are identified as a candidate technology for future widespread use. Since the behavioural dynamics of resonant converters are inherently non-linear, the analysis and design of such systems is extremely complex when compared to other families of converter, and has been a critical factor in impeding their widespread adoption. This thesis therefore aims to provide new tools to aid the designer in overcoming such reservations. Novel analysis and design procedures are developed in Chapters 3 and 4, for the series-parallel inductively-smoothed and capacitively smoothed resonant converters, respectively, which, unlike previously reported techniques, allows a designer with little knowledge of resonant converter systems to readily select preferred components for the resonant tank based on design specifications. Specifically, the analysis in Chapter 3 develops a new methodology that extends 'Fundamental Mode Analysis' (FMA) techniques, and provides a first-order estimate of component values to meet a given specification. Chapter 4 then considers the steady state behaviour of the converter, from a state-plane perspective, and provides exact component values and electrical stress analyses based on ideal converter characteristics. The presented methodology normalises the converter behaviour, such that the gain of the resonant tank (at the resonant frequency and minimum load resistance), and the ratio between the two tank capacitances, fully characterises the behaviour of the converter as the load is varied and the output voltage regulated. To further aid the designer, various new design curves are presented that makes the use of traditional, and complicated, iterative calculation procedures, redundant. Chapter 5 further develops a high speed 1 transient analysis technique for resonant converters that is shown to provide a IOOx reduction in simulation times compared to integration-based methods, by considering only signal envelopes. The technique is shown to significantly aid in the design of variable frequency controllers. Chapters 6 and 7 further consider the control of resonant converters. Specifically, Chapter 6 derives a novel self-oscillating control methodology, which, unlike previously published techniques, approximately linearises the large-signal dynamics of the converter, and thereby readily enables the robust design of an outer loop controller for output-voltage/-current regulation purposes. Additionally, in contrast to other methods for the robust control of resonant converters, little knowledge of the converter state-variables is required, thereby minimising the number of high-bandwidth sensors necessary. The technique simply requires the real-time polarity of current-flow through the series-inductor, and output-voltage/-current, to be known. Through additional (optional) measurement of supply-voltage and a feed-forward control component, the effects of supply-voltage disturbance are shown to be greatly attenuated, thereby requiring reduced outer-loop control action and improving overall regulation performance. Finally, Chapter 7 considers the control of resonant converters when the cost of isolated feedback sensors is prohibitive. Unlike traditional techniques, where the output-voltage is estimated under fixed load conditions, through use of an Extended Kalman Filter observer scheme, non-isolated measurements are used to estimate both the output-voltage and the load-resistance. The load resistance estimation is then used to aid in fault-detection and for improving transient dynamic behaviour via the provision of feed-forward action, resulting in safer converter operation and enhanced regulation performance, and, ultimately, reduced cost.

No description available.

No description available.

High Speed High Power (HSHP) electrical machines push the limits of electromagnetics, material capabilities and construction techniques. In doing so they are able to match the power performance of high speed turbomachinery such as gas turbines, compressors and expanders. This makes them attractive options for direct coupling to such machinery as either a power source or as a generator; eliminating the need for gearboxes and achieving a smaller system size and greater reliability. The design of HSHP machines is a challenging, iterative process. Mechanical, electromagnetic and thermal constraints are all placed on the machine shape, topology, operating point and materials. The designer must balance all of these constraints to find a workable solution that is mechanically stable, can work within the available electrical supply and will not overheat. This thesis researches the fundamental origins and interaction of the mechanical, electromagnetic and thermal constraints on electrical machines. Particular attention was paid to improving the accuracy of traditional mechanical rotor design processes, and improving loss estimation in inverter fed machines. The issues of selecting an appropriate electric loading for low voltage machines and choosing effective, economic cooling strategies were explored in detail. An analytical iterative design process that combines mechanical, electromagnetic and thermal design is proposed; this process balances the need for speed versus accuracy for the initial design of a machine, with Finite Element Analysis used only for final validation of performance and losses. The design process was tested on the design and manufacture of a 1.1MW 30,000rpm PM dynamometer used in an industrial test stand. The machine operating point was chosen to meet a gap in the industrial machines market and exceed the capabilities of other commercially available machines of the same speed. The resulting machine was successfully tested and comfortably meets the performance criteria used in the design process.

This thesis presents a novel adaptive scheme for energy management in stand-alone hybrid power systems. The proposed management system is designed to manage the power flow between the hybrid power system and energy storage elements in order to satisfy the load requirements based on artificial neural network (ANN) and fuzzy logic controllers.  The neural network controller is employed to achieve the maximum power point (MPP) for different types of photovoltaic (PV) panels, based on Levenberg Marquardt learning algorithm. The statistical analysis of the results indicates that the R2 value for the testing set was 0.99.  The advance fuzzy logic controller is developed to distribute the power among the hybrid system and to manage the charge and discharge current flow for performance optimization. The developed management system performance was assessed using a hybrid system comprises PV panels, wind turbine, battery storage, and proton exchange membrane fuel cell (PEMFC). To improve the generating performance of the PEMFC and prolong its life, stack temperature is controlled by a fuzzy logic controller. Moreover, perturb and observe (P&O) algorithm with two different controller techniques - the linear PI and the non-linear passivity-based controller (PBC) - are provided for a comparison with the proposed MPPT controller system. The comparison revealed the robustness of the proposed PV control system for solar irradiance and load resistance changes. Real-time measured parameters and practical load profiles are used as inputs for the developed management system. The proposed model and its control strategy offer a proper tool for optimizing the hybrid power system performance, such as the one used in smart-house applications. The research work also led to a new approach in monitoring PV power stations. The monitoring system enables system degradation early detection by calculating the residual difference between the model predicted and the actual measured power parameters. Measurements were taken over 21 month’s period; using hourly average irradiance and cell temperature. Good agreement was achieved between the theoretical simulation and the real time measurement taken the online grid connected solar power plant.