Satisfying the demand for a more efficient and sustainable energy supply model has presented a new challenge for the energy industry. It has also created an opportunity for alternative and renewable sources of energy generation, which has led to a significant increase in the deployment of renewable technologies in many countries. Recent years have also seen these technologies deployed at a community scale, with remote and isolated communities in particular being regarded as ideal locations. Such systems are capable of providing increasingly viable, standalone alternatives to the centralised energy supply model. This thesis investigates the extent to which the viability of these stand-alone hybrid energy systems could be further improved by implementing domestic demand response, promoted via variable domestic energy pricing. A high resolution,disaggregated model of domestic energy demand at the community level is then developed, supported by the findings of a targeted consumer attitudes survey. This model is combined with a series of demand response algorithms which replicate the response of domestic consumers to energy price variation. Three variable pricing approaches are then applied to the model under a range of conditions, and the impacts examined from both a community-wide and household level perspective. The thesis demonstrates the relevance and potential of stand-alone hybrid applications and the remote/isolated communities in which they are typically deployed. The results find variable domestic energy pricing based on renewable energy supply to be capable of achieving modest yet significant levels of demand response under a broad range of conditions (83% of the scenarios modelled).Further sensitivity analysis shows the pricing strategies to be resilient to changes in supply conditions, thereby illustrating the broad ranging potential of such an approach. However, susceptibility to free-rider behaviour and insensitivity to household elasticity levels suggest the need for additional/supplementary forms of financial incentivisation.

Emerging power system designs are driven towards supporting the diversity of generation supply through increased flexibility and progressive employment of renewable resources, in order to fulfil sustainable and low carbon energy development strategies. The resulting impact on system response, especially during and following disturbances, can incur negative power system stability issues. With particular attention given to the anticipated reduction and variation of system inertia, concerns are growing with respect to power system frequency stability following large disturbances. This is attributed to the potential involvement of acceleration and magnification in frequency excursions due to reduced inertia and differences in generator (particularly converter-interfaced source) control and responses to disturbances. Despite the fact that new techniques, such as those that produce “synthetic” inertial responses, are evolving to compensate for the absence of inherent inertia from renewable resources, their practical integration into the existing grid is limited at the present stage. This is attributed to the uncertainties underlying when and how these techniques should be applied, with a major barrier to their deployment being a lack of prevailing system inertia information. As the exact amount of real-time response required cannot be known with a high degree of confidence, a risk of “over-responding” would be incurred if inertial responses are deployed widely throughout the system. Moreover, the suitability of adopting present-day frequency-based protection settings in conjunction with aforementioned techniques in future power networks has not been fully investigated, where frequency stability margins, necessitating active regulation, could dynamically vary. As such, the work reported in this thesis focuses on evaluating the impact of variable inertia on the performance of existing frequency-based protections and the feasibility of introducing adaptive solutions as a flexible and reliable approach to improve the performance of affected frequency protection schemes, thereby enhancing future system frequency performance. There are two major contributions in this thesis. Firstly, a Switching Markov Gaussian Model (SMGM) has been proposed with which the real-time inertia estimates can be profiled from observed frequency variations during normal system operation. An optimised error of lower than 10% (taken for a system of an overall inertia equal to 3 seconds) was produced for 95% of the daily estimation if being calibrated with the equivalent inertia derived from generation dispatch data on a half-hourly basis and its robustness can be maintained for a period of up to two hours when losing frequency observations. Secondly, a zonal adaptive Distributed Generation (DG) anti-islanding protection scheme has been developed and demonstrated with protection settings being adjusted in response to estimated levels of system inertia. Enhancement of the performance of DG anti-islanding protection has been tested and demonstrated on a reduced GB power network model. Validity and robustness have been analysed, along with discussions of configuration adjustments and practicalities of adopting reliable adaptive protection schemes.

The increased load demand and the development of distributed generation technologies present challenges to the existing low-voltage power distribution networks. In particular, numbers of high-capacity power electronic interfaces, such as electric vehicle (EV) chargers and embedded photovoltaic (PV) generation, have increased significantly. In comparison with conventional AC systems, low-voltage DC (LVDC) systems offer several potential benefits, including improved utilisation of cable voltage ratings, and elimination of reactive current and skin effect issues. LVDC distribution also complements the growth of power electronic loads having an implicit DC stage as part of their grid interface. However the DC-AC conversion stage at the customer end is one of the main challenges for LVDC distribution due to the widespread existence of AC loads. To overcome this limit, a high-performance modular multilevel converter (MMC) with parallel-connected MOSFETs is proposed in this thesis. It allows the converter to operate at relatively high voltage with low harmonic content, without the use of large AC filters. MMC also has low switching frequency, and facilitates the use of MOSFETs with the feature of synchronous rectification which provide lower conduction loss and allows parallel-connection to further reduce the losses. Power losses are calculated to show that the efficiency of MMC can exceed that of a conventional 2-level converter. Comparative analysis was carried out for a conventional 2-level converter, a SiC MOSFET 2-level converter, a Si MOSFET MMC and a GaN HEMT MMC, in terms of power loss, power quality, converter cost, and heat sink size. The analysis suggests that the 5-level MMC with parallel-connected Si MOSFETs may be an efficient alternative for this LVDC application. The optimal number of parallel-connected MOSFETs was then investigated. In addition, thermal measurement was developed to verify the loss calculation. A detailed converter design was conducted with current control methods to eliminate circulating current distortion for single-phase MOSFET MMC. Then a single-phase 5-level MMC prototype was built to validate the control methods proposed.

Offshore wind energy is progressing rapidly and playing an increasingly important role in electricity generation. Since the Kyoto Protocol in February 2005, Europe has been substantially increasing its installed wind capacity. Compared to onshore wind, offshore wind allows the installation of larger turbines, more extensive sites, and encounters higher wind speed with lower turbulence. On the other hand, harsh marine conditions and the limited access to the turbines are expected to increase the cost of operation and maintenance (O&M costs presently make up approximately 20-25% of the levelised total lifetime cost of a wind turbine). Efficient condition monitoring has the potential to reduce O&M costs. In the analysis of the cost effectiveness of condition monitoring, cost and operational data are crucial. Regrettably, wind farm operational data are generally kept confidential by manufacturers and wind farm operators, especially for the offshore ones. To facilitate progress, this thesis has investigated accessible SCADA and failure data from a large onshore wind farm and created a series of indirect analysis methods to overcome the data shortage including an onshore/offshore failure rate translator and a series of methods to distinguish yawing errors from wind turbine nacelle direction sensor errors. Wind turbine component reliability has been investigated by using this innovative component failure rate translation from onshore to offshore, and applies the translation technique to Failure Mode and Effect Analysis for offshore wind. An existing O&M cost model has been further developed and then compared to other available cost models. It is demonstrated that the improvements made to the model (including the data translation approach) have improved the applicability and reliability of the model. The extended cost model (called StraPCost+) has been used to establish a relationship between the effectiveness of reactive and condition-based maintenance strategies. The benchmarked cost model has then been applied to assess the O&M cost effectiveness for three offshore wind farms at different operational phases. Apart from the innovative methodologies developed, this thesis also provides detailed background and understanding of the state of the art for offshore wind technology, condition monitoring technology. The methodology of cost model developed in this thesis is presented in detail and compared with other cost models in both commercial and research domains.

A growing recognition of anthropogenic climate change has led to carbon reduction and renewable energy targets being institutionalised within the UK’s energy policy. Meeting these targets will require a fundamental restructuring of the current electricity system to allow for the long term sustainability of electricity generation. This thesis argues that large scale electricity generation from offshore wind technology will have a key role in driving the sustainability transition within the electricity system. It is argued that the offshore wind technology, like other technologies, is embedded in wider social, political and economic institutions. This means that offshore wind is a socio-technical system and its development involves interactions between the technical and non-technical elements which are socially constructed within existing institutions. The aim of this thesis is to contribute to the understanding of the interaction between technology, institutions and actors in the sustainability transition of the electricity system. The thesis plans to fulfil methodological insights to investigate the factors that affect the development of the offshore wind system within a socio-technical transition towards sustainability in the electricity system. For this purpose, empirical data were generated from 41 semi-structured interviews with principal decision makers in industry and local authority positions, observations of industry and government events, and industry reports and related policy document analysis. The analysis employs a novel analytical framework that draws from two established theories in the literature: the Multi-Level Perspective (MLP) and Social Construction of Technological System (SCOT), and incorporates insights from transition studies. This thesis finds a new form of interactions between socio-technical elements of the system in the UK energy transition which leads to different transition pathways to a low carbon electricity system with regard to offshore wind development. The thesis provides a broad understanding of the development of the offshore wind system within the processes of socio-technical transition towards sustainability as well as within the UK’s energy policy. A number of policy implications and recommendations are also made of relevance to a broad academic and policy focused audience.

The combination of ubiquitous computing and emerging energy technologies is radically changing the home energy landscape. Domestic micro-generation, dominated by solar photovoltaic, is increasing at a rapid pace. This represents an opportunity for creating and altering energy behaviours. However, these transformations generate new challenges that we call the domestic energy gap: domestic electricity consumption and microgeneration are out of sync. Micro-generation is mainly uncontrollable production relying on weather while domestic energy consumption tends to happen mostly during the evening. This thesis focuses on understanding and supporting new domestic practices in the context of domestic solar electricity generation, looking at ‘Demand-Shifting’. Specifically, we look at how can digital tools leverage Demand-Shifting practices in the context of domestic micro-generation? Relying on a mixed-method approach, we provide a qualitative and quantitative answer with the collaboration of 38 participating households in several field studies including two spanning more than eight months. Through a deep investigation of laundry and electric mobility routines in the context of domestic micro-generation, we emphasised a natural engagement into Demand-Shifting which appeared as a complex and time-consuming task for participants which was not visible when we analysed their quantitative data. We revealed this complexity through Participatory Data Analyses, a method we designed to analyse the data in collaboration with the participating householders. This provided us with a comprehensive view of the relationship between domestic micro-generation and daily routines. Finally, we highlight the need for timely and contextual support through the deployment of interventions in-the-wild. Building on discussions of our findings in perspective of the literature, we propose a conceptual framework to support domestic interactive Demand-Shifting.

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This study focuses on the design, construction and experimental evaluation of a thermoacoustic electricity generator prototype with a push-pull linear alternator. The push-pull coupling offers a solution to run the looped-tube thermoacoustic engine at high acoustic impedance using one alternator. The novel configuration of the engine consists of two identical half-wavelength stages with an alternator connected between them. A simulation was carried out using the DeltaEC programme. The modelling started by investigating the required acoustic field for the alternator. The engine modelling has been done as half of the engine which is one-stage, because the DeltaEC shooting method showed that it was unable to run two identical stages. The engine is 16.02 m long and run at 55.1 Hz. The simulation showed that it is possible to produce more than 133 W of electricity at a thermal-to-electric efficiency of 23% while using helium pressurized at 28 bar. In practice, the engine failed to self-start. After exciting it to run by an external pulse, an electric power of 48.6 W was generated with a thermal-to-electric efficiency of 2.7%. The high heat leak detected was reduced by installing an insulating gasket between the ambient heat exchanger and regenerator holder, which encouraged the electricity generation to increase. The engine became self-starting when the regenerator thickness was reduced from 73 mm to 71.8 mm. The maximum generated electric power was 73.3 W at 3.33% thermal-to-electric efficiency at a heating power of 2200 W, and a maximum efficiency of 3.6% was achieved at 71.9 W electric power at a heating power of 2000 W. The success of the two-stage engine with a push-pull linear alternator encouraged modelling and design of a four-stage engine with two push-pull linear alternators able to generate up to 269 W of electricity, theoretically.

Solid oxide fuel cells (SOFCs) are gaining prominence as power sources amongst other types of fuel cells due to their high electric energy efficiencies, their ability to integrate with other energy cycles in a hybrid system, fuel choice flexibility and low pollutant emissions. Operation of an SOFC involves complex coupling of the electrochemical reactions, chemical reactions and transport phenomena simultaneously in the cell’s main components consisting of gas channels, porous electrodes and the dense ceramic electrolyte. Consequently, mathematical modelling of these processes becomes an essential research tool aiming to provide detailed insight, while reducing cost, time and the effort associated with experimentation. The main aim of this thesis is to develop mathematical models in the cell and at system level to better understand the complex operation of SOFCs and its associated cycle under practical conditions with the aim of enhancing the power output and efficiency of the cell. At the cell level, a two dimensional along the channel micro-scale isothermal model of a SOFC is developed and validated against experimental data and other simulated result from literature. The steady state behaviour of the cell was determined by numerical solution of the combined transport, continuity and kinetic equations. The model is capable of predicting the cell performance including polarisation behaviour and power output. The model is used to study the effect of the support structure, geometric parameters and the effect of operating conditions on cell performance. Several parametric studies, such as the effect of operating conditions and geometric parameters on cell performance with a view to optimising the cell. Also, at the cell level, a two dimensional along the channel model was developed which integrates a heat transfer model and direct internal reforming kinetics into the earlier developed isothermal model. This non-isothermal model was also validated against experimental data. The developed model not only predicts the performance of the SOFC at different design and operating conditions, it also provides an insight on the different phenomena and the distributions of current density, temperature and gas pressures within the cell. Microstructural parametric studies of the reaction layer were also carried out. Solid oxide fuel cells (SOFCs) are gaining prominence as power sources amongst other types of fuel cells due to their high electric energy efficiencies, their ability to integrate with other energy cycles in a hybrid system, fuel choice flexibility and low pollutant emissions. Operation of an SOFC involves complex coupling of the electrochemical reactions, chemical reactions and transport phenomena simultaneously in the cell’s main components consisting of gas channels, porous electrodes and the dense ceramic electrolyte. Consequently, mathematical modelling of these processes becomes an essential research tool aiming to provide detailed insight, while reducing cost, time and the effort associated with experimentation. The main aim of this thesis is to develop mathematical models in the cell and at system level to better understand the complex operation of SOFCs and its associated cycle under practical conditions with the aim of enhancing the power output and efficiency of the cell. At the cell level, a two dimensional along the channel micro-scale isothermal model of a SOFC is developed and validated against experimental data and other simulated result from literature. The steady state behaviour of the cell was determined by numerical solution of the combined transport, continuity and kinetic equations. The model is capable of predicting the cell performance including polarisation behaviour and power output. The model is used to study the effect of the support structure, geometric parameters and the effect of operating conditions on cell performance. Several parametric studies, such as the effect of operating conditions and geometric parameters on cell performance with a view to optimising the cell. Also, at the cell level, a two dimensional along the channel model was developed which integrates a heat transfer model and direct internal reforming kinetics into the earlier developed isothermal model. This non-isothermal model was also validated against experimental data. The developed model not only predicts the performance of the SOFC at different design and operating conditions, it also provides an insight on the different phenomena and the distributions of current density, temperature and gas pressures within the cell. Microstructural parametric studies of the reaction layer were also carried out. Solid oxide fuel cells (SOFCs) are gaining prominence as power sources amongst other types of fuel cells due to their high electric energy efficiencies, their ability to integrate with other energy cycles in a hybrid system, fuel choice flexibility and low pollutant emissions. Operation of an SOFC involves complex coupling of the electrochemical reactions, chemical reactions and transport phenomena simultaneously in the cell’s main components consisting of gas channels, porous electrodes and the dense ceramic electrolyte. Consequently, mathematical modelling of these processes becomes an essential research tool aiming to provide detailed insight, while reducing cost, time and the effort associated with experimentation. The main aim of this thesis is to develop mathematical models in the cell and at system level to better understand the complex operation of SOFCs and its associated cycle under practical conditions with the aim of enhancing the power output and efficiency of the cell. At the cell level, a two dimensional along the channel micro-scale isothermal model of a SOFC is developed and validated against experimental data and other simulated result from literature. The steady state behaviour of the cell was determined by numerical solution of the combined transport, continuity and kinetic equations. The model is capable of predicting the cell performance including polarisation behaviour and power output. The model is used to study the effect of the support structure, geometric parameters and the effect of operating conditions on cell performance. Several parametric studies, such as the effect of operating conditions and geometric parameters on cell performance with a view to optimising the cell. Also, at the cell level, a two dimensional along the channel model was developed which integrates a heat transfer model and direct internal reforming kinetics into the earlier developed isothermal model. This non-isothermal model was also validated against experimental data. The developed model not only predicts the performance of the SOFC at different design and operating conditions, it also provides an insight on the different phenomena and the distributions of current density, temperature and gas pressures within the cell. Microstructural parametric studies of the reaction layer were also carried out. At the system level, the SOFC was integrated in a hybrid gas turbine plant. The integrated cycle was modelled using energy and exergy thermodynamic analysis. The analysis was done using the non-isothermal models developed for SOFC at the cell level and through the development of thermodynamic models for the other components such as the compressors, turbines, mixers, recuperators and combustors in the hybrid system. Performance comparison of two different hybrid configurations was carried out. Electrical efficiency, fuel utilisation efficiency, and exergy destruction were used in assessing the system performance. The results from the developed models shows that the anode supported SOFCs gives the best cell performance amongst other support structures when operated at intermediate temperatures and that the cathode ohmic overpotential is the single largest contributor to the cell potential loss. / Also, the inclusion of the heat transfer model and internal reforming kinetics significantly improves the cell predictions. The study on the effect of integrating the SOFC in a hybrid system showed an overall improvement with respect to electrical efficiency.