This research has assessed the environmental and economic sustainability of domestic micro-generation technologies under UK conditions as both individual technologies and as part of a range of future energy supply scenarios for the domestic sector extending to 2050. A life cycle approach has been used for both environmental and economic assessment considering the relevant sustainability impacts, which include global warming potential, the depletion of fossil fuels, human toxicity and life cycle cost. The micro-generation technologies studied were selected on the basis of their ability to contribute to current and future energy supply and also their suitability under UK conditions. These technologies were micro-wind, solar photovoltaics, micro-combined heat and power, heat pumps and solar thermal water heating. The technologies were compared with one another and with the incumbent technologies, which were grid electricity and natural gas condensing boilers. Three journal papers have been published as a result of this research. The evaluation of micro-generation technologies on a life cycle basis indicated that despite reducing certain environmental impacts, all technologies increased at least one and as many as eight environmental impacts compared to their current fossil-fuel alternatives. All micro-generation technologies would reduce global warming and fossil fuel depletion compared to conventional technologies, highlighting their potential to contribute to energy policy goals. However, they cannot currently compete with conventional technologies for capital cost, although their life cycle costs – taking into account incentives from schemes such as Feed-in Tariffs – can be competitive. Considering both environmental and economic implications suggested that Stirling engine micro-combined heat and power is one of the most sustainable options for heat and electricity generation. The results also suggested that heat pumps should not be receiving incentives from the Government due to their poor environmental performance. Four potential future energy supply scenarios for the UK domestic sector were studied extending to 2050. The scenarios varied in terms of the level of effort made to improve the environmental and economic sustainability of the sector. Scenario 1 involved no further implementation of micro-generation beyond 2009, increasing energy demand and a grid electricity dominated by fossil fuels. In contrast, Scenario 4 portrayed a future where there is 1 micro-generation technology per dwelling, a 50% reduction in demand and almost complete decarbonisation of the grid mix. The results indicated that a huge transformation of the sector is required to achieve the 80% reduction in CO2 emissions by 2050. This would include halving energy demand, almost complete decarbonisation of grid electricity and the installation of a micro-generation unit in every dwelling. To conclude, despite the level of interest micro-generation is currently receiving, this work suggested their usage may not necessarily be as beneficial as some believe. Their use does reduce greenhouse gas emissions and fossil fuel consumption; however, to have any influence on energy policy goals this use would have to be widespread. Furthermore, reduced emissions will come at the expense of other environmental impacts. Finally, with a number of the technologies not yet cost competitive – even with incentives – the Government focus on measures to reduce demand and decarbonise the grid may prove to be a better option as this work suggested that energy policy goals could be achieved without high penetration of micro-generation.

A stall-regulated wind turbine with fixed-speed operation provides a configuration which is one of the cheapest and simplest forms of wind generation and configurations. This type of turbine, however, is non-optimal at low winds, stresses the component structure and gives rise to significant power peaks during early stall conditions at high wind speeds. These problems can be overcome by having a properly designed generator speed control. Therefore, to track the maximum power locus curve at low winds, suppress the power peaks at medium winds, limit the power at a rated level at high winds and obtain a satisfactory power-wind speed curve performance (that closely resembles the ideal power-wind speed curve) with minimum stress torque simultaneously over the whole range of the wind speed variations, the availability of active control is vital. The main purpose of this study is to develop an internal model control (IMC) design for the squirrel-cage induction generator (SCIG), coupled with a full-rated power converter of a small (25 kW), stall-regulated, variable-speed wind-turbine (SRVSWT) system, which is subject to variations in the generator speed, electromagnetic torque and rotor flux. The study was done using simulations only. The objective of the controller was to optimise the generator speed to maximise the active power generated during the partial load region and maintain or restrict the generator speed to reduce/control the torque stress and the power-peaking between the partial and full load regions, before power was limited at the rated value of 25 kW at the full load region. The considered investigation involved estimating the proportional-integral (PI) and integral-proportional (IP) controllers parameter values used to track the stator-current producing torque, the rotor flux and the angular mechanical generator speed, before being used in the indirect vector control (IVC) and the sensorless indirect vector control (SLIVC) model algorithms of the SCIG system. The design of the PI and IP controllers was based on the fourth-order model of the SCIG, which is directly coupled to the full-rated power converter through the machine stator, whereas the machine rotor is connected to the turbine rotor via a gearbox. Both step and realistic wind speed profiles were considered. The IMC-based PI and IP controllers (IMC-PI-IP) tuning rule was proven to have smoothened the power curve and shown to give better estimation results compared to the IMC-based PI controllers (IMC-PI), Ziegler-Nichols (ZN) and Tyreus-Luyben (ZN) tuning rules. The findings also showed that for the SRVSWT system that employed the IVC model algorithm with the IMC-PI-IP tuning rule, considering the application of a maintained/constant speed (CS) strategy at the intermediate load region is more profitable than utilizing SRVSWT with the modified power tracking (MoPT) strategy. Besides that, the finding also suggested that, for the IMC-PI-IP approach, the IVC does provide better power tracking performance than the SLIVC model algorithm.

The air hybrid engine absorbs the vehicle kinetic energy during braking, stores it in an air tank in the form of compressed air, and reuses it to start the engine and to propel a vehicle during cruising and acceleration. Capturing, storing and reusing this braking energy to achieve stop-start operation and to give additional power can therefore improve fuel economy, particularly in cities and urban areas where the traffic conditions involve many stops and starts. In order to reuse the residual kinetic energy, the vehicle operation consists of 3 basic modes, i.e. Compression Mode (CM), Expander Mode (EM) and normal firing mode, as well as stop-start operation through an air starter. A four-cylinder 2 litre diesel engine has been modelled to operate in four air hybrid engine configurations so that the braking and motoring performance of each configuration could be studied. These air hybrid systems can be constructed with production technologies and incur minimum changes to the existing engine design. The regenerative engine braking and starting capability is realised through the employment of an innovative simple one-way intake system and a production cam profile switching (CPS) mechanism. The hybrid systems will allow the engine to be cranked by the compressed air at moderate pressure without using addition starters or dedicated valves in the cylinder head. Therefore, the proposed air hybrid engine systems can be considered as a cost-effective regenerative hybrid powertrain and can be implemented in vehicles using existing production technologies. A novel cost-effective pneumatic regenerative stop-start hybrid system, Regenerative Engine Braking Device (RegenEBD), for buses and commercial vehicles is presented. RegenEBD is capable of converting kinetic energy into pneumatic energy in the compressed air saved in an air tank using a production engine braking device and other production type automotive components and a proprietary intake system design. The compressed air is then used to drive an air starter to achieve regenerative stop-start operations. The proposed hybrid system can work with the existing vehicle transmission system and can be implemented with the retro-fitted valve actuation device and a sandwich block mounted between the cylinder head and the production intake manifold. Compression mode operation is achieved by keeping the intake valves from fully closed throughout the four-strokes through a production type variable valve exhaust brake (VVEB) device on the intake valves. As a result, the induced air could be compressed through the opening gap of intake valves into the air tank through the intake system of proprietary design. The compressed air can then be used to crank the engine directly through the air expander operation or indirectly through the action of an air starter in production. A single cylinder camless engine has been set up and operated to evaluate the compression mode performance of two air hybrid concepts. The experimental results are then compared with the computational output with excellent agreement. In order to evaluate the potential of the air hybrid engine technologies, a new vehicle driving cycle simulation program has been developed using Matlab Simulink. An air hybrid engine sub-model and methodology for modelling the air hybrid engine’s performance have been proposed and implemented in the vehicle driving cycle simulation. The NEDC analysis of a Ford Mondeo vehicle shows that the vehicle can achieve regenerative stop-start operations throughout the driving cycle when it is powered by a 2.0litre diesel engine with air hybrid operation using a 40litre air tank of less than 10bar pressure. The regenerative stop-start operation can lead to 4.5% fuel saving during the NEDC. Finally, the Millbrook London Transport Bus (MLTB) driving cycle has been used to analyse the effectiveness of RegenEBD on a double deck bus powered by a Yuchai diesel engine. The results show that 90% stop-starts during the MLTB can be accomplished by RegenEBD and that a significant fuel saving of 6.5% can be obtained from the regenerative stop-start operations.

More stringent Euro 6 and LEV III emission standards will immediately begin execution on 2014 and 2015 respectively. Accurate air/fuel ratio control can effectively reduce vehicle emission. The simulation of engine dynamic system is a very powerful method for developing and analysing engine and engine controller. Currently, most engine air/fuel ratio control used look-up table combined with proportional and integral (PI) control and this is not robust to system uncertainty and time varying effects. This thesis first develops a simulation package for a port injection spark-ignition engine and this package include engine dynamics, vehicle dynamics as well as driving cycle selection module. The simulations results are very close to the data obtained from laboratory experiments. New controllers have been proposed to control air/fuel ratio in spark ignition engines to maximize the fuel economy while minimizing exhaust emissions. The PID control and fuzzy control methods have been combined into a fuzzy PID control and the effectiveness of this new controller has been demonstrated by simulation tests. A new neural network based predictive control is then designed for further performance improvements. It is based on the combination of inverse control and predictive control methods. The network is trained offline in which the control output is modified to compensate control errors. The simulation evaluations have shown that the new neural controller can greatly improve control air/fuel ratio performance. The test also revealed that the improved AFR control performance can effectively restrict engine harmful emissions into atmosphere, these reduce emissions are important to satisfy more stringent emission standards.

The technologies of urban wind turbines have been rapidly developed in recent years, but urban wind turbines have not found a wide application due to the limitations of their designs. The power output of urban wind turbine is significantly affected by urban terrain, which can cause low speed flow with frequent change of its direction. Thus, there is a need for a new wind turbine to meet the requirements of an urban wind turbine. In this study, a novel wind turbine for urban areas was designed and developed. The investigations of the novel urban wind turbine were carried out by using computational fluid dynamic (CFD) simulations and wind tunnel tests. The results from the investigation have shown that the novel wind turbine has a great potential to harvest wind energy in urban areas. A detailed study of effects of each parameter on wind energy concentration of the novel wind turbine was carried out with CFD simulations. According to the simulation results, the shroud structure of the novel wind turbine was modified and the dimensions of the final structure were identified. It was determined that the capability of wind energy concentration of the novel wind turbine shroud has been significantly improved through the structure optimisations. Furthermore, guide vane and impulse turbine were implemented in the novel wind turbine. The flow characteristics through the guide vane was studied and discussed. It was found that the wind flow characteristics can be properly modified by implementing guide vane and the structure of impulse turbine was suitable to be implemented in the novel wind turbine due to the flow characteristic through the guide vane.

The exploitation of small horizontal axis wind turbines provides a clean, prospective and viable option for energy supply. Although great progress has been achieved in the wind energy sector, there is still potential space to reduce the cost and improve the performance of small wind turbines. An enhanced understanding of how small wind turbines interact with the wind turns out to be essential. This work investigates the aerodynamic design and analysis of small horizontal axis wind turbine blades via the blade element momentum (BEM) based approach and the computational fluid dynamics (CFD) based approach. From this research, it is possible to draw a series of detailed guidelines on small wind turbine blade design and analysis. The research also provides a platform for further comprehensive study using these two approaches. The wake induction corrections and stall corrections of the BEM method were examined through a case study of the NREL/NASA Phase VI wind turbine. A hybrid stall correction model was proposed to analyse wind turbine power performance. The proposed model shows improvement in power prediction for the validation case, compared with the existing stall correction models. The effects of the key rotor parameters of a small wind turbine as well as the blade chord and twist angle distributions on power performance were investigated through two typical wind turbines, i.e. a fixed-pitch variable-speed (FPVS) wind turbine and a fixed-pitch fixed-speed (FPFS) wind turbine. An engineering blade design and analysis code was developed in MATLAB to accommodate aerodynamic design and analysis of the blades. The linearisation for radial profiles of blade chord and twist angle for the FPFS wind turbine blade design was discussed. Results show that, the proposed linearisation approach leads to reduced manufacturing cost and higher annual energy production (AEP), with minimal effects on the low wind speed performance. Comparative studies of mesh and turbulence models in 2D and 3D CFD modelling were conducted. The CFD predicted lift and drag coefficients of the airfoil S809 were compared with wind tunnel test data and the 3D CFD modelling method of the NREL/NASA Phase VI wind turbine were validated against measurements. Airfoil aerodynamic characterisation and wind turbine power performance as well as 3D flow details were studied. The detailed flow characteristics from the CFD modelling are quantitatively comparable to the measurements, such as blade surface pressure distribution and integrated forces and moments. It is confirmed that the CFD approach is able to provide a more detailed qualitative and quantitative analysis for wind turbine airfoils and rotors. With more advanced turbulence model and more powerful computing capability, it is prospective to improve the BEM method considering 3D flow effects.

Dans ce travail, on présente une étude des performances d’un capteur solaire plan double passe destiné à la production de l’air chaud permettant d’alimenter et d’améliorer les techniques de séchage. On analyse les cas d’un absorbeur avec et sans ailettes.Les modèles théoriques relatifs au capteur à air double passe avec et sans ailettes ont été établis et résolus numériquement à l’aide de codes élaborés en Fortran pour obtenir une approche globale de leur comportement ou alors à l’aide de Comsol multiphysique pour une étude plus locale. Un dispositif expérimental a été conçu pour valider les résultats obtenus numériquement. Une des particularités du capteur mis au point au laboratoire est relative à son système d'isolation. À cet effet, un matériau local composé de tiges de mil broyées (biosourcé) a été réalisé dans le but d’augmenter les performances du capteur solaire. Les propriétés des matériaux biosourcés utilisés pour l’isolation ont été identifiées à l’aide de moyens existant au laboratoire. Une comparaison des températures mesurées et calculées a permis de valider les deux approches expérimentale et numérique. L’évaluation des performances a montré une forte influence du débit et du rayonnement solaire sur le rendement énergétique du capteur solaire double passe avec ailettes. L’approche globale des bilans thermique au sein du capteur solaire repose principalement sur une bonne connaissance des coefficients d’échange entre le fluide caloporteur et l’absorbeur, un travail d’estimation de ces coefficients d’échange convectif est proposé dans la dernière partie de ce travail.Mots clés : Capteur solaire, double passe, tige de mil broyée, matériau biosourcé, modélisation numérique, expérimentale, performance. / In this work, we present a study of the performance of a double pass flat solar collector for the production of hot air to supply and improve drying techniques. The cases of an absorber with and without fins are analyzed.Theoretical models for the double pass solar collector with and without fins have been established and solved numerically using codes developed in Fortran to obtain a global approach. Comsol Multi-physics code is used for a more local study. An experimental device has been designed to validate the results obtained numerically. One of the particularities of the solar collector developed in the laboratory is its insulation system. For this, a local bio-sourced material composed of crushed millet stems has been developed to increase the performance of the solar collector. The properties of the bio-sourced materials used for insulation were characterized by using available laboratory testing model. A comparison of the measured and calculated temperatures validated both the experimental and numerical approaches. The performance evaluation showed a strong influence of the flow rate and solar radiation on the energy efficiency of the double pass finned solar collector. The global approach to heat balances within the solar collector is mainly based on the heat transfer coefficients between the fluid and the absorber. An estimation of these coefficients is proposed in the last part of this work.Keywords: Solar collector, double pass, millet rod crushed, biosourced material, numerical modeling, experiment, performance.

The purpose of this research is to propose a novel wind turbine for an omni-flow wind energy system and investigate its aerodynamic performance. The geometry of the novel wind turbine is based upon the impulse turbine technology which has been successful in wave energy. In this study, both numerical and experimental studies were conducted to evaluate the aerodynamic features of this wind turbine. The numerical method was validated by a comparison between numerical and experimental results over a range of tip speed ratios. Results obtained from experiments and simulations indicate that the proposed wind turbine can be employed. Additionally, on the basis of the analyses performed, this new wind turbine has the potential for having a good startup feature, which means that this wind turbine can be suitable for applications in an urban environment. As an important component, the stator of this wind turbine can increase the passing flow velocity by 20%. Meanwhile, the passing flow direction also can be optimised by the stator. Aerodynamics of the wind turbine was analysed under the non-uniform flow condition, because the flow is non-uniform inside the omni-flow wind energy system. It was found that the maximum power coefficient of such a turbine under the non-uniform flow condition is lower than that under the uniform flow condition. Due to the non-uniform flow, the blades experience different flow velocities, and as a consequence, undergo different aerodynamic loads during one operation cycle. Thus the generated torque and thrust on a blade are subjected to frequent and periodical changes. Influences of the geometrical parameters on the aerodynamic characteristics of this wind turbine were investigated. From the initial study, it was found that changes of hub-to-tip ratios, numbers of blades, aerofoils and numbers of guide vanes, can significantly affect the II power performance. Additionally, the wind turbine obtained high values of maximum torque coefficients with changing geometrical parameters.

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Thermal energy accounts for 49% of the National annual energy budget of the United Kingdom. In a typical household, the consumption of thermal energy makes up to 77% of its annual energy consumption, made of space heating and hot water production. Intermittent renewable energy sources are often used to reduce the domestic energy expenditure of national energy systems such as the electric grid or the natural gas network. Energy storage, and increasingly heat storage, is often described as one way to overcome the unpredicatable nature of many renewable energy systems. This thesis investigates the use of a latent heat storage system, which uses the enthalpy of transition between two physical states, as a means to store thermal energy at a low thermal loss. To achieve this, a phase change material (PCM), a material with a high enthalpy of transition, is allowed to supercool and enter a metastable state. A novel trigger mechanism is presented and refined to initiate nucleation in the supercooled PCM, beginning the phase transition and releasing the enthalpy of transition. From over 150 PCMs which are described in the literature, four are investigated in detail for their suitability in this application. A particular PCM, CaCl2.6H2O is investigated further and its issue of incongruent melting is successfully suppressed. The trigger mechanism presented uses a Peltier heat pump to locally cool a small amount of PCM, contained within a latent heat store. The supercooled PCM was cooled to a critical point, its autonucleation temperature, where a stable nucleus is spontaneously formed through heterogeneous nucleation. The trigger mechanism was demonstrated to work on multiple PCMs. The trigger mechanism was then implemented into a latent heat storage system, reffered to as a heat battery. The heat battery was filled with a characterised eutectic PCM mixture, CaCl2.6H2O + 5% KCl (w.t.). The trigger mechanism was demonstrated to initiate nucleation within the heat battery. The work demonstrates the ability for a heat battery to operate using a supercooled PCM and activation mechanism, and then highlights the limitations of such an approach. Future work is identified, which must first be tackled in order to construct a fully technically viable system.