Over the last couple of decades, there has been increased interest in environmentally friendly technologies. One of the renewable energy sources that has experienced huge growth over the years is wind power with the introduction of new wind farms all over the world, and advances in wind power technology that have made this source more efficient. This recognition, together with an increased drive towards ensuring the sustainability of wind energy systems, has led many to forecast the drivers for future performance. This study aims to identify the most sustainable wind turbine design option for future grid electricity within the context of sustainable development. As such, a methodology for sustainability assessment of different wind turbine design options has been developed taking into account environmental, data uncertainty propagation and economic aspects. The environmental impacts have been estimated using life cycle assessment, data uncertainty has been quantified using a hybrid DQI-statistical method, and the economic assessment considered payback times. The methodology has been applied to a 1.5 MW wind turbine for an assessment of the current situation and potential technology improvement opportunities. The results of this research show that overall, the design option with the single-stage/permanent magnet generator is the most sustainable. More specifically, the baseline turbine performs best in terms of embodied carbon and embodied energy savings. On the other hand, the design option with the single-stage/permanent magnet generator performs best in terms of wind farm life cycle environmental impacts and payback time compared to the baseline turbine. With respect to the design options with increased tower height, it is estimated that both designs are the least preferred options given their payback times. Therefore, the choice of the most sustainable design option depends crucially on the importance placed on different sustainability indicators which should be acknowledged in decision making and policy.

Global climate change is one of the greatest challenges of the 21st century. Rising ambient temperatures and deterioration of weather patterns are anticipated to result from increased atmospheric concentrations of greenhouse gases caused in part by the use of fossil fuels for electricity generation and domestic heating purposes. The possibility of a global temperature rise of between 1 degree C and 4.5 degree Celsius has led to considerable research efforts into the effects of changes in temperature and other climatic variables. The increasing use of private capital in the energy industry has altered the focus from the provision of a service to the need to make profits from the production and sale of a commodity. Additionally, with respect to Luxembourg, the dependency on imported energy is an important risk factor. This thesis presents biomass as an essential alternative to substitute for some of the fossil fuels in the domain of heat, cooling and power generation. The results presented show an increase in energy utilisation and thus energy efficiency and reduction in emissions when used in combined generation modes as opposed to single generation. These results are gathered through meticulous analytical models, computational fluid dynamics (CFD), and laboratory testing of real life biomass systems. The technologies and analysis investigated here are targeted at those involved in climate change research, providing them with valuable data on the energy analysis of biomass and its associated emissions, highlighting the potential for reduction in pollutions when biomass is used instead of fossil fuels; in energy policy making; investors; engineers; and all others involved in the biomass design and operation of combined generation of biomass applications.

This research is in the area of Thermal Energy Conversion, more specifically, in the conversion of solar thermal energy. This form of renewable energy can be utilised for production of power by using thermo-mechanical conversion systems – Stirling engines. The advantage of such the systems is in their capability to work on low and high temperature differences which is created by the concentrated solar radiation. To design and build efficient, high performance engines in a feasible period of time it is necessary to develop advanced mathematical models based on thermodynamic analysis which accurately describe heat and mass transfer processes taking place inside machines. The aim of this work was to develop such models, evaluate their accuracy by calibrating them against published and available experimental data and against more advanced three-dimensional Computational Fluid Dynamics models. The refined mathematical models then were coupled to Genetic Algorithm optimisation codes to find a rational set of engine’s design parameters which would ensure the high performance of machines. The validation of the developed Stirling engine models demonstrated that there was a good agreement between numerical results and published experimental data. The new set of design parameters of the engine obtained from the optimisation procedure provides further enhancement of the engine performance. The mathematical modelling and design approaches developed in this study with the use of optimization procedures can be successfully applied in practice for creation of more efficient and advanced Stirling engines for power production.

This thesis explores students’perceptions and practices within the context of a Mechanical Engineering undergraduate degree at a UK Higher Education institution. This engineering education research is situated in the pragmatic paradigm and is informed by a relational view of learning. The study explores the perceptions of students throughout the second year of their programme and also investigates their practices during the same time period. The research employs a mixed-methods exploratory methodology with data collection led by a dominant qualitative phase and followed by a quantitative phase. Data is integrated to present a holistic understanding of students’ perceptions and practices. The results demonstrate the importance for academia to consider students’ expectations and perceptions and to understand students’ actual practices. Analysis of the data has enabled the context to be defined from a student perspective; showing four key areas of context as being the staff-student relationships, students and student cultures, the teaching and assessment context, and the course contexts. The connection between students’perceptions and their practices is clearly established in the data. The integrated findings highlight the complexities involved for students in carrying out the practice of learning in a complex environment alongside their own perceptions of the discipline, the programme, their peers and staff. Combining the two data types has enabled the significance of perceptions to be highlighted, the vast elements of context to be demonstrated and finally recommendations to be produced to inform the design and execution of engineering education. Specific attention is drawn to findings which suggest further explanatory work is required to explore aspects such as; students’perceptions of importance, their participation in informal peer working, the distinction between procedural and conceptual learning for the discipline and the expectation of professionalism that students hold.

The work develops the application of evolutionary algorithms in the domain of automotive heat exchanger design. The principal employed is that of computer regulated changes to a physical model which attempts optimisation using methods analogous to biological evolution. It shows that the use of airside fins with differing louvre angles can enhance the performance of automotive heat exchangers by a useful margm. This has been achieved with a wind tunnel model that allows automatic configuration of the louvre angles, and novel instrumentation allowing heat transfer performance to be assessed in terms of shear and drag forces acting on the louvres. During the investigation an important coupling between the behaviour of adjacent louvres was discovered, manifested as a loss in useful shear force at around ±12° relative angle. The work as a whole shows that specific louvre angle selections and quantitative estimates of the potential performance gains could be made with the following improvements to the physical model and search algorithms. The number of louvre rows should be doubled (to 16) to better represent typical matrices and the instrumented louvres should be centrally positioned in the air stream. Improved data filtering is required for reliable operation and the specific figure of merit has been shown to be an important factor in the optimisation process. A parallel area of application for the optimisation strategies was the solution of the Wilson plot problem. This represents a novel approach to the analysis of heat exchanger experimental test data where an alternative curve fitting and visualisation format allows more accurate models to be established. By these methods functions defining heat transfer coefficients for both sides of a heat exchanger may be determined that give a fit to experimental data to within less than 1. 5% on measured overall heat transfer coefficient.

This work is concerned with the development of a new quantitative kinetic model for the analysis of hydrocarbon fuel droplet heating and evaporation, suitable for practical engineering applications. The work mainly focuses on the following two areas. Firstly, a new molecular dynamics (MD) algorithm for the simulation of complex hydrocarbon molecules, with emphasis on the evaporation/condensation process of liquid n-dodecane (C12H26), which is used as an approximation for Diesel fuel, has been developed. The analysis of n-dodecane molecules has been reduced to the analysis of simplified molecules, consisting of pseudoatoms, each representing the methyl (CH3) or methylene (CH2) groups. This analysis allows us to understand the underlying physics of the evaporation/condensation process of n-dodecane molecules and to estimate the values of its evaporation/condensation coefficients for a wide range of temperatures related to Diesel engines. Nobody, to the best of our knowledge, has considered MD simulation of molecules at this level of complexity. Secondly, a new numerical algorithm for the solution of the Boltzmann equation, taking into account inelastic collisions between complex molecules, has been developed. In this algorithm, additional dimensions referring to inelastic collisions have been taken into account alongside three dimensions describing the translational motion of molecules as a whole. The conservation of the total energy before and after collisions has been considered. A discrete number of combinations of the values of energy corresponding to translational and internal motions of molecules after collisions have been allowed and the probabilities of the realisation of these combinations have been assumed to be equal. This kinetic model, with the values of the evaporation coefficient estimated based on MD simulations, has been applied to the modelling of the heating and evaporation processes of n-dodecane droplets in Diesel engine-like conditions. In the previously developed kinetic models, applied to this modelling, all collisions were assumed to be elastic and the evaporation coefficient was assumed equal to 1. It is shown that the effects of inelastic collisions lead to stronger increase in the predicted droplet evaporation time relative to the hydrodynamic model, compared with the similar increase predicted by the kinetic model considering only elastic collisions. The effects of a non-unity evaporation coefficient are shown to be weak at gas temperatures around or less than 1,000 K but noticeable for gas temperatures 1,500 K. The application of the rigorous kinetic model, taking into account the effects of inelastic collisions and a non-unity evaporation coefficient, and the model considering the temperature gradient inside droplets is recommended when accurate predictions of the values of droplet surface temperature and evaporation time in Diesel engine-like conditions are essential.