The cumulative global photovoltaic (PV) capacity has been growing exponentially around the world, especially due to the installation of grid connected photovoltaic (GCPV) plants. Fault detection and analysis are important for the efficiency, reliability and safety of solar photovoltaic (PV) systems. Even This thesis reports the results of the research work conducted to invent novel fault detection algorithms and evaluate their deployment in multiple existing PV installation, and empirically validate their performance. A major contribution of this thesis is the development of PV fault detection algorithms based on two indicators named power ratio (PR) and voltage ratio (VR). Both ratios are used to identify the type of the fault that occurs in the PV modules, in PV string, and/or in maximum power point tracking (MPPT) unit. Three AI based algorithms were also used to detect faults in PV modules. The first algorithm uses six regions of the power and voltage ratio in order to detect faults in PV systems. The average detection accuracy for the algorithm is equal to 94.74%. However, Mamdani Fuzzy Logic system has been used to enhance the occurrence of fault detection in the PV installations which resulted in an increase to 99.12%. The second proposed PV fault detection algorithm detects defective bypass diodes in PV modules using Mamdani Fuzzy Logic. Whereas, a third PV detection algorithm is based on artificial neural networks (ANN) networks. Four different ANN models have been modelled, which can be classified as follows: - 2 inputs, 5 outputs using 1 hidden layer - 2 inputs, 5 outputs using 2 hidden layers - 2 inputs, 9 outputs using 1 hidden layer - 2 inputs, 9 outputs using 2 hidden layers The output results for the last ANN network had the highest overall fault detection accuracy of 92.1%. In this thesis, the development of two hot spot mitigation techniques used in PV modules will be discussed. These techniques are capable of enhancing the output power of PV modules which are affected by hot spots and partial shading conditions. The detection of hot spots was captured using i5 FLIR thermal imaging camera. Finally the thesis describes the impact of PV micro cracks on the output power of PV modules. A new statistical analysis approach using T-test and F-test was used to identify the significance impact of the cracks on the output power performance of the PV modules. This is developed using LabVIEW software.

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With dwindling worldwide petroleum supplies, there is an ever increasing pressure on the oil industry to develop new reservoir recovery mechanisms or maximise the effectiveness of those currently utilised. Fluctuations of reservoir recovery as a result of nearby seismic activity has been observed, initiating a range of studies into what is causing this effect. The generation of ultrasonic wave fields due to the dispersion of seismic wave fields as they travel through saturated porous rock has been shown, both analytically and experimentally. The feasibility of these generated ultrasonic waves being capable of this observed modification to reservoir is investigated. For the initial stage of this research, the feasibility of changing the behaviour of fluid in rock using an ultrasonic field is considered. Research into the interaction between acoustic waves, the porous rock and the pore fluid indicates two key areas of permeability enhancement - increasing rock permeability and modifying the fluid behaviour within the pores. By increasing the permeability of the rock, previously unobtainable sources may be recovered and less energy would be necessary to obtain these reserves. Cavitation erosion or localised rock weakening due regions of high stress resulting from complex internal wave interactions are the two mechanisms proposed to increase permeability. Modification of the relative fluid behaviours within the rock as a result of mechanical agitation of the fluid from peristaltic transport and cavitation bubbles generated due to the acoustic field was explored. Sandstone cores saturated partially with tap water were placed in a degassed fluid and a low or high acoustic field applied. Tensile strength measurements are taken following exposure to the acoustic field and measurements compared to control samples. Samples were weighed prior to and following testing to determine fluid and gas motion between the surrounding fluid and pore volume. Samples exposed to the low amplitude acoustic pressure field showed no change in tensile strength when compared to control samples. The high pressure acoustic field caused samples to have an increase of strength when compared to the control batch of samples. The partial saturation of the samples exposed to the acoustic pressure field showed an increased in mass following exposure. An exchange of gas bubbles trapped within the pores and fluid with the surrounding degassed water explains this mass increase during testing.

Monolithically integrating multiple sensing technologies shows a great potential to perform quantitative measurements for multiple biomarkers of diseases and also provide more insight towards one single biochemical event. The localised surface plasmon resonance spectroscopy measures the change in the refractive index arising from the molecular adsorption on the metallic nanostructures. Acoustic sensors, such as surface acoustic wave sensor and quartz crystal microbalance, measure the variation of its mechanical oscillation caused by the sum of the deposited molecules and the solvent coupled to the adsorbed molecules. Both techniques are known independently as having applications in in-situ, label-free sensing and analysis of biological binding reactions. Due to their complementary properties, the integration of both can prove to be a valuable tool for studying biomolecules on sensing surface. This thesis reports on the development of a hybrid biosensing device that integrates localised surface plasmonic sensing and acoustic sensing technologies. Gold nanodisk arrays as localised surface plasmon resonance sensing device was studied in visible region using three substrates: borosilicate glass, lithium niobate and quartz. The design, simulation, fabrication and characterisation of the gold nanodisk arrays, and the sensing performance optimisation were investigated using glass substrate. Lithium niobate, as a piezoelectric material has surface acoustic wave compatibility and this study can pave the way towards the development of hybrid sensing devices. The study on lithium niobate demonstrated the feasibility of a localised surface plasmon resonance device utilising a high refractive index, birefringent and piezoelectric substrate. Using quartz as the substrate, the design and fabrication of a hybrid sensor were performed, which integrated localised surface plasmonic resonance into a quartz crystal microbalance for studying biochemical surface binding reactions. The coupling of localised plasmon resonance nanostructures and a quartz crystal microbalance allows optical spectra and quartz crystal microbalance resonant frequency shifts to be recorded simultaneously, and analysed in real time for a given surface adsorption process. This integration has the potential to be miniaturised for application in point-of-care diagnostics.

Designs for geostationary (GEO) solar power satellites (SPS) are extremely large in scale, more than one order of magnitude larger than the International Space Station. In this thesis a detailed study of the orbit dynamics of SPS is performed. Analytical equations, derived by the process of averaging of the SPS equations of motion, are used to determine the long-term orbital evolution. Previous SPS studies have simply assumed a GEO as the operational orbit, and then designed control systems for maintaining the orbit within acceptable nominal values. It is found that an alternative SPS orbital location known as the geosynchronous Laplace plane orbit (GLPO) is superior to GEO in many aspects. An SPS in GLPO requires virtually no fuel to maintain its orbit, minimises the risk of debris creation at geosynchronous altitude, and is extremely robust operationally, i.e. loss of control is inconsequential. The GLPO SPS requires approximately 10^5 kg less fuel per year compared to a GEO SPS while providing near equivalent power delivery. Although savings in orbit control are achieved, depending on the mass distribution of the SPS, attitude control costs may be incurred by placing an SPS in GLPO. Consideration of the attitude dynamics of SPS has motivated the development of a model for the rotational dynamics of a body which includes energy dissipation and the effects of external torques. Multiple spring-damper masses are used to provide a mechanism for energy dissipation. This rotational dynamics model is used to assess the naturally stable attitude configurations of a SPS design in geosynchronous orbit subject to gravity gradient torque. It is found that for a large planar array, a dynamically stable configuration requiring nominal orbit-attitude control is possible. This involves rotating around the maximum axis of inertia at the orbit rate, with the minimal axis aligned in the radial direction. It will be shown that a SPS in this configuration while in GLPO requires virtually no orbit or attitude control. The most significant result of the research in this thesis is proving that a SPS can operate in GLPO with nominal orbit control and yet still deliver almost equivalent power to the Earth’s surface as the same SPS would in a controlled GEO.

Most desired applications for planning and scheduling typically have the characteristics of a continuous changing world. Unfortunately, traditional classical planning does not possess this characteristic. This drawback is because most real-world situations involve quantities and numeric values, which cannot be adequately represented in classical planning. Continuous planning in domains that are represented with rich notations is still a great challenge for AI. For instance, changes occurring due to fuel consumption, continuous movement, or environmental conditions may not be adequately modelled through instantaneous or even durative actions; rather these require modelling as continuously changing processes. The development of planning tools that can reason with domains involving continuous and complex numeric fluents would facilitate the integration of automated planning in the design and development of complex application models to solve real world problems. Traditional urban traffic control (UTC) approaches are still not very efficient during unforeseen situations such as road incidents when changes in traffic are requested in a short time interval. For such anomalies, we need systems that can plan and act effectively in order to restore an unexpected road traffic situation into a normal order. In the quest to improve reasoning with continuous process within the UTC domain, we investigate the role of Model Predictive Control (MPC) approach to planning in the presence of mixed discrete and continuous state variables within a UTC problem. We explore this control approach and show how it can be embedded into existing, modern AI Planning technology. This approach preserves the many advantages of the AI Planning approach, to do with domain independence through declarative modelling, and explicit reasoning while leveraging the capability of MPC to deal with continuous processes. We evaluate the possibility of reasoning with the knowledge of UTC structures to optimise traffic flow in situations where a given road within a network of roads becomes unavailable due to unexpected situations such as road accidents. We specify how to augment the standard AI planning engine with the incorporation of MPC techniques into the central reasoning process of a continuous domain. This approach effectively utilises the strengths of search-based and model-simulation-based methods. We create a representation that can be used to capture declaratively, the definitions of processes, actions, events, resources resumption and the structure of the environment in a UTC scenario. This representation is founded on world states modelled by mixed discrete and continuous state variables. We create a planner with a hybrid algorithm, called UTCPLAN that combines both AI planning and MPC approach to reason with traffic network and control traffic signal at junctions within the network. The experimental objective of minimising the number of vehicles in a queue is implemented to validate the applicability and effectiveness of the algorithm. We present an experimental evaluation showing that our approach can provide UTC plans in a reasonable time. The result also shows that the UTCPLAN approach can perform well in dealing with heavy traffic congestion problems, which might result from heavy traffic flow during rush hours.

The use of Mid-infrared (mid-IR) imagers has great potential for a number of applications in gas sensing and medical diagnostics, but so far for many of those non-defence fields it has been significantly limited by their high price tag. One of the reasons behind the great cost of mid-IR imagers is that most of them need to operate at cryogenic temperatures. Thanks to more than half a century of research, state-of-the-art mid-IR photodetectors have finally achieved premium detection performance without the need for cryogenic cooling. Some of them have even demonstrated very promising results, suggesting room temperature operation is on the horizon. As a result, the cost associated with cooling equipment has been significantly suppressed. However, most mid-IR imagers are still based on hybrid technologies needing a great number of die-level process steps and being prone to connection failure during thermal cycles. The high manufacturing cost this entails is also preventing a wider diffusion of mid-IR imagers. Currently, there is still a lack of an effective monolithic approach able to achieve low-cost mass production of mid-IR imagers in the same way as monolithic integration has been widely used for imagers working at visible wavelengths. This thesis presents a novel monolithic approach for making mid-IR imagers based on co-integration of mid-IR photodetectors with GaAs-based MESFETs on the same chip. The initial focus of the project was the development of the fabrication steps for delivery of prototype devices. In order to achieve monolithic fabrication of pixel devices made in either indium antimonide (InSb) or indium arsenide antimonide (InAsSb) on a gallium arsenide (GaAs) substrate, various highly controllable etch processes, both wet and dry etch based, were established for distinct material layers. Moreover, low temperature annealed Ohmic contacts to both antimonide-based materials and GaAs were used. The processing temperatures used never exceeded 180˚C, preventing degradation of photodetector performance after fabrication of transistors, thus avoiding well-known thermal issues of InSb fabrication. Furthermore, an intermediate step based on polyimide was developed to provide a smoothing section between the lower MESFET and upper photodetector regions of the pixel device. The polyimide planarisation enabled metal interconnects between the fabricated devices regardless of the considerable etch step ( > 6 µm) created after multiple mesa etches. Detailed electrical and optical measurements demonstrated that the devices were sensitive to mid-IR radiation in the 3 to 5 µm range at room temperature, and that each pixel could be isolated from its contacts by switching off the co-integrated MESFET. Following the newly developed fabrication flow, InSb-based mid-IR imaging arrays (in two sizes, 4×4 and 8×8) are presented here for the first time, with pixel addressing achieved by monolithically integrated GaAs MESFETs. By demonstrating real-time imaging results obtained from these array devices at room temperature, implementation of a new type of monolithic focal plane array for mid-IR imaging has been confirmed. The device is suitable for further scaling (up to 64×64 pixel and beyond) and potential commercialisation. More importantly, the monolithic approach developed in this work is very flexible, as a number of III-V materials with mid-IR detecting capabilities can be grown on GaAs substrates, meaning alternative semiconductor layer structures could also be investigated in the near future.

Since the first contact and fusion of an egg and sperm and throughout development, a cell lives a life of constant communication with its environment. Cells interact with the external environment via a layer of proteins and respond to not only biochemical cues but also physical properties including stiffness and topography of adjacent surfaces. However, even though polymeric biomaterials have been described as one of the cornerstones of tissue engineering, the effect of an intrinsic polymer property known as mobility on cell behaviour is poorly characterised. Mobility is a physical property of polymers inversely proportional to the glass transition temperature (Tg); the temperature at which polymers undergo a transition between a rubbery viscous state to a glassy brittle solid. Therefore, films of four poly(alkyl acrylates) with similar surface chemistry but different glass transition temperatures achieved by varying branch chain lengths (1, 2, 4 or 6 methyl groups) were used in this work to investigate the role of polymer mobility on cell behaviour. I verified using atomic force microscopy the similarity in topography and stiffness between the four substrate surfaces and ascertained that fibronectin molecules adsorb in a globular conformation on the polymer with the shortest side chain (1 methyl group) compared with a more extended conformation on the rest of the polymers. My study of the fibronectin coatings using fluorescence recovery after photobleaching (FRAP) on the different polymer surfaces suggested that the mobility of the polymer substrate is translated to the interfacial protein layer. This interesting finding highlighted a possible pathway for cells cultured on fibronectin coated polymer surfaces to detect the underlying polymer mobility via the fibronectin coating. The interaction of cells with surfaces occurs via membrane proteins which interact with specific structural sites within extracellular matrix proteins; these include the cell binding site (RGD: Arginine Glycine Aspartic acid amino acid motif) and the Synergy site (PHSRN: Proline Histidine Serine Asparagine amino acid motif). My ELISA analyses indicated a higher exposure of these important cell-binding sites on the more extended fibronectin compared with the globular one however, this did not correlate to the mobility of polymers or the mobility of the fibronectin layer. This was also the case for myogenic cell differentiation, which was indiscriminately higher on polymers with extended fibronectin, however, cytoskeletal contractility was found to play an essential role in the myogenic differentiation of cells on these polymers in a mobility dependent manner. We then sought to understand the role of 21 mobility in modulating osteogenic differentiation of human MSCs in the presence and absence of stimulation with BMP-2. The Fibronectin network-forming polymer with the lowest mobility (side chain of 2 methyl groups) induced the highest expression of osteogenic markers in the absence of BMP-2 stimulation. My mechanistic studies using specific inhibitors also revealed that the Erk1/2 pathway was required for this increase in osteogenic markers, while contractility, unlike in myogenesis produced only minimal effects on osteogenic differentiation. In this set of polymers, mobility increases with side chain length, while all the polymers with more than one methyl group in their side chain induced the independent formation fibronectin networks upon adsorption. The polymer with two methyl groups in its side chain is characterised with the lowest mobility among the three fibrillogenesis - inducing polymers, and the highest expression of osteogenic markers in the absence of BMP-2. In the presence of BMP-2, smad phosphorylation was also higher on this polymer suggesting a combined synergistic effect towards osteogenic differentiation provided by the simultaneous activation of the Erk1/2 pathway and high phosphorylation of smad1/5/8. My observations suggest that fibronectin fibrils coating a polymer with low mobility may be most suited for osteogenic differentiation of hMSCs by simultaneously exposing cell-binding sites to a higher degree. Thus, inducing Erk1/2 signalling and presenting BMP-2 in a manner that stimulates the highest phosphorylation of smad1/5/8 hence achieving a stronger synergistic effect on the overall expression of osteogenic markers. The findings from this work strongly support previous studies suggesting that polymer mobility is a subtle change in the substrate with significant downstream biological significance and is crucial to understand to improve the application of polymeric biomaterials.

Silicon compatible light sources have been referred to as the \holy grail" for Si photonics. Such devices would give the potential for a range of applications; from optical interconnects on integrated circuits, to cheap optical gas sensing and spectroscopic devices on a Si platform. Whilst numerous heterogeneous integration schemes for integrating III-V lasers with Si wafers are being pursued, it would be far easier and cheaper to use the epitaxial tools already in complementary-metal-oxide-semiconductor (CMOS) lines, where Ge and SiGe chemical vapour deposition is used in a number of advanced technology nodes. Germanium is an effcient absorber, but a poor emitter due to a band-structure which is narrowly indirect, but by only 140 meV. Through the application of strain, or by alloying with Sn, the Ge bandstructure can be engineered to become direct bandgap, making it an effcient light emitter. In this work, silicon nitride stressor technologies, and CMOS compatible processes are used to produce levels of tensile strain in Ge optical micro-cavities where a transition to direct bandgap is predicted. The strain distribution, and the optical emission of a range of Ge optical cavities are analyzed, with an emphasis on the effect of strain distribution on the material band-structure. Peak levels of strain are reported which are higher than that reported in the literature using comparable techniques. Furthermore, these techniques are applied to GeSn epi-layers and demonstrate that highly compressive GeSn alloys grown pseudomorphically on Ge virtual substrates, can be transformed to direct bandgap materials, with emission >3 m wavelength { the longest wavelength emission demonstrated from GeSn alloys. Such emission is modeled to have a good overlap with methane absorption lines, indicating that there is huge potential for the such technologies to be used for low cost, Si compatible gas sensing in the mid-infrared.