Les données sismologiques enregistrées sur les îles océaniques offrent l'opportunité d'analyser la houle via sa signature dans le "bruit" microsismique. Nous avons d'abord analysé les sources de bruit « secondaires », qui sont générées par l'interaction entre des vagues de même période dans une tempête, un cyclone ou par le phénomène de réflexion des vagues sur la côte. L'analyse des « microséismes secondaires », à l'échelle du bassin océanique, permet d'assurer un suivi spatio-temporel de la source qui les génère, même si elle est distante de plusieurs milliers de km des stations sismiques d'enregistrement. À plus long terme, leur étude permet d'assurer un suivi climatique global de l'activité des vagues dans une région donnée. Nous avons également étudié les sources de bruit « primaires », qui sont générées par l'interaction directe de la houle avec la côte. L'analyse des « microséismes primaires » permet de caractériser la houle localement par son amplitude, sa période et sa direction de propagation. Il est alors possible d'utiliser un capteur sismique comme substitut d'un houlographe. Dans le contexte des îles Éparses et de La Réunion, nous avons étudié plusieurs épisodes de houles extrêmes qui les touchent fréquemment et qui peuvent avoir d'importantes répercutions sociales ou environnementales. Enfin, en utilisant un réseau temporaire de stations sismologiques à La Réunion, nous avons analysé les variations du niveau de bruit microsismique pour caractériser l'impact des houles extrêmes sur les différentes façades de l'île. Cette étude permet d'identifier les sites les plus exposés aux vagues qui présentent un intérêt pour la récupération de cette énergie renouvelable encore trop sous-exploitée. / Seismic data recorded on oceanic islands can be used to analyze the swell through its signature in the microseismic noise. We first analysed the "secondary" noise sources, which are generated by the interaction of ocean waves with similar period within a storm, a cyclone or by the reflection phenomena off the coast. By analyzing secondary microseisms at the scale of the oceanic basin, we first performed a spatio-temporal tracking of the source, even localized thousands km off the recording seismic stations. Secondly, in the long-term, they can be used to follow the global climate change related to the ocean waves activity in a specific region. We also studied the "primary" seismic noise sources, which are created by the direct interaction of ocean waves with the coast. By analyzing these primary microseisms, we succeeded to characterize ocean waves locally in terms of amplitude, period, and, sometimes, direction of propagation. This showed that it is possible to use a seismic station as an ocean waves gauge to get precious swell data, particularly in remote and poorly instrumented areas. In the context of the Iles Éparses and of La Réunion Island, we studied a few extreme swells, which occur there frequently and can have strong social and environmental consequences. Finally, by using a temporary network of seismic stations installed in La Reunion, we studied the spatial variations of the seismic noise level across the island to characterize the swell impact on the different coasts. This study enables us to identify the most exposed spots to the swell, which may be attractive for generating renewable energy with this powerful resource yet underexploited.

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Plugged and abandoned well pads throughout the Uintah Basin face reclamation challenges due to factors including a harsh climate, invasive species, and high salt loads. Finding ways to alleviate soil sodicity could improve soil reclamation success. Gypsum, sulfur, activated carbon, and Biochar are being applied to improve soil parameters negatively impacted by sodicity, but the direct impact of these amendments on Uintah Basin soils is still largely unknown. The aim of this study was two-fold. (1) Evaluate the effectiveness of gypsum, sulfuric acid, Biochar, activated carbon, and combinations of these amendments in reducing the impact of soil sodicity of the Desilt and Conglomerate soils by measuring amendment impact on percent dispersion, saturated hydraulic conductivity, crust bulk density, infiltration, and crust formation. (2) Compare a crust bulk density method using ImageJ to the clod wax density method and a modified linear extensibility percent equation to the linear extensibility percent equation to assess whether the novel methods can be used to accurately measure and calculate soil crust bulk density and shrink swell potential while reducing human error and analysis time.

To understand and to predict the weather and climate, numerical models are important tools and it is crucial that the controlling processes are described correctly. Since 70% of the global surface is covered with water the description how the ocean and atmosphere communicates has a considerable impact. The ocean–atmosphere exchange occurs through transport of momentum (friction) and heat, governed by turbulent eddies. The sea surface is also an important source of turbulence in both directions. The scales of the turbulent eddies cannot be resolved in ocean and climate models. Therefore, the turbulent exchanges have to be related to mean variables, such as wind speed and temperature differences. By using measurements, new methods to describe the air–sea exchange during two specific processes were developed. These processes are the so-called UVCN-regime (Unstable Very Close to Neutral stratification) and swell, i.e. waves which are not produced by the local wind. These processes were included in an ocean model and in a regional atmospheric climate model and the impact was investigated. The UVCN-regime enhances the heat transport significantly during the autumn and winter months in the ocean model. This results in a shallower well-mixed surface layer in the ocean. Wind-following swell reduces the surface friction, which is very important for the atmosphere. Some secondary effects in the climate model are reduced low-level cloud cover and reduced precipitation by more than 10% over sea areas. Locally and for short periods the impact is large. It is important to include the UVCN-regime and the swell impact in models, to make simulations more reliable.

Atmospheric models are strongly dependent on the turbulent exchange of momentum, sensible heat and moisture (latent heat) at the surface. Oceans cover about 70% of the Earth’s surface and understanding the processes that control air-sea exchange is of great importance in order to predict weather and climate. In the atmosphere, for instance, hurricane development, cyclone intensity and track depend on these processes. Ocean waves constitute an obvious example of air-sea interaction and can cause the air-flow over sea to depend on surface conditions in uniquely different ways compared to boundary layers over land. When waves are generated by wind they are called wind sea or growing sea, and when they leave their generation area or propagate faster than the generating wind they are called swell. The air-sea exchange is mediated by turbulent eddies occurring on many different scales. Field measurements and high-resolution turbulence resolving numerical simulations have here been used to study these processes. The standard method to measure turbulent fluxes is the eddy covariance method. A spatial separation is often used between instruments when measuring scalar flux; this causes an error which was investigated for the first time over sea. The error is typically smaller over ocean than over land, possibly indicating changes in turbulence structure over sea. Established and extended analysis methods to determine the dominant scales of momentum transfer was used to interpret how reduced drag and sometimes net upward momentum flux can persist in the boundary layer indirectly affected by swell. A changed turbulence structure with increased turbulence length scales and more effective mixing was found for swell. A study, using a coupled wave-atmosphere regional climate model, gave a first indication on what impact wave mixing have on atmosphere and wave parameters. Near surface wind speed and wind gradients was affected especially for shallow boundary layers, which typically increased in height from the introduced wave-mixing. A large impact may be expected in regions of the world with predominant swell. The impact of swell waves on air-sea exchange and mixing should be taken into account to develop more reliable coupled Earth system models.

Ces travaux de thèse concernent l’étude de l’ensemble de la chaîne de puissance d’un système hydrolien utilisant des systèmes de stockage d’énergie pour améliorer la qualité de la puissance produite et la capacité de gestion des échanges d’énergie. Dans un premier temps, les différentes technologies de stockage d’énergie et leurs applications pour lisser les fluctuations de la puissance produite par le système hydrolien sont étudiées et comparées. Ensuite, une stratégie de lissage des fluctuations de la puissance, dues à l’effet de houle (fluctuations de courte durée), est proposée : elle associe une stratégie MPPT avec filtrage (au niveau de la génératrice) à l’utilisation de supercondensateurs pour lisser la puissance injectée au réseau. Puis il est proposé d’utiliser des batteries à circulation d’électrolyte pour la gestion quotidienne de la puissance d’une hydrolienne dans le contexte d’un réseau électrique isolé. Un système hybride hydrolien/batteries/diesel est étudié pour deux configurations simples : le cas d’une alimentation avec une hydrolienne comme sources principales et le cas où les générateurs diesels sont considérés comme sources dominantes. Enfin, des stratégies de limitation de puissance basées sur le défluxage de la génératrice pour contrôler la puissance de l’hydrolienne dans le cas de vitesses de courants marins élevées sont proposées. Dans ce contexte, le contrôle à puissance constante et à puissance maximale en cours de défluxage sont comparés. L’influence des paramètres de la génératrice sur les caractéristiques de fonctionnement commun de la turbine et la génératrice est également étudiée. / This PhD thesis models the whole power chain of a marine current turbine (MCT) system and investigates the use of energy storage devices to improve power quality and energy management capability. First, various energy storage technologies concerning their applications to address the power fluctuation phenomena in tidal current generation system are reviewed and compared. Then, a two-stage power smoothing control strategy for compensating swell-induced short-time fluctuations is proposed. The proposed control strategy uses a modified MPPT with filter strategy on the generator-side and supercapacitors on the grid-side for injecting a smoothed power to the grid. Afterwards, a flow battery system for daily energy management of a hybrid MCT/battery/diesel system is proposed. The MCT dominant power supply case and an island power supply (with diesel generators as the main source) are investigated. Finally, power limitation controls with a robust flux-weakening strategy for a PMSG-based non-pitchable MCT system are proposed for over-rated marine current speed periods. In this context, the constant power control and maximum power control modes at the flux-weakening stage are compared; and the influence of the generator parameters on the joint operating characteristics of the turbine and generator are also discussed.

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Dans le cadre de la présente thèse, a été étudié l’impact de la texturation par traitement thermo-mécanique DIC (Détente Instantanée Contrôlée) sur le séchage de divers produits alimentaires. Ce prétraitement a induit une amélioration de la cinétique de l’opération de séchage quand elle est limitée par le transfert interne de la matière couplé au rétrécissement du produit. Ainsi, la diminution du temps de séchage a atteint 67% dans le cas de l’oignon et 77% dans le cas du cassis. Quant à la diffusivité effective Deff, elle a augmenté par rapport à la matière première jusqu’à 246% pour les pépins et 795% pour les déchets de canneberge, 336% pour l’oignon et 1223% pour le cassis. Dans le cas des produits étudiés, la pression de vapeur de traitement DIC a généralement un effet significatif positif sur la cinétique de séchage et d’extraction des différentes molécules. Concernant les caractérisatiques des produits, nous constatons l’impact positif du traitement par DIC quant aux principales caractéristiques de la matière. Ainsi, les composés phénoliques apparaissent plus disponibles à la suite du traitement adéquat par DIC. Le contenu en composés phénoliques et la capacité antioxydante étant supérieurs dans les produits traités par DIC, la qualité nutritionnelle s’est ainsi également trouvée améliorée. Avec une dégradation thermique négligeable, le traitement DIC implique un effet mécanique dû à la détente instantanée, ce qui permet la rupture de certaines structures cellulaires de la matière et l’augmentation de la quantité maximale extractible. Les caractéristiques physiques diverses (masse volumique apparente et taux relatif d’expansion), les caractéristiques microstructurelles (mesurées par microscopie électronique à balayage) et fonctionnelles d’interaction avec l’eau (réhydratation, teneur en eau, isotherme de sorption, microbiologie et contenu nutritionnel...) peuvent être optimisées en fonction des conditions opératoires DIC, selon les besoins du consommateur. / The present PhD work concerns the effect of thermo-mechanical texturing by DIC (Instantaneous Controlled Pressure-Drop) on fruit and vegetable drying. This pretreatment dramatically improves drying kinetics when the internal mass transfer coupled to the shrinkage of the product, is the limiting process. Indeed, the drying time decreased by 67% in the case of onion and 77% for blackcurrants, while the effective diffusivity Deff increased up to 246%, 795%, 336%, and 1223% for cranberry seed and waste, onion and blackcurrants, respectively. With these products, the saturated steam pressure generally has a significant positive effect on the drying kinetics.DIC treatment significantly improves the main nutritional and functional characteristics of the fruits and vegetables, with more available phenols and higher antioxidant activity. As thermal degradation is negligible, the DIC treatment involves micromechanical effect linked to the instant pressure drop, which allows cell to break and structure to be more porous such increasing the maximum extractable amount. Various physical, microstructural and functional characteristics of new textured material allow water interaction to be completely modified in terms of rehydration kinetics and capacity, sorption isotherm, microbiological and nutritional content... depending on operating DIC conditions, which can be optimized according to the consumer needs.

Demand for electrical power is increasing everyday. Along with the increase in power demand, the characteristics of the loads are also changing. From being high power consuming, simple, robust loads, today loads are more efficient, but at the same time more sensitive. The performance and life of these highly sensitive loads depend a lot on the quality of power supplied to them. <p>Power quality is any deviation of the voltage or current waveform from its normal sinusoidal waveshape. These disturbances include, but are not limited to, sag, undervoltage, interruption, swell, overvoltage, transients, harmonics, voltage flicker and any other distortions to the sinusoidal waveform. Occurrence of one or more of such disturbances is called a power quality event. Automatic classification of these disturbances is important for quick determination of the causes and to characterize possible impacts of the disturbances.<p>Modern microprocessor based protective relays have numerous integrated functions that allow them to provide information on power quality events. It is proposed to utilize the existing numerical relays to analyze the quality of power at any point in the power system. The numerical relays can be programmed to capture the oscillographic waveform or any disturbance on the analogue signal or change of state of the digital signals and store it in the form of Common Format For Transient Data Exchange (COMTRADE) format. These records are then transferred to a central monitoring workstation for off-line analysis. <p>This thesis describes a technique to automate the classification and analysis of the power quality events using relay recorded data. The technique uses voltage duration and magnitude (as specified in the IEEE Std. 1159 - 1995, IEEE Recommended Practice for Monitoring Electric Power Quality) of three phases to detect and classify the events. The classified results are then presented in a user-friendly graphical form. Fast Fourier Transform (FFT) is used to estimate the fundamental frequency and harmonic components in power systems. The graphical user interface of the power quality analysis tool is developed using Microsoft Visual C++ IDE and the algorithms are programmed in C++. <p>The proposed technique was tested using data obtained by simulating different power system disturbances as well as on the data recorded by relays. The algorithms were able to classify the power quality events accurately. In the future, this facility will: enhance the real time monitoring of power quality and provide statistical analysis of available power quality data. From the utility viewpoint, it would allow them to monitor power quality in a cost effective manner and assist in preventive and predictive maintenance besides helping them to fix differential tariff based on the quality of the delivered power. It may also turn out to be a smart tool for them to penalize the consumer polluting the power quality.