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Microalgae are more and more studied for their energy potential and various applications. However, the actual production processes (open and closed photobioreactor) use a lot of energy and aren't productive enough. This thesis presents a novel process of microalgae culture, with an airlift system coupled to a thin plate. The photobioreactor is experimentally characterized and modeled for many aspects. Hydrodynamics of the system is modeled to predict the fluid behavior in the system. Mass transfers are modeled using the two film model. The model allows knowing minimum carbon needs for microalgae culture. It also allows evaluating dissolved oxygen concentration in the photobioreactor and its elimination efficiency. Oxygen is inhibiting the culture at high concentration. Heat transfers are also modeled, allowing to know climate parameters impact (sunshine, ambient air temperature) on culture temperature. All models are assembled in a global model. This model is compared to microalgae culture experimental results. Finally, the global model is used to study a more complex system: culture thin plates are integrated on the walls of buildings. Global model allow studying different orientation effects on temperature and productivity of the system. Culture is optimized for energy consumption and some perspectives on energy integration of such a system are proposed. Les microalgues sont de plus en plus regardées pour leurs potentiels énergétiques et leurs nombreuses applications. Mais les systèmes de production actuels, que se soit les systèmes dits ouvert comme les bassins ou les systèmes fermés, appelés photobioréacteurs, sont très énergivores et pas assez productifs. Cette thèse propose un nouveau concept de photobioréacteur, composé d'un airlift et d'une plaque mince. Le photobioréacteur est caractérisé expérimentalement et est modélisé sous plusieurs aspects. L'hydrodynamique du système est modélisée pour prédire le comportement des fluides dans le système. Les phénomènes de transferts de masse sont modélisés par le modèle des deux films. La modélisation permet de connaitre l'apport minimum nécessaire en dioxyde de carbone pour la culture des microalgues et permet d'évaluer la concentration en oxygène dissous dans le photobioréacteur. Elle permet aussi d'évaluer son élimination par le système, l'oxygène étant inhibant pour la culture. Les phénomènes de transferts de chaleur sont aussi modélisés, permettant de connaitre l'impact des différents paramètres (ensoleillement, température de l'air ambiant) sur la température de culture. Ces différents modèles sont rassemblés en un modèle global qui est comparé aux résultats expérimentaux de culture d'algues. Le modèle global est ensuite utilisé dans un contexte plus complexe : l'intégration des plaques minces du photobioréacteur aux parois d'un bâtiment. Le modèle global permettra d'étudier l'effet les différentes orientations (Nord, Sud, Est, Ouest en vertical sur les façades et à l'horizontal sur les toits) sur les températures et productivité du système. La consommation d'énergie de la culture est optimisée grâce au modèle. A la suite de cette optimisation, certaines perspectives sur l'intégration énergétique d'un tel système sont proposées.

Marine renewable energies (MRE) allow the diversification of the energy mix and are thus developing rapidly. The extraction of tidal energy is one of the most promising MRE and is nowadays in a preindustrial phase. The Alderney Race (Raz Blanchard in French), situated between the island of Alderney (Channel Islands) and the Cap de la Hague in France, capitalizes a resource estimated between 5 and 14 TWh/year. This great tidal resource attracts tidal energy developers. Harnessing the high potential of the Alderney Race requires deploying numerous turbines in arrays. The purpose of this paper is to investigate the influence of the wake effects on the electrical dynamics of commercial tidal farms. The proposed methodology is applied to a hypothetical tidal farm in the Alderney Race. The influence of the wake effects on the power produced by a tidal farm is assessed by comparing simulations where the effect is neglected to simulations with wake effects. Two operational conditions are analyzed: Normal operation (one-day simulation with varying tidal speed); grid disturbances (voltage dip at the tidal farm point of common coupling). Simulations show that neglecting the wake effect implies significant errors in active power estimation at the point of common coupling during normal operation. Moreover, differences in the behavior of the system during voltage dip occur if the wake effect is not taken into account.

Le « grand débat sur la transition énergétique » lancé par le gouvernement à lasuite de la conférence environnementale déploie beaucoup d’énergies et accapare l’attention des médias. Ce qui mobilise désormais, ce n’est plus l’action face auchangement climatique, mais la transition énergétique dont le climat ne sembleconstituer que l’une des composantes. La dérive sémantique, observée en France aussi bien qu’à l’étranger, n’est pas anodine : ce concept à géométrie variable peut en réalitéjustifier des orientations et stratégies politiques qui se tournent le dos. Il est urgent de définir avec plus de rigueur ce qu’on appelle une transition énergétique et le type de celle qu’on veut mettre en œuvre. Les implications en sont importantes pour la prise dedécision comme le montre l’exemple du gaz de schiste pris ici en illustration.

This paper formulates an optimality criterion for the selection of synchrophasor signals to be used in ambient mode estimators. This criterion, which is associated with each measured signal and each dominant mode, is defined as the asymptotic variance of the corresponding estimated mode damping ratio. The value of the criterion is computed directly from an estimated autoregressive moving average (ARMA) model. Because the online computation of the defined criterion (for each measured signal in the system) may be computationally expensive, a fast pre-selection method for initial signal ranking is formulated. The pre-selection method is used to effectively determine a set of the candidate signals for which the formal criterion is evaluated in a second stage. The methodology is illustrated using synthetic measurements from the KTH Nordic 32 and the IEEE 39-bus test systems.

Understanding the genetic bases underlying climate adaptation is a key element to predict the potential of species to face climate warming. Although substantial climate variation is observed at a micro-geographic scale, most genomic maps of climate adaptation have been established at broader geographical scales. Here, by using a Pool-Seq approach combined with a Bayesian hierarchical model that control for confounding by population structure, we performed a genome-environment association (GEA) analysis to investigate the genetic basis of adaptation to six climate variables in 168 natural populations of Arabidopsis thaliana distributed in south-west of France. Climate variation among the 168 populations represented up to 24% of climate variation among 521 European locations where A. thaliana inhabits. We identified neat and strong peaks of association, with most of the associated SNPs being significantly enriched in likely functional variants and/or in the extreme tail of genetic differentiation among populations. Furthermore, genes involved in transcriptional mechanisms appear predominant in plant functions associated with local climate adaptation. Globally, our results suggest that climate adaptation is an important driver of genomic variation in A. thaliana at a small spatial scale and mainly involves genome-wide changes in fundamental mechanisms of gene regulation. The identification of climate-adaptive genetic loci at a micro-geographic scale also highlights the importance to include within-species genetic diversity in ecological niche models for projecting potential species distributional shifts over short geographic distances.

Abstract A good understanding of the mechanical behaviour of the reactor pressure vessel (RPV) lower head is necessary both for severe accident assessment and for the definition of appropriate accident mitigation strategies. Indeed, a well-characterized failure of the lower head leads to a better evaluation of the quantity and kinetics with which core material can escape into the containment. These are the initial conditions for several ex-vessel events such as direct heating of the containment or molten core–concrete interaction. In this context, the objectives of the joint on-going work of the WP10-2 group of SARNET are: (1) improvement of predictability of the time, mode and location of RPV failure; (2) development of adequate models with the ultimate aim of being included into integral codes; (3) interpretation/analysis of experiments with models/codes combined with sensitivity studies; and (4) better understanding of the breach opening process in order to better characterize the corium release into the containment. Different approaches are considered: a simplified but well predicting model recently implemented in the severe accident Astec and Icare-Cathare codes, and viscoplasticity models implemented in the Cast3m, Ansys and Code_Aster finite element codes. Several failure criteria are considered: stress criterion, strain criterion and damage evaluation (coupled way or post-evaluation). In this paper, the OLHF-1 experiment has been used to assess the models, to perform sensitivity studies and to evaluate failure criteria that could be applied in the case of reactors. All the partners performed 2D axisymmetric analyses, allowing the evaluation of time, mode and location of vessel failure. Nevertheless, CEA conducted further 3D calculations in order to study crack propagation and the corresponding results will be presented separately at the end of the paper. The numerical formulation of the different models used is given and a comparison of experimental and numerical results is presented. The paper also shows the progress made with the objective of defining failure criteria that can be used for reactor vessel applications.