Énergie des vagues | EPFL Graph Search

L'énergie des vagues, ou énergie houlomotrice, est une énergie marine utilisant l'énergie contenue dans le mouvement de la houle, soit les oscillations de la surface de l'eau. Cette énergie ne doit pas être confondue avec l'énergie marémotrice, laquelle utilise l'énergie des marées. La faisabilité de son exploitation a été étudiée, en particulier au Portugal, au Royaume-Uni et en Australie. Le Conseil mondial de l'énergie a évalué à 10% le potentiel théorique de la demande annuelle mondiale d’électricité qui pourrait être couvert par l'énergie houlomotrice (dont en France métropolitaine, principalement sur la façade atlantique avec une puissance installée de 10 à ). Histoire La première utilisation de l'énergie des vagues fut probablement un système permettant d'actionner des cloches destinées à prévenir, dans la brume, de la proximité de certaines bouées de signalisation maritime. Victor Hugo évoque, dans l'Homme qui rit, une . Plus historique est la cloche de Bell rock,

Experimental analysis of suprathermal electrons generated by electron cyclotron waves in tokamak plasmas

Dahye Choi

This thesis focuses on the physics of suprathermal electrons generated by electron cyclotron (EC) waves in tokamak plasmas, which play an important role in the physics of current drive and energetic particle-driven instabilities. The suprathermal electron dynamics and their effect on the plasma stability have been experimentally studied utilizing high power EC waves, in the TCV tokamak of the Swiss Plasma Center at EPFL, Switzerland. A hard X-ray diagnostic, which measures the bremsstrahlung radiation of the suprathermal electrons in radial and energy spaces, has been mainly used for the analysis, and the measurement has been compared to an estimation made by Fokker-Planck modeling coupled with a hard X-ray synthetic diagnostic. In order to study the response of the suprathermal electrons to ECCD, ECCD modulation discharges have been developed. The time evolution of the hard X-ray profiles has been measured using coherent averaging techniques in order to observe the creation and relaxation of suprathermal electrons. Time-dependent Fokker-Planck modeling coupled with the hard X-ray synthetic diagnostic has been used to compare the experimental and simulation results, with various suprathermal electron transport models. A dependency of the radial transport of suprathermal electrons on the EC wave power has been demonstrated and a possibility of EC wave scattering has been addressed. The effect of the suprathermal electron population on the plasma stability has been studied, and in particular the destabilization and dynamics of the electron fishbone mode. The response of hard X-ray profiles to the internal kink mode has been observed directly by the hard X-ray diagnostic for the first time, at the frequency of the mode. The experimental evidence and a solution of a linear fishbone dispersion relation coupled to the Fokker-Planck modeling demonstrate the role of suprathermal electrons in destabilizing the fishbone mode and in particular the interaction of trapped electrons with the mode. This work provides the framework for a comprehensive understanding of the physics of suprathermal electrons related to ECCD, and explains how ECCD-generated suprathermal electrons behave in real and velocity spaces, and how they interact with and are redistributed by the MHD mode.

EPFL2020

Concurrent Voltage Control and Dispatch of Active Distribution Networks by means of Smart Transformer and Storage

Konstantina Christakou, Xiang Gao, Mario Paolone, Fabrizio Sossan

Dispatching active distribution networks is expected to play an important role in the smart grid technologies. Voltage control is also starting to be widely proposed to avoid voltage violations in the electrical grid. The integration of the storage in the so called smart transformer (ST), which is a solid state transformer with control and communication functionalities, can help combine both the services. The added value of such a configuration is that it allows the full decoupling of the reactive power flows between the medium voltage (MV) and low voltage (LV) networks. We show the augmented flexibility of such a configuration by proposing a control strategy where, i, the storage system is used to achieve dispatched-by-design operation of the LV network active power flow, and, ii, the two ST power converters to control the voltage in both the MV and LV grid on a best effort basis. The control strategy is validated by simulations using the IEEE 34-node MV test feeder and the Cigre LV reference network. Moreover, control performance is benchmarked against a conventional network setup, where the BESS is connected to the LV network through a DC/AC power converter and the ST transformer is replaced by a conventional transformer.

2018

Experimental analysis of suprathermal electrons generated by electron cyclotron waves in tokamak plasmas

Dahye Choi

EPFL2020