Puissance nominale | EPFL Graph Search

La puissance nominale, dans l'industrie de l'électricité, est, pour un générateur d'une unité de production électrique, la puissance maximale qu’il peut fournir, de manière permanente sur le réseau ; c’est aussi, pour un récepteur électrique, la puissance électrique consommée dans des conditions normales. La puissance est exprimée en watts dans le Système international. L'association d'opérateurs de centrales électriques VGB Powertech définit la puissance nominale d'une unité de production électrique comme . Cette valeur doit être déterminée de manière que les variations annuelles des conditions d'opération (par exemple la température de l'air ou de la source froide d'une centrale thermique) se compensent en moyenne. Ces conditions nominales correspondent généralement à des conditions idéales de production et la puissance nominale correspond alors à une puissance de production maximale, bien que ce ne soit pas toujours le cas. La valeur de la puissance est mesurée aux bornes de sortie de l'unité de production, c'est-à-dire après déduction de la puissance absorbée par les auxiliaires de l'unité et des pertes dans les transformateurs considérés comme faisant partie intégrante de l'unité de production. Le terme « puissance installée » est également utilisé pour définir la capacité maximale théorique de production d'électricité de l'ensemble du parc des centrales d'un type donné ou dans un pays donné ; le terme « puissance crête » est parfois utilisé dans le cas d'installations photovoltaïques. Dans le cas des centrales thermiques, la puissance nominale est parfois déterminée en été quand la puissance électrique délivrée est plus faible à cause de la température plus élevée de la source froide, ce qui dégrade le rendement thermique et donc la puissance délivrée ; par contre, en hiver la température de la source froide est plus basse qu’en été, ce qui améliore le rendement thermique et la puissance délivrée qui peut donc dépasser la capacité nominale déterminée en été.

Converter placement in the interconnection of railway power grid and public power grid based on cost-reliability approach

Mokhtar Bozorg, Daniel Lopez

The railway load in Switzerland is expected to increase in the next years. Increasing the capacity of the interconnection between the railway power system and the public grid is a reasonable solution to deal with this problem. This paper proposes a way to find the locations and capacities for new interconnections and the capacity expansion for the existing one. To show the effectiveness of the proposed model, the networks in the Suisse Romande region (French part of Switzerland) is considered as a case study.

2013

Metabolic modeling and experimental studies on carbon and energy metabolism of Mycobacterium tuberculosis

Muhittin Emre Özdemir

Tuberculosis is an ancient human disease affecting millions of people every year. The common causative agent, Mycobacterium tuberculosis, is a peculiar pathogen that can persist in the host tissues for decades. Many of the key attributes of M. tuberculosis can be traced to its metabolism. Therefore, novel insights into the metabolism of this bacterium could lead to the identification of new drug targets as well as better methods to understand the mechanism of action of anti-tuberculosis drugs. Analysis of the metabolic network of this bacterium using a genome-scale model offers an unconventional approach to understanding utilization of metabolic pathways of this pathogen during growth and non-replicating persistence. Metabolic adaptation of a pathogen is central to its life style in vivo. To understand the capacity and limitations of M. tuberculosis, we developed an updated and thermodynamically curated genome scale model – iOS783. This model has been verified with respect to the observed phenotypes for targeted gene deletion studies reported previously. Evaluation of iOS783 with thermodynamics based flux balance analysis (TFBA) improved overall reliability of the model results and led to identification of possible bottleneck reactions. In addition, several new hypotheses were generated with iOS783, involving the role of isocitrate lyase enzymes, propionate toxicity, and energy metabolism of this pathogen. Analysis of iOS783 for conditional gene essentiality emphasizes the importance of the carbon source available to the pathogen. Several genes show a conditional impact on biomass production rate of the model, depending on the availability of carbohydrates or fatty acids as the carbon substrate. Conditional essentiality is even more pronounced when ATP replenishment capacity is used as a measure of a pathogen’s ability to survive under stress in a non-growing state. As expected, ATP synthase plays a major role in estimations of ATP replenishment capacity based on iOS783. Curiously, computational analysis of the metabolic network with ATP synthase activity blocked indicates that the damaged network can use substrate-level phosphorylation reactions to sustain ATP production to fulfill non-growth-associated ATP requirements when glucose is available. In order to establish the dependence of M. tuberculosis on ATP synthase, we attempted to construct a deletion of the chromosomal atp operon. Our results show that the native copy of these genes can be deleted only when a second set of genes are introduced elsewhere in the genome, indicating essentiality of the ATP synthase for growth. Although our results indicate that ATP synthase is essential for growth, we observed carbon source specific efficacy of an ATP synthase inhibitor, bedaquiline, on M. tuberculosis. These experimental results are consistent with ATP turnover estimations based on modeling results. Furthermore, analysis of iOS783 suggests a novel role in energy metabolism for recently described glycine dehydrogenase (GDH) on energy metabolism. Deletion of ald gene responsible for GDH activity reduces the ATP replenishment capacity of iOS783, especially during metabolism of fatty acid derivative carbon sources. Consistent with these modeling results, wetlab experiments designed to test this hypothesis show that bedaquiline has a stronger bactericidal effect on an M. tuberculosis ∆ald mutant, compared to the wild-type parental strain, when cells are cultured in medium containing acetate as the carbon source. Metabolic modelling is already well established as an invaluable tool for engineering of strains with desired characteristics. For pathogenic species, however, the application of this approach has so far been quite limited. The work presented in this thesis exemplifies an interdisciplinary approach combining computational modeling and experimental studies of M. tuberculosis metabolism. First, iOS783 was utilized to interpret existing experimental results and to generate novel hypotheses, thereby providing the impetus for new wetlab experiments. Conversely, results from iOS783-inspired wetlab experiments were used to further refine and expand the iOS783 model. This cyclic exchange between computational modeling and wetlab experimentation illustrates how a close interdisciplinary partnership can create a positive feedback loop that enriches both disciplines.

EPFL2013

Metabolic modeling and experimental studies on carbon and energy metabolism of Mycobacterium tuberculosis

Muhittin Emre Özdemir

EPFL2013