Flexibility and reliability in long-term planning exercices dedicated to the electricity sector

Disponible sur le site du World Energy Council : http://www.worldenergy.org/documents/congresspapers/363.pdfInternational audienceLong-term planning models are useful to build plausible options for future energy systems and must consequently address the technological feasibility and associated cost of these options. This paper focuses on the electricity sector and on problems of exibility and reliability in power systems in order to improve results provided by long-term planning exercises: exibility needs are integrated as an additional criterion for new investment decisions and, reliability requirements are assessed through the level of electrical losses they induced and a related cost. These approaches are implemented in a long-term planning model and demonstrated through a study of the Reunion Island

Impacts of intermittent sources on the quality of power supply: The key role of reliability indicators

International audienceThe reliability of power supply, defined as the ability to recover a steady-state condition after a sudden disturbance, is crucial for operating power systems. It is usually ensured by controlling voltage and frequency deviations and involves events occurring from a few milliseconds to a few hours. However, reliability requirements are largely ignored when dealing with long-term issues. To reconcile such contrasting timescales, it seems logical to rely on energy considerations based on thermodynamics. Two reliability indicators, assessing the magnetic and kinetic energy reserves of a power system, are derived from this approach. They enable to quantify the reliability of a given production mix and make it possible to choose between increasing shares of intermittent sources and maintaining an expected level of reliability. Since the indicators tackle reliability issues without focusing on a specific timescale, they are effective for both discussing the long-term evolution of reliability and improving the real-time management of a power system

Long term planning tools and reliability needs: focusing on the Reunion Island

http://ab3e.org.br/rio2010/conference-program/concurrent-sessions/june07/International audienceIn this paper, we tackle the issue of reliability of supply in future power systems. To build plausible options for future energy systems, long-term planning models such as the Markal/TIMES family of models must address the technological and economical feasibility of these options. This paper focuses on the electricity sector and how to take reliability into account when designing future power systems in long-term planning exercises. This approach is implemented and demonstrated through the development of a TIMES model for the Reunion Islan

Reliability in future electricity mixes: the question of distributed and renewables sources

http://www.aaee.at/2009-IAEE/details.phpInternational audiencePushed by the need for carbon emission abatement and the expected depletion of fossil fuels, electricity generation is entering a period of signicant change. At this point in time, the issue of integrating distributed and renewable energy sources puts a question mark over the future shape of the electricity industry. In this paper, we are interested in the level of reliability of future electricity mixes and whether or not these changes will impact the level of reliability. Consequently, we propose a methodology for assessing the reliability of power systems based on a number of aggregated physical properties. Finally, we exhibit “reliability indicators", which provide valuable comments on reliability using distributed and renewable energy sources. To sum up, changes in the electricity industry must be made carefully with respect to reliability requirements

TIMES model for the Reunion Island: addressing reliability of electricity supply

International audienceThe Reunion Island aims to have in 2030 an energy consumption based to 100% on renewable energy sources. In 2008, the total primary energy consumption was 1295 ktoe, and as most of small islands, the Reunion Island was highly dependent on fossil fuel imports (86.5%). This paper focuses on the target applied to the electricity sector, where the current use of renewable energy sources is 36%. To build plausible options for future energy systems, we rely on long-term planning models { such as the MARKAL/TIMES family of models. The MARKAL/TIMES models optimize energy systems in the long-term with an explicit bottom-up approach through a description of individual technologies. In this paper, we present the results obtained with a TIMES model dedicated to the supply and power sectors of the Reunion Island. We also tackle the technological and economical feasibilities of electricity systems provided by this model, considering in particular the incentives' system and the reliability of electricity supply

The cost of reliability of supply in future power systems

http://ab3e.org.br/rio2010/conference-program/concurrent-sessions/june-09/International audienceIn order to build plausible options for future energy systems, long-term planning models must consequently address the technological feasibility and associated cost of these options. This paper focuses on the electricity sector and on problems of reliability of supply for future power systems. We propose a methodology for assessing the reliability of power systems based on a number of aggregated physical properties. Our aim is to take reliability into account when designing future power systems and to improve results provided by long-term planning exercises

Les fonds d’archives consacrés à Liouville : de la bibliothèque de l’Institut de France au « Fonds Drouineau / Liouville » des archives de l’Ecole polytechnique

Comme le signale Jesper Lützen dans son entretien, les archives concernant Liouville sont nombreuses et ont été étudiées par différents historiens. Nous nous proposons ici de faire un inventaire des principaux fonds à disposition en insistant particulièrement le nouveau fonds Liouville cédé par Michel Drouineau aux archives de l’École polytechnique. Les fonds d'archives publiques : Paris & Berlin L’article d’Erwin Neuenschwander intitulé « Correspondance inédite et documents biographiques pr..

Thermal tolerance of allis shad (Alosa alosa) embryos and larvae: Modeling and potential applications

International audienceThe objective of this study was to assess the potential effects of climate change on the survival of allis shad early life history stages. Embryos and larvae were exposed to temperatures ranging from 5 to 35 °C. No embryonic survival was recorded at extreme temperatures (≤10 and ≥30 °C), and no larval survival was observed at 5 or 35 °C. Based on these experimental results, a survival model was developed to predict survival rates at different temperatures for embryos and larvae up to 14 days post hatch. The model confirmed that embryonic daily survival is more impacted by temperature than larval survival. The highest survival rates (greater than 80%) were found for temperatures between 15.7 and 25.6 °C for embryos and between 14.6 and 26.7 °C for larvae. This survival model can be used to explore the impact of temperature on recruitment of allis shad in southern France. Preliminary analysis from two different rivers suggests that cold temperatures may have a strong impact on embryonic and larval survival

A Bayesian framework to objectively combine metrics when developing stressor specific multimetric indicator

In the context of the European Water Framework Directive (WFD), monitoring programs and related indicators have been developed to assess anthropogenic impacts on various components of aquatic ecosystems. While great precautions are usually taken when selecting and calculating relevant core metrics, little attention is generally paid to the generation of the multimetric indicator, i.e. the combination of the different core metrics. Indeed, most multimetric indicators are generated by simply averaging or summing metrics, without taking into account their sensitivity and their variability. Moreover, few indicators provide a rigorous estimate of the uncertainty of the assessments, while this estimation is essential for managers. In this context, we developed a Bayesian framework to build multimetric indicators aiming at improving those two weaknesses. This framework is based on two phases. First, pressure-impact statistical models are developed to quantify the impact of pressure on various fish metrics. Then the Bayesian theorem is applied to estimate probabilities of being at a certain anthropogenic pressure level from fish observation and pressure-impact models outputs. The Bayesian theorem allows to combine objectively the different core metrics, taking into account their sensitivity and their variability, and to provide rigorous uncertainty quantification, which is especially valuable in the WFD context. The method is applied as illustrative example on transitional French water bodies to demonstrate its relevance, especially in the Water Framework Directive context though the method is generic enough to be applied in various contexts

Synchrony in whitefish stock dynamics: disentangling the effects of local drivers and climate

Synchronic variations in abundance in populations of the same species are common phenomena encountered in various environments, including lakes, and different taxa of freshwater fishes. This phenomenon can be caused by similar environmental conditions across physically separated populations. In the context of the ongoing climate change, it is essential to test this hypothesis, identify the factors driving the synchrony and elucidate the mechanisms, in the attempt to improve fisheries management. This study investigates synchronic variations in European whitefish (Coregonus spp.) populations in five peri-alpine lakes. The hypothesis suggests that shared biotic or abiotic factors contribute to similar trends in whitefish landings. Environmental and seasonal variables impacting the early life stages of the species were analyzed, and the Euclidean distances between the multivariate time series were calculated to identify similarities or dissimilarities in lake environmental parameters. We found that regional winter and spring temperatures were consistent across the lakes, but these factors did not fully account for variations in landings statistics. Wind intensity, water level and zooplankton abundance showed lake-specific patterns that could better explain local conditions and dynamics. Linear models did not reveal a coherent correlation with a common environmental variable across all lakes. However, distinct relationships were found in four of the lakes, with local factors significantly contributing to abundance variations. The spring abundance of Daphnia spp., a primary food source for whitefish larvae, was the main factor correlated with fish landing trends in Lake Geneva and Lake Bourget. Higher availability of Daphnia spp. may decrease intraspecific competition and density-dependent mortality. In Lake Neuchâtel, winter water temperature was negatively correlated with fish abundance proxies, suggesting that warmer winters may compromise reproduction success. Lake Annecy saw an increase in whitefish landings following a substantial reduction in fishing efforts during the late 2000s. A significant negative correlation was found between whitefish landings and fishing efforts. No relationship was found for Lake Aiguebelette, maybe due to a lack of zooplankton data. In conclusion, the observed synchrony in the European whitefish population is likely driven by a combination of interacting environmental and anthropogenic factors rather than a single common variable. Further research and a more detailed dataset are needed to better understand these complex relationships.   Article cover image: Whitefish (Credit: Rémi Masson