Marginalisme | EPFL Graph Search

Le marginalisme est un mouvement intellectuel économique qui promeut une méthode d'analyse économique basée sur le raisonnement à la marge, résultant de « l'utilité marginale » (l'utilité de la dernière unité consommée). Il façonne le courant de l'école néoclassique à la fin du XIXe siècle. Cette théorie résulte de travaux menés dans la seconde moitié du de façon indépendante par des chercheurs comme Léon Walras, Carl Menger et William Stanley Jevons. Surnommée « révolution marginaliste », elle contribue fortement à la formation des écoles néoclassique et autrichienne. Histoire Précédents Le raisonnement marginal, qui s'attache à prendre en compte l'effet d'une unité supplémentaire, est ancien. La première publication qui théorise l'utilité marginale est le fait de Daniel Bernoulli, dans Specimen theoriae novae de mensura sortis. Cette théorie remonte à Gabriel Cramer dans un courrier privé à Nicolas Bernoulli dans une tentative de réponse au paradoxe de Saint

Electricity market operations under increasing uncertainty

Farzaneh Abbaspourtorbati

Decision making in electricity markets under uncertainty has worldwide gained attention due to an increasing number of uncertain parameters associated to technology developments and market evolution. Hence, the market operator faces new challenges pertaining to technical and economic aspects of electricity markets. To tackle these challenges, appropriate models are necessary. This dissertation aims to analyze some of the challenges pertaining to the management in electricity markets under uncertainty and to provide the market operator with the models that enable it to make informed decisions in such uncertain market environments. In the context above, we categorize market operation problems into the following four groups. With the aim of obtaining informed day-ahead decisions in the presence of a number of intra-day markets and high renewable production, we propose a multi-stage stochastic clearing model, where the first stage represents the day-ahead market, n stages model n intra-day markets, and a final stage represents real-time operation. The proposed multi-stage clearing model considers not only different realizations of renewable power output, but also how these realizations evolve from day-ahead forecasts into real-time values, and allows flexibility for the contribution of renewable production in both the day-ahead and intra-day markets in form of scheduled productions and their adjustments. This improves the market outcomes and integration of renewable generation. With the purpose of obtaining marginal prices with cost-recovery features, we develop novel pricing methodologies in the presence of non-convexities and uncertainty in the market. These models minimize the duality gap of a stochastic non-convex clearing model and the dual problem of a relaxed version of this original model subject to primal constraints, dual constraints, cost-recovery constraints, and integrity constraints. The prices obtained deviate in the least possible manner from conventional marginal prices. This implies that a minimum deviation from the optimal value of social welfare is also guaranteed. Moreover, the new prices preserve the short-term economic efficiency and long-term cost recovery properties of marginal prices, while eliminating a need for uplifts. We provide insightful analyses on the impact of demand flexibility on the operational and economic aspects of the power system operation. We investigate how market prices are affected by flexible demands and what economic consequences are observed. For this purpose, we consider a system with high renewable production and a number of comparatively expensive fast-ramping units, which are flexible to react to the uncertainty pertaining to renewable power production. We investigate the role of flexible demands froman economic viewpoint, particularly the impact of flexible demands on demand revenues. Lastly, we develop a risk-neutral two-stage stochastic clearing model and a risk-averse one for reserve markets. We particularly focus on the Swiss reserve market, which consists of a weekly market with a gate closure one week ahead of real-time operation and a daily market with a gate closure two days ahead of real time. The decision-making problem consists of determining which amount of reserves to procure in the weekly market and which one in the daily market. If a risk-averse instance of this two-stage model is also proposed.

EPFL2017

Pricing Electricity Through a Stochastic Non-Convex Market-Clearing Model

Farzaneh Abbaspourtorbati, Antonio J. Conejo

This paper proposes a pricing scheme for the day-ahead market in power systems with a large percentage of renewable stochastic production. To clear the day-ahead market, instead of a simplistic deterministic model, we use a two-stage stochastic programming model that embodies a prognosis of future operating conditions. Non-convexities due to start-up costs and the on/off status of generators and their minimum power outputs are properly taken into account. Our goal is to obtain uniform day-ahead clearing prices that deviate in the least possible manner from marginal prices and that allow producers to recover their costs without uplifts. The proposed methodology is illustrated using a simple example and a realistic case study.

Ieee-Inst Electrical Electronics Engineers Inc2017

Elevated CO2 Leads to Enhanced Photosynthesis but Decreased Growth in Early Life Stages of Reef Building Coralline Algae

Niclas Heidelberg Lyndby

Crustose coralline algae (CCA) are key organisms in coral reef ecosystems, where they contribute to reef building and substrate stabilization. While ocean acidification due to increasing CO2 can affect the biology, physiology and ecology of fully developed CCA, the impacts of elevated CO2 on the early life stages of CCA are much less explored. We assessed the photosynthetic activity and growth of 10-day-old recruits of the reef-building crustose coralline alga Porolithon cf. onkodes exposed to ambient and enhanced CO2 seawater concentration causing a downward shift in pH of ∼0.3 units. Growth of the CCA was estimated using measurements of crust thickness and marginal expansion, while photosynthetic activity was studied with O2 microsensors. We found that elevated seawater CO2 enhanced gross photosynthesis and respiration, but significantly reduced vertical and marginal growth of the early life stages of P. cf. onkodes. Elevated CO2 stimulated photosynthesis, particularly at high irradiance, likely due to increased availability of CO2, but this increase did not translate into increased algal growth as expected, suggesting a decoupling of these two processes under ocean acidification scenarios. This study confirms the sensitivity of early stages of CCA to elevated CO2 and identifies complexities in the physiological processes underlying the decreased growth and abundance in these important coral reef builders upon ocean acidification.

2019

Electricity market operations under increasing uncertainty

Farzaneh Abbaspourtorbati

EPFL2017