Modelos de explotación a corto plazo de centrales hidroeléctricas : Aplicación a la generación hidroeléctrica con velocidad variable

En esta tesis, se estudia con detalle el problema de planificación de la operación o la explotación a corto plazo de una central hidroeléctrica tomadora de precios que vende su energía en un mercado eléctrico liberalizado y organizado sobre la base de un sistema de ofertas de compra y venta de energía, poniendo un énfasis especial en el caso de las centrales con una capacidad de regulación semanal, diaria o menor, en las que es muy importante tener en cuenta, en el corto plazo, el efecto de la variación del salto, o del volumen. Analizando los modelos de explotación a corto plazo descritos en la bibliografía, se detectan en éstos ciertas limitaciones que pueden resumirse en los siguientes puntos: a) Es frecuente ignorar en los estudios a corto plazo la influencia de la variación del volumen del embalse a lo largo del periodo de explotación. b) Se recurre generalmente a dividir el problema en dos partes o problemas distintos: la asignación óptima de grupos y el despacho económico o de carga de los grupos asignados. En esta tesis, se desarrollan tres modelos de explotación a corto plazo originales, que se basan respectivamente en programación lineal entera mixta, programación no lineal y programación dinámica. Los tres modelos resuelven simultáneamente la asignación y el despacho económico de los grupos de la central y los dos últimos tienen en cuenta el efecto de la variación del salto durante el proceso de optimización, superando así las principales limitaciones de la mayoría de los modelos existentes. Los tres modelos se apoyan en la metodología que se propone en la tesis para obtener la característica de generación de la central, quedando implícitos en la solución de los tres modelos el estado óptimo (arranque/parada) y la potencia que producen todos los grupos de la central. Los tres modelos se apoyan además en una serie de procedimientos iterativos, de modelado y de discretización, algunos de los cuales son originales, y otros se basan parcialmente en procedimientos conocidos. Para comprobar la validez de los modelos, se estudia con éstos la explotación a corto plazo de una central de referencia formada por dos grupos generadores, bajo distintas condiciones de operación Además del desarrollo de nuevos modelos de explotación a corto plazo, se encuentran entre los objetivos de esta tesis la aplicación de los modelos desarrollados a una central de generación hidroeléctrica con velocidad variable y su utilización como herramienta de apoyo en estudios de rentabilidad de centrales hidroeléctricas. De acuerdo con los objetivos previstos, se describe en la tesis la metodología a seguir para aplicar los modelos desarrollados a una central de velocidad variable y se estudia la explotación a corto plazo de la central de referencia con dos grupos de velocidad variable bajo distintas condiciones de operación, demostrándose que, al permitir que los grupos de la central giren siempre a su velocidad óptima, aumentan considerablemente: a) El rango de caudales turbinables para cada nivel o volumen de embalse. b) La carrera de embalse aprovechable para producir energía. c) La potencia que produce la central en las mismas condiciones de caudal y salto. d) Los ingresos que recibe la central por vender su energía en el mercado. Cabe destacar que la aplicación de estos modelos a una central de velocidad variable constituye una de las principales aportaciones de esta tesis, ya que no se ha encontrado en la bibliografía ningún modelo de explotación a corto plazo aplicado a una central de este tipo. Por último, se presenta en esta tesis una metodología para estimar, a partir de unas previsiones de aportaciones y de precios horarios, los ingresos anuales que produce una central hidroeléctrica, utilizando los modelos desarrollados. Aplicando esta metodología se obtienen unos resultados más precisos que los que se obtienen en la mayoría de los estudios de rentabilidad consultados, ya que se tienen en cuenta los siguientes aspectos: a) La variación del rendimiento global de la planta en función de las condiciones de operación y del número de grupos que están en funcionamiento. b) La variación horaria de los precios de venta de la energía. c) La capacidad de gestión de la central para maximizar sus ingresos, distribuyendo el agua de la mejor forma posible entre todas las etapas del periodo de estudio, y para maximizar la energía generada en cada etapa, repartiendo de forma óptima el agua asignada entre todos los grupos disponibles. Cabe señalar que toda la tesis se desarrolla bajo un enfoque determinista en lo que se refiere al tratamiento de las aportaciones, los precios y la disponibilidad de los grupos. In this thesis, the short-term scheduling of a price-taker hydropower plant that sells its energy in pool-based electricity market is studied in detail, with special emphasis in the case of plants associated to a reservoir the regulating capability of which is weekly, daily or even smaller, where it is specially important to consider, in the short-term, the influence of the head, or volume, variation. When analyzing the short-term scheduling models found in the technical literature, it is noticeable that there are some limitations that can be summarized as follows: a) In short-term studies, it is usual to neglect the influence of the head, or volume, variation throughout the time horizon. b) The short-term scheduling problem is generally decomposed into two different problems: the unit commitment and the economic dispatch of the committed units. In this thesis, three novel short-term scheduling models, based respectively on mixed integer linear programming, nonlinear programming and dynamic programming are developed. The three models solve simultaneously the commitment and load dispatch of all the plant generating units, and the last two models consider also the influence of the head, or volume, variation during the optimization process, thus overcoming the main limitations found in the existing models. The three models are based on the methodology proposed in this thesis to obtain the plant generation characteristic, which implicitly includes the optimal status (on/off) and the power produced by all the plant generating units. Furthermore, these models use some iterative, modelling and discretization procedures, some of which are original, whereas others are partially based on known procedures. In order to check the validity of these models, they are applied to solve the short-term scheduling of a hydropower plant with two generating units, under different operating conditions. Besides the development of new short-term scheduling models, two more objectives are pursued in this work: the application of the developed models to an adjustable speed hydropower plant and the use of these models as a supporting tool to estimate the economic feasibility of a hydropower plant project. According to the proposed objectives, the application of the developed models to an adjustable speed hydropower plant is discussed in this thesis. The results of the short-term scheduling of a hydropower plant with two adjustable speed generating units are presented. It is demonstrated that, by allowing all the plant generating units to run at their optimal speed, an increase in the following magnitudes results: a) The range of operating flows for each reservoir level or volume. b) The range of operating volumes to produce energy. c) The power produced by the plant under the same operating conditions. d) The income that the plant receives from selling energy in the electricity market. It is worthy to mention that the application of the developed models to an adjustable speed hydropower plant is one of the main contributions of this thesis, provided that, so far, no short-term scheduling model applied to such type of hydropower plants has been found in the technical literature. Finally, it is presented a methodology based on the developed models to estimate the annual income of a hydropower plant, given a series of forecasted water inflows and energy prices. Compared with usual procedures, the approach proposed in this thesis leads to more accurate results, since the following aspects are considered in detail: a) The variation of the plant efficiency with the operating conditions and the number of generating units in operation. b) The hourly variation of the energy prices. c) The management capability of the plant to optimally distribute the water among the available generating units and throughout the time, thus maximizing the energy generated stage and the income that the plant receives from selling energy. It is important to note that the entire thesis is developed in a deterministic framework in that respect to the water inflows, the energy prices and the units’ availability

Materiales para la elaboración de un Manual de referencia de lingüística románica.

Sin resume

Cabré, M. Teresa: «A l'entorn de la paraula. Lexicologia general» (Vol. 1) y «Lexicologia catalana» (Vol. II).

Sin resume

Contribution of a pumped-storage hydropower plant to reduce the scheduling costs of an isolated power system with high wind power penetration

AbstractThe paper aims at demonstrating that the consideration of constant start-up costs and ramps of the thermal generating units for assessing the contribution of pumped-hydro energy storage to reduce the scheduling costs of hydrothermal power systems with high wind penetration, may yield unrealistic results. For this purpose, an isolated power system is used as a case study. The contribution of a pumped-storage hydropower plant to reduce the system scheduling costs is assessed in the paper by using a hydrothermal weekly unit commitment model. The model considers different start-up costs and ramps of the thermal generating units as a function of the start-up type. The effects of including pumped hydro energy storage in the system on the integration of wind energy, and on the start-ups and capacity factors of the thermal generating units are also evaluated. The results of the paper demonstrate that the consideration of constant start-up costs and ramps of the thermal generating units yields unrealistic results, and that the pumped-storage hydropower plant may help reduce the system scheduling costs by 2.5–11% and integrate wind power and may allow dispensing with some inflexible thermal generating units

Submarine Basaltic Magmatism in the Subbetic Basin (Southern Spain): Insights into Melt-Weakening Processes during Mesozoic Continental Rifting

Mantle-derived volcanic rocks from the Subbetic hyperextended basin in SE Spain provide new insights into the composition and mechanical behavior of the mantle during continental rifting. The present study describes a sequential restored cross-section along with geochemical characteristics of the basaltic rocks interbedded within the Mesozoic succession of the basin. Sedimentary stacking patterns of minibasins above the mobilized salt reflect the relationships with coeval basaltic volcanism. We recognize two type localities on the basis of volcanic facies, the presence of shallow intrusive bodies, and age of the associated sedimentary formations. The first type corresponds to subaqueous pillow-lava flows and subvolcanic sills and dikes associated with Lower Jurassic marly limestones and Middle Jurassic oolitic limestones. The Jurassic basalts present enriched MORB compositions with moderate La/Sm and low Sm/Yb ratios. Interestingly, a significant group of this Jurassic basaltic magmatism departs from the typical MORB-OIB array, showing deep Nb-Ta negative anomalies and high Th/Nb ratios. The second type comprises subaqueous lava flows, also including pillow-shaped basalts interlayered with hyaloclastite deposits and Upper Cretaceous clays, radiolarites, and marly limestones. The Cretaceous magmatism is characterized by highly enriched MORB compositions. Furthermore, the moderate Sm/Yb values and the positive correlation between LREE/HREE and Zr point to the involvement of deep (Grt-present) mantle sources in the origin of the Cretaceous basaltic melts. We interpret the Lower- Middle Jurassic calc-alkaline signal as due to the partial melting of recycled crustal rocks within the upper mantle, i.e., associated with remnants of pre-Mesozoic subducted slabs. These characteristics are similar to those described in Triassic basaltic rocks widespread throughout the External Zone of the Betic Cordillera. Mantle-derived basalts interlayered within the Lower Jurassic syn-rift deposits indicate that melting and deformation within the lithospheric mantle was initiated early during continental rifting. Accordingly, we suggest that Early to Middle Jurassic mantle melts promoted failure within the upper mantle, thus contributing to the inception of lithospheric-scale shear zones, which, in turn, controlled the evolution of this magma-poor hyperextended margin. Subsequently, rift evolution gave way to the activation of deeper melt sources in the mantle and an increase of the alkaline signature at the Cretaceous time.Spanish Geological SurveyJunta de Andalucia A-RNM-005-UGR18 PY20-01387Spanish Government REViSE-Betics-PID2020-119651RB-I0

Preliminary investigation on the use of waste cork dust as filler in hot-mix asphalt

Este póster foi presentado no congreso "Cork in Science and Applications 2019. New Trends in Cork Innovation: From the Wine Industry to the New Applications" que foi organizado polo Institut Catalá del Suro e que tivo lugar en Palafrugell (Girona) o 22 e 23 de maio de 2019.[Abstract:] The cork contains significant amounts of a biopolymer called suberin (45%). Polymers have been frequently used in the manufacture of hot-mix asphalt (HMA) to improve their properties. At the Universidade da Coruña (UDC), a preliminary investigation was carried out in which the feasibility of using waste cork dust from the manufacture of plugs, as filler in the manufacture of HMA was analyzed. Firstly, the aggregate-binder adhesion was analyzed by means of two types of tests: the boiling water test and the rolling bottle method. The performance of the cork filler was compared with the performance of conventional natural filler. In both tests it was obtained that with the cork filler, the aggregate-binder adhesion was better than with the natural filler. Secondly, a HMA type AC 22 bin S was manufactured, with a bitumen content of 3.8%. Indirect tensile test after immersion in water were conducted, in order to compare the moisture damage resistance of mixtures made with filler cork and natural filler. It was concluded that the filler cork helped to slightly improve the water resistance of the mixture. Although further investigation is needed, it can be stated that the filler cork could replace the conventional natural filler in the production of HMA

Towards Formal Interaction-Based Models of Grid Computing Infrastructures

Grid computing (GC) systems are large-scale virtual machines, built upon a massive pool of resources (processing time, storage, software) that often span multiple distributed domains. Concurrent users interact with the grid by adding new tasks; the grid is expected to assign resources to tasks in a fair, trustworthy way. These distinctive features of GC systems make their specification and verification a challenging issue. Although prior works have proposed formal approaches to the specification of GC systems, a precise account of the interaction model which underlies resource sharing has not been yet proposed. In this paper, we describe ongoing work aimed at filling in this gap. Our approach relies on (higher-order) process calculi: these core languages for concurrency offer a compositional framework in which GC systems can be precisely described and potentially reasoned about.Comment: In Proceedings DCM 2013, arXiv:1403.768

Adhesion Analysis of Waste Cork Dust as Filler for Bituminous Mixtures

No libro: Wastes: Solutions, Treatments and Opportunities III: Selected Papers from the 5th International Conference Wastes 2019, September 4-6, Lisbon, Portugal (pp.1-6). CRC Press, 2020. ISBN 978-0-367-25777-4[Abstract] Suberin is a biopolymer that can be found in high amounts in natural cork. As is well known, polymers can be used as bitumen modifiers to improve the properties of bituminous mixtures. This paper describes laboratory adhesion analysis that was conducted to analyse the use of waste cork dust as a filler in hot-mix asphalt (HMA). The performance of the waste cork dust as a filler was compared with that of a typically used natural filler and with Portland cement. These three fillers were characterized by their grain size distributions, morphological studies, and X-ray fluorescence spectroscopy experiments. The adhesion between the aggregates and the binder was analysed using two adhesion tests: a “boiling water test” and using the “roll-ing bottle method”. Both tests led to the same result: the waste cork dust was a better filler than the natural filler.https://doi.org/10.1201/978042928979

Behavior of the Fiber and the Base Points of Parametrizations Under Projections

This is the author’s version of a work that was accepted for publication\ud in Mathematics in Computer Science.\ud Changes resulting from the publishing process, such as peer review,\ud editing, corrections, structural formatting, and other quality control\ud mechanisms may not be reflected in this document.\ud Changes may have been made to this work since it was submitted for\ud publication. A definitive version was subsequently published\ud in Mathematics in Computer Science Volume 7, Issue 2 (2013), Page\ud 167-184 DOI 10.1007/s11786-013-0139-8Given a rational parametrization P( t ), t = (t1, . . . , tr ), of an r-dimensional unirational variety, we\ud analyze the behavior of the variety of the base points of P( t ) in connection to its generic fibre, when successively\ud eliminating the parameters ti . For this purpose. we introduce a sequence of generalized resultants whose primitive\ud and content parts contain the different components of the projected variety of the base points and the fibre.\ud In addition, when the dimension of the base points is strictly smaller than 1 (as in the well known cases of curves\ud and surfaces), we show that the last element in the sequence of resultants is the univariate polynomial in the corresponding\ud Gröbner basis of the ideal associated to the fibre; assuming that the ideal is in t1-general position and\ud radical.This work has been partially supported by the Spanish Ministerio de Ciencia e Innovación under the project\ud MTM2008-04699-C03-01 and by the Ministerio de Economía y Competitividad under the project MTM2011-25816-C02-01;\ud both authors are members of the of the Research Group ASYNACS (Ref. CCEE2011/R34)

Computation of the degree of rational surface parametrizations

A rational affine parametrization of an algebraic surface establishes a rational correspondence of the affine plane with the surface. We consider the problem of computing the degree of such a rational map. In general, determining the degree of a rational map can be achieved by means of elimination theoretic methods. For curves, it is shown that the degree can be computed by gcd computations. In this paper, we show that the degree of a rational map induced by a surface parametrization can be computed by means of gcd and univariate resultant computations. The basic idea is to express the elements of a generic fibre as the finitely many intersection points of certain curves directly constructed from the parametrization, and defined over the algebraic closure of a field of rational functions