A cyclic time-dependent Markov process to model daily patterns in wind turbine power production

Wind energy is becoming a top contributor to the renewable energy mix, which raises potential reliability issues for the grid due to the fluctuating nature of its source. To achieve adequate reserve commitment and to promote market participation, it is necessary to provide models that can capture daily patterns in wind power production. This paper presents a cyclic inhomogeneous Markov process, which is based on a three-dimensional state-space (wind power, speed and direction). Each time-dependent transition probability is expressed as a Bernstein polynomial. The model parameters are estimated by solving a constrained optimization problem: The objective function combines two maximum likelihood estimators, one to ensure that the Markov process long-term behavior reproduces the data accurately and another to capture daily fluctuations. A convex formulation for the overall optimization problem is presented and its applicability demonstrated through the analysis of a case-study. The proposed model is capable of reproducing the diurnal patterns of a three-year dataset collected from a wind turbine located in a mountainous region in Portugal. In addition, it is shown how to compute persistence statistics directly from the Markov process transition matrices. Based on the case-study, the power production persistence through the daily cycle is analysed and discussed

Portugal

In the past decades, Portugal has had little development of wind power plant installations, mainly due to the low tariffs practised. However, at the end of 2001, the scenario changed with the publication of new legislation and tariffs. By 2003, that change became reflected in the implementation of new wind park projects and a strong increase in the development rate of capacity installed. In the following sections, a synthesis of the past as well as a summary of the current situation is presented with a main focus on the Portuguese current state of development and trends

The Future Energy Mix Paradigm: How to Embed Large Amounts of Wind Generation While Preserving the Robustness and Quality of the Power Systems?

The 2001/77/CE Renewable Energies European Directive together with Kyoto Protocol ratification by many countries, supported by some Governments vision and strong objectives on the reduction of external oil dependence, put Europe and other developed economies in the front line to achieve a remarkable wind energy penetration within ten years time. These goals will not be achieved without technical costs and risks, but mainly,without a careful planning and assessment of the power system behaviour with large amounts of wind generation (SRA, 2008; IEAWind, 2008).These days, one of the most relevant difficulties the wind sector faces was caused by this technology own extreme success. The high capacity installed in the last decade introduced a brand new set of power system technological concerns that recently became one of the more referenced subjects among developers, network planners and system operators. These concerns are not anymore a negligible distribution grid integration issue that some years ago the experts tended not to give too much relevance since they were easily solved and even more easily avoided through good design and planning, but this is a real power system operation and planning challenge (Holttinen et al, 2009): will the power systems be capable to cope with the specificities of the wind power production in large quantities (aka “high penetration”) without requiring new wind park models, system operation tools,increased performance of the wind turbines or even a change in the Transmission System Operators (TSOs) conventional mode of operation? The recent concern of the TSOs is very legitimate, since it is their responsibility to design and manage the power system global production and its adjustment to the consumer loads as well as to assure the technical quality of the overall service, both in steady-state and under transient occurrences

Portugal

During 2005, Portugal reinforced the tendency shown during 2004 of high growth rate of wind capacity installation. Also visible was some simplification of critical administrative processes concerning the implementation of renewable energy projects and, for the second year in a row, Portugal almost doubled the installed wind power capacity. In the following sections, a synthesis of the actual situation is presented with a main focus on the Portuguese current state of development and trends

Impact of Wind Generation Fluctuations in the Design and Operation of Power Systems

In this paper, the impact of the wind time variability and the spatial smoothing effect in mountainous complex terrains, usually taken as 1/sqrt(N) for fast fluctuations, is studied. The dimension of the regions, the type of electrical clustering of large numbers of wind turbines and the local meteorological effects are addressed and conclusions drawn on selected experimental case studies

Portugal

During 2004, Portugal reversed the tendency of slow wind capacity growth observed in previous years. The publication of legislation and tariffs at the end of 2001 and subsequent government simplifi cation of administrative processes concerning the implementation of renewable energy projects resulted in nearly doubled capacity in Portugal during 2004. In the following sections, a summary of the events of the year is presented with a main focus on the current state of development and trends

Portugal

Portugal has few indigenous energy resources, such as those that satisfy the majority of the energy needs of the economically developed countries, such as oil, gas, and coal. This situation leads to a large dependence on foreign economies for fossil primary resources. In this context, the contribution of renewable energies and the need to improve their penetration becomes of strategic relevance for the country’s development. In 2006, the total renewable sources installed capacity was 6,961 MW. The total electric energy production from renewables has shown an impressive 86% growth rate with respect to the end of 2005, its final value being reported as 16,120 GWh. This growth was strongly correlated with the variation in hydropower production, about 124%. In what concerns to wind energy, as will be shown in the next paragraphs, there was a moderate growth in the installed capacity when compared to previous years. In 2006, the 2005 policy continuance was verified, with special relevance to the ending of the first phase of the 1,500 MW public call for wind park grid connection opened in July 2005

Impact of weather conditions on the windows of opportunity for operation of offshore wind farms in portugal

The deployment of offshore wind parks face several challenges. Among them are the difficulties introduced by the atmospheric and sea conditions in accessing those wind parks. A window of opportunity is a timeframe when weather and sea conditions are acceptable and enable to perform specific tasks in the installation and operation/maintenance of the offshore wind park. This study identifies typical time periods of windows of opportunity to access three offshore Portuguese maritime regions. The accessibility conditions also take into account the system type transportation method for local access, namely, rubber boat, boat with OAS or helicopter. It was concluded that Portugal has adequate conditions for offshore site maintenance strategies, with a large number of windows of opportunity, but they are relatively short, therefore the installation of offshore wind parks must be carefully planned. This is an important factor in favor of the offshore wind farm deployments on the country

Periferias de Roma, encuesta multidisciplinar sobre la transformación de los modelos de asentamiento

El fenómeno de las periferias es moderno, nació durante el siglo XIX.Sin embargo, las definiciones tradicionales no son adecuadas para describir hoy las dinámicas complejas que involucran las grandes (y menos grandes) áreas urbanas. Por lo tanto, para hablar de la periferia es necesario revisar el significado de esta palabra e investigar las periferias urbanas contemporáneas desde diferentes perspectivas.El estudio de los fenómenos territoriales ha sido durante mucho tiempo la prerrogativa de varias disciplinas: planificación urbana, geografía, sociología, antropología, economía, etc., son unas de las que han contribuido a enriquecer la información patrimonial sobre la ciudad y el territorio. Sobre todo, en cuanto al fenómeno de la sub-urbanización, en su base hay un claro componente cultural. El desafío que surge hoy es el de la integración entre las plataformas de datos y el intercambio. El objetivo es crear una base de datos de información permanente capaz de respaldar las elecciones de políticas y las estrategias de intervención.Este estudio integra el enfoque de Estudios Urbanos con el de Geografía Urbana, superponiendo técnicas para leer fenómenos urbanos basados en herramientas geográficLa escena romana es un rico contenedor de periferias, diferentes y desiguales, a menudo la escena de una degradación generalizada. Surgen, en la mayoría de los casos, desde el final de la Segunda Guerra Mundial y siguen creciendo hasta hoy, solo en parte siguiendo el diseño general de los planes urbanos. En Roma, las incomodidades de los nuevos barrios periféricos, principalmente diseñadas por el Plan del 1965 consisten en dificultades de movilidad y congestión del tráfico, falta de homogeneidad de distribución y escasez de servicios públicos y una dilatación general de las distancias y de los desplazamientos. El resultado hodierno es un mosaico con muchas piezas faltantes, fragmentos urbanos que producen fragmentación espacial y donde solo casos esporádicos de movilización espontánea por parte de grupos de ciudadanos han corregido la situación de hecho, rediseñando parcialmente las periferias en cuestión.La expansión de Roma hacia el mar atravesó el siglo pasado. Esta área, durante las décadas posteriores al final de la Segunda Guerra Mundial, se ha convertido en una inmensa periferia que ha alcanzado a más de 120,000 habitantes en un área cinco veces más grande que la ciudad cercana de Ostia Lido (que, sin embargo, tiene menos de 100,000 habitantes) y una densidad de población que no supera los 25 habitantes por hectárea. Es una periferia heterogénea, predominantemente ilegal, que une la ausencia sustancial de espacios de relaciones públicas y de lugares centrales, al carácter provisional que acentúa su carácter periférico.Es una periferia heterogénea, predominantemente ilegal, que une la ausencia sustancial de espacios públicos de relaciones, de lugares centrales, a la naturaleza provisional que acentúa su carácter periférico. En esta área, el proceso de asentamiento, después de la Segunda Guerra Mundial, comienza debido a las necesidades básicas: vivir, trabajar, etc. Sin embargo, entre los años Cincuenta y Sesenta del siglo XX comenzó a cambiar sus caracteres hacia el modelo norteamericano del suburbio. Durante treinta años se han transformado los conceptos de vida, de ciudad y de periferia. Pero este fenómeno está acompañado por un deterioro sensible de la calidad de vida y, en consecuencia, del medio ambiente. El análisis del uso del suelo ha confirmado este cambio, devolviendo un modelo de asentamiento periurbano / suburbano con densidad baja o muy baja, donde un número muy bajo de habitantes se opone a un consumo de tierra significativo.Por lo tanto, intervenir en la periferia implica una opinión sobre la periferia que es sustancialmente diferente del sentimiento de quienes viven allí. Para ellos, este modelo de ciudad no es necesariamente negativo, sino que tiene una serie de problemas urbanísticos relacionados con la movilidad, los servicios públicos, la seguridad urbana, etc.El ensayo indicará las diferentes opciones para la regeneración urbana de los suburbios contemporáneos. Desde la Grilla Teórica (Vittorini, 1985; Cerasoli, 2010), un instrumento de rehabilitación de las periferias finalizados a la reorganización de la estructura espacial, cuyos elementos son la calidad del espacio público de relación, la permeabilidad de la estructura urbana y la complejidad de los usos. Hasta las consideraciones que surgen de las enseñanzas recientes de Serge Latouche, teórico de la economía del decrecimiento, de Zigmund Bauman, quien introdujo el concepto de sociedad líquida, hasta llegar a la Encíclica Laudato Si’ de Papa Francisco, que es un tratado de política territorial sostenible.El fenomen de les perifèries és modern, va néixer durant el segle XIX.No obstant això, les definicions tradicionals no són adequades per descriure avui les dinàmiques complexes que involucren les grans (i menys grans) àrees urbanes. Per tant, per parlar de la perifèria cal revisar el significat d'aquesta paraula i investigar les perifèries urbanes contemporànies des de diferents perspectives.L'estudi dels fenòmens territorials ha estat durant molt temps la prerrogativa de diverses disciplines: planificació urbana, geografia, sociologia, antropologia, economia, etc., són unes de les que han contribuït a enriquir la informació patrimonial sobre la ciutat i el territori. Sobretot, pel que fa al fenomen de la sub-urbanització, en la seva base hi ha un clar component cultural. El desafiament que sorgeix avui és el de la integració entre les plataformes de dades i l'intercanvi. L'objectiu és crear una base de dades d'informació permanent capaç de donar suport a les eleccions de polítiques i les estratègies d'intervenció.Aquest estudi integra l'enfocament d'Estudis Urbans amb el de Geografia Urbana, superposant tècniques per llegir fenòmens urbans basats en eines GeogràfiquesL'escena romana és un ric contenidor de perifèries, diferents i desiguals, sovint l'escena d'una degradació generalitzada. Sorgeixen, en la majoria dels casos, des del final de la Segona Guerra Mundial i segueixen creixent fins avui, només en part seguint el disseny general dels plans urbans. A Roma, les incomoditats dels nous barris perifèrics, principalment dissenyades pel Pla de l'any 1965 consisteixen en dificultats de mobilitat i congestió del trànsit, manca d'homogeneïtat de distribució i escassetat de serveis públics i una dilatació general de les distàncies i dels desplaçaments. El resultat hodierno és un mosaic amb moltes peces per fer, fragments urbans que produeixen fragmentació espacial i on només casos esporàdics de mobilització espontània per part de grups de ciutadans han corregit la situació de fet, redissenyant parcialment les perifèries en qüestió.L'expansió de Roma cap al mar va travessar el segle passat. Aquesta àrea, durant les dècades posteriors al final de la Segona Guerra Mundial, s'ha convertit en una immensa perifèria que ha arribat a més de 120,000 habitants en una àrea cinc vegades més gran que la ciutat propera d'Ostia Lido (que, però, té menys de 100,000 habitants) i una densitat de població que no supera els 25 habitants per hectàrea. És una perifèria heterogènia, predominantment il·legal, que uneix l'absència substancial d'espais de relacions públiques i de llocs centrals, al caràcter provisional que accentua el seu caràcter perifèric.És una perifèria heterogènia, predominantment il·legal, que uneix l'absència substancial d'espais públics de relacions, de llocs centrals, a la naturalesa provisional que accentua el seu caràcter perifèric. En aquesta àrea, el procés d'assentament, després de la Segona Guerra Mundial, comença a causa de les necessitats bàsiques: viure, treballar, etc. No obstant això, entre els anys Cinquanta-Seixanta del segle XX va començar a canviar els seus caràcters cap al model nord-americà del suburbi. Durant trenta anys s'han transformat els conceptes de vida, de ciutat i de perifèria. Però aquest fenomen està acompanyat per un deteriorament sensible de la qualitat de vida i, en conseqüència, del medi ambient. L'anàlisi de l'ús del sòl ha confirmat aquest canvi, retornant un model d'assentament periurbà / suburbà amb densitat baixa o molt baixa, on un nombre molt baix d'habitants s'oposa a un consum de sòl significatiu. Per tant, intervenir en la perifèria implica una opinió sobre la perifèria que és substancialment diferent del sentiment dels que hi viuen. Per a ells, aquest model de ciutat no és necessàriament negatiu, sinó que té una sèrie de problemes urbanístics relacionats amb la mobilitat, els serveis públics, la seguretat urbana, etc. L'assaig d'indicar les diferents opcions per a la regeneració urbana dels suburbis contemporanis. Des de la Grilla Teòrica (Vittorini, 1985; Cerasoli, 2010), un instrument de rehabilitació de les perifèries finalitzats a la reorganització de l'estructura espacial, els elements són la qualitat de l'espai públic de relació, la permeabilitat de l'estructura urbana i la complexitat dels usos. Fins a les consideracions que sorgeixen dels ensenyaments recents de Serge Latouche, teòric de l'economia del decreixement, de Zigmund Bauman, qui va introduir el concepte de societat líquida, fins arribar a l'Encíclica Laudato Si 'de Papa Francisco, que és un tractat de política territorial sostenible.The outskirt phenomenon is modern; it was born during the nineteenth century.The traditional definitions, however, are unsuitable to describe today the complex dynamics that involve large (and less large) urban areas. Therefore, to speak about outskirt it is necessary to review the meaning of this word and investigate the contemporary urban peripheries from different perspectives.The study of territorial phenomena has long been the prerogative of various disciplines: urban planning, geography, sociology, anthropology, economics, etc. are among those that have contributed to enriching the heritage information on city and territory. Above all, as regards the phenomenon of suburbanization, at their base there is a clear cultural component. The challenge that arises today is that of integration between data and sharing platforms. The goal is to build a permanent information baggage able to support policy choices and intervention strategies. This study integrates the approach of Urban Studies with that of Urban Geography, superimposing techniques for reading urban phenomena based on geographical tools.The Roman scene is a rich box of outskirts, different and uneven, often the scene of a widespread degradation. They arise, in most cases, since the end of the World War II and growing until today, only in part following the overall design of urban plans. In Rome, the discomforts of the new peripheral neighbourhoods, principally designed by the 1965 Urban Plan consist in difficulties of mobility and traffic congestion, distribution inhomogeneity and scarcity of public services and an overall dilation of distances and displacements. Today´s result is a mosaic with many missing pieces, urban fragments that produce spatial fragmentation and where only sporadic cases of spontaneous mobilization by groups of citizens have correct the factual situation, partially redeveloping the outskirts concerned.The expansion of Rome towards the sea went through the last century. This area over the decades following the end of World War II has become an immense outskirt that has reached more than 120,000 inhabitants in an area five times larger than the nearest city of Ostia Lido (which, however, has just under 100,000 inhabitants) and a population density that does not exceed 25 inhabitants per hectare. It is a heterogeneous outskirt, prevalently illegal, that unites the substantial absence of public space of relations, of central places, to the provisional nature that accentuates its peripheral character. In this area the settlement process, after the Second World War, begins due to basic needs- living, working, etc. -, however between the Fifties and Sixties of twentieth century it began to change its characters towards the North American model of the Suburb. During thirty years the concepts of living, of city and of outskirt have been transformed. But this phenomenon is accompanied by a sensitive decay of the quality of life and, consequently, of the environment.The land use analysis has confirmed this change, returning a peri-urban / suburban settlement model with low or very low density, where a very low number of inhabitants are opposed to a significant land consumption. Therefore, to intervene in the outskirt implies an opinion about the outskirts that is substantially different from the feeling of those who live there. For them, this model of city is not necessarily negative but has a series of urban planning problems related to mobility, the public services, urban security, etc.The essay will indicate the different options for urban regeneration of contemporary suburbs. It will range from the Theoretical grid (Vittorini, 1988; Cerasoli, 2008), an instrument of rehabilitation of the peripheries finalized to the reorganization of the spatial structure, whose elements are the quality of the public space of relation, the permeability of the urban structure and the complexity of the uses. Up to considerations that arise from the recent teachings of Serge Latouche, theoretician of the economy of degrowth, of Zigmund Bauman, who introduced the concept of liquid society, until arriving at the Encyclical Laudato Si’ of Pope Francis, that is a treaty of sustainable territorial policy.Peer Reviewe