Power system stability of a small sized isolated network supplied by a combined wind-pumped storage generation system: a case study in the Canary Islands

Massive integration of renewable energy sources in electrical power systems of remote islands is a subject of current interest. The increasing cost of fossil fuels, transport costs to isolated sites and environmental concerns constitute a serious drawback to the use of conventional fossil fuel plants. In a weak electrical grid, as it is typical on an island, if a large amount of conventional generation is substituted by renewable energy sources, power system safety and stability can be compromised, in the case of large grid disturbances. In this work, a model for transient stability analysis of an isolated electrical grid exclusively fed from a combination of renewable energy sources has been studied. This new generation model will be installed in El Hierro Island, in Spain. Additionally, an operation strategy to coordinate the generation units (wind, hydro) is also established. Attention is given to the assessment of inertial energy and reactive current to guarantee power system stability against large disturbances. The effectiveness of the proposed strategy is shown by means of simulation results.

Wind intermittency and CO2 reductions: the case of the spanish power system

Renewable energy sources are believed to reduce drastically greenhouse gas emissions that would otherwise be generated from fossil fuels used to generate electricity. This implies that a unit of renewable energy will replace a unit of fossil-fuel, with its CO2 emissions, on an equivalent basis (with no other effects on the grid). But, the fuel economy and emissions in the existing power systems are not proportional with the electricity production of intermittent sources due to cycling of the fossil fuel plants that make up the balance of the grid (i.e. changing the power output makes thermal units to operate less efficiently). This study focuses in the interactions between wind generation and thermal plants cycling, by establishing the levels of extra fuel use caused by decreased efficiencies of fossil back-up for wind electricity in Spain. We analyze the production of all thermal plants in 2011, studying different scenarios where wind penetration causes major deviations in programming, while we define a procedure for quantifying the carbon reductions by using emission factors and efficiency curves from the existing installations. The objectives are to discuss the real contributions of renewable energies to the environmental targets as well as suggest alternatives that would improve the reliability of future power systems.

New method for analytical photovoltaic parameters identification: meeting manufacturer���s datasheet for different ambient conditions

At present, photovoltaic energy is one of the most important renewable energy sources. The demand for solar panels has been continuously growing, both in the industrial electric sector and in the private sector. In both cases the analysis of the solar panel efficiency is extremely important in order to maximize the energy production. In order to have a more efficient photovoltaic system, the most accurate understanding of this system is required. However, in most of the cases the only information available in this matter is reduced, the experimental testing of the photovoltaic device being out of consideration, normally for budget reasons. Several methods, normally based on an equivalent circuit model, have been developed to extract the I-V curve of a photovoltaic device from the small amount of data provided by the manufacturer. The aim of this paper is to present a fast, easy, and accurate analytical method, developed to calculate the equivalent circuit parameters of a solar panel from the only data that manufacturers usually provide. The calculated circuit accurately reproduces the solar panel behavior, that is, the I-V curve. This fact being extremely important for practical reasons such as selecting the best solar panel in the market for a particular purpose, or maximize the energy extraction with MPPT (Maximum Peak Power Tracking) methods.

Evaluaci��n del dispositivo Raspberry Pi como elemento de despliegue de servicios en el marco de las Smart Grids

La tendencia actual de las redes de telecomunicaciones conduce a pensar en un futuro basado en el concepto emergente de las Smart Cities�� que tienen como objetivo el desarrollo urbano basado en un modelo de sostenibilidad que responda a las necesidades crecientes de las ciudades. Dentro de las Smart Cities podemos incluir el concepto de Smart Grid, el cual est�� referido a sistemas de administraci��n y producci��n de energ��a eficientes, que permitan un sistema energ��tico sostenible, y que den cabida a las fuentes de energ��a renovables. Sistemas de este tipo se muestran a los usuarios como un conjunto de servicios con los que interactuar sin ser tan s��lo un mero cliente, sino un agente m��s del entorno energ��tico. Por otro lado, los sistemas de software distribuidos son cada vez m��s comunes en una infraestructura de telecomunicaciones cada vez m��s extensa y con m��s capacidades. Dentro de este ��mbito tecnol��gico, las arquitecturas orientadas a servicios han crecido exponencialmente sobre todo en el sector empresarial. Con sistemas basados en estas arquitecturas, se pueden ofrecer a empresas y usuarios sistemas software basados en el concepto de servicio. Con la progresi��n del hardware actual, la miniaturizaci��n de los equipos es cada vez mayor, sin renunciar por ello a la potencia que podemos encontrar en sistemas de mayor tama��o. Un ejemplo es el dispositivo Raspberry Pi, que contiene un ordenador plenamente funcional contenido en el tama��o de una cajetilla de tabaco, y con un coste muy reducido. En este proyecto se pretenden aunar los tres conceptos expuestos. De esta forma, se busca utilizar el dispositivo Raspberry Pi como elemento de despliegue integrado en una arquitectura de Smart Grid orientada a servicios. En los trabajos realizados se ha utilizado la propuesta definida por el proyecto de I+D europeo e-GOTHAM, con cuya infraestructura se ha tenido ocasi��n de realizar diferentes pruebas de las descritas en esta memoria. Aunque esta arquitectura est�� orientada a la creaci��n de una Smart Grid, lo experimentado en este PFG podr��a encajar en otro tipo de aplicaciones. Dentro del estudio sobre las soluciones software actuales, se ha trabajado en la evaluaci��n de la posibilidad de instalar un Enterprise Service Bus en el Raspberry Pi y en la optimizaci��n de la citada instalaci��n. Una vez conseguida una instalaci��n operativa, se ha desarrollado un controlador de un dispositivo f��sico (sensor/actuador), denominado Dispositivo L��gico, a modo de prueba de la viabilidad del uso del Raspberry Pi para actuar como elemento en el que instalar aplicaciones en entornos de Smart Grid o Smart Home. El ��xito logrado con esta experimentaci��n refuerza la idea de considerar al Raspberry Pi, como un importante elemento a tener en cuenta para el despliegue de servicios de Smart Cities o incluso en otros ��mbitos tecnol��gicos. ABSTRACT. The current trend of telecommunication networks lead to think in a future based on the emerging concept of Smart Cities, whose objective is to ensure the urban development based on a sustainable model to respond the new necessities of the cities. Within the Smart cites we can include the concept of Smart Grid, which is based on management systems and efficient energy production, allowing a sustainable energy producing system, and that includes renewable energy sources. Systems of this type are shown to users as a set of services that allow users to interact with the system not only as a single customer, but also as other energy environment agent. Furthermore, distributed software systems are increasingly common in a telecommunications infrastructure more extensive and with more capabilities. Within this area of technology, service-oriented architectures have grown exponentially especially in the business sector. With systems based on these architectures, can be offered to businesses and users software systems based on the concept of service. With the progression of the actual hardware, the miniaturization of computers is increasing, without sacrificing the power of larger systems. An example is the Raspberry Pi, which contains a fully functional computer contained in the size of a pack of cigarettes, and with a very low cost. This PFG (Proyecto Fin de Grado) tries to combine the three concepts presented. Thus, it is intended to use the Raspberry Pi device as a deployment element integrated into a service oriented Smart Grid architecture. In this PFG, the one proposed in the European R&D e-GOTHAM project has been observed. In addition several tests described herein have been carried out using the infrastructure of that project. Although this architecture is oriented to the creation of a Smart Grid, the experiences reported in this document could fit into other applications. Within the study on current software solutions, it have been working on assessing the possibility of installing an Enterprise Service Bus in the Raspberry Pi and optimizing that facility. Having achieved an operating installation, it has been developed a driver for a physical device (sensor / actuator), called logical device, for testing the feasibility of using the Raspberry Pi to act as an element in which to install applications in Smart Grid and Smart Home Environments. The success of this experiment reinforces the idea of considering the Raspberry Pi as an important element to take into account in the deployment of Smart Cities services or even in other technological fields.

Desarrollo de una aplicaci��n Android para administraci��n y gesti��n de la informaci��n de registro de servicios en una plataforma SOA

Este Proyecto Fin de Grado est�� enmarcado dentro de las actividades del GRyS (Grupo de Redes y Servicios de Pr��xima Generaci��n) con las Smart Grids. En la investigaci��n actual sobre Smart Grids se pretenden alcanzar los siguientes objetivos: . Integrar fuentes de energ��as renovables de manera efectiva. . Aumentar la eficiencia en la gesti��n de la demanda y suministro de forma din��mica. . Reducir las emisiones de CO2 dando prioridad a fuentes de energ��a verdes. . Concienciar del consumo de energ��a mediante la monitorizaci��n de dispositivos y servicios. . Estimular el desarrollo de un mercado vanguardista de tecnolog��as energ��ticamente eficientes con nuevos modelos de negocio. Dentro del contexto de las Smart Grids, el inter��s del GRyS se extiende b��sicamente a la creaci��n de middlewares sem��nticos y tecnolog��as afines, como las ontolog��as de servicios y las bases de datos sem��nticas. El objetivo de este Proyecto Fin de Grado ha sido dise��ar y desarrollar una aplicaci��n para dispositivos con sistema operativo Android, que implementa una interfaz gr��fica y los m��todos necesarios para obtener y representar informaci��n de registro de servicios de una plataforma SOA (Service-Oriented Architecture). La aplicaci��n permite: . Representar informaci��n relativa a los servicios y dispositivos registrados en una Smart Grid. . Guardar, cargar y compartir por correo electr��nico ficheros HTML con la informaci��n anterior. . Representar en un mapa la ubicaci��n de los dispositivos. . Representar medidas (voltaje, temperatura, etc.) en tiempo real. . Aplicar filtros por identificador de dispositivo, modelo o fabricante. . Realizar consultas SPARQL a bases de datos sem��nticas. . Guardar y cagar consultas SPARQL en ficheros de texto almacenados en la tarjeta SD. La aplicaci��n, desarrollada en Java, es de c��digo libre y hace uso de tecnolog��as est��ndar y abiertas como HTML, XML, SPARQL y servicios RESTful. Se ha tenido ocasi��n de probarla con la infraestructura del proyecto europeo e-Gotham (Sustainable-Smart Grid Open System for the Aggregated Control, Monitoring and Management of Energy), en el que participan 17 socios de 5 pa��ses: Espa��a, Italia, Estonia, Finlandia y Noruega. En esta memoria se detalla el estudio realizado sobre el Estado del arte y las tecnolog��as utilizadas en el desarrollo del proyecto, la implementaci��n, dise��o y arquitectura de la aplicaci��n, as�� como las pruebas realizadas y los resultados obtenidos. ABSTRACT. This Final Degree Project is framed within the activities of the GRyS (Grupo de Redes y Servicios de Pr��xima Generaci��n) with the Smart Grids. Current research on Smart Grids aims to achieve the following objectives: . To effectively integrate renewable energy sources. . To increase management efficiency by dynamically matching demand and supply. . To reduce carbon emissions by giving priority to green energy sources. . To raise energy consumption awareness by monitoring products and services. . To stimulate the development of a leading-edge market for energy-efficient technologies with new business models. Within the context of the Smart Grids, the interest of the GRyS basically extends to the creation of semantic middleware and related technologies, such as service ontologies and semantic data bases. The objective of this Final Degree Project has been to design and develop an application for devices with Android operating system, which implements a graphical interface and methods to obtain and represent services registry information in a Service-Oriented Architecture (SOA) platform. The application allows users to: . Represent information related to services and devices registered in a Smart Grid. . Save, load and share HTML files with the above information by email. . Represent the location of devices on a map. . Represent measures (voltage, temperature, etc.) in real time. . Apply filters by device id, model or manufacturer. . SPARQL query semantic database. . Save and load SPARQL queries in text files stored on the SD card. The application, developed in Java, is open source and uses open standards such as HTML, XML, SPARQL and RESTful services technologies. It has been tested in a real environment using the e-Gotham European project infrastructure (Sustainable-Smart Grid Open System for the Aggregated Control, Monitoring and Management of Energy), which is participated by 17 partners from 5 countries: Spain, Italy, Estonia, Finland and Norway. This report details the study on the State of the art and the technologies used in the development of the project, implementation, design and architecture of the application, as well as the tests performed and the results obtained.

Evaluaci��n de la tecnolog��a CAES como sistema de almacenamiento de energ��a e��lica. Caso de estudio en Espa��a

Se presenta a continuaci��n un modelo de una planta del almacenamiento de energ��a mediante aire comprimido siguiendo un proceso adiab��tico. En esta planta la energ��a e��lica sobrante se usa para comprimir aire mediante un tren de compresi��n de 25 MW, el aire comprimido ser�� despu��s almacenado en una caverna de sal a 770 metros de profundidad. La compresi��n se llevar�� a cabo por la noche, durante 6 horas, debido a los bajos precios de electricidad. Cuando los precios de la electricidad suben durante el d��a, el aire comprimido es extra��do de la caverna de sal y es utilizado para producir energ��a en un tren de expansi��n de 70 MW durante 3 horas. La localizaci��n elegida para la planta es el norte de Burgos (Castilla y Le��n, Espa��a), debido a la coincidencia de la existencia de muchos parques e��licos y una formaci��n con las propiedades necesarias para el almacenamiento. El aspecto m��s importante de este proyecto es la utilizaci��n de un almacenamiento t��rmico que permitir�� aprovechar el calor de la compresi��n para calentar el aire a la entrada de la expansi��n, eliminando combustibles f��siles del sistema. Por consiguiente, este proyecto es una atractiva soluci��n en un posible futuro con emisiones de carbono restringidas, cuando la integraci��n de energ��a renovable en la red el��ctrica supone un reto importante. ABSTRACT: A model of an adiabatic compressed air energy storage plant is presented. In this plant surplus wind energy is used to compress air by means of a 25 MW compression train, the compressed air will be later stored in a salt cavern at 770 meters depth. Compression is carried out at night time, during 6 hours, because power prices are lower. When power prices go up during the day, the compressed air is withdrawn from the salt cavern and is used to produce energy in an expansion train of 70 MW during 3 hours. The chosen location for the plant is in the north of Burgos (Castilla y Le��n, Spain), due to both the existence of several wind farms and a suitable storage facility with good properties at the same place. The relevance of this project is that it is provided with a thermal storage, which allows using the generated heat in the compression for re-heating the air before the expansion, eliminating fossil fuels from the system. Hence, this system is an attractive load balancing solution in a possibly carbon-constrained future, where the integration of renewable energy sources into the electric grid is a major challenge.

Nueva tecnolog��a para la separaci��n de gases atmosf��ricos y captura de di��xido de carbono por aplicaci��n de campos electromagn��ticos y fotoionizaci��n

Son numerosos los expertos que predicen que hasta pasado 2050 no se utilizar��n masivamente las energ��as de origen renovable, y que por tanto se mantendr�� la emisi��n de di��xido de carbono de forma incontrolada. Entre tanto, y previendo que este tipo de uso se mantenga hasta un horizonte temporal a��n m��s lejano, la captura, concentraci��n y secuestro o reutilizaci��n de di��xido de carbono es y ser�� una de las principales soluciones a implantar para paliar el problema medioambiental causado. Sin embargo, las tecnolog��as existentes y en desarrollo de captura y concentraci��n de este tipo de gas, presentan dos limitaciones: las grandes cantidades de energ��a que consumen y los grandes vol��menes de sustancias potencialmente da��inas para el medioambiente que producen durante su funcionamiento. Ambas razones hacen que no sean atractivas para su implantaci��n y uso de forma extensiva. La soluci��n planteada en la presente tesis doctoral se caracteriza por la ausencia de residuos producidos en la operaci��n de captura y concentraci��n del di��xido de carbono, por no utilizar substancias qu��micas y f��sicas habituales en las t��cnicas actuales, por disminuir los consumos energ��ticos al carecer de sistemas m��viles y por evitar la regeneraci��n qu��mica y f��sica de los materiales utilizados en la actualidad. As�� mismo, plantea grandes retos a futuras innovaciones sobre la idea propuesta que busquen fundamentalmente la disminuci��n de la energ��a utilizada durante su funcionamiento y la optimizaci��n de sus componentes principales. Para conseguir el objetivo antes citado, la presente tesis doctoral, una vez establecido el planteamiento del problema al que se busca soluci��n (cap��tulo 1), del estudio de las t��cnicas de separaci��n de gases atmosf��ricos utilizadas en la actualidad, as�� como del de los sistemas fundamentales de las instalaciones de captura y concentraci��n del di��xido de carbono (cap��tulo 2) y tras una definici��n del marco conceptual y te��rico (cap��tulo 3), aborda el dise��o de un prototipo de ionizaci��n fot��nica de los gases atmosf��ricos para su posterior separaci��n electrost��tica, a partir del estudio, adaptaci��n y mejora del funcionamiento de los sistemas de espectrometr��a de masas. Se dise��ar��n y desarrollar��n los sistemas b��sicos de fotoionizaci��n, mediante el uso de fuentes de fotones coherentes, y los de separaci��n electrost��tica (cap��tulo 4), en que se basa el funcionamiento de este sistema de separaci��n de gases atmosf��ricos y de captura y concentraci��n de di��xido de carbono para construir un prototipo a nivel laboratorio. Posteriormente, en el cap��tulo 5, ser��n probados utilizando una matriz experimental que cubra los rangos de funcionamiento previstos y aporte suficientes datos experimentales para corregir y desarrollar el marco te��rico real, y con los que se pueda establecer y corregir un modelo f��sico��� matem��tico de simulaci��n (cap��tulo 6) aplicable a la unidad en su conjunto. Finalmente, debido a la utilizaci��n de unidades de ionizaci��n fot��nica, sistemas l��seres intensos y sistemas el��ctricos de gran potencia, es preciso analizar el riesgo biol��gico a las personas y al medioambiente debido al impacto de la radiaci��n electromagn��tica producida (cap��tulo 7), minimizando su impacto y cumpliendo con la legislaci��n vigente. En el cap��tulo 8 se plantear�� un dise��o escalable a tama��o piloto de la nueva tecnolog��a propuesta y sus principales modos de funcionamiento, as�� como un an��lisis de viabilidad econ��mica. Como consecuencia de la tesis doctoral propuesta y del desarrollo de la unidad de separaci��n atmosf��rica y de captura y concentraci��n de di��xido de carbono, surgen diversas posibilidades de estudio que pueden ser objeto de nuevas tesis doctorales y de futuros desarrollos de ingenier��a. El cap��tulo 9 tratar�� de incidir en estos aspectos indicando l��neas de investigaci��n para futuras tesis y desarrollos industriales. ABSTRACT A large number of experts predict that until at least 2050 renewable energy sources will not be massively used, and for that reason, current Primary Energy sources based on extensive use of fossil fuel will be used maintaining out of control emissions, Carbon Dioxide above all. Meanwhile, under this scenario and considering its extension until at least 2050, Carbon Capture, Concentration, Storage and/or Reuse is and will be one of the main solutions to minimise Greenhouse Gasses environmental effect. But, current Carbon Capture and Storage technology state of development has two main problems: it is a too large energy consuming technology and during normal use it produces a large volume of environmentally dangerous substances. Both reasons are limiting its development and its extensive use. This Ph Degree Thesis document proposes a solution to get the expected effect using a new atmospheric gasses separation system with the following characteristics: absence of wastes produced, it needs no chemical and/or physical substances during its operation, it reduces to minimum the internal energy consumptions due to absence of mobile equipment and it does not need any chemical and/or physical regeneration of substances. This system is beyond the State of the Art of current technology development. Additionally, the proposed solution raises huge challenges for future innovations of the proposed idea finding radical reduction of internal energy consumption during functioning, as well as regarding optimisation of main components, systems and modes of operation. To achieve this target, once established the main problem, main challenge and potential solving solutions (Chapter 1), it is established an initial starting point fixing the Atmospheric Gasses Separation and Carbon Capture and Storage developments (Chapter 2), as well as it will be defined the theoretical and basic model, including existing and potential new governing laws and mathematical formulas to control its system functioning (Chapter 3), this document will deal with the design of an installation of an operating system based on photonic ionization of atmospheric gasses to be separated in a later separation system based on the application of electrostatic fields. It will be developed a basic atmospheric gasses ionization prototype based on intense radioactive sources capable to ionize gasses by coherent photonic radiation, and a basic design of electrostatic separation system (Chapter 4). Both basic designs are the core of the proposed technology that separates Atmospheric Gasses and captures and concentrates Carbon Dioxide. Chapter 5 will includes experimental results obtained from an experimental testing matrix covering expected prototype functioning regimes. With the obtained experimental data, theoretical model will be corrected and improved to act as the real physical and mathematical model capable to simulate real system function (Chapter 6). Finally, it is necessary to assess potential biological risk to public and environment due to the proposed use of units of intense energy photonic ionization, by laser beams or by non���coherent sources and large electromagnetic systems with high energy consumption. It is necessary to know the impact in terms of and electromagnetic radiation taking into account National Legislation (Chapter 7). On Chapter 8, an up scaled pilot plant will be established covering main functioning modes and an economic feasibility assessment. As a consequence of this PhD Thesis, a new field of potential researches and new PhD Thesis are opened, as well as future engineering and industrial developments (Chapter 9).

State of the Art and Future Trends in Grid Codes Applicable to Isolated Electrical Systems

Isolated electrical systems lack electrical interconnection to other networks and are usually placed in geographically isolated areas���mainly islands or locations in developing countries. Until recently, only diesel generators were able to assure a safe and reliable supply in exchange for very high costs for fuel transportation and system operation. Transmission system operators (TSOs) are increasingly seeking to replace traditional energy models based on large groups of conventional generation units with mixed solutions where diesel groups are held as backup generation and important advantages are provided by renewable energy sources. The grid codes determine the technical requirements to be fulfilled by the generators connected in any electrical network, but regulations applied to isolated grids are more demanding. In technical literature it is rather easy to find and compare grid codes for interconnected electrical systems. However, the existing literature is incomplete and sparse regarding isolated grids. This paper aims to review the current state of isolated systems and grid codes applicable to them, specifying points of comparison and defining the guidelines to be followed by the upcoming regulations.

State of the Art and Future Trends in Grid Codes Applicable to Isolated Electrical Systems

Electrical power systems are changing their traditional structure, which was based on a little number of large generating power plants placed at great distances from loads by new models that tend to split the big production nodes in many smaller ones. The set of small groups which are located close to consumers and provide safe and quality energy is called distributed generation (DG). The proximity of the sources to the loads reduces losses associated with transportation and increases overall system efficiency. DG also favors the inclusion of renewable energy sources in isolated electrical systems or remote microgrids, because they can be installed where the natural resource is located. In both cases, as weak grids unable to get help from other nearby networks, it is essential to ensure appropriate behavior of DG sources to guarantee power system safety and stability. The grid codes sets out the technical requirements to be fulfilled for the sources connected in these electrical networks. In technical literature it is rather easy to find and compare grid codes for interconnected electrical systems. However, the existing literature is incomplete and sparse regarding isolated electrical systems and this happens due to the difficulties inherent in the pursuit of codes. Some countries have developed their own legislation only for their island territory (as Spain or France), others apply the same set of rules as in mainland, another group of island countries have elaborated a complete grid code for all generating sources and some others lack specific regulation. This paper aims to make a complete review of the state of the art in grid codes applicable to isolated systems, setting the comparison between them and defining the guidelines predictably followed by the upcoming regulations in these particular systems.

A multi-level analysis of innovation diffusion: The case of solar photovoltaic systems in Germany and the disillusion of grid parity

��Suministrar��n las fuentes de energ��a renovables toda la energ��a que el mundo necesita alg��n d��a? Algunos argumentan que s��, mientras que otros dicen que no. Sin embargo, en algunas regiones del mundo, la producci��n de electricidad a trav��s de fuentes de energ��a renovables ya est�� en una etapa prometedora de desarrollo en la que su costo de generaci��n de electricidad compite con fuentes de electricidad convencionales, como por ejemplo la paridad de red. Este logro ha sido respaldado por el aumento de la eficiencia de la tecnolog��a, la reducci��n de los costos de producci��n y, sobre todo, los a��os de intervenciones pol��ticas de apoyo financiero. La difusi��n de los sistemas solares fotovoltaicos (PV) en Alemania es un ejemplo relevante. Alemania no s��lo es el pa��s l��der en t��rminos de capacidad instalada de sistemas fotovoltaicos (PV) en todo el mundo, sino tambi��n uno de los pa��ses pioneros donde la paridad de red se ha logrado recientemente. No obstante, podr��a haber una nube en el horizonte. La tasa de difusi��n ha comenzado a declinar en muchas regiones. Adem��s, las empresas solares locales ��� que se sabe son importantes impulsores de la difusi��n ��� han comenzado a enfrentar dificultades para manejar sus negocios. Estos acontecimientos plantean algunas preguntas importantes: ��Es ��sta una disminuci��n temporal en la difusi��n? ��Los adoptantes continuar��n instalando sistemas fotovoltaicos? ��Qu�� pasa con los modelos de negocio de las empresas solares locales? Con base en el caso de los sistemas fotovoltaicos en Alemania a trav��s de un an��lisis multinivel y dos revisiones literarias complementarias, esta tesis doctoral extiende el debate proporcionando riqueza m��ltiple de datos emp��ricos en un conocimiento de contexto limitado. El primer an��lisis se basa en la perspectiva del adoptante, que explora el nivel "micro" y el proceso social que subyace a la adopci��n de los sistemas fotovoltaicos. El segundo an��lisis es una perspectiva a nivel de empresa, que explora los modelos de negocio de las empresas y sus roles impulsores en la difusi��n de los sistemas fotovoltaicos. El tercero an��lisis es una perspectiva regional, la cual explora el nivel "meso", el proceso social que subyace a la adopci��n de sistemas fotovoltaicos y sus t��cnicas de modelado. Los resultados incluyen implicaciones tanto para acad��micos como pol��ticos, no s��lo sobre las innovaciones en energ��a renovable relativas a la paridad de red, sino tambi��n, de manera inductiva, sobre las innovaciones ambientales impulsadas por las pol��ticas que logren la competitividad de costes. ABSTRACT Will renewable energy sources supply all of the world energy needs one day? Some argue yes, while others say no. However, in some regions of the world, the electricity production through renewable energy sources is already at a promising stage of development at which their electricity generation costs compete with conventional electricity sources���, i.e., grid parity. This achievement has been underpinned by the increase of technology efficiency, reduction of production costs and, above all, years of policy interventions of providing financial support. The diffusion of solar photovoltaic (PV) systems in Germany is an important frontrunner case in point. Germany is not only the top country in terms of installed PV systems��� capacity worldwide but also one of the pioneer countries where the grid parity has recently been achieved. However, there might be a cloud on the horizon. The diffusion rate has started to decline in many regions. In addition, local solar firms ��� which are known to be important drivers of diffusion ��� have started to face difficulties to run their businesses. These developments raise some important questions: Is this a temporary decline on diffusion? Will adopters continue to install PV systems? What about the business models of the local solar firms? Based on the case of PV systems in Germany through a multi-level analysis and two complementary literature reviews, this PhD Dissertation extends the debate by providing multiple wealth of empirical details in a context-limited knowledge. The first analysis is based on the adopter perspective, which explores the ���micro��� level and the social process underlying the adoption of PV systems. The second one is a firm-level perspective, which explores the business models of firms and their driving roles in diffusion of PV systems. The third one is a regional perspective, which explores the ���meso��� level, i.e., the social process underlying the adoption of PV systems and its modeling techniques. The results include implications for both scholars and policymakers, not only about renewable energy innovations at grid parity, but also in an inductive manner, about policy-driven environmental innovations that achieve the cost competiveness.

Desarrollo de un Procedimiento Basado en Algoritmos de Optimizaci��n para el Dimensionado de Absorbedores Puntuales Aplicados a la Conversi��n de Energ��a Undimotriz

La energ��a transportada por el oleaje a trav��s de los oc��anos (energ��a undimotriz) se enmarca dentro de las denominadas energ��as oce��nicas. Su aprovechamiento para generar energ��a el��ctrica (o ser aprovechada de alguna otra forma) es una idea reflejada ya hace m��s de dos siglos en una patente (1799). Desde entonces, y con especial intensidad desde los a��os 70, ha venido despertando el inter��s de instituciones ligadas al I+D+i y empresas del sector energ��tico y tecnol��gico, debido principalmente a la magnitud del recurso disponible. Actualmente se puede considerar al sector en un estado precomercial, con un amplio rango de dispositivos y tecnolog��as en diferente grado de desarrollo en los que ninguno destaca sobre los otros (ni ha demostrado su viabilidad econ��mica), y sin que se aprecie una tendencia a converger un ��nico dispositivo (o un n��mero reducido de ellos). El recurso energ��tico que se est�� tratando de aprovechar, pese a compartir la caracter��stica de no-controlabilidad con otras fuentes de energ��a renovable como la e��lica o la solar, presenta una variabilidad adicional. De esta manera, diferentes localizaciones, pese a poder presentar recursos de contenido energ��tico similar, presentan oleajes de caracter��sticas muy diferentes en t��rminos de alturas y periodos de oleaje, y en la dispersi��n estad��stica de estos valores. Esta variabilidad en el oleaje hace que cobre especial relevancia la adecuaci��n de los dispositivos de aprovechamiento de energ��a undimotriz (WEC: Wave Energy Converter) a su localizaci��n, de cara a mejorar su viabilidad econ��mica. Parece razonable suponer que, en un futuro, el proceso de dise��o de un parque de generaci��n undimotriz implique un redise��o (en base a una tecnolog��a conocida) para cada proyecto de implantaci��n en una nueva localizaci��n. El objetivo de esta tesis es plantear un procedimiento de dimensionado de una tecnolog��a de aprovechamiento de la energ��a undimotriz concreta: los absorbedores puntuales. Dicha metodolog��a de dise��o se plantea como un problema de optimizaci��n matem��tico, el cual se resuelve utilizando un algoritmo de optimizaci��n bioinspirado: evoluci��n diferencial. Este planteamiento permite automatizar la fase previa de dimensionado implementando la metodolog��a en un c��digo de programaci��n. El proceso de dise��o de un WEC es un problema de inger��a complejo, por lo que no considera factible el planteamiento de un dise��o completo mediante un ��nico procedimiento de optimizaci��n matem��tico. En vez de eso, se platea el proceso de dise��o en diferentes etapas, de manera que la metodolog��a desarrollada en esta tesis se utilice para obtener las dimensiones b��sicas de una soluci��n de referencia de WEC, la cual ser�� utilizada como punto de partida para continuar con las etapas posteriores del proceso de dise��o. La metodolog��a de dimensionado previo presentada en esta tesis parte de unas condiciones de contorno de dise��o definidas previamente, tales como: localizaci��n, caracter��sticas del sistema de generaci��n de energ��a el��ctrica (PTO: Power Take-Off), estrategia de extracci��n de energ��a el��ctrica y concepto concreto de WEC). Utilizando un algoritmo de evoluci��n diferencial multi-objetivo se obtiene un conjunto de soluciones factibles (de acuerdo con una ciertas restricciones t��cnicas y dimensionales) y ��ptimas (de acuerdo con una serie de funciones objetivo de pseudo-coste y pseudo-beneficio). Dicho conjunto de soluciones o dimensiones de WEC es utilizado como caso de referencia en las posteriores etapas de dise��o. En el documento de la tesis se presentan dos versiones de dicha metodolog��a con dos modelos diferentes de evaluaci��n de las soluciones candidatas. Por un lado, se presenta un modelo en el dominio de la frecuencia que presenta importantes simplificaciones en cuanto al tratamiento del recurso del oleaje. Este procedimiento presenta una menor carga computacional pero una mayor incertidumbre en los resultados, la cual puede traducirse en trabajo adicional en las etapas posteriores del proceso de dise��o. Sin embargo, el uso de esta metodolog��a resulta conveniente para realizar an��lisis param��tricos previos de las condiciones de contorno, tales como la localizaci��n seleccionada. Por otro lado, la segunda metodolog��a propuesta utiliza modelos en el domino estoc��stico, lo que aumenta la carga computacional, pero permite obtener resultados con menos incertidumbre e informaci��n estad��stica muy ��til para el proceso de dise��o. Por este motivo, esta metodolog��a es m��s adecuada para su uso en un proceso de dimensionado completo de un WEC. La metodolog��a desarrollada durante la tesis ha sido utilizada en un proyecto industrial de evaluaci��n energ��tica preliminar de una planta de energ��a undimotriz. En dicho proceso de evaluaci��n, el m��todo de dimensionado previo fue utilizado en una primera etapa, de cara a obtener un conjunto de soluciones factibles de acuerdo con una serie de restricciones t��cnicas b��sicas. La selecci��n y refinamiento de la geometr��a de la soluci��n geom��trica de WEC propuesta fue realizada a posteriori (por otros participantes del proyecto) utilizando un modelo detallado en el dominio del tiempo y un modelo de evaluaci��n econ��mica del dispositivo. El uso de esta metodolog��a puede ayudar a reducir las iteraciones manuales y a mejorar los resultados obtenidos en estas ��ltimas etapas del proyecto. ABSTRACT The energy transported by ocean waves (wave energy) is framed within the so-called oceanic energies. Its use to generate electric energy (or desalinate ocean water, etc.) is an idea expressed first time in a patent two centuries ago (1799). Ever since, but specially since the 1970���s, this energy has become interesting for R&D institutions and companies related with the technological and energetic sectors mainly because of the magnitude of available energy. Nowadays the development of this technology can be considered to be in a pre-commercial stage, with a wide range of devices and technologies developed to different degrees but with none standing out nor economically viable. Nor do these technologies seem ready to converge to a single device (or a reduce number of devices). The energy resource to be exploited shares its non-controllability with other renewable energy sources such as wind and solar. However, wave energy presents an additional short-term variability due to its oscillatory nature. Thus, different locations may show waves with similar energy content but different characteristics such as wave height or wave period. This variability in ocean waves makes it very important that the devices for harnessing wave energy (WEC: Wave Energy Converter) fit closely to the characteristics of their location in order to improve their economic viability. It seems reasonable to assume that, in the future, the process of designing a wave power plant will involve a re-design (based on a well-known technology) for each implementation project in any new location. The objective of this PhD thesis is to propose a dimensioning method for a specific wave-energy-harnessing technology: point absorbers. This design methodology is presented as a mathematical optimization problem solved by using an optimization bio-inspired algorithm: differential evolution. This approach allows automating the preliminary dimensioning stage by implementing the methodology in programmed code. The design process of a WEC is a complex engineering problem, so the complete design is not feasible using a single mathematical optimization procedure. Instead, the design process is proposed in different stages, so the methodology developed in this thesis is used for the basic dimensions of a reference solution of the WEC, which would be used as a starting point for the later stages of the design process. The preliminary dimensioning methodology presented in this thesis starts from some previously defined boundary conditions such as: location, power take-off (PTO) characteristic, strategy of energy extraction and specific WEC technology. Using a differential multi-objective evolutionary algorithm produces a set of feasible solutions (according to certain technical and dimensional constraints) and optimal solutions (according to a set of pseudo-cost and pseudo-benefit objective functions). This set of solutions or WEC dimensions are used as a reference case in subsequent stages of design. In the document of this thesis, two versions of this methodology with two different models of evaluation of candidate solutions are presented. On the one hand, a model in the frequency domain that has significant simplifications in the treatment of the wave resource is presented. This method implies a lower computational load but increased uncertainty in the results, which may lead to additional work in the later stages of the design process. However, use of this methodology is useful in order to perform previous parametric analysis of boundary conditions such as the selected location. On the other hand, the second method uses stochastic models, increasing the computational load, but providing results with smaller uncertainty and very useful statistical information for the design process. Therefore, this method is more suitable to be used in a detail design process for full dimensioning of the WEC. The methodology developed throughout the thesis has been used in an industrial project for preliminary energetic assessment of a wave energy power plant. In this assessment process, the method of previous dimensioning was used in the first stage, in order to obtain a set of feasible solutions according to a set of basic technical constraints. The geometry of the WEC was refined and selected subsequently (by other project participants) using a detailed model in the time domain and a model of economic evaluation of the device. Using this methodology can help to reduce the number of design iterations and to improve the results obtained in the last stages of the project.

Urban wind energy: empirical optimization of high-rise building roof shape for the wind energy exploitation

El programa Europeo HORIZON2020 en Futuras Ciudades Inteligentes establece como objetivo que el 20% de la energ��a el��ctrica sea generada a partir de fuentes renovables. Este objetivo implica la necesidad de potenciar la generaci��n de energ��a e��lica en todos los ��mbitos. La energ��a e��lica reduce dr��sticamente las emisiones de gases de efecto invernadero y evita los riesgos geo-pol��ticos asociados al suministro e infraestructuras energ��ticas, as�� como la dependencia energ��tica de otras regiones. Adem��s, la generaci��n de energ��a distribuida (generaci��n en el punto de consumo) presenta significativas ventajas en t��rminos de elevada eficiencia energ��tica y estimulaci��n de la econom��a. El sector de la edificaci��n representa el 40% del consumo energ��tico total de la Uni��n Europea. La reducci��n del consumo energ��tico en este ��rea es, por tanto, una prioridad de acuerdo con los objetivos "20-20-20" en eficiencia energ��tica. La Directiva 2010/31/EU del Parlamento Europeo y del Consejo de 19 de mayo de 2010 sobre el comportamiento energ��tico de edificaciones contempla la instalaci��n de sistemas de suministro energ��tico a partir de fuentes renovables en las edificaciones de nuevo dise��o. Actualmente existe una escasez de conocimiento cient��fico y tecnol��gico acerca de la geometr��a ��ptima de las edificaciones para la explotaci��n de la energ��a e��lica en entornos urbanos. El campo tecnol��gico de estudio de la presente Tesis Doctoral es la generaci��n de energ��a e��lica en entornos urbanos. Espec��ficamente, la optimization de la geometr��a de las cubiertas de edificaciones desde el punto de vista de la explotaci��n del recurso energ��tico e��lico. Debido a que el flujo del viento alrededor de las edificaciones es exhaustivamente investigado en esta Tesis empleando herramientas de simulaci��n num��rica, la mec��nica de fluidos computacional (CFD en ingl��s) y la aerodin��mica de edificaciones son los campos cient��ficos de estudio. El objetivo central de esta Tesis Doctoral es obtener una geometr��a de altas prestaciones (u ��ptima) para la explotaci��n de la energ��a e��lica en cubiertas de edificaciones de gran altura. Este objetivo es alcanzado mediante un an��lisis exhaustivo de la influencia de la forma de la cubierta del edificio en el flujo del viento desde el punto de vista de la explotaci��n energ��tica del recurso e��lico empleando herramientas de simulaci��n num��rica (CFD). Adicionalmente, la geometr��a de la edificaci��n convencional (edificio prism��tico) es estudiada, y el posicionamiento adecuado para los diferentes tipos de aerogeneradores es propuesto. La compatibilidad entre el aprovechamiento de las energ��as solar fotovoltaica y e��lica tambi��n es analizado en este tipo de edificaciones. La investigaci��n prosigue con la optimizaci��n de la geometr��a de la cubierta. La metodolog��a con la que se obtiene la geometr��a ��ptima consta de las siguientes etapas: - Verificaci��n de los resultados de las geometr��as previamente estudiadas en la literatura. Las geometr��as b��sicas que se someten a examen son: cubierta plana, a dos aguas, inclinada, abovedada y esf��rica. - An��lisis de la influencia de la forma de las aristas de la cubierta sobre el flujo del viento. Esta tarea se lleva a cabo mediante la comparaci��n de los resultados obtenidos para la arista convencional (esquina sencilla) con un parapeto, un voladizo y una esquina curva. - An��lisis del acoplamiento entre la cubierta y los cerramientos verticales (paredes) mediante la comparaci��n entre diferentes variaciones de una cubierta esf��rica en una edificaci��n de gran altura: cubierta esf��rica estudiada en la literatura, cubierta esf��rica integrada geom��tricamente con las paredes (planta cuadrada en el suelo) y una cubierta esf��rica acoplada a una pared cilindrica. El comportamiento del flujo sobre la cubierta es estudiado tambi��n considerando la posibilidad de la variaci��n en la direcci��n del viento incidente. - An��lisis del efecto de las proporciones geom��tricas del edificio sobre el flujo en la cubierta. - An��lisis del efecto de la presencia de edificaciones circundantes sobre el flujo del viento en la cubierta del edificio objetivo. Las contribuciones de la presente Tesis Doctoral pueden resumirse en: - Se demuestra que los modelos de turbulencia RANS obtienen mejores resultados para la simulaci��n del viento alrededor de edificaciones empleando los coeficientes propuestos por Crespo y los propuestos por Bechmann y S��rensen que empleando los coeficientes est��ndar. - Se demuestra que la estimaci��n de la energ��a cin��tica turbulenta del flujo empleando modelos de turbulencia RANS puede ser validada manteniendo el enfoque en la cubierta de la edificaci��n. - Se presenta una nueva modificaci��n del modelo de turbulencia Durbin k ��� e que reproduce mejor la distancia de recirculaci��n del flujo de acuerdo con los resultados experimentales. - Se demuestra una relaci��n lineal entre la distancia de recirculaci��n en una cubierta plana y el factor constante involucrado en el c��lculo de la escala de tiempo de la velocidad turbulenta. Este resultado puede ser empleado por la comunidad cient��fica para la mejora del modelado de la turbulencia en diversas herramientas computacionales (OpenFOAM, Fluent, CFX, etc.). - La compatibilidad entre las energ��as solar fotovoltaica y e��lica en cubiertas de edificaciones es analizada. Se demuestra que la presencia de los m��dulos solares provoca un descenso en la intensidad de turbulencia. - Se demuestran conflictos en el cambio de escala entre simulaciones de edificaciones a escala real y simulaciones de modelos a escala reducida (t��nel de viento). Se demuestra que para respetar las limitaciones de similitud (n��mero de Reynolds) son necesarias mediciones en edificaciones a escala real o experimentos en t��neles de viento empleando agua como fluido, especialmente cuando se trata con geometr��as complejas, como es el caso de los m��dulos solares. - Se determina el posicionamiento m��s adecuado para los diferentes tipos de aerogeneradores tomando en consideraci��n la velocidad e intensidad de turbulencia del flujo. El posicionamiento de aerogeneradores es investigado en las geometr��as de cubierta m��s habituales (plana, a dos aguas, inclinada, abovedada y esf��rica). - Las formas de aristas m��s habituales (esquina, parapeto, voladizo y curva) son analizadas, as�� como su efecto sobre el flujo del viento en la cubierta de un edificio de gran altura desde el punto de vista del aprovechamiento e��lico. - Se propone una geometr��a ��ptima (o de altas prestaciones) para el aprovechamiento de la energ��a e��lica urbana. Esta optimizaci��n incluye: verificaci��n de las geometr��as estudiadas en el estado del arte, an��lisis de la influencia de las aristas de la cubierta en el flujo del viento, estudio del acoplamiento entre la cubierta y las paredes, an��lisis de sensibilidad del grosor de la cubierta, exploraci��n de la influencia de las proporciones geom��tricas de la cubierta y el edificio, e investigaci��n del efecto de las edificaciones circundantes (considerando diferentes alturas de los alrededores) sobre el flujo del viento en la cubierta del edificio objetivo. Las investigaciones comprenden el an��lisis de la velocidad, la energ��a cin��tica turbulenta y la intensidad de turbulencia en todos los casos. ABSTRACT The HORIZON2020 European program in Future Smart Cities aims to have 20% of electricity produced by renewable sources. This goal implies the necessity to enhance the wind energy generation, both with large and small wind turbines. Wind energy drastically reduces carbon emissions and avoids geo-political risks associated with supply and infrastructure constraints, as well as energy dependence from other regions. Additionally, distributed energy generation (generation at the consumption site) offers significant benefits in terms of high energy efficiency and stimulation of the economy. The buildings sector represents 40% of the European Union total energy consumption. Reducing energy consumption in this area is therefore a priority under the "20-20-20" objectives on energy efficiency. The Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings aims to consider the installation of renewable energy supply systems in new designed buildings. Nowadays, there is a lack of knowledge about the optimum building shape for urban wind energy exploitation. The technological field of study of the present Thesis is the wind energy generation in urban environments. Specifically, the improvement of the building-roof shape with a focus on the wind energy resource exploitation. Since the wind flow around buildings is exhaustively investigated in this Thesis using numerical simulation tools, both computational fluid dynamics (CFD) and building aerodynamics are the scientific fields of study. The main objective of this Thesis is to obtain an improved (or optimum) shape of a high-rise building for the wind energy exploitation on the roof. To achieve this objective, an analysis of the influence of the building shape on the behaviour of the wind flow on the roof from the point of view of the wind energy exploitation is carried out using numerical simulation tools (CFD). Additionally, the conventional building shape (prismatic) is analysed, and the adequate positions for different kinds of wind turbines are proposed. The compatibility of both photovoltaic-solar and wind energies is also analysed for this kind of buildings. The investigation continues with the buildingroof optimization. The methodology for obtaining the optimum high-rise building roof shape involves the following stages: - Verification of the results of previous building-roof shapes studied in the literature. The basic shapes that are compared are: flat, pitched, shed, vaulted and spheric. - Analysis of the influence of the roof-edge shape on the wind flow. This task is carried out by comparing the results obtained for the conventional edge shape (simple corner) with a railing, a cantilever and a curved edge. - Analysis of the roof-wall coupling by testing different variations of a spherical roof on a high-rise building: spherical roof studied in the litera ture, spherical roof geometrically integrated with the walls (squared-plant) and spherical roof with a cylindrical wall. The flow behaviour on the roof according to the variation of the incident wind direction is commented. - Analysis of the effect of the building aspect ratio on the flow. - Analysis of the surrounding buildings effect on the wind flow on the target building roof. The contributions of the present Thesis can be summarized as follows: - It is demonstrated that RANS turbulence models obtain better results for the wind flow around buildings using the coefficients proposed by Crespo and those proposed by Bechmann and S0rensen than by using the standard ones. - It is demonstrated that RANS turbulence models can be validated for turbulent kinetic energy focusing on building roofs. - A new modification of the Durbin k ��� e turbulence model is proposed in order to obtain a better agreement of the recirculation distance between CFD simulations and experimental results. - A linear relationship between the recirculation distance on a flat roof and the constant factor involved in the calculation of the turbulence velocity time scale is demonstrated. This discovery can be used by the research community in order to improve the turbulence modeling in different solvers (OpenFOAM, Fluent, CFX, etc.). - The compatibility of both photovoltaic-solar and wind energies on building roofs is demonstrated. A decrease of turbulence intensity due to the presence of the solar panels is demonstrated. - Scaling issues are demonstrated between full-scale buildings and windtunnel reduced-scale models. The necessity of respecting the similitude constraints is demonstrated. Either full-scale measurements or wind-tunnel experiments using water as a medium are needed in order to accurately reproduce the wind flow around buildings, specially when dealing with complex shapes (as solar panels, etc.). - The most adequate position (most adequate roof region) for the different kinds of wind turbines is highlighted attending to both velocity and turbulence intensity. The wind turbine positioning was investigated for the most habitual kind of building-roof shapes (flat, pitched, shed, vaulted and spherical). - The most habitual roof-edge shapes (simple edge, railing, cantilever and curved) were investigated, and their effect on the wind flow on a highrise building roof were analysed from the point of view of the wind energy exploitation. - An optimum building-roof shape is proposed for the urban wind energy exploitation. Such optimization includes: state-of-the-art roof shapes test, analysis of the influence of the roof-edge shape on the wind flow, study of the roof-wall coupling, sensitivity analysis of the roof width, exploration of the aspect ratio of the building-roof shape and investigation of the effect of the neighbouring buildings (considering different surrounding heights) on the wind now on the target building roof. The investigations comprise analysis of velocity, turbulent kinetic energy and turbulence intensity for all the cases.