Determination of the hydrodynamic performance of marine propellers using fibre Bragg gratings

Downloading of the abstract is permitted for personal use only. A critical aspect in the design of marine propellers is their hydrodynamic performance which, when evaluated experimentally, requires a number of parameters to be monitored at the same time, i.e.The thrust and torque a propeller generates as well as the propeller shaft and vessel speed. In this investigation, three of those parameters are measured using Fibre Bragg Grating-based sensors, thus allowing for computationally derived performance values to be verified. For that purpose, open water tests were carried out where an instrumented propeller shaft was installed into a research vessel and measurements taken, evaluated and the results compared favorably with advanced computer-based simulations

Analysis and improvements for solar trackers movement: applied to backtracking

El Sol es considerado como una fuente de energía inagotable, por lo que su estudio y caracterización constituyen una de las principales líneas de investigación, con el objeto de evaluar su incidencia en instalaciones de captación solar. En instalaciones PV con seguidores solares, resulta de suma importancia el estudio de aquellas variables susceptibles de proporcionar la orientación óptima para conseguir la máxima eficiencia desde el punto de vista energético. La irradiancia global se considera un parámetro fundamental para la caracterización solar, por lo que sus componentes (directa, difusa y reflejada) deben ser evaluadas para su óptima utilización. La componente directa está estrechamente ligada con la geometría Sol-Tierra ya que sus rayos asociados provienen directamente de la ubicación del Sol. Por otro lado, la componente difusa está formada por los rayos que llegan desde todas las direcciones de la bóveda celeste exceptuando la dirección Tierra-Sol, mientras que la componente reflejada depende del coeficiente de reflexión de la superficie también denominado albedo. Modelos de irradiancia tales como el de Hay-Davies y el modelo de Pérez, permiten relacionar la función de irradiancia con el vector solar ( ) y el vector normal de los colectores ( ). De esta forma, mediante un proceso de optimización basado en multiplicadores de Lagrange sujeto a una serie de restricciones impuestas, se consigue conocer a priori la orientación óptima de los colectores. Esta caracterización del óptimo del vector normal al colector ( ) se consigue tanto en seguidores solares de 1 como de 2 ejes, lo que establece un punto de partida para realizar el estudio de la interferencia entre seguidores, y, por consiguiente, determinar la existencia de sombreamiento. El análisis de dicho sombreamiento se realiza mediante elementos vectoriales tanto en el plano (1 eje) como en el espacio (2 ejes), empleando un criterio dicotómico basado en el álgebra de Minkowski. La determinación de la existencia de sombreo permite paralelamente establecer una alternativa a la orientación inicial mediante una reorientación del seguidor (retroseguimiento), siempre lo más próxima al valor de irradiancia óptima. En este contexto, la presente tesis doctoral avanza en el estudio del comportamiento de seguidores solares. Los objetivos explicitados en cada artículo son: - Maximizar la captación de radiación solar en seguidores de 1 y 2 ejes. - Optimizar trayectorias de seguimiento y su interacción con las variables del terreno. - Monitorizar el sistema de seguimiento. - Evaluar todas las componentes de irradiancia global (directa, difusa y reflejada). - Estudiar los efectos negativos de sombreamiento entre colectores y actuaciones a seguir en caso de que se produzca dicho efecto. - Proponer técnicas de retroseguimiento. - Estudiar la influencia de la geometría de colectores PV en la captación radiativa.The sun is considered to be an inexhaustible source of energy, so its study and characterisation are two of the main lines of research, to evaluate with the aim of evaluating its impact on solar collection installations. In PV installations with solar trackers, it is extremely important to study those variables likely to provide the optimum orientation to achieve maximum efficiency from the energy point of view. Global irradiance is considered a fundamental parameter for solar characterisation, so its components (direct, diffuse and reflected) must be evaluated for its use. The direct component is closely linked to the Sun-Earth geometry as its associated rays come directly from the location of the Sun. On the other hand, the diffuse component is formed by the rays reaching from all directions of the celestial vault except the Earth-Sun direction, while the reflected component depends on the reflection coefficient of the surface, also called albedo. Irradiance models such as Hay-Davies and Perez, allow the irradiance function to be related to the solar vector ( ) and the normal vector of the collectors ( ). In this way, by means of an optimisation process based on Lagrange multipliers subject to a series of imposed restrictions, the optimal orientation of the collectors is known a priori. This characterisation of the optimum normal vector to the collector ( ) is achieved in both 1- axis and 2-axis solar trackers, which establishes a baseline for performing the study of interference between trackers, and, therefore, determining the existence of shading. The analysis of this shading is performed using vector elements both in the plane (1-axis) and in space (2-axis), using a dichotomous criterion based on Minkowski algebra. The determination of the existence of shading allows at the same time to establish an alternative to the initial orientation by means of a reorientation of the tracker (backtracking), but always as close as possible to the optimum irradiance value. In this context, this doctoral thesis advances in the study on the behaviour of solar trackers. The objectives expressed in each article are: - Maximising solar radiation collection in 1- and 2-axis trackers. - Optimising tracking trajectories and its interaction with terrain variables. - Monitoring the tracking system. - Evaluating all the global irradiance components (direct, diffuse and reflected). - Studying the negative effects of shading between collectors and actions to be adopted in the event of this effect occurring. -Proposing back-tracking techniques. - Studying the influence of the geometry of PV collectors on radiative capture

Study of the Dependence of Solar Radiation Regarding Design Variables in Photovoltaic Solar Installations with Optimal Dual-Axis Tracking

Solar tracking is an efficient strategy to increase the radiative capture of photovoltaic collectors. Within the multiple efforts made in recent decades to improve the production of these facilities, various works have studied solutions to optimize the number of rotation axes (single or dual rotation axes), the degree of collector coverage, the distances between trackers, the geometric arrangement of trackers or the minimization of shading between collectors. However, although in this type of installation it is common to find collectors with geometric shapes other than rectangles, no studies on the influence of the shape of the collectors on the radiative incidence are found in the literature. In this connection, the present work systematically addresses the study of incident solar radiation in photovoltaic installations with dual-axis trackers with collectors of different geometric shapes. By means of the exhaustive study, the conclusion is drawn that, for dual-axis photovoltaic installations with an optimal tracking strategy, the main variables that influence the annual radiative incidence are the spacing between collectors, the coverage ratio (GCR), and the collector surface, while the type of arrangement of collectors and the shape of these do not show predictive values

New Omnidirectional Sensor Based on Open-Source Software and Hardware for Tracking and Backtracking of Dual-Axis Solar Trackers in Photovoltaic Plants

In this work, an omnidirectional sensor that enables identification of the direction of the celestial sphere with maximum solar irradiance is presented. The sensor, based on instantaneous measurements, functions as a position server for dual-axis solar trackers in photovoltaic plants. The proposed device has been developed with free software and hardware, which makes it a pioneering solution because it is open and accessible as well as capable of being improved by the scientific community, thereby contributing to the rapid advancement of technology. In addition, the device includes an algorithm developed ex professo that makes it possible to predetermine the regions of the celestial sphere for which, according to the geometric characteristics of the PV plant, there would be shading between the panels. In this way, solar trackers do not have to locate the Sun’s position at all times according to astronomical models, while taking into account factors such as shadows or cloudiness that also affect levels of incident irradiance on solar collectors. Therefore, with this device, it is possible to provide photovoltaic plants with dual-axis solar tracking with a low-cost device that helps to optimise the trajectory of the trackers and, consequently, their radiative capture and energy production

Benchmarking Analysis of the Panorama of Grid-Connected PV Installations in Spain

Renewable energies play an important role as a solution to the challenge of satisfying the growing global energy demand without jeopardizing the achievements in the fight against climate change. Given this panorama, different countries, including Spain, have developed policies to promote renewable energies. One of the technologies that benefit from these policies is photovoltaics. In Spain, the number of grid-connected photovoltaic installations has increased significantly in recent years. It is interesting to analyze the panorama of these facilities and identify the trends in their design criteria. In this line, in this work, the projects of 70 grid-connected photovoltaic installations distributed across Spain were analyzed. For that purpose, benchmarking techniques were applied, facilitating the systematization of information, the intercomparison of plants and the identification of trends and efficient solutions. A set of characteristic indicators of each installation was defined, and a statistical analysis of them was developed. Likewise, a tool was developed that allows the designers of this type of photovoltaic plant to compare the design parameters chosen for their installations with those of the surrounding area. Therefore, this work provides knowledge about the current panorama of photovoltaic implementation applicable to its future advan

Morphometry of the Glomerular Tuft During Normal Postnatal Growth in Female Rats. Effects of Age, Location of Glomeruli and Methods of Obtaining and Processing the Renal Tissue

Total glomerular filtration rate depends upon the structural integrity, number and area of glomeruli. Counting  the number of glomeruli as well as measuring glomerular area or volume is nowadays widely employed  in human and experimental biology. Although functional and morphological differences between superficial and juxtamedullary glomeruli have  been described, this is not always taken into account in morphometric studies. The aim of this paper was to  study in female rats the area of juxtamedullary glomeruli and the area of superficial glomeruli as well as the  influence of the age of rats and the methods of obtaining and processing the renal tissue. The glomerular area was larger in kidneys collected in liquid nitrogen and smaller in those fixed in Bouin  (See Materials and Methods); 4% formaldehyde. These results were obtained in superficial and in juxtamedullary  glomeruli (F=29.60, p<0.0001).  Glomerular area increased with time in superficial as well as in juxtamedullary glomeruli (F=9.21,  p<0.0001). The area of the juxtamedullary glomeruli was significantly higher (F=329.29, p<0.0001) than that of superficial  glomeruli, independently of the different methods of obtaining and processing renal tissue, or the  age of the animals. The results indicate that glomerular area is greater in juxtamedullary glomeruli, increases with age, and  that different methods of obtaining and processing the renal tissue do have influence on glomerular size.

Analysis of the Influence of Terrain Orientation on the Design of PV Facilities with Single-Axis Trackers

This paper investigates how to optimally orient the photovoltaic solar trackers of an axis parallel to the terrain, applying the sky model of Hay–Davies. This problem has been widely studied. However, the number of studies that consider the orientation (inclination and azimuth of the terrain) is very limited. This paper provides an examination of incident solar irradiance that can be extended to terrain with variable orientation and in consideration of different azimuths of the axis of rotation. Furthermore, a case study of the south of Spain is provided, considering different inclination and orientation terrain values. The results obtained in this study indicate, as a novelty, that for lands that are not south facing, the rotation axis azimuth of solar trackers should be different from zero and adjusted to the same direction as the land azimuth in order to maximize energy production. Annual energy production is sensitive to changes in the rotation axis azimuths of solar trackers (an influence of around 3% of annual energy production)

Nivel de formación sobre sexualidad humana en estudiantes del primer ciclo en la Universidad Católica Santo Toribio de Mogrovejo, año 2010

La sexualidad humana es un concepto que abarca distintos ámbitos. Generalmente la sociedad tiende a relacionarlo con la parte reproductiva, sin embargo no solo atañe a lo sexual propiamente dicho, pues también comprende a la parte afectiva, de allí que se hable de una salud sexual y afectiva. El presente trabajo tiene como finalidad determinar el nivel de formación sobre sexualidad humana en estudiantes del primer ciclo en la Universidad Católica Santo Toribio de Mogrovejo, año 2010. Para la realización de la investigación se empleó un estudio descriptivo primario de tipo transversal, utilizándose el consentimiento informado para proceder a la encuesta elaborada por los autores en conjunto con un experto en el tema, siendo ésta revisada por dos sacerdotes y una psicóloga, y previamente empleada en prueba piloto. Ésta se aplicó en el muestreo obtenido estadísticamente de una población total de 1496 estudiantes 2010-I. Resultando los sujetos a investigar 424 estudiantes, considerados según estratos según facultad: ciencias empresariales, derecho, humanidades, ingeniería y medicina. Sin embargo la muestra de estudio se incrementó durante el proceso, haciendo un total de 439 estudiantes. Para el análisis de los datos se empleó tablas de frecuencias, diagramas de barras, diagrama de sectores y el programa Estadístico Excel. Se concluyó que de los 439 estudiantes del primer ciclo de USAT 2010-I entrevistados: el 19% presentó nivel alto de formación sobre sexualidad humana; el 62%, predominante, presentó un nivel medio, mientras que el restante, 18%, presentó nivel bajo