Evaluation of three solar and daylighting control systems based on Calumen II, Ecotect and Radiance simulation programs to obtain an energy efficient and healthy interior in the experimental building prototype SDE10

Evaluation of three solar and daylighting control systems based on Calumen II, Ecotect and Radiance simulation programs to obtain an energy efficient and healthy interior in the experimental building prototype SDE10

Comparisson of hydrogen applications for storage and energy vector

For the decades to come can be foreseen that electricity and water will keep be playing a key role in the countries development, both can be considered the most important energy vectors and its control can be crucial for governments, companies and leaders in general. Energy is essential for all human activities and its availability is critical to economic and social development. In particular, electricity, a form of energy, is required to produce goods, to provide medical assistance and basic civic services in education, to assure availability of clean water, to create conducive environment for prosperity and improvement, and to keep an acceptable quality of life. The way in which electricity is generated from different resources varies through the different countries. Nuclear energy controlled within reactors to steam production, gas, fuel-oil and coal fired in power stations, water, solar and wind energy among others are employed, sometimes not very efficiently, to produce electricity. The so call energy mix of an individual country is formed up by the contribution of each resource or form of energy to the electricity generation market of the so country. During the last decade the establishment of proper energy mixes for countries has gained much importance, and energy drivers should enforce long term plans and policies. Hints, reports and guides giving tracks on energy resources contribution are been developed by noticeable organisations like the IEA (International Energy Agency) or the IAEA (International Atomic Energy Agency) and the WEC (World Energy Council). This paper evaluates energy issues the market and countries are facing today regarding energy mix scheduling and panorama. This paper revises and seeks to improve methodology available that are applicable on energy mix plan definition. Key Factors are identified, established and assessed through this paper for the common implementation, the themes driving the future energy mix methodology proposal. Those have a clear influence and are closely related to future environmental policies. Key Factors take into consideration sustainability, energy security, social and economic growth, climate change, air quality and social stability. The strength of the Key Factors application on energy system planning to different countries is contingent on country resources, location, electricity demand and electricity generation industry, technology available, economic situation and prospects, energy policy and regulation

Frequency control support of a wind-solar isolated system by a hydropower plant with long tail-race tunnel

Pumped storage hydro plants (PSHP) can provide adequate energy storage and frequency regulation capacities in isolated power systems having significant renewable energy resources. Due to its high wind and solar potential, several plans have been developed for La Palma Island in the Canary archipelago, aimed at increasing the penetration of these energy sources. In this paper, the performance of the frequency control of La Palma power system is assessed, when the demand is supplied by the available wind and solar generation with the support of a PSHP which has been predesigned for this purpose. The frequency regulation is provided exclusively by the PSHP. Due to topographic and environmental constraints, this plant has a long tail-race tunnel without a surge tank. In this configuration, the effects of pressure waves cannot be neglected and, therefore, usual recommendations for PID governor tuning provide poor performance. A PI governor tuning criterion is proposed for the hydro plant and compared with other criteria according to several performance indices. Several scenarios considering solar and wind energy penetration have been simulated to check the plant response using the proposed criterion. This tuning of the PI governor maintains La Palma system frequency within grid code requirements.

On the charged particle drag acting on LAGEOS

A recent study by the authors points to Charged Particle Drag (CPD) as a contributor to revisit in the LAGEOS non-gravitational perturbations problem. Such perturbations must account for dynamical contributions in the order of pms−2 . The simulated effect takes into account: (i) spatial and temporal variations of the plasmatic parameters (temperature and concentration of the species), (ii) spacecraft potential variations caused by both the eclipse passages and variations in the parameters mentioned above, and (iii) solar and geomagnetic conditions. Furthermore, recent theoretical improvements concerning scattering drag overcome previous limitations allowing for a complete formulation of this effect. For each satellite the lifetime CPD instantaneous acceleration is computed. The plasmatic parameters have been obtained fromthe Sheffield Coupled Thermosphere-Ionosphere-Plasmasphere (SCTIP) semi-empirical model (up to the polar region), as well as alytical/empirical approximations based on spacecraft measurements for the auroral and polar regions. Results show that maximum amplitudes for LAGEOSI are larger than those for LAGEOS-II: −85 pms−2 and −70 pms−2 respectively. This is due to the almost (magnetically) polar orbit configuration of the first, producing larger combinations of plasmatic parameter values. High solar activity has a huge impact in the resulting LAGEOS accelerations: it yields a perfect modulation of the resulting acceleration with maximum amplitudes up to a factor of 10 when comparing low and high activity periods. On the other hand, the impact of the geomagnetic activity results into a reduction of the effect itself, probably due to a decrease in the hydrogen concentration for high energy input periods. The acceleration results will be used in a refined orbit computation in a subsequent investigation.

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 energía eléctrica sea generada a partir de fuentes renovables. Este objetivo implica la necesidad de potenciar la generación de energía eólica en todos los ámbitos. La energía eólica reduce drásticamente las emisiones de gases de efecto invernadero y evita los riesgos geo-políticos asociados al suministro e infraestructuras energéticas, así como la dependencia energética de otras regiones. Además, la generación de energía distribuida (generación en el punto de consumo) presenta significativas ventajas en términos de elevada eficiencia energética y estimulación de la economía. El sector de la edificación representa el 40% del consumo energético total de la Unión Europea. La reducción del consumo energético en este área es, por tanto, una prioridad de acuerdo con los objetivos "20-20-20" en eficiencia energética. La Directiva 2010/31/EU del Parlamento Europeo y del Consejo de 19 de mayo de 2010 sobre el comportamiento energético de edificaciones contempla la instalación de sistemas de suministro energético a partir de fuentes renovables en las edificaciones de nuevo diseño. Actualmente existe una escasez de conocimiento científico y tecnológico acerca de la geometría óptima de las edificaciones para la explotación de la energía eólica en entornos urbanos. El campo tecnológico de estudio de la presente Tesis Doctoral es la generación de energía eólica en entornos urbanos. Específicamente, la optimization de la geometría de las cubiertas de edificaciones desde el punto de vista de la explotación del recurso energético eólico. Debido a que el flujo del viento alrededor de las edificaciones es exhaustivamente investigado en esta Tesis empleando herramientas de simulación numérica, la mecánica de fluidos computacional (CFD en inglés) y la aerodinámica de edificaciones son los campos científicos de estudio. El objetivo central de esta Tesis Doctoral es obtener una geometría de altas prestaciones (u óptima) para la explotación de la energía eólica en cubiertas de edificaciones de gran altura. Este objetivo es alcanzado mediante un análisis exhaustivo de la influencia de la forma de la cubierta del edificio en el flujo del viento desde el punto de vista de la explotación energética del recurso eólico empleando herramientas de simulación numérica (CFD). Adicionalmente, la geometría de la edificación convencional (edificio prismático) es estudiada, y el posicionamiento adecuado para los diferentes tipos de aerogeneradores es propuesto. La compatibilidad entre el aprovechamiento de las energías solar fotovoltaica y eólica también es analizado en este tipo de edificaciones. La investigación prosigue con la optimización de la geometría de la cubierta. La metodología con la que se obtiene la geometría óptima consta de las siguientes etapas: - Verificación de los resultados de las geometrías previamente estudiadas en la literatura. Las geometrías básicas que se someten a examen son: cubierta plana, a dos aguas, inclinada, abovedada y esférica. - Análisis 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 comparación de los resultados obtenidos para la arista convencional (esquina sencilla) con un parapeto, un voladizo y una esquina curva. - Análisis del acoplamiento entre la cubierta y los cerramientos verticales (paredes) mediante la comparación entre diferentes variaciones de una cubierta esférica en una edificación de gran altura: cubierta esférica estudiada en la literatura, cubierta esférica integrada geométricamente con las paredes (planta cuadrada en el suelo) y una cubierta esférica acoplada a una pared cilindrica. El comportamiento del flujo sobre la cubierta es estudiado también considerando la posibilidad de la variación en la dirección del viento incidente. - Análisis del efecto de las proporciones geométricas del edificio sobre el flujo en la cubierta. - Análisis 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 simulación del viento alrededor de edificaciones empleando los coeficientes propuestos por Crespo y los propuestos por Bechmann y Sórensen que empleando los coeficientes estándar. - Se demuestra que la estimación de la energía cinética turbulenta del flujo empleando modelos de turbulencia RANS puede ser validada manteniendo el enfoque en la cubierta de la edificación. - Se presenta una nueva modificación del modelo de turbulencia Durbin k — e que reproduce mejor la distancia de recirculación del flujo de acuerdo con los resultados experimentales. - Se demuestra una relación lineal entre la distancia de recirculación en una cubierta plana y el factor constante involucrado en el cálculo de la escala de tiempo de la velocidad turbulenta. Este resultado puede ser empleado por la comunidad científica para la mejora del modelado de la turbulencia en diversas herramientas computacionales (OpenFOAM, Fluent, CFX, etc.). - La compatibilidad entre las energías solar fotovoltaica y eólica en cubiertas de edificaciones es analizada. Se demuestra que la presencia de los módulos 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 (túnel de viento). Se demuestra que para respetar las limitaciones de similitud (número de Reynolds) son necesarias mediciones en edificaciones a escala real o experimentos en túneles de viento empleando agua como fluido, especialmente cuando se trata con geometrías complejas, como es el caso de los módulos solares. - Se determina el posicionamiento más adecuado para los diferentes tipos de aerogeneradores tomando en consideración la velocidad e intensidad de turbulencia del flujo. El posicionamiento de aerogeneradores es investigado en las geometrías de cubierta más habituales (plana, a dos aguas, inclinada, abovedada y esférica). - Las formas de aristas más habituales (esquina, parapeto, voladizo y curva) son analizadas, así como su efecto sobre el flujo del viento en la cubierta de un edificio de gran altura desde el punto de vista del aprovechamiento eólico. - Se propone una geometría óptima (o de altas prestaciones) para el aprovechamiento de la energía eólica urbana. Esta optimización incluye: verificación de las geometrías estudiadas en el estado del arte, análisis de la influencia de las aristas de la cubierta en el flujo del viento, estudio del acoplamiento entre la cubierta y las paredes, análisis de sensibilidad del grosor de la cubierta, exploración de la influencia de las proporciones geométricas de la cubierta y el edificio, e investigación 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 análisis de la velocidad, la energía cinética 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.

Aerodinámica experimental de elementos de parques energéticos

La creciente demanda de energía eléctrica y la necesidad de implementar energías no contaminantes hace que las llamadas tecnologías verdes sean cada día más solicitadas. Entre estas tecnologías encontramos la energía solar y la energía eólica; ambas tienen una trayectoria de uso e investigación bastante amplia, sin embargo aún presentan problemas de fondo que impiden dar mayor impulso a su uso. El objetivo de la presente tesis es presentar soluciones a problemas de optimización en campos conversores de energía. Para ello se analizan y resuelven dos problemas por medio de técnicas de aerodinámica experimental: el primero sobre campos de colectores solares y el segundo sobre campos eólicos. Las técnicas de medición utilizadas en aerodinámica, y en el presente trabajo, son: medición de cargas, anemometría de hilo caliente, velocimetría por imagen de partículas y escaneo de presiones; además de un análisis estadístico de los datos. En el primer caso se ensayan experimentalmente colectores solares parabólicos en donde, por cuestiones de seguridad o por protección contra el viento, se utilizan cercas. Éstas modifican el comportamiento del flujo corriente abajo y se ha encontrado que la distancia a la cual se colocan, así como el tipo de cercas (sólida o permeable), modifican las cargas estructurales a las que los colectores están expuestos. Los resultados demuestran que existe una distancia crítica en la cual la presencia de la cerca aumenta la carga en lugar de disminuirla, por lo cual la selección adecuada del parapeto y la distancia a la cual se coloca son de suma importancia para la optimización de la estructura. En el segundo caso se ensaya experimentalmente y simula numéricamente la estela de turbinas eólicas por medio de discos porosos. En donde un disco permeable simula el rotor de una turbina. El disco es capaz de semejar la estela y los efectos que ésta puede causar corriente abajo. Los resultados muestran que seleccionando adecuadamente la porosidad, es posible simular coeficientes de empuje similares a los desarrollados por los aerogeneradores, además la estela y sus efectos son semejantes a los medidos en campo. ABSTRACT The called green energy technologies are increasingly required because of the growing demand for electricity and the need to implement nonpolluting energy. Among the green energy technologies it is found the solar and the wind energy, both have a history of use and fairly extensive research; however they still have problems which limit to give them further impetus to its use. The aim of this thesis is to present solutions to optimization problems in energy harvesting. To this end it is analysed, and solved, two problems by means of techniques in experimental aerodynamics: the first issue with regard to parabolic troughs and the second about wind farms. The measurement techniques commonly used in aerodynamics, and used in this research work, are: measurement of loads, hot wire anemometry, particle image velocimetry and scanning of pressures; where data are collected and then an statistical analysis is done. In the first case it is tested parabolic troughs where, either for security reasons or protection against the wind actions, fences are used. These fences modify the behaviour of flow downstream and it was found that the distance at which they are placed, and the type of fences (solid or permeable) modify the structural loads to which the parabolic troughs are exposed. The results show that there is a critical distance at which the presence of the fence increases the load instead of protecting the parabolic trough, hence making the proper selection of the parapet and the distance at which it stands are paramount for the optimization of the structure. In the second case it is tested, experimentally and numerically, the wake of wind turbines by means of porous disks; where the permeable disc simulates a turbine rotor. The disc is able to mimic the wake and the effects that it can cause downstream. The results show that by properly selecting the porosity, it is possible to simulate drag coefficients similar to those developed by wind turbines; moreover the porous disk wake and its effects are similar to those measured on field.

Outreach Testing of Ancient Astronomy

This work is an outreach approach to an ubiquitous recent problem in secondary-school education: how to face back the decreasing interest in natural sciences shown by students under ‘pressure’ of convenient resources in digital devices/applications. The approach rests on two features. First, empowering of teen-age students to understand regular natural events around, as very few educated people they meet could do. Secondly, an understanding that rests on personal capability to test and verify experimental results from the oldest science, astronomy, with simple instruments as used from antiquity down to the Renaissance (a capability restricted to just solar and lunar motions). Because lengths in astronomy and daily life are so disparate, astronomy basically involved observing and registering values of angles (along with times), measurements being of two types, of angles on the ground and of angles in space, from the ground. First, the gnomon, a simple vertical stick introduced in Babylonia and Egypt, and then in Greece, is used to understand solar motion. The gnomon shadow turns around during any given day, varying in length and thus angle between solar ray and vertical as it turns, going through a minimum (noon time, at a meridian direction) while sweeping some angular range from sunrise to sunset. Further, the shadow minimum length varies through the year, with times when shortest and sun closest to vertical, at summer solstice, and times when longest, at winter solstice six months later. The extreme directions at sunset and sunrise correspond to the solstices, swept angular range greatest at summer, over 180 degrees, and the opposite at winter, with less daytime hours; in between, spring and fall equinoxes occur, marked by collinear shadow directions at sunrise and sunset. The gnomon allows students to determine, in addition to latitude (about 40.4° North at Madrid, say), the inclination of earth equator to plane of its orbit around the sun (ecliptic), this fundamental quantity being given by half the difference between solar distances to vertical at winter and summer solstices, with value about 23.5°. Day and year periods greatly differing by about 2 ½ orders of magnitude, 1 day against 365 days, helps students to correctly visualize and interpret the experimental measurements. Since the gnomon serves to observe at night the moon shadow too, students can also determine the inclination of the lunar orbital plane, as about 5 degrees away from the ecliptic, thus explaining why eclipses are infrequent. Independently, earth taking longer between spring and fall equinoxes than from fall to spring (the solar anomaly), as again verified by the students, was explained in ancient Greek science, which posited orbits universally as circles or their combination, by introducing the eccentric circle, with earth placed some distance away from the orbital centre when considering the relative motion of the sun, which would be closer to the earth in winter. In a sense, this can be seen as hint and approximation of the elliptic orbit proposed by Kepler many centuries later.