Análise econômica do uso de célula a combustível para acionamento de ônibus urbano

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de critérios para seleção de adesivos utilizados na fabricação de pás de turbinas eólicas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ferramenta computacional para análise do potencial de bombeamento de água utilizando aerogeradores de pequeno porte acoplados a motobombas por meio de inversores de frequência

O objetivo desta dissertação é desenvolver uma ferramenta computacional para a análise do potencial de bombeamento de água com base nos valores de velocidades de vento de uma localidade, utilizando um aerogerador de pequeno porte acoplado a um conjunto motobomba convencional, por intermédio de um inversor de frequência. No trabalho são apresentados dois métodos para o cálculo da vazão. O método 1 utiliza um modelo teórico, enquanto que no método 2 o modelamento é feito a partir de dados de bombeamento obtidos em laboratório. Os dois métodos descrevem o funcionamento de um sistema de bombeamento de água envolvendo os equipamentos citados. Utilizando os modelos matemáticos descritos, foi criado um programa em linguagem Delphi®, para a obtenção dos valores de vazão e volume de água bombeada, além do número de pessoas que podem ser atendidas, com base nos dados de velocidade de vento do local, para com isso, ser possível analisar a viabilidade ou não de instalação do sistema. O funcionamento do programa é descrito através de um exemplo, que contém valores reais de velocidade de vento, e cujos resultados são analisados de forma a possibilitar seu entendimento.

Expansão térmica de nanotubos de carbono de duas camadas

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Prediseño de modelos a escala para el estudio de fenómenos dinámicos de interacción suelo-estructura en aerogeneradores off-shore sobre monopilotes

Máster Universitario en Eficiencia Energética (SIANI)

Development of a microgrid with renewable energy sources and electrochemical storage system integration

Beside the traditional paradigm of "centralized" power generation, a new concept of "distributed" generation is emerging, in which the same user becomes pro-sumer. During this transition, the Energy Storage Systems (ESS) can provide multiple services and features, which are necessary for a higher quality of the electrical system and for the optimization of non-programmable Renewable Energy Source (RES) power plants. A ESS prototype was designed, developed and integrated into a renewable energy production system in order to create a smart microgrid and consequently manage in an efficient and intelligent way the energy flow as a function of the power demand. The produced energy can be introduced into the grid, supplied to the load directly or stored in batteries. The microgrid is composed by a 7 kW wind turbine (WT) and a 17 kW photovoltaic (PV) plant are part of. The load is given by electrical utilities of a cheese factory. The ESS is composed by the following two subsystems, a Battery Energy Storage System (BESS) and a Power Control System (PCS). With the aim of sizing the ESS, a Remote Grid Analyzer (RGA) was designed, realized and connected to the wind turbine, photovoltaic plant and the switchboard. Afterwards, different electrochemical storage technologies were studied, and taking into account the load requirements present in the cheese factory, the most suitable solution was identified in the high temperatures salt Na-NiCl2 battery technology. The data acquisition from all electrical utilities provided a detailed load analysis, indicating the optimal storage size equal to a 30 kW battery system. Moreover a container was designed and realized to locate the BESS and PCS, meeting all the requirements and safety conditions. Furthermore, a smart control system was implemented in order to handle the different applications of the ESS, such as peak shaving or load levelling.

Effect of mesh distortion on the accuracy of high order vorticity-velocity CFD approaches

The numerical solution of the incompressible Navier-Stokes equations offers an alternative to experimental analysis of fluid-structure interaction (FSI). We would save a lot of time and effort and help cut back on costs, if we are able to accurately model systems by these numerical solutions. These advantages are even more obvious when considering huge structures like bridges, high rise buildings or even wind turbine blades with diameters as large as 200 meters. The modeling of such processes, however, involves complex multiphysics problems along with complex geometries. This thesis focuses on a novel vorticity-velocity formulation called the Kinematic Laplacian Equation (KLE) to solve the incompressible Navier-stokes equations for such FSI problems. This scheme allows for the implementation of robust adaptive ordinary differential equations (ODE) time integration schemes, allowing us to tackle each problem as a separate module. The current algortihm for the KLE uses an unstructured quadrilateral mesh, formed by dividing each triangle of an unstructured triangular mesh into three quadrilaterals for spatial discretization. This research deals with determining a suitable measure of mesh quality based on the physics of the problems being tackled. This is followed by exploring methods to improve the quality of quadrilateral elements obtained from the triangles and thereby improving the overall mesh quality. A series of numerical experiments were designed and conducted for this purpose and the results obtained were tested on different geometries with varying degrees of mesh density.

Energy harvesting from body motion using rotational micro-generation

Autonomous system applications are typically limited by the power supply operational lifetime when battery replacement is difficult or costly. A trade-off between battery size and battery life is usually calculated to determine the device capability and lifespan. As a result, energy harvesting research has gained importance as society searches for alternative energy sources for power generation. For instance, energy harvesting has been a proven alternative for powering solar-based calculators and self-winding wristwatches. Thus, the use of energy harvesting technology can make it possible to assist or replace batteries for portable, wearable, or surgically-implantable autonomous systems. Applications such as cardiac pacemakers or electrical stimulation applications can benefit from this approach since the number of surgeries for battery replacement can be reduced or eliminated. Research on energy scavenging from body motion has been investigated to evaluate the feasibility of powering wearable or implantable systems. Energy from walking has been previously extracted using generators placed on shoes, backpacks, and knee braces while producing power levels ranging from milliwatts to watts. The research presented in this paper examines the available power from walking and running at several body locations. The ankle, knee, hip, chest, wrist, elbow, upper arm, side of the head, and back of the head were the chosen target localizations. Joints were preferred since they experience the most drastic acceleration changes. For this, a motor-driven treadmill test was performed on 11 healthy individuals at several walking (1-4 mph) and running (2-5 mph) speeds. The treadmill test provided the acceleration magnitudes from the listed body locations. Power can be estimated from the treadmill evaluation since it is proportional to the acceleration and frequency of occurrence. Available power output from walking was determined to be greater than 1mW/cm³ for most body locations while being over 10mW/cm³ at the foot and ankle locations. Available power from running was found to be almost 10 times higher than that from walking. Most energy harvester topologies use linear generator approaches that are well suited to fixed-frequency vibrations with sub-millimeter amplitude oscillations. In contrast, body motion is characterized with a wide frequency spectrum and larger amplitudes. A generator prototype based on self-winding wristwatches is deemed to be appropriate for harvesting body motion since it is not limited to operate at fixed-frequencies or restricted displacements. Electromagnetic generation is typically favored because of its slightly higher power output per unit volume. Then, a nonharmonic oscillating rotational energy scavenger prototype is proposed to harness body motion. The electromagnetic generator follows the approach from small wind turbine designs that overcome the lack of a gearbox by using a larger number of coil and magnets arrangements. The device presented here is composed of a rotor with multiple-pole permanent magnets having an eccentric weight and a stator composed of stacked planar coils. The rotor oscillations induce a voltage on the planar coil due to the eccentric mass unbalance produced by body motion. A meso-scale prototype device was then built and evaluated for energy generation. The meso-scale casing and rotor were constructed on PMMA with the help of a CNC mill machine. Commercially available discrete magnets were encased in a 25mm rotor. Commercial copper-coated polyimide film was employed to manufacture the planar coils using MEMS fabrication processes. Jewel bearings were used to finalize the arrangement. The prototypes were also tested at the listed body locations. A meso-scale generator with a 2-layer coil was capable to extract up to 234 µW of power at the ankle while walking at 3mph with a 2cm³ prototype for a power density of 117 µW/cm³. This dissertation presents the analysis of available power from walking and running at different speeds and the development of an unobtrusive miniature energy harvesting generator for body motion. Power generation indicates the possibility of powering devices by extracting energy from body motion.

Effect of high order interpolation in the stability and efficiency of the time-integration process in vorticity-velocity CFD algorithms

The numerical solution of the incompressible Navier-Stokes Equations offers an effective alternative to the experimental analysis of Fluid-Structure interaction i.e. dynamical coupling between a fluid and a solid which otherwise is very complex, time consuming and very expensive. To have a method which can accurately model these types of mechanical systems by numerical solutions becomes a great option, since these advantages are even more obvious when considering huge structures like bridges, high rise buildings, or even wind turbine blades with diameters as large as 200 meters. The modeling of such processes, however, involves complex multiphysics problems along with complex geometries. This thesis focuses on a novel vorticity-velocity formulation called the KLE to solve the incompressible Navier-stokes equations for such FSI problems. This scheme allows for the implementation of robust adaptive ODE time integration schemes and thus allows us to tackle the various multiphysics problems as separate modules. The current algorithm for KLE employs a structured or unstructured mesh for spatial discretization and it allows the use of a self-adaptive or fixed time step ODE solver while dealing with unsteady problems. This research deals with the analysis of the effects of the Courant-Friedrichs-Lewy (CFL) condition for KLE when applied to unsteady Stoke’s problem. The objective is to conduct a numerical analysis for stability and, hence, for convergence. Our results confirmthat the time step ∆t is constrained by the CFL-like condition ∆t ≤ const. hα, where h denotes the variable that represents spatial discretization.

Aerodynamic study of airfoils geometric imperfections at low Reynolds number

The interest of this study is based on the observation that some manufacturing processes of various vehicles wings, such as unmanned aerial vehicle (UAV), or blades, such as wind turbine blades, or other devices that use aerodynamic profiles, produce imperfections in the leading edge or open trailing edge with bigger thickness than original airfoil, because, for example, they are manufactured in two parts, top surface and bottom surface and subsequently joined. In this last step might appear a sliding between the top surface and the bottom surface having a small step on the leading edge or a small thickness gain can occur on the trailing edge. Normally these imperfections are corrected through a refill and/or sanding processes using many hours of manual labor. Therefore the initial objective of this research is to determine the level of influence in the aerodynamic characteristics at low Reynolds numbers (Lissaman, 1981, Carmichael, 1981, Nagamatsu and Cuche, 1981, Schmitz, 1957, Cebeci, 1989, Mueller and Batill, 1982) of these imperfections in the manufacture, and determine whether there may be a value for which it would not be necessary to correct them

Parque eólico Cassino

La energía eólica, así como otras energías renovables, ha experimentado en la última década un gran auge que va extendiéndose alrededor de todo el mundo, cada vez más concienciado de la importancia de las energías renovables como una fuente alternativa de energía. Se han sumado al reto todos los países acogidos al Protocolo de Kyoto, que a fin de reducir emisiones están potenciando la energía eólica como la fuente de energía renovable hoy día más viable para la generación eléctrica. Brasil alcanzó en 2011 los 1.509 MW instalados, lo que representa el 50% de Latinoamérica, seguido por México con el 31%. Las características del sector eléctrico así como un marco legal favorable y el alto potencial eólico, hacen que la perspectiva de crecimiento en este tipo de energía sea muy favorable durante los próximos años, con estimaciones de unos 20.000 MW para 2020. El asentamiento del sector en el país de algunos de los fabricantes más importantes y los avances en cuanto a eficiencia de los aerogeneradores, mayor aprovechamiento de la energía de los vientos menos intensos, amplía las posibles ubicaciones de parques eólicos permitiendo una expansión grande del sector. El parque eólico objeto del proyecto está ubicado en el estado de Rio Grande do Sul, al sur del país, y está constituido por 33 aerogeneradores de 2,0 MW de potencia unitaria, lo que supone una potencia total instalada de 66 MW. La energía eléctrica generada en él será de 272,8 GWh/año. Esta energía se venderá mediante un contrato de compraventa de energía (PPA, Power Purchase Agreement) adjudicado por el gobierno Brasileño en sus sistemas de subasta de energía. En el proyecto se aborda primeramente la selección del emplazamiento del parque eólico a partir de datos de viento de la zona. Estos datos son estudiados para evaluar el potencial eólico y así poder optimizar la ubicación de las turbinas eólicas. Posteriormente se evalúan varios tipos de aerogeneradores para su implantación en el emplazamiento. La elección se realiza teniendo en cuenta las características técnicas de las máquinas y mediante un estudio de la productividad del parque con el aerogenerador correspondiente. Finalmente se opta por el aerogenerador G97-2.0 de GAMESA. La ejecución técnica del parque eólico se realiza de forma que se minimicen los impactos ambientales y de acuerdo a lo establecido en el Estudio de Impacto Ambiental realizado. Este proyecto requiere una inversión de 75,4 M€, financiada externamente en un 80 % y el 20 % con recursos propios del promotor. Del estudio económico-financiero se deduce que el proyecto diseñado es rentable económicamente y viable, tanto desde el punto de vista técnico como financiero. Abstract Wind energy, as well as other renewable energies, has experienced over the last decade a boom that is spreading around the world increasingly aware of the importance of renewable energy as an alternative energy source. All countries that ratified the Kyoto Protocol have joined the challenge promoting wind energy in order to reduce emissions as the more feasible renewable energy for power generation. In 2011 Brazil reached 1509 MW installed, 50% of Latin America, followed by Mexico with 31%. Electric sector characteristics as well as a favorable legal framework and the high wind potential, make the perspective of growth in this kind of energy very positive in the coming years, with estimates of about 20,000 MW by 2020. Some leading manufacturers have settled in the country and improvements in wind turbines efficiency with less intense winds, make higher the number of possible locations for wind farms allowing a major expansion of the sector. The planned wind farm is located in the state of Rio Grande do Sul, in the south of the Brazil, and is made up of 33 wind turbines of 2,0 MW each, representing a total capacity of 66 MW. The electricity generated, 272,8 GWh/year will be sold through a power purchase agreement (PPA) awarded by the Brazilian government in its energy auction systems. The project deals with the site selection of the wind farm from wind data in the area. These data are studied to evaluate the wind potential and thus optimize the location of wind turbines. Then several types of turbines are evaluated for implementation at the site. The choice is made taking into account the technical characteristics of the machines and a study of the productivity of the park with the corresponding turbine. Finally selected wind turbine is Gamesa G97-2.0. The technical implementation of the wind farm is done to minimize environmental impacts as established in the Environmental Impact Study. This project requires an investment of 75,4 M€, financed externally by 80% and 20% with equity from the promoter. The economic-financial study shows that the project is economically viable, both technically and financially.

Flow and wakes in complex terrain and offshore. Model development and verification in UPWIND

The paper presents research conducted in the Flow workpackage of the EU funded UPWIND project which focuses on improving models for flow within and downwind of large wind farms in complex terrain and offshore. The main activity is modelling the behaviour of wind turbine wakes in order to improve power output predictions.

CFD modelling of the interaction between the Surface Boundary Layer and rotor wake. Comparison of results obtained with different turbulence models and mesh strategies

A simplified CFD wake model based on the actuator disk concept is used to simulate the wind turbine, represented by a disk upon which a distribution of forces, defined as axial momentum sources, are applied on the incoming non-uniform flow. The rotor is supposed to be uniformly loaded, with the exerted forces function of the incident wind speed, the thrust coefficient and the rotor diameter. The model is tested under different parameterizations of turbulence models and validated through experimental measurements downwind of a wind turbine in terms of wind speed deficit and turbulence intensity.

Validation of a CFD wake model based on the actuator disk technique and the thrust coefficient. Preliminary results

A simplified CFD wake model based on the actuator-disk concept is used to simulate the wind turbine, represented by an actuator disk upon which a distribution of forces, defined as axial momentum sources, are applied on the incoming flow. The rotor is supposed to be uniformly loaded, with the exerted forces as a function of the incident wind speed, the thrust coefficient and the rotor diameter. The model is validated through experimental measurements downwind of a wind turbine in terms of wind speed deficit. Validation on turbulence intensity will also be made in the near future.

Critical comparative evaluation of design methodologies for the ultimate limit state of fatigue in concrete structures

La aparición de la fatiga ha sido ampliamente investigada en el acero y en otros materiales metálicos, sin embargo no se conoce en tanta profundidad en el hormigón estructural. Esto crea falta de uniformidad y enfoque en el proceso de verificación de estructuras de hormigón para el estado límite último de la fatiga. A medida que se llevan a cabo más investigaciones, la información sobre los parámetros que afectan a la fatiga en el hormigón comienzan a ser difundidos e incluso los que les afectan de forma indirecta. Esto conlleva a que se estén incorporando en las guías de diseño de todo el mundo, a pesar de que la comprobación del estado límite último no se trata por igual entre los distintos órganos de diseño. Este trabajo presentará un conocimiento básico del fenómeno de la fatiga, qué lo causa y qué condiciones de carga o propiedades materiales amplían o reducen la probabilidad de fallo por fatiga. Cuatro distintos códigos de diseño serán expuestos y su proceso de verificación ha sido examinado, comparados y valorados cualitativa y cuantitativamente. Una torre eólica, como ejemplo, fue analizada usando los procedimientos de verificación como se indica en sus respectivos códigos de referencia. The occurrence of fatigue has been extensively researched in steel and other metallic materials it is however, not as broadly understood in concrete. This produces a lack of uniformity in the approach and process in the verification of concrete structures for the ultimate limit state of fatigue. As more research is conducted and more information is known about the parameters which cause, propagate, and indirectly affect fatigue in concrete, they are incorporated in design guides around the world. Nevertheless, this ultimate limit state verification is not addressed equally by various design governing bodies. This report presents a baseline understanding of what the phenomenon of fatigue is, what causes it, and what loading or material conditions amplify or reduce the likelihood of fatigue failure. Four different design codes are exposed and their verification process has been examined, compared and evaluated both qualitatively and quantitatively. Using a wind turbine tower structure as case study, this report presents calculated results following the verification processes as instructed in the respective reference codes.