Dissertations / Theses on the topic 'Savonius wind turbina'

The diploma thesis is focused on designer works of Savounius rotor for Raječko location. Finish of this design work is equipment, which will be used in this location as decentralized source of electrical energy. In thesis are written manufacturing processes as so as the process of design part including the calculation part, which is focused on characteristic quantity of Savonius rotor. Thesis is finished by econominal assessment of project.

Il crescente fabbisogno energetico e la necessità di ridurre l'inquinamento atmosferico stanno spingendo la ricerca verso soluzioni alternative di produzione di energia. Una di queste potrebbe essere l'inserimento di turbine eoliche ad asse verticale (VAWT), come quella Savonius, nella generazione distribuita. La Savonius ha un design semplice e può generare potenza anche a basse velocità del vento quindi, con l'obiettivo di aumentarne il coefficiente di potenza, sono state studiate delle pale con una forma alternativa a quella tradizionale semicilindrica. Una volta selezionato il design con le migliori prestazioni in termini di coppia e coefficienti di potenza, questi parametri sono stati studiati in funzione degli angoli azimutali, del tip speed ratio (TSR) e del numero di Reynolds. Inoltre sono stati analizzati i campi di velocità e pressione nel dominio circostante la turbina eolica. Tutte le indagini sono state eseguite con un'analisi fluidodinamica computazionale (CFD), realizzata con il software Star-CCM+, e considerando come dominio computazionale un cilindro avente le dimensioni di una galleria del vento. Nonostante la potenza estraibile da questo prototipo di turbina eolica sia bassa a causa della piccola taglia, il coefficiente di potenza massimo, mediato su una rotazione, raggiunge il valore di 0.24 quando il TSR è pari a 0.85. Quindi il nuovo aerogeneratore risulta avere un’efficienza maggiore di quella raggiunta dalla turbina Savonius avente pale con forma tradizionale e che è stata analizzata come confronto. In quest'ultimo caso, infatti, il coefficiente di potenza medio massimo è 0.22, quando il TSR è 0.75. Il nuovo prototipo è anche stato costruito e testato nella galleria del vento in collaborazione con due studenti dell’”Ecole d’Ingénieurs Polytechnique de l’Université de Tours”: Maxime Collet e Romain Guehennec. E’ stato dimostrato che al crescere della velocità del vento, aumenta quasi linearmente la velocità di rotazione della turbina eolica.

Small wind turbine installations have a variety of potential uses, each with unique performance demands and operating conditions. Many applications require that the turbine is placed in wind conditions that are not ideal for optimum operation. Better predictive techniques can improve wind turbine performance through improved control strategies and enhanced designs. Conventional methods of wind power design and control utilize an average power coefficient. In this thesis, various techniques to predict the transient power coefficient of a wind turbine are developed. The operation of a Savonius wind turbine is accurately represented, with a new model which considers the flow distributions to predict the changes in power output at all rotor positions. Another model is developed that represents the dynamics of a small horizontal wind turbine, including the effect of transient wind conditions on rotor speed and acceleration. These can supplement current methods to determine turbine placement, selection and categorization.

A Savonius wind turbine is a self-starting vertical axis rotor. It can be designed to be compact in size and also produces less noise which makes it suitable to integrate into urban spaces such as rooftops and sign-poles. These characteristics make it interesting from a sustainability point of view, especially when aiming to increase the decentralization of electricity production. This thesis aimed to investigate the aerodynamic performance of different two-bladed Savonius profiles by varying the blade arc angle and the overlap ratio. For evaluation, the dimensionless power coefficient and torque coefficient were investigated over different tip speed ratios. The study was conducted numerically with 2D simulations in Ansys Fluent. The partial differential equations describing the characteristics of the flow, including the flow turbulence effects, were solved with the Reynolds-average Navier Stokes in combination with the k-omega SST model. A validation was performed by comparing data from simulated and experimental tests of a semi-circular profile and a Benesh profile. The investigation of the blade arc angle and overlap ratio was performed on a Modified Bach profile. The profile with a blade arc angle of 130 degrees and an overlap ratio of 0.56 generated a maximal power coefficient of 0.267 at a tip speed ratio of 0.9. This blade configuration generated the best performance of all conducted simulations in this project. However, this project contained uncertainties since simulations can never be an exact description of reality. The project was also limited by the computational power available. Nevertheless, according to the conducted simulations, it was observed that a higher blade arc angle and a larger overlap ratio seem to generate higher efficiency.
En Savonius vindturbin är en självstartande vertikalaxlad rotor som kan utformas i en kompakt design samtidigt som den producerar mindre oljud än horisontalaxlade vindkraftverk. Dagens hållbarhetssträvan i kombination med Savonius turbinens karakteristiska egenskaper gör den till ett potentiellt starkt vertyg för vindenergi. Då den kan placeras på exempelvis hustak eller skyltstolpar, utan att störa närliggande omgivning, finns det många möjliga sätt att implementera och integrera den i samhällets infrastruktur. Målet med detta projekt var att undersöka den aerodynamiska prestationen för Savoniusturbiner med två blad genom att variera bladvinkeln och överlappningsförhållandet. För att jämföra de olika profilerna användes den dimensionslösa effektkoefficienten och momentkoefficienten. Dessa koefficienter beräknades i förhållande till löptalet. Studien utfördes numeriskt med 2D-simuleringar i Ansys Fluent. De partiella differentialekvationerna som beskriver flödets egenskaper, inkluderat turbulenseffekterna, löstes med Reynolds-average Navier Stokes i kombination med k-ω SST modellen. En validering utfördes genom att jämföra data med simulerade och experimentella värden av en Semi-circular profil och en Benesh profil. Studien av bladvinkel och överlappningsförhållandet utgick från en Modified Bach profil. Den mest effektiva profilen hade en bladvinkel av 130 grader och ett överlappsförhållande på 0,56. Den genererade en maximal effektkoefficient av 0,267 vid löptal 0,9. Projektet innehöll en del osäkerheter då simuleringar aldrig kan beskriva verkligheten till fullo. Den tillgängliga beräkningskapaciteten begränsade även projektet ytterligare. Trots vissa begränsningar, visar ändå utförda simuleringar att ökad bladvinkel och ökat överlappningsförhållande genererar högre effekt.

This project was conducted within Stand up for wind and Stand up for energy.

The objective of the thesis is to establish methodology for development of a wind turbine, simple in design and easy to maintain, for possible application in developing countries. To that end the Savonius configuration is analyzed in detail both experimentally and analytically to lay a sound foundation for its performance evaluation. Following a brief review of relevant significant contributions in the field (Chapter I), an extensive wind tunnel test-program using scale models is described which assesses the relative influence of system parameters such as blade geometry, gap-size, overlap, aspect ratio, Reynolds number, blockage, etc., on the rotor output. The parametric study leads to an optimum configuration with an increase in efficiency by around 100% compared to the reported efficiency of ≈ 12 — 15%. Of particular interest is the blockage correction procedure which is vital for application of the wind tunnel results to a prototype design, and facilitates comparison of data obtained by investigators using different models and test facilities. With the design and performance results in hand, Chapters III — VI focus attention on analytical approaches to complement the test procedure. Using the concept of a central vortex, substantiated by a flow visualization study, Chapter III develops a semi-empirical approach to predict the rotor performance using measured stationary blade pressure data. The objective here is to provide a simple yet reliable design tool which can replace dynamical testing with a significant saving in time, effort, and cost. The simple approach promises to be quite effective in predicting the rotor performance, even in the presence of blockage, and should prove useful at least in the preliminary design stages. Chapter IV describes in detail a relatively more sophisticated and rigorous Boundary Element Approach using the Discrete Vortex Model. The method attempts to represent the complex unsteady flow field with separating shear layers in a realistic fashion consistent with the available computational tools. Important steps in the numerical analysis of this challenging problem are discussed at some length in Chapter V and a performance evaluation algorithm established. Of considerable importance is the effect of computational parameters such as number of elements representing the rotor blade, time-step size, location of the nascent vortices, etc., on the accuracy of results and the associated cost. Results obtained using the Discrete Vortex Model are presented and discussed in Chapter VI, for both stationary as well as rotating Savonius configurations. A detailed parametric study provides fundamental information concerning the starting and dynamic torque time histories, power coefficient, evolution of the wake, Strouhal number, etc. A comparison with the flow visualization and wind tunnel test data (Chapter II) shows remarkable correlation suggesting considerable promise for the approach. The thesis ends with concluding remarks and a few suggestions concerning possible future research in the area.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate

Neste trabalho, são apresentados a discussão de conceitos fundamentais, a metodologia e os resultados de simulações numéricas baseadas no Método de Volumes Finitos do escoamento de ar sobre algumas opções de configurações de turbinas eólicas do tipo Savonius, com e sem estatores, em operação e, também, em condições estáticas, como as encontradas nas partidas das mesmas. Comparam-se os resultados para diferentes domínios computacionais, bem como alternativas de discretização espacial e temporal, visando apresentar a influência desses sobre os valores obtidos e estabelecer os parâmetros computacionais adequados para a análise das turbinas em estudo. Nas simulações numéricas, desenvolvidas empregando o programa comercial Star-CCM+, a equação da continuidade e as equações de Navier-Stokes com médias de Reynolds são resolvidas, juntamente com as equações de um modelo de turbulência adequado, que é escolhido, para a obtenção dos campos de pressão e de velocidade do escoamento. Emprega-se um domínio contendo uma região com malha móvel, na qual o rotor é inserido. A cada simulação, a velocidade angular da região de malha móvel é especificada de maneira a variar a razão de velocidade de ponta do rotor. Através da integração das forças ocasionadas devido aos gradientes de pressão e das forças originadas pelo atrito viscoso sobre as pás do rotor eólico, obtém-se o coeficiente de torque em cada simulação. O torque e as forças atuantes no rotor também são obtidos de forma semelhante. Com esses dados, outros parâmetros como a potência e o coeficiente de potência são obtidos. Análises dos principais parâmetros de desempenho do rotor Savonius são realizadas e indicam uma boa concordância com resultados experimentais e de simulações numéricas realizadas por outros autores. Os resultados obtidos nas simulações apresentaram-se bastante representativos do fenômeno analisado.
This research work presents a discussion of basic concepts, the methodology and the results of numerical simulations based on Finite Volume Method for the air flow through some configuration options of the Savonius wind turbines, with and without stators, in operation, and also under static conditions, such as those found in the self starting. Results for different computational domains, as well as alternative spatial and temporal discretization are compared, in order to present the influence of these on the obtained values from the computational analysis of the turbines in study. In the numerical simulations, performed using the commercial software Star-CCM+, the equation of continuity and the Reynolds Averaged Navier-Stokes Equations were solved, together with the equations of a turbulence model appropriate, which is chosen, so that the fields of pressure and velocity could be found. It was used, in the calculations, a domain containing a region with a moving mesh, in which the rotor was inserted. In each simulation, the rotational rate of the moving mesh region was specified so as to vary the tip speed ratio of rotor. Through the integration of the forces arising due to the pressure gradients and the forces originated from the viscous friction on the wind rotor blades, the moment coefficient could be obtained in each simulation. The moment and forces acting on the rotor were also obtained similarly. With these data, other parameters such as the power and the power coefficient of the wind rotor could be obtained. Analysis of the principals performance parameters of the Savonius wind rotor were performed and indicated a good agreement with experimental results and numerical simulations performed by other authors. The simulations results are quite representative of the phenomenon analyzed.

O presente trabalho apresenta um estudo numérico e experimental sobre o desempenho aerodinâmico de turbinas eólicas de eixo vertical envolvendo rotores Savonius convencional de duplo-estágio e helicoidal. O estudo experimental é realizado no Túnel Aerodinâmico Professor Debi Pada Sadhu, do Laboratório de Mecânica dos Fluidos da UFRGS. As simulações numéricas são realizadas com o software Fluent/ANSYS utilizando o Método dos Volumes Finitos. São comparados os coeficientes de torque estático e dinâmico, o coeficiente de potência, além de uma análise aerodinâmica das duas turbinas. As medições são realizadas empregando Tubos de Pitot, um torquímetro estático digital e um torquímetro simples construído para a medição do torque dinâmico. As turbinas são fabricadas através da técnica de prototipagem 3D, com uma semelhança de dimensões e parâmetros. As soluções numéricas são resolvidas através da equação da continuidade, das equações de Navier-Stokes com médias de Reynolds (RANS) e pelo modelo de turbulência k-ω SST. A qualidade da malha utilizada é avaliada através do método de Índice de Convergência de Malha (GCI), para três diferentes tamanhos de malha. São feitas análises dos rotores na forma estática para diferentes ângulos de incidência e com a turbina em rotação são feitas análises para diferentes razões de velocidades de ponta de pá (λ). Resultados demonstram que a turbina helicoidal apresenta um coeficiente de torque positivo para todos os ângulos do rotor, assim como a turbina convencional de dois estágios. O coeficiente de torque dinâmico da turbina helicoidal é superior ao da turbina de duplo-estágio para a maioria dos casos, e também apresenta menor oscilação de torque ao longo de cada rotação. Por consequência, o coeficiente de potência do rotor helicoidal também se tornou superior, com um valor máximo encontrado na ordem de 11,8% para um λ de 0,65 no caso experimental, e de 8,4% para o mesmo λ no caso numérico, quando comparado com o rotor de duplo-estágio. Os erros relativos entre as simulações numéricas e os resultados experimentais estão entre 2,16% e 13,4%. Uma estimativa de potência gerada é feita para ambos os casos, para uma razão de velocidade de ponta de 0,65, onde a turbina helicoidal apresenta melhores resultados em relação ao rotor de duplo-estágio, na ordem de 13,6% para uma velocidade de 10,4 m/s.
This paper presents a numerical and experimental study of vertical axis wind turbine performance comparison involving two-stage and helical Savonius rotors. The experimental study is conducted in the Aerodynamic Tunnel Professor Debi Pada Sadhu at the Fluid Mechanics Laboratory of the UFRGS. The numerical simulations are performed with the Fluent/ANSYS software using the Finite Volumes Method. The static and dynamic torque coefficients, the power coefficients, and an aerodynamic analysis of the two turbines are compared. Measurements are made using Pitot tubes, a digital static torque wrench and a simple wrench constructed for the dynamic torque measurement. The aerodynamics rotors are manufactured by 3D prototyping technique with similar dimensions and parameters. Numerical solutions are solved by the continuity equation, the Reynolds Averaged Navier-Stokes (RANS) equations and the turbulence model k-ω SST. The quality of the mesh used is evaluated used the Grid Convergence Index (GCI) method, for three different mesh sizes. The rotors analyzes are made in static form for different angles of incidence and for the rotating turbine analyzes are made for differents tip speed ratio (λ). Results show that the helical turbine has a positive static torque coefficient for any rotor angles, as well as conventional two-stage turbine. The dynamic torque coefficient of the helical turbine is higher than the two-stage turbine for most cases and also shows less torque variation along each rotation. Consequently, the power coefficient of the helical rotor also become higher, with a maximum value found on the order of 11.8% for a λ of 0.65 in the experimental case, and 8.4% for the same λ number when compared with the two-stage rotor. The relative errors between the numerical simulations and the experimental results are between 2.16% and 13.4%. A generated power estimate is made for both cases, for a tip speed ratio of 0.65, where the helical turbine provides better results compared to two-stage rotor in order of 13.6% for a velocity of 10.4 m/s.

The aim of this Master Thesis is to study numerically the aerodynamic performance of two small examples of horizontal axis domestic wind turbines: a conventional Savonius rotor, designed and built by a group of students of the Polytech of Tours (France), and its optimization, a helical Savonius rotor. In the first research project, the exploration is conducted even experimentally, testing the turbine in a wind tunnel present in the Polytech. The numerical investigation is carried out by the use of a software based on Computational Fluid Dynamics named Star CCM+, which helps studying the main fluid dynamics aspects as flow velocity, pressure and coefficients of performance. The second project consists in a helical Savonius rotor: according to the literature, the helical shape, comparing with the conventional Savonius rotor, usually shows better performances. After the 3D design on Catia, the turbine was printed using the 3D printer, on a reduced scale. CFD simulations allow to study the fluid dynamic features. Afterwards, thanks to a comparison between the two Savonius models, the performance enhancement of the new one is shown, together with a practical understanding gained of the parameters influencing aerodynamics the most. By means of the simulations, the helical rotor presents a power coefficient of 10%, which is better than the one of the conventional rotor, found at 7% for the same Tip Speed Ratio. Consequently, even the power produced by the new turbine, resulted to be better than the conventional windmill.

Since the turn of the century, the talk about the limited reserve of fossil fuels and the effects of their burning on our climate has become a major topic of the media. The evidence is staggering and as a consequence most of our world’s countries have started an energy transition. The main goal is to get away from fossil fuels and use “renewable energies”, so called because the resources are constantly renewed and compared to fossil fuels seem infinite. Energies such as solar, wind, biomass and geothermal are examples of such sources of renewables. Denmark is the current leader in wind generated electricity, California and Spain are showing how to harness the power of the Sun, and all those efforts to generate more with renewables has to be matched with the effort to make those solutions more efficient and more attractive to other countries who still view fossil fuels as the easy solution and keep on using them. With the knowledge available now renewables it feels for some that burning fossil fuels is a primitive solution. Nonetheless it should be the duty of engineers to enlarge and better that knowledge for everyone to use. Now more specifically about wind energy. Humans have harvested the energy in the wind for more than 2000 years (the Persians used windmills around 200 B.C.) and with time our technology has improved. They have designed incredible new machines such as the Savonius and Darreus type turbines and their knowledge of fluid dynamics has permitted the implementation of new streamlined blades that harvest more energy from the wind. Albert Betz has shown that a maximum of 59% was the limit for the efficiency of a wind-turbine. They have been getting closer to this number with the years but there is still room for improvement on certain types of turbines. Vertical axis wind turbines (or VAWTs) have always been considered not as suitable for energy production as horizontal type wind turbines. It is true because not all blades are exposed to the wind at all times (like in a horizontal axis wind turbine), but new studies have proved that streamlining the blades a certain way and adding a wing like thickness to them improved the overall efficiency of the turbine. Knowing that and considering that HAWTs are significantly cheaper to produce and maintain than HAWTS, it makes them a more viable solution notably for local decentralized production in isolated areas of the world.That leads to Peru. Peru is a fast growing still yet a 3rd world country. Its potential for renewable energies production (especially wind energy) is tremendous, yet the great amount of gas and oil available in the underground and them coming at a cheap price does not encourage the government to subsidize renewables. It leaves Peru dependent on foreign investments to develop this sector and takes away a great opportunity to forego its energetical transition and get ahead of competition in South America. Some projects have surfaced notably in northern Peru, in the Trujillo region, but there are few compared to the mega industry of oil and gas. This thesis paper has for goal to further the knowledge of wind turbines in the context of hoping to change Peru’s view on their use and also for the world to use as a database for further research and other works.
Tesis

There is an urgent need for economical, clean, sustainable energy supplies, not only in densely populated areas where electricity grids are appropriate, but also in rural areas where stand-alone power supply systems are often more suitable. Although electrical power supply is very versatile and convenient, it introduces unnecessary complexity for some off-grid applications where direct mechanical shaft power can conveniently be provided by a wind turbine. Wind energy is one of the more promising renewable energy sources. Most wind turbines are of the horizontal axis type, but vertical axis wind turbines or VAWTs have some advantages for direct mechanical drive applications. They need no tail or yaw mechanism to orient them into the wind and power is easily transmitted via a vertical shaft to a load at ground level. Blades may be of uniform section and untwisted, making them relatively easy to fabricate or extrude, unlike the blades of horizontal axis wind turbines (HAWTs) which should be twisted and tapered for optimum performance. Savonius rotor VAWTs are simple and may have a place where the power requirement is only a few Watts, but they are inefficient and uneconomical for applications with larger power requirements. VAWTs based on the Darrieus rotor principle are potentially more efficient and more economical, but those with fixed pitch blades have hitherto been regarded as unsuitable for stand-alone use due to their lack of starting torque and low speed torque. This starting torque problem can be overcome by using variable pitch blades, but most existing variable pitch VAWTs, variously known as giromills or cycloturbines, need wind direction sensors, microprocessors and servomotors to control the blade pitch, making them impracticable for stand-alone, non-electrical applications. A simpler but less well known concept is passive or self-acting variable pitch in which the blades are free to pitch under the combined action of aerodynamic and inertial forces in such a way that a favourable blade angle of attack is maintained without the complexity of conventional variable pitch systems. Several fonns of self-acting variable pitch VAWTs or SAPVAWTs have been described in the literature, several patents exist for variants on the concept, and at least two companies world-wide have attempted to commercialise their designs. However the aerodynamic behaviour of these devices has been little understood and most designs appear to have been based on nothing more than a qualitative appreciation of the potential advantages of the concept. This thesis assesses the potential of both fixed and passive variable pitch vertical axis wind turbines to provide economical stand-alone power for direct mechanical drive applications. It is shown that the starting torque and low speed torque problems of VAWTs can be overcome either by passive variable pitch or by a combination of suitable blade aerofoil sections, either rigid or flexible, and transmissions which unload the rotor at low speeds so that high starting torque is not necessary. The work done for this thesis is made up of a sequence of stages, each following logically from the previous one: 1. Several tasks have been identified which could be performed effectively by a self-starting vertical axis wind turbine using direct mechanical drive. These include, a. pumping water, b. purifying and/or desalinating water by reverse osmosis, c. heating and cooling using vapour compression heat pumps, d. mixing and aerating water bodies and e. heating water by fluid turbulence. Thus it is apparent that such a system has the potential to make a useful contribution to society. 2. A literature survey of existing VAWT designs has been carried out to assess whether any are suitable for these applications. 3. As no suitable existing design was identified, an improved form of SAPVAWT has been developed and patented. 4. To optimise the performance of the improved SAPVAWT, a mathematical model has been developed in collaboration with Mr Leo Lazauskas of the University of Adelaide (see Kirke and Lazauskas, 1991, Lazauskas and Kirke, 1992). As far as the author of the present thesis is aware, this is the only existing mathematical model able to predict the performance of this particular type of SAPVAWT, and one of only two worldwide which model SAPVAWTs. 5. In order to use the mathematical model to predict the performance of a given SAPVAWT, it is necessary to have lift, drag and moment data for the aerofoil profile to be used, over a wide range of incidence and Reynolds numbers. A literature search has revealed large gaps in the existing data. 6. Wind tunnel testing has been carried out to assess the effect of camber on the performance of one set of NACA sections at low Reynolds number, and performance figures for other sections have been estimated by interpolation from existing data. 7. Using the assembled aerofoil data, both experimental and estimated, the mathematical model has been used to predict the performance of both fixed and variable pitch VAWTs. It has been found to predict correctly the performance of known fixed pitch VAWTs and has then been used to predict the performance of fixed pitch VAWTs with cambered blades using newly developed profiles that exhibit superior characteristics at low Reynolds numbers. Results indicate that fixed pitch VAWTs using these blade sections should self-start reliably. 8. To validate the mathematical model predictions for self-acting variable pitch, a two metre diameter physical model has been built and tested in a wind tunnel, and acceptable agreement has been obtained between predicted and measured performance. 9. To demonstrate the performance of a SAP VA WT under field conditions, a six metre diameter turbine has been designed, fabricated, erected and tested. 10. Because a prime mover such as a wind turbine is of no use unless it drives a toad, particular attention has been paid to the behaviour of complete systems, including the wind turbine, the transmission and the load. It is concluded that VAWTs with the improved self-starting and low speed torque characteristics described in this thesis have considerable potential in stand-alone, direct mechanical drive applications.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 26).
The D-lab Honduras team designed and constructed a wind-powered water pump in rural Honduras during IAP 2007. Currently, the system does not work under its own power and water must be pumped by hand. This thesis seeks to explore a variety of mechanism and aerodynamic changes to allow the system to function as designed. The novel modifications to the Savonius rotor that were made do not seem to improve its performance. Within the constraints of the installed components, the current rotor should perform well pending other changes. The most promising improvements to the system are weight reducing and friction reducing measures, and in combination with understanding the wind conditions in the immediate vicinity of the rotor, changes will be made this summer so that unassisted wind pumping will be possible.
by Aron Zingman.
S.B.

La technique d'intégration des systèmes éoliens verticaux (VAWT) au service des logements individuels, collectifs et tertiaires est une approche intéressante pour les acteurs de la maitrise d'énergie pour promouvoir une utilisation rationnelle de l'énergie. Le choix de l'implantation d'une éolienne en milieu urbain est déterminé par la hauteur des bâtiments, la vitesse du vent et l'intensité de turbulence du site. Les conditions de vents sévères à faible altitude sont favorables à une implantation de VAWT. Dans certaines villes, la hauteur moyenne des bâtiments est relativement faible et ceci fait qu'en ces lieux, les VAWTs sont appréciables par rapport aux HAWTs. La mécanique des fluides numériques (CFD) est mise en œuvre pour modéliser les écoulements d'air au travers d'éoliennes et des bâtiments. Un problème CFD modélisé avec un modèle de turbulence approprié donneront des résultats de simulations qui s'approcheront des réalités physiques et des résultats de l'expérimentation. Dans cette étude, les modèles standard k-" et SST k-! ont été utilisés. Après analyse des possibilités d'intégration d'une VAWT, la toiture reste la zone d'intégration la plus intéressante. En plus de l'étude aérodynamique, nous avons entamé une modélisation électrique de la chaîne de conversion de l'éolienne en utilisant le logiciel Matlab/Simulink. Le travail a été effectué dans le but de déterminer la puissance électrique susceptible d'être produite par l'éolienne. Pour finaliser cette étude, un modèle de couplage électrique de VAWTs avec un bâtiment considéré comme un modèle de charge est présenté
The building integration of the vertical axis wind turbine (VAWT) to supply the individual, collective and tertiary residences consumption is an interesting approach that can help architects and the actors of the energy control to promote a rational use of renewable energy in the in homes. The choice of the location of the urban wind turbine type is determined by building height, wind speed and turbulence intensity of the site. The severe conditions of wind at low altitude are favorable for a VAWT installation. In some cities, the average buildings height is low, in these places, the VAWTs must be appreciable compared to the HAWTs. The modelling of the air flow through the wind turbine and the couple building-wind turbine involves the computation fluid dynamics (CFD). A problem modeled with a suitable turbulence model will give results that approach the physical reality and the experiment results. In this study, the standard k-" and SST k-! models were used. After analyzing the possibilities of VAWT integration, the roof is the most interesting integration area. In addition to CFD method, we have started to study the electrical model of the VAWT. The work was conducted to determine the electrical power generated by the wind turbine using Matlab/Simulink software. To complete the study, a VAWT model coupled with a building where the building is considered as a consumption model is presented

Oblast problémů, ze kterých konkrétní téma projektu vychází, zahrnuje současnou globální transformaci zdrojů energie a jejich dodávek se zvláštní pozorností na obnovitelné zdroje energie. Důraz je kladen zejména na hodnoty jež přináší produkt určený k užívání ve veřejných prostorách. Autorovým zadáním bylo navrhnout osvětlovací jednotku nezávislou na vnějším zdroji napájení. Cílem návrhu je přehodnotit způsob, jakým jsou dnes technologie využívání sluneční a větrné energie běžně používány, a navrhnout řešení přinášející nové vlastnosti a užitné hodnoty pro přímého uživatele i celou společnost. Autor přináší návrh produktu jenž je reakcí na současné globální hrozby a příležitosti. Výsledkem projektu je návrh pouliční lampy kombinující fotovoltaický článek a větrnou turbínu s cílem získat elektrickou energii jež je dočasně akumulována a následně dodávána svítidlu. V návrhu je kladen důraz na požadavky ergonomie a estetickou hodnotu produktu. Navržené řešení znamená finanční přínos z hlediska šetření neobnovitelnými zdroji energie a případnými finančními výhodami pro investora plynoucími z provozování veřejného osvětlení. Pouliční lampa nezávislá na vnějším zdroji napájení má navíc menší negativní dopad na životní prostředí a představuje technologie využívání větrné a solární energie v přívětivé a nerušivé podobě.

碩士
清雲科技大學
電機工程所
99
Savonius rotors were doubted to be an efficient machine to produce electricity due to its lower power efficiency. But Savonius rotors are known to have many advantages like simple structure and low cost for manufacture. With the new development of low angular speed electricity generators, more and more researches are in progress to promote the efficiency of Savonius rotors. Computational fluid dynamics (CFD) method is applied in this paper to simulate and compare the torques on different blade structures and their related equilibrium angular speeds of Savonius rotors to find the optimized overlap ratio of blades. Results show that the tendency of static torque variation with rotation angle is similar to the dynamic one. Based on the root mean square method, the amplitude of static torque is about one and half times of the dynamic one. The optimized overlap ratio is found to be 0.15 by the analysis of average static torque, but 0 by the analysis of equilibrium angular speed. Further analysis on the estimated output power shows that the maximum point is associated with the overlap ratio 0.15. Thus, we proposed 0.15 is the optimized overlap ratio. This value can be an important reference for the design of Savonius rotor.

碩士
國立交通大學
工學院碩士在職專班精密與自動化工程組
99
The purpose of this thesis is to build a variable Savonius wind turbine model and perform the motion simulation and design. In motion simulation part, we used UG NX to model a Savonius wind turbin with variable blade and exported this model into ADAMS. And ADAMS can generate a graphics output file which may be to view an animation of the motion simulation. The analysis results compared with wind tunnel experiment ,and ADAMS are obtained good agreements in this case. The experimental method was developed to measures the reaction torque and rpm varying with angle of rotation. It is useful for the construction of the methodology of designing and analysis mode for wind turbine blades.

A nanogrid system for supplying neutrino detectors on Antarctica with electricity is designed and built. The nanogrid system could later on be implemented in various configurations where suppling electricity to neutrino detectors is one area of use. The energy system that is acting on site in Antarctica is based around solar panels to provide power to the measuring equipment. However, providing electricity in such a way is not optimal due to its failure in delivering electricity at times. A nanogrid that can stand the demands of constant energy supply to the measurement station are therefore constructed. The energy sources that are integrated into the nanogrid are an innovation in vertical axis wind turbine and photovoltaics. The wind turbine innovation is tested under real conditions for the first time. In the constructed nanogrid, there are also integrated energy storage consisting of battery cells that are coupled together to a coherent unit. Measurement equipment is also implemented for analyzation of acting wind turbine as well as different types of safety equipment for redundancy in the system. In the nanogrid, a rectifier for AC to DC transformation is constructed. An inverter for DC to AC transformation is also implemented for supplying electricity to the equipment that are acting on the grid. The system is tested under real conditions. The whole system could observe partially function and configurated well to the various parts of the whole system. Further optimisation of some parts of the system from the prototype is needed.

碩士
長庚大學
機械工程學系
105
Since the variation of wind direction does not affect the performance of vertical-axis wind turbines (VAWT), they are suitable for installing in metropolitan area where the wind direction varies constantly due to the vortexes induced by high rise buildings. Among all VAWTs, the power coefficient, CP, of H-rotors can be as high as 0.45, which is even higher than that of some small horizontal axis wind turbines. However, a dead band of negative CP in the lower range of the tip speed ratio (TSR) of the H-rotors prevents them from self starting and consequently reaching the high CP. Therefore, this study is an attempt using a Savonius wind turbine (S-rotor) of variable pitch and smaller radius at the center of an H-rotor that would self start the rotor, carry the H-rotor blades through the dead band, reduce the negative impact in high TSR range, and brake the rotor at high wind. Firstly, an optimization method is used to design the S-rotor blades that have the largest starting torque, which is the smallest torque in all direction for the optimal set of geometric factors. Secondly, the upper limit of the dead band is found as a function of wind speeds with the double-multiple stream tube model. A model of the optimized S-rotor is fabricated and tested in a wind tunnel to find the maximum TSR as a function of wind speed. Then the TSR is adjusted to be the TSR of H-rotor. Comparing the two, one can find the wind speed and the rotational speed of the rotor assembly that passes the dead band. Under this condition, the blades of the S-rotor transform into a cylinder in order to reduce drag as the H-rotor blades pickup the speed. Then, a mechanism is designed to vary the pitch of the S-type blades for performing the above mentioned function as well as braking the rotor with air when rotor speed exceeds a maximum value so as to protect the rotor from breaking by strong winds. Finally, a prototype of the combined rotor is tested on a vehicle mounted test bench. The results show that the experimental data are very different from theoretical prediction. The main reason for this is that the theoretical analysis does not consider the negative torque of the H-rotor and the shielding effect of the H-rotor blades. Therefore, it may be concluded that the H-rotor with fixed pitch blades cannot go across the dead band with the help of S-rotor. Using variable pitch blades for the H-rotor may be the only solution to the problem because the negative torque of variable pitch blades is only one half that of fixed pitch blades.

碩士
國立臺北科技大學
機電整合研究所
101
Wind energy has once again sparked the discussion of the use of green energy because of energy shortage and climate anomalies and recent price increases on the petroleum. Savonius wind turbine has the advantages of low noise, simple structure, low cost and isn’t influenced by wind direction, etc. Expectedly, the drag type wind turbine will gradually become the mainstream in wind power generation. The purpose of this study is to developed a cone-shaped Savonius wind turbine power generation systems by implementation. For this cone-shaped Savonius wind turbine, the aerodynamic performance is explored experimentally and the flow field characteristic is analyzed numerically. Based on the existing turbine model available in the literature, a modified Savonius turbine profile with larger frontal area is created, which both aerodynamic performance and flow field around the turbine are investigated. The results show that (1) for a nine-blade cone-shaped Savonius wind turbine with upward spiral appearance, when the wind acts on the blade, the airflow is directed upward due to the larger stagnation-zone pressure and the spiral shape effect; (2) compared to horizontal-axis wind turbine, the cone-shaped Savonius wind turbine does not require wind-pursuing system and has the advantage easily starting under the low-speed wind condition. Therefore, it can be used in city building rooftop where the wind speed and direction are uncertain; (3) the cone-shaped Savonius wind turbine with zero loading will be able to start running only at wind speed 2m /s. When the wind speed is 10m/s, the fastest speed of cone-shaped wind turbine can be up to 280rpm,which the output voltage is 3.25 volts; (4) the cone-shaped Savonius wind turbine under the operating condition of wind speed 10m/s and loading 5Ω will generate maximum instantaneous power 0.917W.

碩士
中原大學
工業與系統工程研究所
99
Green energy is an alternative key to fossil fuels and the future life. In oil prices led to rises in the cost of power generation and global environmental degradation, coupled with chemical fuel of human dependence on oil is high, resulting in inadequate development of other energy technologies all the circumstances. The importance of renewable energy gradually, regeneration energy technologies can contribute to clean and secure energy in the human environment. Wind energy becomes a new source of energy because of its clean, inexhaustible, low-cost and other characteristics. Our world is facing environmental changes and growing energy needs, wind energy and wind power technology can help solve these issues. In this study, the case-Savonius wind rotor of the vertical axis small wind turbine will affect the design of parts of the fan capacity wind blades as the main object of study, the extraction of blade design factors research, development can be adapted to their environment and security design of wind turbines. In this study, combining patent analysis and TRIZ theory with the collation of literature Savonius windmill to build a Savonius wind turbine blade design factors table, and draw the Savonius wind rotor blade graphics for assessment of stress. In this study, Autodesk Inventor's 3D parametric design feature to create the model diagram via the Taguchi method of orthogonal array, configured to be 18 Savonius wind rotor blade models, and use the built-in stress analysis of Autodesk Inventor environment to experiment, and get Savonius windmill blades for the deformation under different pressures and stress of the data. We calculate the average SN ratio by the resulting map for each model. The SN cytokine response analysis and variance analysis to identify the design factors of importance, and to complete a continuous Savonius windmill blade design factor extraction process. The conclusion may provide the safety basis and reference in Savonius windmill fields related to technology development and fan design.

碩士
國立屏東科技大學
車輛工程系所
99
The aim of present thesis is to investigate the aerodynamic performance of a novel vertical-axis wind turbine (VAWT) with CFD method. The novel wind turbine blades system is composed of one or two outer rings of NACA blades and inner ring of semi-circular plates. The NACA series blades with high lift/drag ratio were used to generate enough torque force when the wind turbine is started. The inner portion of wind turbine is equipped with three to four pieces of curved plates which was considered to be worked at low wind speed environment. Two profiles of NACA series blades as NACA0018 and NACA4412 were settled on outer rings of turbine blades and their effect on the aerodynamic data were tested. The unsteady flow structure around the wind turbine blades were obtained by solving the Reynolds-averaged Navier-Stokes equations in Fluent software. After testing various scheme to discrete the pressure term in momentum equation, the “Coupled” scheme is selected. The MRF scheme is applied to model the dynamic motion of multi-layers of wind blades. The power coefficient with respect to the tip velocity ratio is provided and discussed. Results indicated that the wind turbine with additioned blade of NACA0018 and NACA4412 can generate 3.4 times of power output as compared with that only equipped of curved-plates in central portion.