Academic literature on the topic 'Savonius wind rotor'

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.

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.

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.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Engineering<br>Science, Environment, Engineering and Technology<br>Full Text

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.<br>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.<br><p>This project was conducted within Stand up for wind and Stand up for energy.</p>

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Includes bibliographical references (p. 26).<br>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.<br>by Aron Zingman.<br>S.B.

This master‘s thesis deals with the simulation of small wind power plant with Savonius-Darrieus rotor. On the base of the actuator disk theory the performance of modeled power plant is predicted in theoretical part and the power coefficient as well. The process of designing the wind model is also described in this theoretical part. The practical part of this thesis is dedicated to the creating a model of DS300 vertical axis hybrid wind turbine in Matlab/Simulink. This model was used to generating of the power curve of modeled wind power plant and for the computing of power and total produced energy during an average and above-average day as well. The whole thesis is enclosed by evaluating of obtained results.

Praca doktorska podejmuje problematykę badania innowacyjnej elektrowni wiatrowej stworzonej do pracy w instalacjach przydomowych o małej mocy<br>This PhD thesis undertakes an issue of the innovative wind mill dedicated to small power plant installation for individual household use

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<br>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.