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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Gabriele Bedon University of Padua, Italy
Co-authors:
Mauro Scungio (1) F P Fausto Arpino (1) Marco Profli (2) Moreno Rotondi (2) Valerio Focanti (2) Gabriele Bedon (3)
(1) University of Cassino and Lazio Meridionale, Cassino (FR), Italy (2) Briareo S.r.l., Ferentino (FR), Italy (3) University of Padova, Padova (PD), Italy

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Mr. Gabriele Bedon is a Ph.D. Student in Energy Engineering at University of Padua, Italy. His main research topics involve the aerodynamic simulation with semi-analytical models of the Darrieus wind turbines and their airfoil optimization with advanced optimization algorithms. He graduated at University of Padua in Mechanical Engineering and at Denmark Technical University in M.Sc. in Engineering, Sustainable Energy. He is currently cooperating with both Universities to improve the design of several projects.


Poster

Poster Download poster (11.45 MB)

Abstract

Wind tunnel testing of scaled models of a newly developed Darrieus-style vertical axis wind turbine

Introduction

Renewable sources of energy, needed because of the increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in wind energy. Among the different typologies, small scale vertical axis wind turbines (VAWT) have the greatest potential for off grid power generation at low wind speeds. In the present work, wind tunnel investigations about the performance of an innovative configuration of Darrieus-style vertical axis wind turbine has been made on scaled models specifically developed for small scale energy conversion at low wind speeds.

Approach

The micro turbine under investigation consists of three pairs of airfoils. Each pair consists of a main and auxiliary airfoil with a chord length of 47 mm and 27 mm, respectively, the angle of attach is 13°, the auxiliary airfoil is placed in advanced position with respect to the main one. A standard Darrieus configuration, consisting of three single airfoils, was also tested for comparison. The length of the blades and rotor diameter are 150 mm and 200 mm, respectively. The experiments were conducted in a closed circuit wind tunnel facility available at the industrial measurement laboratory (LaMI) of the University of Cassino and Lazio Meridionale. A brushless motor, acting as a generator, was directly connected to the wind rotor; series of resistors were used to simulate a variable load; electrical power and rotational speed was measured by a power analyser. From these data, power and torque coefficients were calculated.

Main body of abstract

The experiments were conducted for wind speeds ranging from 6 m/s to 15 m/s. The auxiliary blade have demonstrated to give more torque at the lower wind speeds with respect to a standard Darrieus rotor, resulting in higher values of the power and torque coefficients for wind speeds ranging from 6 m/s to 11 m/s, in which the standard Darrieus was not able to sustain its rotation. For wind speed of 11 m/s, the proposed micro turbine showed a power coefficient value 10 % higher than the standard Darrieus, while from 12 m/s to 15 m/s, the standard rotor showed power coefficient values between 3 % to 9 % greater than the proposed configuration. The torque coefficient was greater for the proposed rotor for all the wind speeds analyzed, showing values between 8 % to 20 % higher in the range 11 m/s – 15 m/s. The maximum power coefficients were found for almost constant tip speed ratio (TSR) value of 1.2 for the standard Darrieus, while for the proposed new configuration, these values were found for TSR varying between 0.8 for the lowest wind speed, to 1.1 for the highest.

Conclusion

From the wind tunnel measured data, it was found that the proposed newly developed rotor has a better performance in terms of torque coefficient with respect to a standard Darrieus configuration for all the wind speeds considered, while in terms of power coefficient, the standard Darrieus configuration has a slightly better performance for the highest wind speed analysed. The proposed micro turbine configuration showed very good performance for the lower wind speeds, in which the standard Darrieus was not able to produce power. In conclusion, the proposed new micro turbine configuration showed an overall better performance, compared to a standard Darrieus rotor, which result in a better conversion of wind energy for very low wind speeds.


Learning objectives
The results from the present experiments could be of great interest for wind energy industry as well as for researchers, since the available technical designs of vertical axis wind turbines must be investigated more in depth for the development of low cost wind energy converters at low wind speeds.