H-Darrieus Wind Turbine with Blade Pitch Control

F Saeed,O Trifu,I Paraschivoiu

doi:10.1155/2009/505343

Abstract

A procedure for computing the optimal variation of the blades' pitch angle of an H-Darrieus wind turbine that maximizes its torque at given operational conditions is proposed and presented along with the results obtained on a 7 kW prototype. The CARDAAV code, based on the “Double-Multiple Streamtube” model developed by the first author, is used to determine the performances of the straight-bladed vertical axis wind turbine. This was coupled with a genetic algorithm optimizer. The azimuthal variation of the blades' pitch angle is modeled with an analytical function whose coefficients are used as variables in the optimization process. Two types of variations were considered for the pitch angle: a simple sinusoidal one and one which is more general, relating closely the blades' pitch to the local flow conditions along their circular path. A gain of almost 30% in the annual energy production was obtained with the polynomial optimal pitch control.

Highlights

Following the 1973 energy crisis, large-scale research and development programs were initiated, directed toward finding replacement solutions to the limited fossil fuel reserves
Its technological progress has been spectacular, especially in the last ten years and, due to its steady growth in competitiveness, wind power developed into a mainstream energy source in many countries worldwide
In the wind power domain two main technologies were considered as having the necessary potential for a viable development: the Horizontal Axis Wind Turbine (HAWT) and the Darrieus-type Vertical Axis Wind Turbine (VAWT)

Summary

Introduction

Following the 1973 energy crisis, large-scale research and development programs were initiated, directed toward finding replacement solutions to the limited fossil fuel reserves. Through further and welltargeted research, increased attention is paid to the known VAWT drawbacks (a somewhat less overall efficiency than the one of an HAWT, difficult/impossible self-starting, lower output due to operation closer to the ground, higher level of vibration caused by the inherent torque ripple and dynamic stall of the blades), at least in the “small wind” domain the VAWT design might become a major player. Among the most important problems that are under study in the VAWT technology, the “variable pitch” for the H-Darrieus turbines is regarded as a promising solution for the alleviation of the negative effects of the blades dynamic stall (efficiency loss, vibration), improvement of the rotor’s self starting qualities, and torque ripple smoothing [1,2,3]. The present study aimed at determining if a more general cyclical pitch variation can be determined, so as to maximize the performance of an H-Darrieus (straight bladed) vertical axis wind turbine at given operation conditions. Several conclusions are formulated at the end of the paper

The Optmization Tool

NACA 0015 blades

Results