Abstract
Vertical-axis wind turbines (VAWTs) have drawn increased attention for off-grid and off-shore power generation due to inherent advantages over the more popular horizontal-axis wind turbines (HAWTs). Among these advantages are generator locale, omni-directionality and simplistic design. However, one major disadvantage is lower efficiency, which can be alleviated through blade pitching. Since each blade must transit both up- and down-stream each revolution, VAWT blade pitching techniques are not yet commonplace due to increased complexity and cost. Utilizing passively-morphing flexible blades can offer similar results as active pitching, requiring no sensors or actuators, and has shown promise in increasing VAWT performance in select cases. In this study, wind tunnel tests have been conducted with flexible and rigid-bladed NACA 0012 airfoils, in order to provide necessary input data for a Double-Multiple Stream-Tube (DMST) model. The results from this study indicate that a passively-morphing VAWT can achieve a maximum power coefficient (Cp) far exceeding that for a rigid-bladed VAWT CP (18.9% vs. 10%) with reduced normal force fluctuations as much as 6.9%. Operational range of tip-speed ratio also is observed to increase by a maximum of 40.3%.
Highlights
IntroductionAcademic Editors: Ioannis K.Chatjigeorgiou and Dimitrios N
Academic Editors: Ioannis K.Chatjigeorgiou and Dimitrios N
Though computing power has increased dramatically in recent history, computational fluid dynamics (CFD) analysis of Vertical-axis wind turbines (VAWTs) is still very computationally expensive [40], especially in three dimensions which is often required for adequately addressing turbulence
Summary
Academic Editors: Ioannis K.Chatjigeorgiou and Dimitrios N. Wind energy has enjoyed a dramatic increase in worldwide capacity in the past few decades. Wind power capacity has grown worldwide from 23,900 megawatts (2001) to 539,581 megawatts (2017) [2]. The annual cost of wind energy has decreased dramatically (40% since 2008) [3]. Awareness of governments around the world and support from corporations and the public alike have made it possible to cut down clean energy costs over the years. The maturity of the industry has grown along with market competitiveness, well-established supply chains and has driven down system costs [4]. In the US, there were zero wind turbines with greater than 100 m diameter before 2008; today, the average diameter installed in the US is 116 m [5]
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