Abstract
Small wind turbines are key devices for micro generation in particular, with a notable contribution to the global wind energy sector. Darrieus turbines, despite being highly efficient among various types of vertical axis turbines, received much less attention due to their starting characteristics and poor performance in low wind speeds. Radically different concepts are proposed as a potential solution to enhance the performance of Darrieus turbine in the weak wind flows, all along the course of Darrieus turbine development. This paper presents a comprehensive review of proposed concepts with the focus set on the low wind speed performance and critically assessing their applicability based on economics, reliability, complexity, and commercialization aspects. The study is first of its kind to consolidate and compare various approaches studied on the Darrieus turbine with the objective of increasing performance at low wind. Most of the evaluated solutions demonstrate better performance only in the limited tip speed ratio, though they improve the low wind speed performance. Several recommendations have been developed based on the evaluated concepts, and we concluded that further critical research is required for a viable solution in making the Darrieus turbine a low speed device.
Highlights
Energy is the vital ingredient for global growth and is undoubtedly the fundamental driver for the economic progress of a country
Though a high coefficient of lift/coefficient of drag (Cl/Cd) ratio is preferred for any airfoil design, a maximum Cl/Cd over a wider range of angle of at tack (AoA) is the desired characteristics for vertical axis wind turbines
The Double Multiple Stream Tube (DMST) validation shows an 8% increment in the power coefficient and 108% improvement with a higher surface roughness than National Advisory Committee for Aeronautics (NACA) 0018
Summary
Energy is the vital ingredient for global growth and is undoubtedly the fundamental driver for the economic progress of a country. The search for a feasible solution to enable a Darrieus turbine to generate optimal power at low wind speed continue for decades. Over these years, countless efforts have been made through experimental, computational and field tests to achieve significant progress in understanding self-starting physics of Darrieus turbine. Countless efforts have been made through experimental, computational and field tests to achieve significant progress in understanding self-starting physics of Darrieus turbine These at tempts substantially improved the starting behavior of these turbines, yet they are still not preferred for low wind speed sites due to their low annual energy output.
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