A wind turbine system gathering the wind and showing a remarkable higher power output performance

What is it about?

We have been investigating the efficient utilization　of　wind　energy　at the Research Institute for Applied Mechanics (RIAM),　Kyushu　University. We have developed a new wind turbine system that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. The shrouded wind turbine with a brimmed diffuser has demonstrated power augmentation by a factor of about 2–5 compared with a bare wind turbine, for a given turbine diameter and wind speed. We have developed the small wind turbines of 1-3kW and a mid-size of 100kW wind-lens turbine for practical application. Aiming at harnessing offshore wind energy, we developed a floating platform equipped with the shrouded turbines of 3kW x 2 units and PV panels of 2kW in Hakata Bay, Fukuoka. In recent years, our concept of the research on renewable Energy is based on a key word of “Small is profitable”. In general, wind turbines which are not needed so large, and floating bodies on the sea are also requested as a medium one. Considering about the social acceptability and environmental problems, using a small and medium size wind-lens turbines, we have been developing a multi-rotor system, namely a clustered wind-lens turbine for obtaining large power output.

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Why is it important?

The important features of this wind turbine equipped with a brimmed diffuser shroud (called Wind Lens Turbine, WLT) are as follows. (1) Two-fivefold increase in output power compared to conventional wind turbines due to concentration of the wind energy (“wind-lens” technology). (2) Brim-based yaw control: The brim at the exit of the diffuser makes wind turbines equipped with a brimmed diffuser rotate following the change in the wind direction, like a weathercock. As a result, the wind turbine automatically turns to face the wind. (3) Significant reduction in wind turbine noise (Fig.3): Basically, an airfoil section of the turbine blade, which gives the best performance in a low-tip speed ratio range, is chosen. Since the vortices generated from the blade tips are considerably suppressed through the interference with the boundary layer within the diffuser shroud, the aerodynamic noise is reduced substantially . (4) Improved safety: The wind turbine, rotating at a high speed, is shrouded by a structure and is also safe against damage from broken blades. (5) As for demerits, wind load to a wind turbine and structural weight are increased. This wind-lens technology is also applicable to water turbine. We have recently showed the same improvement in efficiency using a prototype of water-lens turbine using a water tunnel.

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