Development of a high-performance wind turbine system by concentrating wind energy

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In order to promote the utilization of wind energy, we have developed a new type wind turbine system. The wind turbine system consists of a wind turbine, a diffuser shroud with a ring-shaped brim at the exit periphery and an inlet shroud. We call it as a shrouded wind turbine with a brimmed- diffuser. The brimmed diffuser can accelerate the approaching wind into the wind turbine by capturing and concentrating the surrounding wind. Namely, the wind is induced into the diffuser because of the negative pressure caused by the separation flow from the brim. The ring-shaped plate (brim) generates large eddies downstream which further increases the flow acceleration at the diffuser entrance. To increase the performance of the shrouded wind turbine, we have investigated the optimum design of the brimmed diffuser, inlet shroud and wind turbine itself. As a result, the latest model of shrouded wind turbine has demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about 5 compared with a bare wind turbine. Moreover, the shroud wind turbine has other several important features. Most important features are the safety against the broken blades and the reduction of the blade tip noise by the diffuser.We have also developed a numerical cord for wind system prediction called ‘RIAM-COMPACT'. Using this cord, we can analyze the wind flow over a complex terrain. This cord is based on Large Eddy Simulation as a turbulence model and can provide a flow simulation of an unsteady and turbulent wind field with high accuracy.