Horizontal axis type sail-wing windmills were common in ancient Mediterranean region as the power source for milling and drainage. Typical shape of their wings was triangle characterized by light weight and simple structure. The lightness of the wings contributed to reduce the centrifugal force which damages the blades, and the simplified structure made their construction and repair easy. Due to these merits this type of windmill can be an ideal power source even in present developing countries from a standpoint of appropriate technology.
These years, many micro-scale wind turbines are installed as independent power sources for street lights, signs, or just as monuments in urban areas. Among such trends, sail-wing windmills are revaluated in the modem society because of their safety, reduced noise and attractive appearance.
One of the authors had conducted a study on a triangle type of sail-wing windmill, however, there is no systematic study on various sail-wing shapes until now.
Therefore, in the present study, the authors classified the sail-wings into three types and evaluated their aerodynamic performance to find the optimal shape and configuration experimentally in wind tunnel. The results show that the inversely tapered sail-wing has the maximum power coefficient and over speed governing characteristics.
