Unidirectional Windmill can be used even in low-wind areas to operate shallow water pumps. It can operate at wind speeds of 6-7Km/hr. The windmill construction is based on the principle of helical blade (Theory of Screw Propeller). There are two continuous helical blades on either side of the axle running from one end to the other. The windmill can be considered as a Screw Propeller working in the reverse mode, so as to absorb energy from the mill. Each helical blade consists of four 3mm thick fiber reinforced plastic plate of trapezoidal shape. The outer diameter of the rotor is 3m and diameter of the hollow annular space is 1.1m. The horizontal length of the rotor is 1.75m and the height of the tower is 5m. Two frames with their boxes 3m apart and the tops at 1.87m are fixed in position to accept the rotor shaft (axle). Water drawing, at wind speed of 10km/hr, is 900-1000 liter/hr for a total head of 15m. The windmill can be easily fabricated without sophisticated techniques. The windmill should be built over a well in an open area and in the path of the prevailing well. For best results locate the well where water is not more than 7.5m below the ground surface. Beyond 7.5m, a deep well pump cylinder will be needed and water output will be reduced. Even a hand pump can be adopted to draw water from a depth up to 12m.
Picture of Wndmill