The present scenario of electrical power generation is towards wind and solar power to reduce the global warming which has adverse effects on environment, health, loss of property and lives. Even though there is a lot of wind potential all over the world, the present wind turbines are not preferable for heavy wind zone areas. Self-oriented flap turbine (SOFT) can provide solution in wind power generation even at heavy wind zone areas.
SOFT is a vertical axis wind turbine with flat or curved wings. The rotor consisting at least three equally spaced apart wings mounted on the support structure defining and rotatable about a main vertical axis. Each wing consists single or multiple wind reacting elements called flap (airfoil or non-airfoil) pivotally connected to the wing arms. The wind reacts with the flaps to rotate the shaft. The shaft is coupled to drive the electrical generator or any mechanical load. The flaps are provided with stopper (electromagnetic plunger) arrangement to select/deselect the flaps to increase or decrease the shaft torque or to completely shut down the turbine according to wind speed.
The complete rotation of wing with respect to wind direction is divided into two zones namely, active zone and idle zone. From 0 -180° wing sweep area with reference to the wind direction axis, the wing rotates along the wind producing torque due to wind reaction is called active zone. Due to the reaction of wind on flap produces drag force on wing during its passage in active zone, pushes along the direction of wind, causing the rotor to rotate about its main vertical axis. The drag force exerted on the wing depends on the angle of attack on flap which is the angel between the horizontal wing axis and wind direction axis. Hence at 90° of wing position maximum drag force is exerted, where each flap offers maximum area to react with wind. From 180-360° wing sweep area with reference to the wind direction axis is called idle zone. As the wing passes in idle zone, all its flaps initially move away from stopper and tends to dynamically align with wind direction offering lowest area to move into the wind with negligible reaction on it. Thus the net torque is the resultant of the drag component of the wings that are moving along the wind and wings moving into the wind.
Even though SOFT is mainly focused on wind power generation, it can be used as under water turbine to extract power from free flowing water current.
The SOFT can be easily designed since no complicated aerodynamic shaping is involved compared to conventional wind turbines. The flaps can be made by light weight carbon composite material or with durable cloth reinforced with rigid frame thus reducing the overall weight and economical to manufacture. Lesser the weight of turbine means it can yield the power even at low cut in speeds. Thus the SOFT can be generating power at wide range of wind speeds.