The Flap Turbine (FT) is a novel type of vertical axis turbine (VAT) where the blades are made of movable flaps. These movable flaps, when combined together, act as a sail or blade for the VAT. This type of turbine is also known as a check valve turbine because of the check valve like behavior of the moving flaps. When the sail is moving in the downwind direction, the flaps are closed and will not allow air (water if the turbine operates in the water) to pass through the sail. However, when the sail is moving in the upwind direction the flaps will be in the open position and allow air (or water) pass through the sail.

More www.flapturbine.com