Low-head hydropower extraction based on torsional galloping

Abstract

The work introduces a new concept of hydropower extraction. The proposed idea is to convert the hydrokinetic energy from an incoming flow to mechanical energy by inducing torsional galloping. The capability of this original device to extract energy is verified through experimental tests. The basic part of the device consists of a rectangular flat plate located vertically in the water current, with an elastic axis in its mid-chord length. The elasticity is provided via a torsion spring. According to the observations in the laboratory, as the current speed exceeds a critical velocity, the system becomes unstable, and as a result the flat plate oscillates torsionally about the elastic axis. The self-sustained torsional oscillation is an instability type flow-induced oscillation and is called torsional galloping. Subsequently a transmission system is added to the turbine to convert the torsional oscillation of the flat plate to a rotation. The rotary motion is applied to lift a weight up to a prescribed height. Each weight is lifted up several times to obtain the repeatability. Through the tests done on the device, its feasibility of hydropower extraction is proved. The simplicity of the construction and its capability for low-head water current energy extraction are the main advantages of the system making it a possible solution for low-head hydropower applications.