Wind Energy Harvesting from Wind-Induced Vibration

Abstract

Wind power is a clean energy source and alternative to the non-renewable type of energy sources. One of the challenges in utilizing wind energy is to efficiently harvest the wind energy into a usable electrical power, especially in the regions with low wind speed. This study aims to assess the possibility of harvesting wind energy by using the concept of flow induced vibration of a bluff body. A thin flat plate is introduced downstream of the cylinder as a simple but effective passive wind control. Three conditions have been tested to evaluate its effects on wind energy harvesting: isolated cylinder, flat plate with vibrating cylinder and cylinder with vibrating flat plate. The wind-body interaction is simulated using mesh motion technique available in OpenFOAM, an open source code for Computational Fluid Dynamics, while the harvested energy is calculated based on the work done by the single degree of freedom (SDOF) vibrating body. The study found that the vibrating cylinder with flat plate harvests more energy than the isolated cylinder and the fixed cylinder with vibrating flat plate for a relatively wider range of wind speeds. This is due to the generated transverse force on the cylinder is higher than the transverse force generated on the flat plate. The highest energy produced by the vibrating cylinder with a flat plate is P_gen = 86.97 mW at reduced velocity, U_R = 11, which is 4 times larger than for isolated cylinder with P_gen = 24.50 mW at U_R = 20. For the case of a cylinder with vibrating flat plate, the energy produced is very small with P_gen = 0.6972 mW at U_R = 10. The energy produced by the vibrating body is closely related not only to the wind velocity and vibration amplitude but also highly dependent on the rate at which the vibration occurs (frequency) and the phase difference between vibration and the generated force on the body. In the present study, the vibrating cylinder with flat plate appears to be the best configuration to harvest wind energy compared to the other configurations at reduced velocity U_R = (9-11).