A Seabased wave energy device: An experimental investigation

Abstract

Ocean waves are a largely untapped treasure-house of renewable energy resource, and the potential renewable energy harvested from ocean waves is considerable around the world. Abundant research and development on this field have been conducted to accomplish the aims in different stages, and the technology has been undergoing all the time. However, despite tremendous energy potential, technologies of ocean wave, the wave energy converter (WEC), are still relatively immature compared to other renewable technologies. This thesis presents basic motion character of a WEC device that the performance of one of WECs in relationship between power take off (PTO) part and buoy. The device is a simple 1:50 scaled model which referred to a point absorber buoy device like the device of the Seabased project that the buoy connected with PTO by a wire reacts the water surface to respond excited waves, and drives the PTO with a spring. The tests were conducted in a small water tank. In order to investigate the relationship between buoy performance and PTO part, two different springs were used respectively in PTO, which one spring is stiff and the other one is softer, and model device experienced irregular and regular wave conditions. The softer spring case indicated that the buoy was sensitive to the passing waves but it was hard to provide a restoring force, so the period of one heave motion of buoy was relatively long, which was totally opposed to that of the stiffer spring case. Moreover, the natural frequency of model device was also calculated by mathematical model, and this theoretical value was less than that of experimental value from test. This model device could be improved and perfected and subjected to small scaled water tank tests for offshore device to investigate the basic characters for motion with methods of mathematical model or simulation and experimental results.