Numerical Simulation of Oscillating Water Column Wave Energy Converters

• Main Authors: Yang, Chung-Ying, 楊宗穎
• Other Authors: Lin, Chen-Chou
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/14747013454604375072

碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 103 === The thesis aims to study oscillating water column (OWC) wave energy converters (WEC) that are suitable for the northeast coast of Taiwan, and to simulate the OWC WEC model referring to the Limpet of Scotland by using computational fluid dynamics software ANSYS Fluent. There are three main topics to be studied: 1. to discuss the effect of chamber’s geometry to the conversion efficiency of the OWC WEC, specifically the inclined angle of the back wall; 2. to investigate the influence of the air duct size to the conversion efficiency without turbine installed; 3. to calculate the capture efficiencies of the Wells turbine by applying the preferred model size which is resulted from the above two investigations. From the previous literature, the relative geometric relation between chamber’s front and back walls has significant influence to the wave energy conversion efficiency. The simulation conditions are by fixing the air duct size and changing the inclined angles of the back wall, then to calculate the sum of kinetic energy, potential energy and pressure power, and used it as the criterion of the wave energy conversion efficiency. The air duct size is regarded closely related to Wells turbine’s capture efficiency. Hence, in order to compare the capture efficiency with different air duct sizes, the sum of kinetic energy and pressure power of different cases are calculated and compared as the criterion of capture efficiency. Finally, by using the preferred chamber geometry and the duct size combination based on the previous results, the overall power and capture efficiency are calculated with Wells turbine added. According to the simulation results, the chamber with 90-degree inclined angle of the back wall has the largest wave energy conversion efficiency, but it also has the largest energy loss. A comprehensive study shows that, the size of OWC has the preferred wave energy conversion efficiency with 60-degree back wall inclined angle and 65(mm) of the air duct radius. A simulation is performed to the above preferred geometry with Wells turbine installed. Under the wave conditions of wave height H= 0.07 (m), wave period T= 1.56 seconds, the result shows that the overall power of the OWC WEC is 0.1566 (W), the wave energy conversion efficiency 13.9%, and the Wells turbine’s capture efficiency 55.37%.