New Establishment of the Wave Energy Conversion System in the Ocean with Consideration to Environment and Economical Efficiency

点击翻译按钮获取中文摘要

A wave energy conversion system of Oscillating Water Column (OWC) type is composed of a turbine-generator and an air chamber which changes up-and-down motion of a wave into oscillating airflow. A Wells turbine is the most commonly used air turbine for wave energy conversion systems. This study tries to analyze the mechanism of these three-dimensional flows around the turbine with the flow visualization and the numerical analysis. The important characteristics of the turbine are theoretically derived by the potential theory of cascade. Guide vanes are installed in the Wells turbine in order to improve its efficiency, self-rotating characteristics. This work attempts to explain the role of these guide vanes on the basis of momentum theory. The two dimensional numerical method for analyzing a floating device with an OWC is introduced. The method derives the particular solution that satisfies the boundary condition on the water free surface in the air chamber and on the bottom of the floating device. The optimal profiles are eliminated according to the different conditions from the high efficiency, i.e. the minimum size per a unit power and so on. That the similarity law is considered, when such wave energy conversion system is designed, is very important. It is not important only the exact similarity law, but also the approximate similarity law owing to practical use, and these are described in this paper. In the design, the size of the floating device and the turbine is made small under the same output, securing starting performance. Verification is performed by comparing the technique of a comprehensive simulation with the result of a real sea trial. As mentioned above, in this research, each element characteristic was clarified in the process of the conversion of wave energy into electrical energy through experiments and theoretical analysis, and the design method was established.