Abstract
In recent years, research on wave energy development and utilization has been a hot topic, and many scholars have intensively researched raft-type energy conversion devices. This paper considers an elliptical and cylindrical raft wave energy conversion device from the perspective of stability and bionics to determine the structural parameters that correspond to optimal energy conversion in a three-level sea state. This paper studies the theoretical wave energy capture efficiency of cylindrical floats by drawing an analogy from the theoretical model. In addition, this paper determines the float structural parameters corresponding to the optimum capture efficiency by formulating numerical simulations and optimizing the parameters, such as the axis ratio of the cross-section, the spacing, the draught, the number of floats, the length of the float, the height of float's center of gravity, and others. In the optimization process, these six parameters were briefly analyzed in reference to the design of the Pelamis. The length of the float and the axial ratio of the cross-section are the main factors affecting the capture efficiency of the device. Therefore, the optimization sequence of the six parameters was determined by first controlling the main factors and then controlling the other factors. Then, the values of all the parameters were determined. The structural parameters of the float were observed to significantly influence the energy capturing effect of the device, and its efficiency was increased by intelligently selecting the structural parameters. Finally, the structural parameters of the elliptical and cylindrical raft wave energy conversion device were determined by comparing the capture efficiency under five typical wave conditions (WT.1 to WT.5) in a three-level sea state.
Highlights
Example, the Pelamis wave energy conversion device from Pelamis Wave Power, UK, has been put into commercial use on a large scale
This paper considers an elliptical and cylindrical raft wave energy conversion device from the perspective of stability and bionics to determine the structural parameters that correspond to optimal energy conversion in a three-level sea state
This paper determines the float structural parameters corresponding to the optimum capture efficiency by formulating numerical simulations and optimizing the parameters, such as the axis ratio of the cross-section, the spacing, the draught, the number of floats, the length of the float, the height of float’s center of gravity, and others
Summary
In 1978, Haren[9] carried out a study on hydrodynamics based on the theory of linear shallow long wave potential flow He considered the incident wave, depth of the sea, and economic efficiency to first find a numerical solution to the single and unconstrained floating body hinged on a rigid wall and adjusted the related parameters to derive the general performance of multiple floating hinges. In the study of the raft capturing device structure, the new elliptical cylindrical float form will show greater advantages in stability, but to date, only Zheng[26] has studied this type of float shape He mainly studied the two-dimensional hydrodynamic theory and has not optimized the float shape or geometry.
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