A Fully Enclosed Wave Energy Converter and Effects of Cable-Based Power Take-Off System on Power Absorption

Abstract Existing wave energy converters (WECs) are limited by high unit energy costs, narrow bandwidths, and vulnerability to seawater corrosion, making it difficult for wave energy to compete with solar and wind energy. This paper presents a fully enclosed WEC based on cable-driven parallel mechanisms, which absorbs energy from multiple directions to enhance the total energy absorption efficiency and bandwidth. The configuration of the inner cable-parallel mechanism (CDPM) is the key to this improved absorption efficiency. A configuration synthesis method of cable-driven parallel mechanisms is proposed to generate more configurations for the fully enclosed WEC. The motion equation of the fully enclosed WEC is derived to evaluate the power absorption performance. Moreover, a configuration synthesis method for realizing n-degrees-of-freedom (DOF) configurations in the fully-constrained CDPMs is proposed, and the configurations of these nDOF fully-constrained CDPMs with (n + 1) cables are acquired. Then, the power absorption performance under different power take-off system parameters and wave frequencies is calculated, and the effects of the CDPM configuration are investigated. The results indicate that the proposed WECs exhibit excellent performance in mean absorbed power and bandwidth. Several principles for configuration selection are provided to further improve the performance of the CDPM-based fully enclosed WEC.