Wave energy conversion by multi-mode exciting wave energy converters arrayed around a floating platform

An array of compact, portable and stable Wave Energy Converters (WECs) integrated with an offshore floating platform can reduce the platform's motion response to waves, and extract wave energy simultaneously through multiple Power Take-Off (PTO) units. This paper proposes an innovative hybrid system composed of a cylindrical free-floating platform and four point-absorber type WECs hinged at the external structure of the cylindrical platform. The relative motions between a WEC and the platform drive a PTO-system, and thus desirable wave energy conversion is achieved from combining multiple WECs with multi-mode motions constructively. To confirm feasibility and hydrodynamics performance of the proposed concept, multi-body computational models for different scenarios are developed. The wave focusing toward WECs are realized by the array reflection, while the presence of near-trapping waves amplifies energy dissipation. The seaward and leeward WECs are more sensitive on the array interval than those lateral WECs. Additionally, shallower and deeper submergences are preferred for WECs, respectively, resulting into multi-body resonances across a broadband wave period. For the discrete PTO system, different optimized damping coefficients are recommended to guarantee the high energy absorption regardless of wave periods. The present WEC-platform system can harvest wave energy in an omnidirectional manner.