Analysis of a Floating Wave Energy Converter With Hydraulic-Mechanical Power Take-Off Using WEC-Sim and SIMSCAPE

Abstract

Abstract A novel multibody ‘self-reacting’ floating wave energy converter, which constitutes a set of ‘bean’ shape tubular floats which pitch relative to the central spar (CS) resulting in net heave, is introduced in the present study abbreviated as BFWEC. The frequency-domain modeling is performed assuming potential wave theory (PWT) to obtain the fundamental building blocks viz., hydrodynamic parameters of BFWEC. The unique configuration of BFWEC with a set of four floats around CS projects it to be a novel attribute. The relative motion between CS and floats is enabled using a connecting frame and the hinge joint to each bean float. Time-domain wave-WEC interactions, along with free-decay tests, are modeled and conducted using a highly established and reliable open source MATLAB-Simulink module called WEC-Sim (Wave Energy Converter SIMulator). The CS of six degrees BFWEC with a dominant heave degree is first restricted to be fixed and later enabled to three and six degrees of freedom (D-o-F) to understand the influence of its compliance. The device is restrained and kept in position by fastening four tethers (taut mooring) to the CS by coupling it to a lumped mass stand-alone mooring line feature known as MoorDyn. A hydraulic-mechanical Power take-off (PTO) unit is coupled with BFWEC in SIMSCAPE to understand its overall performance characteristics, which is later compared with linear damping virtual PTO. The performance ratio of the device is then obtained under 0° and 45° regular waves. The critical outcome of the research is to establish a robust green channel by promoting wave energy extraction in the sea states of the Indian sub-continent with a unique and suitable design.