Numerical developments on the E-Motions wave energy converter: Hull design, power take-off tuning and mooring system configuration

Abstract

This paper addresses a recently conducted numerical study on the E-Motions wave energy converter, aimed at improving its energy performance and efficiency. The Potential Flow Theory-based ANSYS® Aqwa™ software was used, being a robust industry-standard code that has been successfully applied to the E-Motions case study, in the past. Data from a preceding physical modelling campaign was applied towards calibration procedures for three platform variants – half-cylinder, half-sphere and trapezoidal prism, with and without the power take-off and subjected to regular waves. A non-dimensional root mean square error minimization approach was employed. Afterwards, the focus shifted towards defining and comparing the performance of sixteen E-Motions sub-variants, which included a new hull shape: enclosed frustum. Two additional stages were carried out: one oriented towards assessing ten power take-off mass-damping combinations and another to the study of four mooring system configurations. Results point towards a very significant hydrodynamic response, particularly within the resonance range and for the half-cylinder and half-sphere sub-variants, and maximum average power outputs of nearly 40 kW. For the best half-cylinder, half-sphere, trapezoidal prism and enclosed frustum sub-variants, the annual energy production estimates, per device, were 141, 110, 106 and 91 MWh/yr, respectively.