Heave Plate Dynamics for a Point Absorbing Wave Energy Converter

Wave energy converters (WECs) often include a submerged heave reaction plate located at a depth where the surrounding water is minimally disturbed by the passing surface waves. Heave plates provide a relatively stationary and artificially massive body to which WECs transfer the reactionary forces generated as their power-takeoffs (PTOs) resist the motion induced by the incoming waves. To date little research has focused on the dynamics of heave plates in the context of wave energy. This paper provides a review of relevant literature, much of which focuses on heave plates used to reduce the heave response of SPAR type oil and natural gas platforms. A numerical analysis of the dynamics of symmetric and asymmetric heave plates is also presented. The time-domain solver TD xxx was used to simulate the WEC and heave plate dynamics in both sinusoidal and spectral seas. The phase relation of the heave plate’s motion relative to that of the surface float provides incite into the importance of added mass in determining system dynamics. The effects on system loading that result from heave plate vertical asymmetry are also considered.