All wave energy converters (WECs) must resist the motion of the incident wave. The reaction forces developed by the power take-off (PTO) of the WEC are either transferred outside the system or to the inertia of the WEC. If the reaction forces are transferred to the inertia of the WEC, the WEC must be massive, and thus expensive. System mass and cost can be reduced through the use of a heave plate. Heave plates are large plates or structures attached to or suspended well below the WEC in water at a depth where the motion of the waves passing over the water’s surface has been substantially attenuated. At this depth, the heave plate can transfer the reaction loads developed by the WEC to the inertia of the water.
Despite their importance to and prevalence in WEC design [1, 2], heave plate dynamics have received little attention in the literature. Parametric studies are needed to understand the effect of variations in design on heave plate performance, and tests at varying scale will be needed to determine how the hydrodynamic performance of a heave plate scales with size.
The hydrodynamic behavior of heave plates is studied in two experiments. First, a custom measurement platform has been built and used to calculate coefficients of drag and added mass for 12-in diameter heave plates forced through sinusoidal oscillations of varying amplitude and frequency. Several heave plate variations were tested, and the results are briefly discussed. Second, the miniWEC, a small wave energy converter is being built and instrumented to study the performance of 60- in diameter heave plates. The results of the forced oscillations in the first experiment were used to inform the design of the heave plates that will be deployed with the miniWEC. These experiments will provide insight into how the hydrodynamic behavior of heave plates scales with heave plate size.