The Use of Hydroelastic Structures in Wave Energy Converters

The Wavepiston modular energy collector is a string of vertical ‘sails’, each comprising several vertical ‘paddles’, that respond primarily in surge to incident wave excitation. In an early device development stage, the sails were designed to allow spacing between the vertical paddles to minimise hydrodynamic forces, in extreme conditions, to improve survivability. However, the benefit for survivability was at the cost of energy absorption performance as a result of a substantial decrease in the sail excitation force. Therefore, flexible paddles, which can deform in response to large surge wave loads, are considered a feasible design strategy to minimise the energy-capture–survivability trade-off. An experimental wave tank test campaign was undertaken to investigate the response of paddle materials, with different paddle flexibility and overlaps, to wave-induced and forced motion excitation. This paper explores how different configurations of these hydroelastic structures affect the wave-induced load experienced by a fixed sail and the wave energy absorption potential of the sail. Two metrics are proposed to assess how different paddle overlaps and material properties affect device performance and survivability at particular deployment locations. The sail response is characterised and depicted through these metrics for increasing excitation amplitudes to provide initial insights into how the sail configuration design choices and materials impact the device capacity factor.