Multi-stable mechanisms for high-efficiency and broadband ocean wave energy harvesting

Here, we show that a nonlinear multi-stable system, composed of a nonlinear restoring mechanism and a linear damper-like generator, can significantly enhance the absorption efficiency of a heaving wave energy converter. This efficiency increase can be as large as few times higher than a wave energy absorber with a classical power take off system composed of a linear spring and a linear generator. Through a quantitative analysis, we also show that a nonlinear multi-stable system broadens the frequency bandwidth of the wave absorber, as well as, the bandwidth of the power take offs damping coefficient. We propose a simple mechanical system that has the required multi-stable response upon which the investigation of this paper is based. Methodology developed and the results obtained here can be readily extended to other types of wave energy converters with one or multi degrees of freedom. (C) 2017 Elsevier Ltd. All rights reserved.