A New Nonlinear Compliant Mechanism for Harvesting Energy from Ocean Waves

Traditonal linear oscillators, such as cantilevers or pendulums, are only sensitive to specific resonant frequencies. They have then very narrow frequency bandwidths when harvesting energy from ocean waves. In order to enhance the dynamic performance of the wave energy converters (WECs), used to expand the autonomy of Lagrangian Drifters, a statically balanced compliant mechanism (SBCM) is investingated. It is based on finite element analysis (FEA) simulaitons. The design of the SBCM is introduced and its static force-displacement curve is obtained in FEA. The dynamic response of the SBCM to harmonic base excitiaons at low frequencies and low accelerations is investigated based on time-domian FEA simulations. The close agreement between simulations, numerial and analytical results verifies that the SBCM is sensitive to ultra-low frequencies with weak accelerations in a wide frequency range. The applicability of the SBCM in WECs is demonstrated by adding PVDF films in the FEA model. In the time-domian simulation, the SBCM-based WEC is excited by the drifter motion pattern obtained from Orcaflex and corresponding to two typical ocean waves (i.e. synthesized Airy and Jonswap models). Relative displacement between the base and mass and the electric outputs are obtained. According to this work, the SBCM provides a structural solution for WECs with enhanced energy harvesting performance.