Design and analysis of a deployable suspended wave energy converter with harmonic response under low-frequency excitation

The wide application and deployment of small-scale floats such as ocean buoys and lifeboats face major challenges due to energy limitations, and the common wave energy converters (WECs) are difficult to extract energy at low wave frequency. To address this problem, this paper proposes a novel Deployable Suspended Wave Energy Converter (DS-WEC). The power supply device of the DS-WEC is suspended beneath the platform using cables, and the device can expand from a folded form suitable for storage and transport into the heave plate form suitable for power generation. The DS-WEC features a unique nonlinear pendulum structure that consists of a Simple and Spring-Damping pendulum series (SSD pendulum), enabling ultraharmonic response under low-frequency excitation and significantly enhancing the energy capture performance. To further analyze the response characteristics and energy capture performance of the DS-WEC, a time-domain hydrodynamic model is established, which is validated via the Wave Energy Converter SIMulator (WEC-Sim). Through systematical analysis of some structural parameters, the spectral characteristics of the DS-WEC response are investigated, and their influence on the primary resonance, harmonic response, and power generation performance of the system are revealed. Under an irregular wave condition, the DS-WEC system achieved a power output of 19.40 W, which is a 31.17 % increase compared to traditional 2DoF heaving WEC system. The results fully demonstrate its significant advantages in ease of deployment and low-frequency energy capture.