Experimental study of a wave energy scavenging system onboard autonomous surface vessels (ASVs)

Abstract

Autonomous Surface Vehicles (ASV) have many potential applications in the maritime industry and ocean science. To subsist in the ocean space, an ASV must have the ability to scavenge energy from the surrounding environment. Waves are an abundant source of energy on the ocean surface and a suitable resource for an ASV to scavenge. Flapping foils have been shown to generate thrust in a wavy flow and power in a uniform flow. The aim of this experimental study is to investigate the relationship between flapping foil propulsion and power generation in the context of ASVs. Initial experiments incorporating fully passive flapping foils submerged at the bow and stern of a surface vessel in head waves were performed in a towing tank. The spring-loaded foils were located at the end of rigid pivot arms protruding at the bow and abaft of the vessel. The pivot arms were free to rotate about a location beneath the keel line and restrained by adjustable rotational dampers. In this free condition, wave energy is recovered in the form of work applied by the flapping foils through the rotary dampers which were used to simulate the damping effects of a power take-off device. Thrust was generated under conditions when the pivot arm was fixed. This system, referred to as the Flapping Energy Utilization and Recovery (FLEUR) system, could serve as a dualpurpose wave energy scavenging propulsor and power generator for long-endurance ASVs.