Wave energy absorption by a submerged air bag connected to a rigid float

TL;DR

This paper introduces a novel wave energy device with a submerged air bag connected to a float, demonstrating its static equilibrium properties and power capture potential through experiments and numerical models.

Contribution

It presents a new wave energy device design and analyzes its static and dynamic behavior, including the unique S-shaped pressure-elevation trajectory.

Findings

Laboratory measurements agree with numerical predictions.

The device exhibits three static equilibrium states at different draughts.

Maximum power capture occurs at the middle static equilibrium.

Abstract

A new wave energy device features a submerged ballasted air bag connected at the top to a rigid float. Under wave action, the bag expands and contracts, creating a reciprocating air flow through a turbine between the bag and another volume housed within the float. Laboratory measurements are generally in good agreement with numerical predictions. Both show that the trajectory of possible combinations of pressure and elevation at which the device is in static equilibrium takes the shape of an S. This means that statically the device can have three different draughts, and correspondingly three different bag shapes, for the same pressure. The behaviour in waves depends on where the mean pressure-elevation condition is on the static trajectory. The captured power is highest for a mean condition on the middle section.