On the efficiency of energy harvesting using vortex-induced vibrations of cables

TL;DR

This paper investigates the efficiency of energy harvesting via vortex-induced vibrations of cables, identifying optimal parameters and comparing configurations to understand how wave types influence energy extraction effectiveness.

Contribution

It introduces a reduced-order wake-oscillator model to analyze and optimize vortex-induced vibration energy harvesting in two cable configurations, providing new insights into efficiency determinants.

Findings

Maximum efficiency close to elastically-mounted rigid cylinder

Standing waves dominate in distributed harvesters

Traveling waves enhance efficiency in hanging cables

Abstract

Many technologies based on fluid-structure interaction mechanisms are being developed to harvest energy from geophysical flows. The velocity of such flows is low, and so is their energy density. Large systems are therefore required to extract a significant amount of energy. The question of the efficiency of energy harvesting using vortex-induced vibrations (VIV) of cables is addressed in this paper, through two reference configurations: (i) a long tensioned cable with periodically-distributed harvesters and (ii) a hanging cable with a single harvester at its upper extremity. After validation against either direct numerical simulations or experiments, an appropriate reduced-order wake- oscillator model is used to perform parametric studies of the impact of the harvesting parameters on the efficiency. For both configurations, an optimal set of parameters is identified and it is shown that the maximum efficiency is close to the value reached with an elastically-mounted rigid cylinder. The variability of the efficiency is studied in light of the fundamental properties of each configuration, i.e. body flexibility and gravity-induced spatial variation of the tension. In the periodically-distributed harvester configuration, it is found that the standing-wave nature of the vibration and structural mode selection play a central role in energy extraction. In contrast, the efficiency of the hanging cable is essentially driven by the occurrence of traveling wave vibrations.