A new pumped-hydro energy storage concept driven by vortex-induced vibrations for sustainable energy applications

This study introduces a novel combined Vortex-Induced Vibrations (VIV) energy conversion and pumped hydro system for electricity generation and energy storage. Unlike traditional VIV energy converters, the proposed novel VIV cylinders work as pumps, elevating water to increase potential energy instead of integrating directly with a generator. As flow reaches the VIV cylinders, vortex shedding occurs, causing the cylinders to move upward and downward. This motion drives tandem pumps attached to either side of the cylinder, propelling water to a higher elevation. Experimental results are obtained from a pump-free, laboratory-scale VIV prototype tested at the ITU Laboratory of Marine Energy Research, focusing on the oscillatory response of the system. Following promising experimental results, the prototype is scaled up by a factor of 10. This study provides a conceptual design and implementation framework, presenting a proof-of-concept evaluation rather than a fully realized system. The scaled-up system includes a 100-cylinder array, each 0.8 m in diameter and 14.23 m in length, which acts as a pump to elevate the current to a reservoir located 30 m above the cylinders. Working depth of the cylinders is considered as 5 m below the free surface water level. The novel-designed VIV cylinders channel the flow through the piping system to the reservoir, which has a capacity of 170,000 m³, ensuring stable and continuous electricity production. It provides over 8 h of constant production of 1.3 MW electricity during the discharge period, aiming to solve problems related to intermittency and production flexibility in the VIV energy conversion system. The system's production capacity is 1.3 MW, with an energy efficiency of 7.6 % under 2.1 m/s water flow. Additionally, a parametric study evaluates the system performance under varying design and operational conditions. Theoretical results from the scaled-up VIV Farm system demonstrate a peak energy capture efficiency of 25.04 % at a flow speed of 1.74 m/s, with an overall system efficiency of 11.03 %. This study shows promising potential for electricity production even with relatively slow water currents below 2 m/s.