Wave energy conversion using coupled balloons: A numerical investigation

Abstract

Most wave energy converters (WECs) feature rigid structures, while flexible WECs have received less attention. This study investigates a novel WEC comprising two balloons coupled through an air duct, designed as a simple and low-cost solution for harnessing wave energy. The performance of the coupled balloon wave energy converter (CBWEC) is assessed through numerical modelling, using the radiation/diffraction software HydroStar. The balloons are idealised as spheres with uniform deformation. A comprehensive parametric study evaluates the device’s performance with varying spacing, submergence, power take-off damping, and additional stiffness. Although the CBWEC was initially conceived as fully submerged, results indicate that without additional negative stiffness, its natural period is too low to resonate with ocean waves. Hence, in the absence of negative stiffness, a floating configuration offers the highest potential power, defined as the area under the power function. Hypothetically introducing negative stiffness significantly improves performance, producing five times more power than the best configuration without it. With appropriate negative stiffness, the submergence of the balloons becomes less critical. These findings will guide upcoming physical experiments to validate the proposed device. While achieving negative stiffness may be challenging in practice, the CBWEC demonstrates reasonable performance even without it, highlighting its potential as a promising WEC.