Mass-modulation schemes for a class of wave energy converters: Experiments, models, and efficacy

• We examine a method to improve the energy harvesting of a wave energy converter.
• The method features mass modulation of the buoy-type wave energy converter.
• The efficacy of the modulation is examined using experiments and numerical models.
• It is demonstrated that mass modulation can improve energy harvesting.

In a recent series of works, mass-modulation schemes have been proposed for a class of ocean wave energy converter (WEC). The goal of the schemes is to improve the energy harvesting capabilities of these devices by taking advantage of the ambient water. However this improvement comes at the cost of increased system complexity and possible impulse loadings at the instances where the mass changes. In the present work, experimental results for a pair of these schemes are presented and one of them is shown to be effective in increasing the energy harvesting potential of a WEC. Building and testing prototype WECs are costly and challenging and so, in order to examine as wide a range of parameters and designs as possible, a detailed two degree-of-freedom model is developed for a WEC equipped with a mass-modulation scheme. Numerical analysis of the model also shows the potential benefits of the mass-modulation scheme.