Simulation study of bi-stable sea wave energy harvesters with electrostatic power take-off

Wave energy converters (WECs) typically rely on the dynamics of a floater to capture mechanical energy from the sea. Most WEC designs leverage a resonant behaviour, which is achieved by tuning the device’s natural frequency with the typical wave incident frequency. This approach, however, faces challenges in real-world conditions because of the high variability and low-bandwidth distribution of the wave frequencies. Even though bi-stable mechanisms have been proposed to enable broadband energy harvesting in WECs, earlier studies often disregard realistic sea states. Moreover, since traditional electromagnetic or hydraulic power take-off (PTO) systems struggle to perform in low frequency and irregular forcing conditions, electrostatic PTO (ES-PTO) systems have been proposed as a promising alternative as they excel at low working frequencies and require fewer mechanical components. This paper presents a simulation study of the dynamics and performance limits of WECs with ES-PTO. Extensive numerical simulations are conducted to evaluate long-term power generation, by comparing the performance of a mono-stable and a bi-stable heaving point absorber (HPA). Results show that bi-stable harvesters can improve energy capture by up to 20% compared to optimally tuned mono-stable ones, particularly in locations with broad wave period distributions. These findings highlight the potential of bi-stable ES-PTO systems in realistic WEC applications.