Bistable energy-harvesting track nonlinear energy sink in offshore wind turbines

Energy harvesting is particularly attractive for offshore structures owing to power supply challenges in offshore regions. Offshore structures simultaneously experience substantial vibrations from combined wind-wave loads, thus necessitating structural vibration control. This study investigates the feasibility of a bistable energy-harvesting track nonlinear energy sink (EHTNES) designed for offshore wind turbines (OWTs) to concurrently control vibrations and harvest energy (i.e., a dual-function device). The EHTNES consists of an electromagnetic damper (EMD), a buck-boost energy harvesting circuit (EHC), and a bistable track nonlinear energy sink. The optimal design of the EHTNES is theoretically presented, and the energy-harvesting damping unit (i.e., EMD plus EHC) is validated through the circuit and cyclic tests with the EHC working as an equivalent constant energy-harvesting resistor. Subsequently, the EHTNES is applied to an OWT, and its performances are evaluated under combined wind-wave loads and compared to an energy-harvesting tuned mass damper (EHTMD). Results show that (1) The damping unit simultaneously provides a controllable damping effect and an energy harvesting function; (2) The EHTNES effectively mitigates OWT responses and harvests considerable power into the battery; (3) Compared with the EHTMD, the control effectiveness of the EHTNES experiences a slight degradation but demonstrates superior control robustness and better stable output power when considering stiffness and damping detuning. This study underscores the practicability of the EHTNES for vibration control and energy harvesting in OWTs, thus offering insights into the development of dual-function devices for offshore structures.