Cable-driven power take-off for WEC-glider: Modeling, simulation, experimental study, and application

In wave energy conversion systems, the Power Take-Off (PTO) is the core component that converts wave motion into electrical energy. This paper focuses on a cable-driven PTO device that utilizes a ball screw directly connected to the generator and is restored by a tension spring. The study involves dynamic modeling, simulations, and experimental research on the device. Under bench test with sinusoidal excitation, the PTO efficiency increases with oscillation frequency and increases then decreases with external resistance. As the cable can only withstand tension, slackening occurs when the external electrical load of the PTO is too large, or when the oscillation frequency of the excitation is too high, leading to a decrease in the power generation. The condition of cable slackness is presented in the study. The maximum PTO efficiency achieved during bench test is 66%. Tank experiments are conducted on the PTO connecting an underwater glider, which achieves an PTO efficiency of 65%. The total energy efficiency of the PTO-connected underwater glider system is 43.7%, higher than the 26.4% efficiency of traditional underwater gliders. The experimental results demonstrate that wave glider powered by pure wave energy can be developed for applications in high latitudes.