Abstract
Wave energy, as a kind of renewable resources with large density of power, has been widely studied in decades. Different types of wave energy converters (WECs) have been proposed, one of which is oscillating-body WEC. The wave-induced oscillation of the floating body is converted to electricity by the Power-Take-Off (PTO) system. For the linear PTO system, the resonance may not be excited in real wave conditions, and this makes the WEC less efficient. In order to improve the power capture performance, a novel nonlinear PTO system has been proposed using the bistable impulse mechanism. An array of fixed outer magnets are used to repel the inner magnet away from the stable position in order to make the system bistable. The model of oscillating-body WEC with the nonlinear PTO system is tested in a wave flume to simulate the power capture performance in regular wave conditions. The piece number of small magnets in every outer magnet is denoted by parameter λ to describe the magnitude of the magnetism. This testing program pays more attention to λ, and mainly focuses on how λ affects the power capture performance with input of different-frequency regular waves. The results indicate that the novel style nonlinear PTO system can increase the power capture ratio for low-frequency regular waves in comparison with the linear PTO system. And the system can further enhance the power capture in low-frequency regular waves by selecting the proper λ. In other words, the novel style nonlinear PTO system can capture the wave power in a “broadened bandwidth”, which could be advantageous in future applications.