Performance investigation of a hydraulic power take-off system for wave energy conversion

Hydraulic power take-off system is used in wave energy conversion, because its characteristics are well-adapted to larger power and low frequency waves. The hydraulic PTO system is composed of a hydraulic; cylinder, two accumulators, check valves bridge circuits and a hydraulic motor. The numerical models are established based on the power take-off system in irregular waves. The performance of a hydraulic power take-off system for wave energy extraction is investigated under different sea states. The Pierson-Moskowitz Spectra is adopted for irregular waves. The influences of the energy period and the significant wave height on the pressure and flow rate dynamic performance , the power extraction , the motor output power and speed are investigated. Results show that the motor speed and the motor output power increase as the significant wave height increases. The hydraulic system conversion efficiency also increases with the increasing of the significant wave height. The system pressure , the motor output power and the motor speed decrease as the wave energy period increases , while the hydraulic system conversion efficiency slightly increases.