Abstract
In this paper, we introduced an intermittent wave energy generator (IWEG) system with hydraulic power take-off (PTO) including accumulator storage parts. To convert unsteady wave energy into intermittent but stable electrical output power, theoretical models, including wave energy capture, hydraulic energy storage, and torque balance between hydraulic motor and electrical generator, have been developed. Then, the integrated IWEG simulator was constructed and tested at the Ningbo Institute of Technology. Through a series of experimental tests, the relationship between operating flow rates and pressure drops across the hydraulic motor was established. Furthermore, on the basis of the pressure drop signal, we proposed a feedback control method on the basis of the pressure drop database as the feedback control signal to eliminate the disturbance of periodic peak pressure impulse through the regulation of the opening ratio of a proportional flow valve and achieved the effective and stable electric power output, albeit intermittently. Compared with the previous complex control theories and algorithms, this method can keep the power output more stable over a wide range of operating conditions. Furthermore, experimental tests indicate that the IWEG system, with hydraulic PTO, including hydraulic accumulator and proportional flow control valve, is simple, reliable, and easy to control. Most importantly, the real-time power output is stable, and power quality and generation efficiency are significantly improved.
Highlights
In recent years, sustainable energy generation has become increasingly important because of the current limitations of the conventional energy resources and the drive to reduce pollution [1]
We presented an intermittent wave energy generator (IWEG) system with hydraulic power take-off (PTO), including accumulator storage parts
A relationship between operating flow rates and pressure drops across the hydraulic motor was established through experimental tests
Summary
Sustainable energy generation has become increasingly important because of the current limitations of the conventional energy resources and the drive to reduce pollution [1]. Stable and smooth power output becomes very difficult, because wave energy is intermittent and the excitation amplitude is oscillating and variable This results in an unstable WEC system, especially a single floating buoy [11]. The electrical power from a single point absorber WEC cannot last for a long time because of intermittent wave energy supply, but we can keep output power on stable in several minutes or even hours [15], which is the main reason for the design of intermittent wave energy generator (IWEG) system presented in this paper. If the pressure and flow rate of the hydraulic oil can be regulated by the valve is open to a certain degree in a controllable way, energy input from oscillating waves with variable amplitudes will still be able to produce the stable and good quality power output. The control signal based on a motor pressure drop database was experimentally obtained from the IWEG system
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