Dynamic performance of key components for hydraulic power take‐off of the wave energy converter

Abstract

Since the input power of the real waves varies continuously and periodically, how to stabilise the operation and generation during wave energy utilisation has become an inevitable and significant topic. This study focuses on the wave energy converter of a hydraulic power takeoff (HPTO) connected to a pendulum and studies the influences of the key components, i.e. the high-pressure accumulator, oil tank and flow control valve, on the operational stability of HPTO by simulations and experiments. Parameters of the high-pressure accumulator are analysed and optimised. The dynamic performance of the HPTO with or without the oil tank is also investigated. Besides, the functions of the flow control valve in the cases of excessive input power and load shedding are given. Results show that the key components play very important roles in the operational stability of HPTO. Reasonable configurations of the high-pressure accumulator and oil tank are significant to improve the quality of output power and stability. Appropriate actions of the flow control valve are beneficial to protection and stability. Therefore, these key components should be considered preferentially during the design of HPTO.

Research on Thermodynamic Characteristics of Hydraulic Power Take-Off System in Wave Energy Converter

“…The main functions of the accumulator are to store energy, stabilize pressure, eliminate periodic fluctuations of the system pressure and flow generated when the cylinder is reversing, and enhance the consistency of the system. The overflow valve can avoid the high pressure in the pipeline, and the function of the flow control valve is to control the flow rate and participate in the control of the power; the oil tank is used to compensate for the leakage and short-term negative pressure that may occur in the system and to supplement the oil pressure in time [9,22,23,26].…”

“…However, the performances, e.g., the pressure consistency, the flow rate consistency, and the efficiency of the hydraulic PTO, are sensitive to operating conditions, and the aforementioned performances may significantly deteriorate when the system states deviate from the optimal states. Consequently, we focus on hydraulic PTO in this paper and investigate the influences of several key elements to their performances [9,10].…”

“…In the past few decades, universities and scientific research institutions have carried out a large amount of research work on hydraulic PTO systems, including structural design and system optimization [9]. Stephen Salter proposed a kind of wave energy generation device named the nodding duck [10].…”

“…Cargo et al realized the maximization of the generated power in different wave period situations by optimizing the size of the hydraulic motor [21]. Chen and Jiang verified that the parameter settings of the key components play an important role in the consistent operation of the hydraulic PTO system through simulation and experiments [9]. Yue proposed integrated characteristic curves in constant voltage conditions, which are used to optimize system design and improve the operating efficiency of the PTO system [22].…”

Power capture performance of a heaving wave energy converter for varying brad/bpto ratio

“…In some PTO applications of WEC systems, a hydraulic system is utilized for power capture [26,29,30]. Due to its capacity for generating large force, this type of PTO unit is very much suitable for offshore applications [29,31].The optimum conditions for various PTO applications are also mentioned by Kim et al [32] in order to increase the energy extraction. Also, Falcao [33] utilized a high-pressure hydraulic PTO system for a heaving WEC to optimize hydraulic PTO parameters in time-domain (TD) model.…”