In order to improve the operating efficiency of hydraulic wave energy converters (WECs)
this paper proposes a multistage energy storage hydraulic PTO system
which achieves multistage energy storage through accumulators and energy storage flywheels. A hydraulic PTO simulation model is established in AMESim to study the impact of energy storage components on system response and analyze the power generation process under different sea conditions. Meanwhile
a scaled hydraulic PTO prototype with a rated power of 100 W is built for performance testing. The study shows that
under medium and low sea conditions
the average conversion efficiency from hydraulic energy to electrical energy reaches 89%
which is 6% higher than the system without the multistage energy storage technology. Under high sea conditions
when energy overflow is triggered
the system can still achieve the 5 kW rated power generation target. The scaled-down prototype's power generation efficiency can reach 45.6%
which is close to the rated 100 W power generation requirement. The simulation and testing methods used in this study can also be extended to other wave energy converter hydraulic PTO systems
providing a basis for parameter optimization and performance improvement of wave energy devices under different sea conditions.
LIANG C W, AI J X, ZUO L.Design, fabrication, simulation and testing of an ocean wave energy converter with mechanical motion rectifier[J]. Ocean engineering, 2017, 136: 190-200.
MARTIN D, LI X F, CHEN C A, et al.Numerical analysis and wave tank validation on the optimal design of a two-body wave energy converter[J]. Renewable energy, 2020, 145: 632-641.
CURTO D, FRANZITTA V, GUERCIO A.Sea wave energy. a review of the current technologies and perspectives[J]. Energies, 2021, 14(20): 6604.
IMAI Y, NAGATA S, MURAKAMI T, et al.Design of a hydraulic power take-off test rig for wave energy converters[C]//2016 Techno-Ocean (Techno-Ocean). Kobe, Japan, 2016: 515-518.
PRUDELL J, STODDARD M, AMON E, et al.A permanent-magnet tubular linear generator for ocean wave energy conversion[J]. IEEE transactions on industry applications, 2010, 46(6): 2392-2400.
ZHANG D H, LI W, YING Y, et al.Wave energy converter of inverse pendulum with double action power take off[J]. Proceedings of the institution of mechanical engineers, part C: journal of mechanical engineering science, 2013, 227(11): 2416-2427.
YEMM R, PIZER D, RETZLER C, et al.Pelamis: experience from concept to connection[J]. Philosophical transactions series A, mathematical, physical, and engineering sciences, 2012, 370(1959): 365-380.
SUN P Y, LI Q, HE H Z, et al.Design and optimization investigation on hydraulic transmission and energy storage system for a floating-array-buoys wave energy converter[J]. Energy conversion and management, 2021, 235: 113998.
CALVÁRIO M, GASPAR J F, KAMARLOUEI M, et al. Oil-hydraulic power take-off concept for an oscillating wave surge converter[J]. Renewable energy, 2020, 159: 1297-1309.
GENG D Z, ZHENG Y, CHEN Q J, et al.Novel hydraulic mechanism-based output power regulation for the wave energy converter[J]. Applied ocean research, 2021, 110: 102587.