A study of the effects of increasing the degrees of freedom of a point-absorber wave energy converter on its harvesting performance

Shami, Elie Al; Wang, Xu; Ji, Xueyu

doi:10.1016/j.ymssp.2019.106281

Cited by 36 publications

(6 citation statements)

References 33 publications

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“…Since the wave generator is equipped with a torsion (spring) pendulum, the reciprocating movements of the stepper motor inside the wave generator come into resonance with the sea wave. Knowing the period of time and the height of the movement of the wave generator in space under sea conditions, as well as knowing the diameter of the gear on the shaft of the stepper motor, we calculated the number of revolutions R n made by the stepper motor using Equation (23). We thus obtained the length of one revolution performed by a stepper motor.…”

Section: Emulation Techniquementioning

confidence: 99%

“…Results from their study suggested that the ModuleRaft WEC operates best by utilizing all directions of wave energy by using a single-point mooring system. Al Shami et al [23] studied the impact of increasing the total number of degrees of freedom by adding submerged objects to a point-absorber WEC. This was aimed at capturing more power with a lower resonant frequency with the same total mass and volume, similar to that of a piezoelectric vibration energy harvester.…”

Section: Introductionmentioning

confidence: 99%

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Design and Construction of a Novel Simple and Low-Cost Test Bench Point-Absorber Wave Energy Converter Emulator System

Agyekum

Praveenkumar

Eliseev³

et al. 2021

Inventions

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This paper proposed a test bench device to emulate or simulate the electrical impulses of a wave energy converter (WEC). The objective of the study is to reconstruct under laboratory conditions the dynamics of a WEC in the form of an emulator to assess the performance, which, in this case, is the output power. The designed emulator device is programmable, which makes it possible to create under laboratory conditions the operating mode of the wave generator, identical to how the wave generator would work under real sea conditions. Any control algorithm can be executed in the designed emulator. In order to test the performance of the constructed WEC emulator, an experiment was conducted to test its power output against that of a real point-absorber WEC. The results indicate that, although the power output for that of the real WEC was higher than the WEC emulator, the emulator performed perfectly well. The relatively low power output of the emulator was because of the type of algorithm that was written for the emulator, therefore increasing the speed of the motor in the algorithm (code) would result in higher output for the proposed WEC emulator.

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Section: Emulation Techniquementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Design and Construction of a Novel Simple and Low-Cost Test Bench Point-Absorber Wave Energy Converter Emulator System

Agyekum

Praveenkumar

Eliseev³

et al. 2021

Inventions

View full text Add to dashboard Cite

show abstract

“…The bistable WEC had higher power capture performance with appropriate device parameters 7 . Additionally, submerged bodies with 2 to 5 degrees of freedom can increase the average captured power of wave energy harvesters 8 . Different point‐absorber converters were investigated from several perspectives 9 .…”

Section: Introductionmentioning

confidence: 99%

Optimization of energy‐capture performance of point‐absorber wave energy converter

Zhang

Deng

et al. 2022

Intl J of Energy Research

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An optimization process is proposed for improving the energy-harvesting efficiency of the point-absorber wave energy converter (WEC) and thus enhancing the utilization of wave energy resources. The multidisciplinary design optimization integration system ISIGHT is adopted to establish an optimization design flow for the shape parameters of the point-absorber WEC. The motion equations of the point-absorber WEC are established according to the potential flow theory, and the wave energy capture capacity per unit is calculated. Considering it as the objective, the point-absorber WEC is modified to improve the energy-capture efficiency by using an optimization function in an approximation model. A comparison indicates that a cylindrical-bottom point-absorber WEC with a diameter of 7 m, draft of 1.8 m, and damping factor of 31 150 NsÁm À1 has the optimal performance and the maximum energy capture capacity. The energy-capture performance of the WEC can be significantly enhanced through this optimization method.

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“…An MPC algorithm uses an internal model of the plant to predict the system's future states [10]. Nonlinear control algorithms can consider the non-ideal operating conditions and nonlinear effects, including but not limited to non-ideal power take-off mechanism [11], nonlinear viscous drag terms [12,13], and nonlinear mooring dynamics [2]. The non-ideality of PTO systems in most literature is limited to the efficiency of the PTO mechanism [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…Nonlinear control algorithms can consider the non-ideal operating conditions and nonlinear effects, including but not limited to non-ideal power take-off mechanism [11], nonlinear viscous drag terms [12,13], and nonlinear mooring dynamics [2]. The non-ideality of PTO systems in most literature is limited to the efficiency of the PTO mechanism [13][14][15][16]. One of the motivations for this research is to consider higher-order nonlinear PTO characteristics as an optimization objective for the NMPC problem.…”

Section: Introductionmentioning

confidence: 99%

Real-Time Nonlinear Model Predictive Controller for Multiple Degrees of Freedom Wave Energy Converters with Non-Ideal Power Take-Off

Haider

Brekken

McCall³

2021

JMSE

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An increase in wave energy converter (WEC) efficiency requires not only consideration of the nonlinear effects in the WEC dynamics and the power take-off (PTO) mechanisms, but also more integrated treatment of the whole system, i.e., the buoy dynamics, the PTO system, and the control strategy. It results in an optimization formulation that has a nonquadratic and nonstandard cost functional. This article presents the application of real-time nonlinear model predictive controller (NMPC) to two degrees of freedom point absorber type WEC with highly nonlinear PTO characteristics. The nonlinear effects, such as the fluid viscous drag, are also included in the plant dynamics. The controller is implemented on a real-time target machine, and the WEC device is emulated in real-time using the WECSIM toolbox. The results for the successful performance of the design are presented for irregular waves under linear and nonlinear hydrodynamic conditions.

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A study of the effects of increasing the degrees of freedom of a point-absorber wave energy converter on its harvesting performance

Cited by 36 publications

References 33 publications

Design and Construction of a Novel Simple and Low-Cost Test Bench Point-Absorber Wave Energy Converter Emulator System

Design and Construction of a Novel Simple and Low-Cost Test Bench Point-Absorber Wave Energy Converter Emulator System

Optimization of energy‐capture performance of point‐absorber wave energy converter

Real-Time Nonlinear Model Predictive Controller for Multiple Degrees of Freedom Wave Energy Converters with Non-Ideal Power Take-Off

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