Performance investigation of a two-raft-type wave energy converter with hydraulic power take-off unit

Liu, Changhai; Yang, Qingjun; Bao, Gang

doi:10.1016/j.apor.2016.12.002

Cited by 43 publications

(13 citation statements)

References 22 publications

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“…A boost pump is also added in the PTO system to provide the extra fluid flow to the hydraulic motor through check valves during a small hydraulic chamber (rod chamber) operation of a hydraulic actuator. This concept also has been used in attenuator type WEC devices such as Pelamis; however, a different configuration of the actuation module was used because of the different operation of this WEC device as described in [88][89][90].…”

Section: Constant-pressure Hydraulic Pto Based On Four-check Valves Cmentioning

confidence: 99%

Hydraulic Power Take-Off Concepts for Wave Energy Conversion System: A Review

et al. 2019

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Ocean wave energy is one of the most abundant energy sources in the world. There is a wide variety of wave energy conversion systems that have been designed and developed, resulting from the different ways of ocean wave energy absorption and also depending on the location characteristics. This paper reviews and analyses the concepts of hydraulic power take-off (PTO) system used in various types of wave energy conversion systems so that it can be a useful reference to researchers, engineers and inventors. This paper also reviews the control mechanisms of the hydraulic PTO system in order to optimise the energy harvested from the ocean waves. Finally, the benefits and challenges of the hydraulic PTO system are discussed in this paper.

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Section: Constant-pressure Hydraulic Pto Based On Four-check Valves Cmentioning

confidence: 99%

Hydraulic Power Take-Off Concepts for Wave Energy Conversion System: A Review

et al. 2019

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“…For example, the Pelamis wave energy conversion device from Pelamis Wave Power, UK, has been put into commercial use on a large scale. At present, there are 5 typical raft devices: Cockerell Raft, 4 MacCabe Wave Pump, 5 Pelamis, 6 DEXA, 7 and M4. 8 Quite a few scholars have intensively researched the raft type energy capturing device.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation and structural optimization based on an elliptical and cylindrical raft wave energy conversion device

Jian-guo

Gao

Zheng

et al. 2018

Journal of Renewable and Sustainable Energy

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In recent years, research on wave energy development and utilization has been a hot topic, and many scholars have intensively researched raft-type energy conversion devices. This paper considers an elliptical and cylindrical raft wave energy conversion device from the perspective of stability and bionics to determine the structural parameters that correspond to optimal energy conversion in a three-level sea state. This paper studies the theoretical wave energy capture efficiency of cylindrical floats by drawing an analogy from the theoretical model. In addition, this paper determines the float structural parameters corresponding to the optimum capture efficiency by formulating numerical simulations and optimizing the parameters, such as the axis ratio of the cross-section, the spacing, the draught, the number of floats, the length of the float, the height of float's center of gravity, and others. In the optimization process, these six parameters were briefly analyzed in reference to the design of the Pelamis. The length of the float and the axial ratio of the cross-section are the main factors affecting the capture efficiency of the device. Therefore, the optimization sequence of the six parameters was determined by first controlling the main factors and then controlling the other factors. Then, the values of all the parameters were determined. The structural parameters of the float were observed to significantly influence the energy capturing effect of the device, and its efficiency was increased by intelligently selecting the structural parameters. Finally, the structural parameters of the elliptical and cylindrical raft wave energy conversion device were determined by comparing the capture efficiency under five typical wave conditions (WT.1 to WT.5) in a three-level sea state.

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“…The frequency response function (FRF) of the wave amplitude-to-complex amplitude of the generalized displacement vector, G(ω), can be described by [27]:…”

Section: Frequency Response Functionmentioning

confidence: 99%

“…By assuming the hydraulic cylinder as a linear damper plus a linear stiffness, Liu et al [27] adopted a generalized displacement vector x(t) = [x0 z0 θ1 θ2] T to describe the motion characteristic of the device and given a four-DOF frequency domain model for waves in the positive x-direction based on the Lagrange's equations, which can be written as:…”

Section: Frequency Domain Analysismentioning

confidence: 99%

State-Space Approximation of Convolution Term in Time Domain Analysis of a Raft-Type Wave Energy Converter

2018

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Two methods, frequency domain analysis and time domain analysis, are widely applied to modeling wave energy converters (WECs). Frequency domain analysis can evaluate the performance of WECs quickly and efficiently, while it refers to a linear model. When it comes to investigations on nonlinear characteristics of the power take-off (PTO) unit of WECs or control for improving the WECs' performance, time domain analysis based on a state-space approximation for the convolution term is more desirable. In this paper, a state-space approximation of the convolution term in a time domain analysis of a raft-type WEC consisting of two rafts and a PTO unit is presented. The state-space model is identified through regression in the frequency domain. Verification of such a type of time domain analysis is conducted by comparison of its simulation results with those calculated by using a frequency domain analysis, and there is a good agreement. Finally, the effects of PTO parameters, wave frequency, surge and heave motions of the joint, and quadratic damping PTO on the power capture ability of the raft-type WEC are investigated.

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Performance investigation of a two-raft-type wave energy converter with hydraulic power take-off unit

Cited by 43 publications

References 22 publications

Hydraulic Power Take-Off Concepts for Wave Energy Conversion System: A Review

Hydraulic Power Take-Off Concepts for Wave Energy Conversion System: A Review

Numerical simulation and structural optimization based on an elliptical and cylindrical raft wave energy conversion device

State-Space Approximation of Convolution Term in Time Domain Analysis of a Raft-Type Wave Energy Converter

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