Determination of optimal parameters for a hydraulic power take-off unit of a wave energy converter in regular waves

Cargo, Christopher; Plummer, Andrew; Hillis, Andrew; Schlotter, Michael

doi:10.1177/0957650911407818

Cited by 49 publications

(37 citation statements)

References 15 publications

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“…The most simple hydraulic transmission systems include a hydraulic cylinder, highand low-pressure accumulators, a rectification bridge and a fixed-displacement hydraulic motor, as suggested in several studies, such as the W2W models presented in [7,[16][17][18], and also in [19], where a W2W model for arrays is proposed.…”

Section: Hydraulic Transmission Systems In Wave Energymentioning

confidence: 99%

Validating a Wave-to-Wire Model for a Wave Energy Converter—Part I: The Hydraulic Transmission System

et al. 2017

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Abstract:Considering the full dynamics of the different conversion stages from ocean waves to the electricity grid is essential to evaluate the realistic power flow in the drive train and design accurate model-based control formulations. The power take-off system for wave energy converters (WECs) is one of the essential parts of wave-to-wire (W2W) models, for which hydraulic transmissions are a robust solution and offer the flexibility to design specific drive-trains for specific energy absorption requirements of different WECs. The potential hydraulic drive train topologies can be classified into two main configuration groups (constant-pressure and variable-pressure configurations), each of which uses specific components and has a particular impact on the preceding and following stages of the drive train. The present paper describes the models for both configurations, including the main nonlinear dynamics, losses and constraints. Results from the mathematical model simulations are compared against experimental results obtained from two independent test rigs, which represent the two main configurations, and high-fidelity software. Special attention is paid to the impact of friction in the hydraulic cylinder and flow and torque losses in the hydraulic motor. Results demonstrate the effectiveness of the models in reproducing experimental results, capturing friction effects and showing similar losses.

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Section: Hydraulic Transmission Systems In Wave Energymentioning

confidence: 99%

Validating a Wave-to-Wire Model for a Wave Energy Converter—Part I: The Hydraulic Transmission System

et al. 2017

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“…These converters are using different operating ideas. Some of these are; oscillating bodies, power buoy, wave dragon, over-topping, pendulum gate, Bristol cylinder, pelamis and oscillating water column converters as presented in [14][15][16][17][18][19][20][21][22]. The operating idea of oscillating bodies converter is based on the relative motion between two parts which is similar to the power buoy operating idea, but oscillating bodies are immersed in the water while power buoy floats above water's surface.…”

Section: Introductionmentioning

confidence: 99%

Efficiency Enhancement of Sea Waves Energy Converter via Lean Principles Using an Effective Mechanical Mechanism

Khader¹,

Nada²

2019

ERJ. Engineering Research Journal

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The extracted crude oil from some world areas can be considered as the main pillar of industrial development. Regrettably, the rapid rate of depletion of this kind of energy's sources in addition to its bad environmental effect can decelerate the industrial progress rate. Consequently, more attention has been directed to generate the needed power from the sustainable clean resources, as a response to the worldwide increased energy demand accompanied with a rapid rate of crude oil consumption in addition to increased environmental consciousness. Seas and oceans waves' energy is one of the renewable clean and cheap energy resources. Many types of energy converters can be used to convert seas waves' energy into cheap electricity. Many of previous scientific work is dealing with the most effective wave's energy converters. Some of the published work preferred the oscillating water column (OWC) converter's usage than the other waves energy's converters, although OWC is dependent on Wells turbines which has relatively low efficiency. This paper deals with enhancing the performance of seas waves' energy converter via lean principles. Therefore, a prototype of the suggested mechanical mechanism has been built and tested which can be used instead of Wells turbine for providing the required motion to the generator.

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“…A particular concern with many existing PTO modelling efforts is that the most common PTO system type developed for commercial WEC prototypes, a hydraulic PTO system, is inherently non-linear [17,18]. A few recent studies, notably [16][17][18][19][20][21][22] have implemented realistic hydraulic PTO models with non-linear dynamics. However, these studies were limited in their scope to single WECs and not WEC farms, furthermore, many of the models quite complicated in their implementation.…”

Section: Introductionmentioning

confidence: 99%

Analyzing the Near-Field Effects and the Power Production of an Array of Heaving Cylindrical WECs and OSWECs Using a Coupled Hydrodynamic-PTO Model

et al. 2018

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The Power Take-Off (PTO) system is the key component of a Wave Energy Converter (WEC) that distinguishes it from a simple floating body because the uptake of the energy by the PTO system modifies the wave field surrounding the WEC. Consequently, the choice of a proper PTO model of a WEC is a key factor in the accuracy of a numerical model that serves to validate the economic impact of a wave energy project. Simultaneously, the given numerical model needs to simulate many WEC units operating in close proximity in a WEC farm, as such conglomerations are seen by the wave energy industry as the path to economic viability. A balance must therefore be struck between an accurate PTO model and the numerical cost of running it for various WEC farm configurations to test the viability of any given WEC farm project. Because hydrodynamic interaction between the WECs in a farm modifies the incoming wave field, both the power output of a WEC farm and the surface elevations in the ‘near field’ area will be affected. For certain types of WECs, namely heaving cylindrical WECs, the PTO system strongly modifies the motion of the WECs. Consequently, the choice of a PTO system affects both the power production and the surface elevations in the ‘near field’ of a WEC farm. In this paper, we investigate the effect of a PTO system for a small wave farm that we term ‘WEC array’ of 5 WECs of two types: a heaving cylindrical WEC and an Oscillating Surge Wave Energy Converter (OSWEC). These WECs are positioned in a staggered array configuration designed to extract the maximum power from the incident waves. The PTO system is modelled in WEC-Sim, a purpose-built WEC dynamics simulator. The PTO system is coupled to the open-source wave structure interaction solver NEMOH to calculate the average wave field η in the ‘near-field’. Using a WEC-specific novel PTO system model, the effect of a hydraulic PTO system on the WEC array power production and the near-field is compared to that of a linear PTO system. Results are given for a series of regular wave conditions for a single WEC and subsequently extended to a 5-WEC array. We demonstrate the quantitative and qualitative differences in the power and the ‘near-field’ effects between a 5-heaving cylindrical WEC array and a 5-OSWEC array. Furthermore, we show that modeling a hydraulic PTO system as a linear PTO system in the case of a heaving cylindrical WEC leads to considerable inaccuracies in the calculation of average absorbed power, but not in the near-field surface elevations. Yet, in the case of an OSWEC, a hydraulic PTO system cannot be reduced to a linear PTO coefficient without introducing substantial inaccuracies into both the array power output and the near-field effects. We discuss the implications of our results compared to previous research on WEC arrays which used simplified linear coefficients as a proxy for PTO systems.

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Determination of optimal parameters for a hydraulic power take-off unit of a wave energy converter in regular waves

Cited by 49 publications

References 15 publications

Validating a Wave-to-Wire Model for a Wave Energy Converter—Part I: The Hydraulic Transmission System

Validating a Wave-to-Wire Model for a Wave Energy Converter—Part I: The Hydraulic Transmission System

Efficiency Enhancement of Sea Waves Energy Converter via Lean Principles Using an Effective Mechanical Mechanism

Analyzing the Near-Field Effects and the Power Production of an Array of Heaving Cylindrical WECs and OSWECs Using a Coupled Hydrodynamic-PTO Model

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