A device to extract energy from water waves

Hermans, A. J.; Sabben, E. Van; Pinkster, J.A.

doi:10.1016/s0141-1187(05)80024-0

Cited by 24 publications

(42 citation statements)

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“…It is relatively simple, fast, and suitable for control design. This was achieved using new analytical formulae, which were derived by the authors and validated with the numerical and experimental results, which were published in previous research (Hermans et al 1990;Siegel et al 2011a, b). These new formulae significantly decrease the calculation time and increase the accuracy of the results, as well as providing useful insight into the nature of the system behaviour.…”

Section: Overview Of Modelling Approachmentioning

confidence: 89%

“…The first prototype concept of a lift force-based WEC, a rotor with a single hydrofoil Rotating Wing, was tested by Hermans et al (1990) in the deep water basin of the Maritime Research Institute, in the Netherlands (MARIN). It was shown that the device rotates at the wave frequency and can absorb energy from waves.…”

Section: Overview Of the Existing Prototypes And Control Strategiesmentioning

confidence: 99%

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A control-orientated analytical model for a cyclorotor wave energy device with N hydrofoils

Ermakov

Ringwood

2021

J. Ocean Eng. Mar. Energy

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We present a new analytical model from which a model-based controller can be derived for a cyclorotor-based wave energy converter (WEC). Few cyclorotor-based WEC concepts and models have previously been studied and only one control strategy for the entire wave cancellation has been tested. Our model is derived for a horizontal cyclorotor with N hydrofoils and is suitable for the application of various control algorithms and the calculation of various performance metrics. The mechanical model is based on Newton’s second law for rotation. The cyclorotor operates in two dimensional potential flow. This paper modeled the velocity field in detail around the turbine with N hydrofoils by explaining each velocity term and estimated the generated torque using two methods (point source method and thin-chord method). The developed model is very convenient for control design, using the power take off torque and hydrofoil pitch angles as control inputs. The authors of this work have derived new, exact analytic functions for the free surface perturbation and induced fluid velocity field caused by hydrofoil rotation. These new formulae significantly decrease the model calculation time and increase the accuracy of the results. The new equations also provide useful insight into the nature of the associated variables, and are successfully validated against the results of physical experiments and numerical calculations previously published by two independent research groups. Representation of hydrofoils as both a point source and a thin chord were analysed, with both models cross-validated for the case of free rotation in monochromatic waves.

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Section: Overview Of Modelling Approachmentioning

confidence: 89%

Section: Overview Of the Existing Prototypes And Control Strategiesmentioning

confidence: 99%

A control-orientated analytical model for a cyclorotor wave energy device with N hydrofoils

Ermakov

Ringwood

2021

J. Ocean Eng. Mar. Energy

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“…A single rotating hydrofoil was first investigated by Hermans et al [11] both numerically and experimentally. While Marburg [12] reported very low wave energy conversion efficiencies (on the order of a few percent) in these experimental investigations, Siegel et al [13] were able to show in simulations that with improved sizing of the WEC as well as by using synchronization of the rotation of the foil with the incoming wave, wave termination with better than 99% inviscid efficiency was possible.…”

Section: Motivation and Objectivesmentioning

confidence: 99%

Wave radiation of a cycloidal wave energy converter

Siegel¹

2015

Applied Ocean Research

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Numerical results from a three-dimensional radiation model are presented where a Cycloidal Wave Energy Converter (WEC) is interacting with an incoming straight crested Airy wave. The radiation model was developed in response to experimental observations from 1:10 scale experiments which were conducted in the Texas A&M Offshore Technology Research center wave basin. These experiments were the first investigations involving a WEC where three dimensional wave radiation effects were present due to the fact that the span of the WEC was much smaller than the width of the basin. The radiation model predicted the observed surface wave patterns in the experiment well, and showed that radiation induced wave focusing increased the recoverable wave power beyond the two-dimensional predictions for small WEC spans, while approaching the two-dimensional limit for very large spans. The numerical model was subsequently used to investigate the sensitivity of the WEC to misalignment between the incoming waves and the WEC shaft as well as the impact of a gap in the blade setup of a double WEC. For misalignment, the loss in efficiency was found to be strongly dependent on the ratio between WEC span and incoming wavelength, where short spans (on the order of one wave length or less) which are realistic for actual ocean deployment showed only minor reductions in efficiency, while very long spans were found to be more sensitive to misalignment. The blade gap in a double WEC setup was found to have a relatively minor effect (up to 30%) on efficiency. Efficiency was found to either increase or decrease depending on the size of the gap.

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“…The fact that the reactive force changes direction though 360 • with each wave passage enables force cancellation if the individual WECs are spaced half a wavelength apart, thus causing reactive forces of same magnitude but opposite direction. A single rotating hydrofoil was first investigated by Hermans et al [9] both numerically and experimentally. While Hermans et al reported very low wave energy conversion efficiencies (on the order of a few percent), Siegel et al [3] were able to show in simulations that with improved sizing of the WEC as well as by using synchronization of the rotation of the foil with the incoming wave, wave termination with better than 99% inviscid efficiency was possible.…”

Section: Motivation and Objectivesmentioning

confidence: 99%

Experimental Investigation of Irregular Wave Cancellation Using a Cycloidal Wave Energy Converter

Siegel

Fagley

Römer

et al. 2012

Volume 7: Ocean Space Utilization; Ocean Renewable Energy

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The ability of a Cycloidal Wave Energy Converter (CycWEC) to cancel irregular deep ocean waves is investigated in a 1:300 scale wave tunnel experiment. A CycWEC consists of one or more hydrofoils attached equidistant to a shaft that is aligned parallel to the incoming waves. The entire device is fully submerged in operation. Wave cancellation requires synchronization of the rotation of the CycWEC with the incoming waves, as well as adjustment of the pitch angle of the blades in proportion to the wave height. The performance of a state estimator and controller that achieve this objective were investigated, using the signal from a resistive wave gage located up-wave of the CycWEC as input. The CycWEC model used for the present investigations features two blades that are adjustable in pitch in real time. The performance of the CycWEC for both a superposition of two harmonic waves, as well as irregular waves following a Bretschneider spectrum is shown. Wave cancellation efficiencies as determined by wave measurements of about 80% for the majority of the cases are achieved, with wave periods varying from 0.4s to 0.75s and significant wave heights of Hs ≈ 20mm. This demonstrates that the CycWEC can efficiently interact with irregular waves, which is in good agreement with earlier results obtained from numerical simulations.

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A device to extract energy from water waves

Cited by 24 publications

References 0 publications

A control-orientated analytical model for a cyclorotor wave energy device with N hydrofoils

A control-orientated analytical model for a cyclorotor wave energy device with N hydrofoils

Wave radiation of a cycloidal wave energy converter

Experimental Investigation of Irregular Wave Cancellation Using a Cycloidal Wave Energy Converter

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