A resonant two body system for a point absorbing wave energy converter with direct-driven linear generator

Engström, Jens; Kurupath, Venugopalan; Isberg, Jan; Leijon, Mats

doi:10.1063/1.3664855

Cited by 66 publications

(44 citation statements)

References 17 publications

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“…As the wave period increases, the capture width ratio decreases, much more rapidly than in the single body system. This was already observed by Engström [39].…”

Section: Resultssupporting

confidence: 71%

“…Ideally, a different body size should be selected for each study location, to match the local wave climate. In this analysis, following Engström et al [38,39], a spherical body was added as the submerged object, in order to modify the natural frequency of the system. The calculations showed that for the least energetic sites (Crotone, Monopoli, Catania, Ortona), the maximum power output is obtained when the system resonates with waves with peak periods of 5.5 s, while at the most energetic sites (Alghero, Mazara del Vallo, Ponza and La Spezia), the optimum natural period of oscillation ranges between 6 and 7 s. More specifically, it is 7 s at Alghero, 6.5 s at Mazara del Vallo and La Spezia and 6 s at Ponza.…”

Section: Simulationsmentioning

confidence: 99%

“…For small point absorber devices, such as the one studied here, the resonant frequency tends to be much higher than the typical sea state frequency, and so, the resonant state is practically impossible to be achieved. One way to increase the natural period of oscillation of a point absorber is by connecting to the floating buoy a deeply submerged object with neutral buoyancy [36][37][38][39]. The additional inertia, due to the submerged body's mass and added mass, allows the decreasing of the natural frequency of the device, which is given by:…”

Section: Simulationsmentioning

confidence: 99%

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Modeling of a Point Absorber for Energy Conversion in Italian Seas

et al. 2013

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Abstract:In the present paper, we investigate the feasibility of wave electricity production in Italian seas by the deployment of the Seabased wave energy converter (WEC). A numerical model of the coupled buoy-generator system is presented, which simulates the behavior of the wave energy converter under regular waves of different wave heights and periods. The hydrodynamic forces, including excitation force, radiation impedance and hydrostatic force, are calculated by linear potential wave theory, and an analytical model is used for the linear generator. Two buoys of different radii are considered to explore the effect of buoy dimension on energy conversion and device efficiency. The power output is maximized by adding a submerged object to the floating buoy, in order to bring the system into resonance with the typical wave frequencies of the sites. The simulation results show a very good agreement with the published data on the Seabased WEC. The model is used to estimate energy production at eight Italian offshore locations. The results indicate that the degree of utilization of the device is higher than 20% at the two most energetic Italian sites (Alghero and Mazara del Vallo) and that it can be considerably increased if the floating body is connected to a submerged object, thanks to the resonant behavior of the WEC. In OPEN ACCESSEnergies 2013, 6 3034 this case, the degree of utilization of the device would be higher than 40% at most of the study sites, with the highest value at Mazara del Vallo. The work enlarges the perspective, to be confirmed by experimental tests and more accurate numerical modeling, on clean electric power production from ocean waves in the Italian seas.

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“…As the wave period increases, the capture width ratio decreases, much more rapidly than in the single body system. This was already observed by Engström [39].…”

Section: Resultssupporting

confidence: 71%

Section: Simulationsmentioning

confidence: 99%

Section: Simulationsmentioning

confidence: 99%

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Modeling of a Point Absorber for Energy Conversion in Italian Seas

et al. 2013

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“…This WEC concept has been validated by theory and extensive real sea trials [9,10]. Early studies indicate how the power output of the WEC is influenced by the sea state, buoy characteristics and PTO damping [11][12][13]. The first is given by the chosen location, but the other two can be altered and optimized in the mechanical design and dimensioning of the buoy and the choice of generator type and load connection.…”

Section: Open Accessmentioning

confidence: 99%

Nonlinear Passive Control of a Wave Energy Converter Subject to Constraints in Irregular Waves

Wang

Isberg

2015

Energies

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This paper investigates a passive control method of a point absorbing wave energy converter by considering the displacement and velocity constraints under irregular waves in the time domain. A linear generator is used as a power take-off unit, and the equivalent damping force is optimized to improve the power production of the wave energy converter. The results from nonlinear and linear passive control methods are compared, and indicate that the nonlinear passive control method leads to the excitation force in phase with the velocity of the converter that can significantly improve the energy production of the converter.

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“…10,11 The researchers at the Swedish Centre for Renewable Electric Energy Conversion at Uppsala University started a wave energy project in 2002. [12][13][14][15][16] This project develops a WEC of point absorber type with a direct-driven linear generator as power take-off (PTO). A buoy located at the ocean surface is connected to a linear generator placed on the seabed via a line.…”

Section: Introductionmentioning

confidence: 99%

Performance of arrays of direct-driven wave energy converters under optimal power take-off damping

et al. 2016

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It is well known that the total power converted by a wave energy farm is influenced by the hydrodynamic interactions between wave energy converters, especially when they are close to each other. Therefore, to improve the performance of a wave energy farm, the hydrodynamic interaction between converters must be considered, which can be influenced by the power take-off damping of individual converters. In this paper, the performance of arrays of wave energy converters under optimal hydrodynamic interaction and power take-off damping is investigated. This is achieved by coordinating the power take-off damping of individual converters, resulting in optimal hydrodynamic interaction as well as higher production of time-averaged power converted by the farm. Physical constraints on motion amplitudes are considered in the solution, which is required for the practical implementation of wave energy converters. Results indicate that the natural frequency of a wave energy converter under optimal damping will not vary with sea states, but the production performance of a wave energy farm can be improved significantly while satisfying the motion constraints. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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A resonant two body system for a point absorbing wave energy converter with direct-driven linear generator

Cited by 66 publications

References 17 publications

Modeling of a Point Absorber for Energy Conversion in Italian Seas

Modeling of a Point Absorber for Energy Conversion in Italian Seas

Nonlinear Passive Control of a Wave Energy Converter Subject to Constraints in Irregular Waves

Performance of arrays of direct-driven wave energy converters under optimal power take-off damping

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