Physical and Mathematical Modeling of a Wave Energy Converter Equipped with a Negative Spring Mechanism for Phase Control

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Abstract

A wave-energy converter has been studied through the combination of laboratory experiments and numerical simulations. The converter model is a semi-submerged axi-symmetric buoy with a circular cross section with a diameter of 26 cm at the water plane. The buoy is pitching about a fixed external axis oriented such that the buoy works primarily in heave. The laboratory model is equipped with a spring mechanism referred to as WaveSpring, which works to shift the resonance period and increase the response bandwidth of the system. A controlled electric actuator was connected and programmed to provide a velocity-proportional force for power extraction. The buoy mass was varied at two levels and the experimental setup was exposed to a selection of regular and irregular waves. The power take-off (PTO) damping was set as a function of sea state. A mathematical model for global motion response was developed based on linear hydrodynamic theory and rigid-body dynamics. Comparison of laboratory measurements and numerical simulation results shows that the dominant physical effects have been well captured by the mathematical model. Overall, the study gives an experimental verification that a negative spring mechanism mounted in parallel with the power take-off machinery of a wave energy converter may be used to increase the average converted power.
Original languageEnglish
Article number2362
JournalEnergies
Volume11
Issue number9
ISSN1996-1073
DOIs
Publication statusPublished - 7 Sep 2018

Fingerprint

Physical Modeling
Phase control
Converter
Mathematical Modeling
Takeoff
Electric actuators
Energy
Mathematical Model
Mathematical models
Rigid Body Dynamics
Numerical Simulation
Computer simulation
Machinery
Irregular
Actuator
Hydrodynamics
Damping
Cross section
Directly proportional
Bandwidth

Keywords

  • Renewable ocean energy
  • Phase control
  • Negative spring
  • Point absorber
  • Hydrostatic stiffness
  • Power take-off

Cite this

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title = "Physical and Mathematical Modeling of a Wave Energy Converter Equipped with a Negative Spring Mechanism for Phase Control",
abstract = "A wave-energy converter has been studied through the combination of laboratory experiments and numerical simulations. The converter model is a semi-submerged axi-symmetric buoy with a circular cross section with a diameter of 26 cm at the water plane. The buoy is pitching about a fixed external axis oriented such that the buoy works primarily in heave. The laboratory model is equipped with a spring mechanism referred to as WaveSpring, which works to shift the resonance period and increase the response bandwidth of the system. A controlled electric actuator was connected and programmed to provide a velocity-proportional force for power extraction. The buoy mass was varied at two levels and the experimental setup was exposed to a selection of regular and irregular waves. The power take-off (PTO) damping was set as a function of sea state. A mathematical model for global motion response was developed based on linear hydrodynamic theory and rigid-body dynamics. Comparison of laboratory measurements and numerical simulation results shows that the dominant physical effects have been well captured by the mathematical model. Overall, the study gives an experimental verification that a negative spring mechanism mounted in parallel with the power take-off machinery of a wave energy converter may be used to increase the average converted power.",
keywords = "Renewable ocean energy, Phase control, Negative spring, Point absorber, Hydrostatic stiffness, Power take-off, Renewable ocean energy, Phase control, Negative spring, Point absorber, Hydrostatic stiffness, Power take-off",
author = "Am{\'e}lie Tetu and Francesco Ferri and Kramer, {Morten Mejlhede} and {Hals Todalshaug}, J{\o}rgen",
year = "2018",
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Physical and Mathematical Modeling of a Wave Energy Converter Equipped with a Negative Spring Mechanism for Phase Control. / Tetu, Amélie; Ferri, Francesco; Kramer, Morten Mejlhede; Hals Todalshaug, Jørgen.

In: Energies, Vol. 11, No. 9, 2362, 07.09.2018.

Research output: Contribution to journalJournal articleResearchpeer-review

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AU - Tetu, Amélie

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N2 - A wave-energy converter has been studied through the combination of laboratory experiments and numerical simulations. The converter model is a semi-submerged axi-symmetric buoy with a circular cross section with a diameter of 26 cm at the water plane. The buoy is pitching about a fixed external axis oriented such that the buoy works primarily in heave. The laboratory model is equipped with a spring mechanism referred to as WaveSpring, which works to shift the resonance period and increase the response bandwidth of the system. A controlled electric actuator was connected and programmed to provide a velocity-proportional force for power extraction. The buoy mass was varied at two levels and the experimental setup was exposed to a selection of regular and irregular waves. The power take-off (PTO) damping was set as a function of sea state. A mathematical model for global motion response was developed based on linear hydrodynamic theory and rigid-body dynamics. Comparison of laboratory measurements and numerical simulation results shows that the dominant physical effects have been well captured by the mathematical model. Overall, the study gives an experimental verification that a negative spring mechanism mounted in parallel with the power take-off machinery of a wave energy converter may be used to increase the average converted power.

AB - A wave-energy converter has been studied through the combination of laboratory experiments and numerical simulations. The converter model is a semi-submerged axi-symmetric buoy with a circular cross section with a diameter of 26 cm at the water plane. The buoy is pitching about a fixed external axis oriented such that the buoy works primarily in heave. The laboratory model is equipped with a spring mechanism referred to as WaveSpring, which works to shift the resonance period and increase the response bandwidth of the system. A controlled electric actuator was connected and programmed to provide a velocity-proportional force for power extraction. The buoy mass was varied at two levels and the experimental setup was exposed to a selection of regular and irregular waves. The power take-off (PTO) damping was set as a function of sea state. A mathematical model for global motion response was developed based on linear hydrodynamic theory and rigid-body dynamics. Comparison of laboratory measurements and numerical simulation results shows that the dominant physical effects have been well captured by the mathematical model. Overall, the study gives an experimental verification that a negative spring mechanism mounted in parallel with the power take-off machinery of a wave energy converter may be used to increase the average converted power.

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KW - Point absorber

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