Influence on Structural Loading of a Wave Energy Converter by Controlling Variable-Geometry Components and the Power Take-Off

Salman Husain, Jacob Davis, Nathan Tom, Krish Thiagarajan, Cole Burge, Nhu Nguyen

Research output: Contribution to conferencePaperpeer-review

2 Scopus Citations

Abstract

Oceans are harsh environments and can impose significant loads on deployed structures. The deployment of wave energy converters (WECs) faces a design challenge with apparently contradictory goals. A WEC should be designed to maximize the energy absorbed while ensuring the operating wave condition does not exceed the failure limits of the device itself. Therefore, the loads endured by the support structure are a design constraint for the system. Adaptability to different sea states is, therefore, highly desirable. This work uses a WECSim model of a variable-geometry oscillating wave energy converter (VGOSWEC) mounted on a support structure simulated under different wave scenarios. A VGOSWEC resembles a paddle pitching about a fixed hinge perpendicular to the incoming wave fronts. Therefore, the hinge experiences loads perpendicular to its axis as it maintains its position. The geometry of the VGOSWEC is varied by opening a series of controllable flaps on the pitching paddle when the structure experiences threshold loads. Because opening the flaps lets the waves transmit through the paddle, it is hypothesized that opening the flaps should result in load shedding at the base of the support structure. The load shedding is achieved by reducing the moments about the hinge axis. This work compares the hydrodynamic coefficients, natural periods, and response amplitude operators from completely closed to completely open configurations of the controllable flaps. The comparisons quantify the effects of letting the waves transmit through the VGOSWEC. This work shows that the completely open configuration can reduce the pitch and surge loads on the base of the support structure by as much as 80%. It was observed that at the paddle's resonance frequency, the loads on the structure increased substantially. This increase in loads can be mitigated by a rotational power take-off damping about the hinge axis. Changing the rotational power take-off damping was identified as an additional design parameter that can be used to control the loads experienced by the WEC's support structure.

Original languageAmerican English
Number of pages13
DOIs
StatePublished - 2022
EventASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2022 - Hamburg, Germany
Duration: 5 Jun 202210 Jun 2022

Conference

ConferenceASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2022
Country/TerritoryGermany
CityHamburg
Period5/06/2210/06/22

Bibliographical note

See NREL/CP-5700-81883 for preprint

NREL Publication Number

  • NREL/CP-5700-84597

Keywords

  • fixed and floating structures
  • marine hydrodynamics
  • ocean engineering
  • power take-off
  • wave energy converter
  • wave loads

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