Balancing the Power-to-Load Ratio for a Novel Variable Geometry Wave Energy Converter with Nonideal Power Take-Off in Regular Waves: Preprint

Nathan Tom, Yi-Hsiang Yu, Alan Wright

Research output: Contribution to conferencePaper

Abstract

This work attempts to balance power absorption against structural loading for a novel variable geometry wave energy converter. The variable geometry consists of four identical flaps that will be opened in ascending order starting with the flap closest to the seafloor and moving to the free surface. The influence of a pitch motion constraint on power absorption when utilizing a nonideal power take-off (PTO) is examined and found to reduce the losses associated with bidirectional energy flow. The power-to-load ratio is evaluated using pseudo-spectral control to determine the optimum PTO torque based on a multiterm objective function. The pseudo-spectral optimal control problem is extended to include load metrics in the objective function, which may now consist of competing terms. Separate penalty weights are attached to the surge-foundation force and PTO control torque to tune the optimizer performance to emphasize either power absorption or load shedding. PTO efficiency is not included in the objective function, but the penalty weights are utilized to limit the force and torque amplitudes, thereby reducing losses associated with bidirectional energy flow. Results from pseudo-spectral control demonstrate that shedding a portion of the available wave energy can provide greater reductions in structural loads and reactive power.
Original languageAmerican English
Number of pages13
StatePublished - 2017
EventEuropean Wave and Tidal Energy Conference - Cork, Ireland
Duration: 27 Aug 20172 Sep 2017

Conference

ConferenceEuropean Wave and Tidal Energy Conference
CityCork, Ireland
Period27/08/172/09/17

NREL Publication Number

  • NREL/CP-5000-68082

Keywords

  • load shedding
  • pseudo-spectral control
  • PTO efficiency
  • variable geometry
  • wave energy converter

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