Design of a Two-Body Wave Energy Converter Featuring Controllable Geometry: Preprint

Nathan Tom, David Ogden, Michaela Byrne

Research output: Contribution to conferencePaper


While the field of wave energy has been the subject of numerical simulation, scale model testing, and precommercial project testing for decades, wave energy technologies remain in the early stages of development and must continuing proving themselves as a promising modern renewable energy field. A wave energy converter (WEC) concept, currently being explored, is hoping to add an extra control option to WEC design is the variable-geometry WEC (VGWEC). These VGWECs attempt to incorporate controllable geometric features to adjust the floating body hydrodynamics to favor either power absorption, load shedding, or other operational goals. These variable geometry components have been proposed to be controlled on a sea-state-to-sea-state or wave-to-wave time scale depending on the force (or toque) and bandwidth limitations of the actuators required to manipulate just the controllable geometric hull features. The opportunities of having control over both the WEC geometry components and the power-take-off (PTO) have the potential to improve overall system performance and reliability if a cost-effective solution can be found for a given WEC architecture. This paper will present the recent developments and results of a VGWEC concept that incorporates variable geometry modules into a two-body WEC. In the proposed VGWEC concept, the variable geometry modules consist of air inflatable bags in the surface float and a water inflatable ring in the subsurface body. The surface float is tethered directly to the subsurface body through tether lines each connected to a separate PTO. Adjusting the geometry of both the surface and subsurface bodies along with the PTO coefficients can be shown to maximize power in design sea states while reducing motion response and PTO forces when transitioning to sea states where rated power is reached and load shedding is prioritized in hopes of increasing the sea state operational map.
Original languageAmerican English
Number of pages14
StatePublished - 2023
EventASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2023) - Melbourne, Australia
Duration: 11 Jun 202316 Jun 2023


ConferenceASME 2023 42nd International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2023)
CityMelbourne, Australia

Bibliographical note

See NREL/CP-5700-87982 for paper as published in proceedings

NREL Publication Number

  • NREL/CP-5700-85028


  • geometry control
  • hydrodynamics
  • wave energy converter


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