Numerical Modelling of a Two-Body Point Absorber Featuring Variable Geometry: Paper No. 2157

David Ogden, Nathan Tom, Jennifer van Rij, Yi Guo, Yi-Hsiang Yu

Research output: Contribution to conferencePaper

1 Scopus Citations


This work presents a novel wave energy converter (WEC) device concept that incorporates variable geometry modules into a two-body point absorber type WEC. The variable geometry modules consist of air inflatable bags in the surface float and a water inflatable ring in the reaction body. The variable geometry floats are able to provide greater control over the device hydrodynamics; they can be inflated or deflated to emphasize either power absorption or load shedding. The device geometry is controlled in a quasi-static fashion, while the power take-off (PTO) unit is controlled on a wave-to-wave timescale. The surface float is tethered directly to the submerged reaction body through PTO tether lines. A linear time-domain analysis, conducted using open-source Wave Energy Converter (WEC-Sim) software, was used to estimate the absorbed power of the WEC in sea states defined by the Wave Energy Prize. WEC power performance was weighted against the expected capital cost of building the load bearing structure of the device, providing an estimated ACE value. The inclusion of the variable geometry modules was shown to be effective in altering the device geometry to improve power capture with a near proportional increase in expected costs, providing a nearly constant power-to-cost ratio.
Original languageAmerican English
Number of pages8
StatePublished - 2021
EventEuropean Wave and Tidal Energy Conference (EWTEC 2021) -
Duration: 5 Sep 20219 Sep 2021


ConferenceEuropean Wave and Tidal Energy Conference (EWTEC 2021)

NREL Publication Number

  • NREL/CP-5700-80114


  • cost of energy
  • hydrodynamic control
  • load reduction
  • two-body point absorber
  • variable geometry


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