Effect of downwind swells on offshore wind energy harvesting - A large-eddy simulation study

Di Yang, Charles Meneveau, Lian Shen

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

The effect of ocean downwind swells on the harvesting of offshore wind energy is studied using large-eddy simulation of fully developed wind turbine array boundary layers, which is dynamically coupled with high-order spectral simulation of sea-surface wave field with and without the presence of a downwind swell. For the two moderate wind speeds of 7m/s and 10m/s considered in this study, the swell is found to induce a temporal oscillation in the extracted wind power at the swell frequency, with a magnitude of 6.7% and 4.0% of the mean wind power output, respectively. Furthermore, the averaged wind power extraction is found to be increased by as much as 18.8% and 13.6%, respectively. Statistical analysis of the wind field indicates that the wind speed in the lower portion of the boundary layer oscillates periodically with fast wind above the swell trough and slow wind above the swell crest, resulting in the observed wind power oscillation. The wind above the swell accelerates due to the strong wave forcing, causes a net upward flux of kinetic energy into the wind turbine layer, and thus acts to increase the extracted wind power of the turbines. For a high wind speed of 17m/s, the wave-induced motion becomes relatively weak and the swell effect on the wind turbine performance diminishes.

Original languageEnglish (US)
Pages (from-to)11-23
Number of pages13
JournalRenewable Energy
Volume70
DOIs
StatePublished - Oct 2014

Keywords

  • Large-eddy simulation
  • Offshore wind energy
  • Swell
  • Turbulence
  • Wind-wave interaction

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