Empirical Correction Ratio and Scale Factor to Project the Extreme Wind Speed Profile for Offshore Wind Energy Exploitation

The typhoon-resistant design should be given priority when constructing offshore wind farms in China coastal waters, where typhoons pose serious threats on the safety of offshore structures. A classical power-law model with the specific exponent of 0.11 has been recommended by the code (IEC 61400-3 2009) to estimate the profile of extreme wind speed versus 50 years return period. Its use in the typhoon-resistant design of offshore wind turbines in China coastal waters has, however, not been validated. In the present study, a series of full-set three-dimensional meteorology simulations are conducted to provide the artificial typhoon wind fields for the evaluation of code recommendations. The simulations reveal that the classical power-law with the exponent of 0.11 is inadequate to estimate the extreme wind speed profile over China coastal waters. Based on the simulated typhoon wind fields, an empirical correction ratio and a scale factor are developed to adjust the classical power-law model to estimate the vertical variation of extreme wind speeds with any desired return periods over China coastal waters. More specifically, the correct ratio revises the power-law model to provide more accurate estimates of 50 years return period extreme wind speed profiles while the scale factor projects extreme wind speeds with other desired return periods.