Assessment of WRF prediction of velocity profile and turbulence intensity by comparison to field measurement

Numerical Weather Prediction models (NWPM) such as Weather Research and Forecasting (WRF) are increasingly used for assessment of offshore wind farms. Prior studies have typically focused on either hub height wind speed over the range relevant to power production or on energy yield from exemplar farms. For design optimisation of wind turbines it is also important to establish peak loading conditions and this requires accurate prediction of both wind shear and turbulent characteristics across the swept area. This is evaluated by comparison to published data at locations near Askervein Hill, Scotland and three met-masts located in the North West of the Indian subcontinent. In regions of flat-terrain the wind speed profile was generally in good agreement with met-mast data, to altitudes of 50 m. At higher altitudes there was greater disparity between predicted and measured velocity with over-prediction of 10% and 9.37% at the flat- and hill-top locations over the range 50 to 300 m respectively. This assessment against multiple met-masts within the same region provides confidence in the prediction of hub height velocity but indicates limitations to the use of such models for characterizing the onset profiles of velocity and turbulence to assess loading of large diameter offshore turbines. The paper discusses implications for turbine loading considering conditions at several potential deployment sites across the Gujarat region, India.