A unified hierarchical wind farm modeling system*

Offshore wind is an abundant energy resource with significant environmental and economic benefits, but as a natural resource, it is variable. A modeling system is developed to improve the design and operation of wind farms by enabling realistic modeling of the atmospheric boundary layer at the wind-farm scale. A hierarchy of modeling methods is used to model the energy flow through the atmosphere, beginning with weather prediction of the entire atmosphere. The output of the global model is then used as input to the Weather Research and Forecasting (WRF) Model, a regional weather model, that captures wind patterns at smaller scales of about 250 meters. The output of the regional model is passed on in turn to a high-resolution large-eddy simulation (LES) model that includes the interaction of the time-depended three-dimensional wind field with the wind farm. To generate a realistic turbulent inflow condition to the wind farm, two concurrently running LES simulations are performed. The auxiliary LES is forced with the WRF model output. A vertical plane from the auxiliary LES provides the inflow fields for the main LES, which includes the wind farm. The present work extends large-eddy simulations of entire wind farms to realistic atmospheric conditions enabling accurate wind farm design, operations, and energy forecasting.