Sunday, 22 January 2012
Effects of Correctly Modeling Boundary-Layer Stratification and Sea State in Offshore Wind Resource Assessment
Hall E (New Orleans Convention Center )
Offshore resource assessment relies on estimating wind speeds at turbine hub height using observations typically made at substantially lower height. The methods used to adjust from observed wind speeds to hub height can impact the resource estimate. Our research presents a comparison of log law adjustment of wind speeds to an adjustment using a complete boundary-layer model. We examine the sensitivity of the height adjustment to varying boundary-layer stratification and sea-state conditions on diurnal, seasonal and annual scales. Using a GE 3.6 MW offshore turbine as a model for a power curve, we calculate capacity factors for estimated wind speeds. Preliminary results indicate three percent increase in capacity factor from one case study in the Nantucket Sound and a two percent decrease from a case study off the coast of Saint Augustine, Florida. The differences result from running the model using neutral atmospheric stability compared to actually calculating the atmospheric stability. These seemingly small differences in capacity can impact profits by plus or minus millions of dollars depending upon the size of the farm and fluctuations in price per kWh throughout the year. A preliminary economic assessment will be provided for a hypothetical wind far. These economic impacts can be a deciding factor in determining whether a resource is viable for development.