Abstract
This report summarizes the offshore wind resource potential, based on map estimates, for the contiguous United States and Hawaii, as of May 2009. The development of this assessment has evolved over multiple stages as new regional meso-scale assessments became available, new validation data were obtained, and better modeling capabilities were implemented. It is expected that further updates to the current assessment will be made in future reports. Offshore wind energy development promises to be a significant domestic renewable energy source, especially for coastal energy loads with limited access to interstate grid transmission. The definition of the magnitude and distribution of this resource required the development of a standard and flexible database. Developed using Geographic Information System (GIS) techniques, the database includes offshore wind resource characteristics such as wind speed, water depth, and distance from shore. It combines the resource characteristics with state administrative areas and quantifies the resource for several scenarios. In the future, the database may be expanded to include other important characteristics such as wave power density, extreme wind and wave, ocean currents, and a number of other parameters important to the design of offshore wind turbines. The primary method used to present the offshore wind resource data are maps that categorize the resource by annual average wind speed at 90 meters (m) above the surface. The resource maps extend from the shoreline out to 50 nautical miles (nm) offshore. Exceptions to the 50 nm mapped distance are the Great Lakes that were mapped in their entirety for the offshore resource and Massachusetts, where the computed resource did not extend 50 nm from the edge of the Nantucket Island and Martha’s Vineyard in southeastern Massachusetts. The offshore maps for some states do not extend 50 nm because of state and administrative boundaries. There were several sources for the offshore resource maps. The oldest offshore wind resource maps were generated from data mapped as part of onshore state wind resource mapping projects. Recently, some regions have had their resource maps updated using the latest computer mapping techniques optimized for offshore modeling. For this evaluation, updated maps were available for the offshore areas of Georgia, Texas/Louisiana, northern New England (Massachusetts, New Hampshire, and Maine), and states that border the Great Lakes. The preliminary numerical modeling was performed by AWS Truepower (AWST), of Albany, New York, under subcontract to the National Renewable Energy Laboratory (NREL), using their proprietary MesoMap system. The preliminary model estimates were validated by NREL using data from a variety of sources including ocean buoys, marine automated stations, Coast Guard stations and lighthouses, and satellite-derived 10-m wind speeds over the ocean estimated from the “state of the sea” as measured by microwave imaging. Final modifications to the preliminary estimates were agreed to after consultations between NREL and AWST. AWST adjusted the model output to reflect the modifications and sent the final grids to NREL, where the data were converted into wind resource maps. The calculation of the offshore wind resource estimates for states without updated maps depended on the availability of older offshore wind maps that were completed as part of onshore wind 2 mapping projects. Where older preliminary and final offshore wind maps were available, the wind speed data from those maps were interpolated to 90 m height and, if necessary, extrapolated to the 50 nm lines. The offshore areas treated in this manner included the Atlantic coast, from Rhode Island to South Carolina, the Pacific coast, from California to Washington, and Hawaii. The states of Florida, Alabama, and Mississippi did not have any preliminary or final wind maps available. The offshore wind resource for these states is not included in this report