Offshore Wind Site Ranking Methodology


Overall Ranking

Rank 331 with Exclusions


Land-based wind power currently supplies about 1% of the US electricity demand. According to the Energy Policy Act of 2005, wind energy is proposed to meet a 20% share in the nation’s energy supply portfolio by 2030. In this context, offshore wind energy has an important role to play in planning America’s energy future. Based on a recent estimate by NREL, there is a total of 51,500 MW of potential wind power within 5–20 nautical miles of the coast in New England. A considerable portion of this power can be obtained in the waters off the coast off Massachusetts. For cost-effectiveness, offshore wind farms should be located in areas with high wind speeds, in shallow waters, a short distance from shore, with a deep layer of sand at the sea bottom. Wind speed, however, tends to increase with distance from shore and developments further from shore tend to have a smaller aesthetic impact. At this point, there is a need for assessments of offshore wind power potential in the country.

This project defines a GIS-based ranking method for estimating the potential wind resource in a large offshore area based on mean wind speed, bathymetry, and distance from shore; and uses this method to perform a survey of the offshore wind energy resource in the waters of Massachusetts.

This project provides a consolidated database of the factors that pertain to offshore wind farm micro-siting including wind speed, bathymetry, distance from shore and various exclusions. A survey area that extends from one nautical mile from shore to the end of the US Exclusive Economic Zone is defined and then analyzed as an array containing cells of 200 m x 200 m in size. Wind speed, bathymetry and distance from shore data-layers are used to create individual ranking layers. By overlaying these layers, available areas are determined and then ranked for overall suitability. Rankings with six different weighting schemes are performed. A normalized ranking is developed that assigns values of 0–1 to each cell in the survey area. On average 7% of the survey area is characterized as having an excellent resource (rated 0.8–1) and 91% of the total survey area has a good resource (0.5–0.8). The author suggests further analysis on four zones with high rankings: Nantucket Island and proximity, east of Cape Cod, northern shore of Massachusetts and Georges Bank. The results are presented as GIS-based maps.