Why Nantucket Sound is Right for Cape Wind

Very windy site

Cape Wind’s Scientific Data Tower on Horseshoe Shoal records an average wind speed of 19 ½ miles per hour at the elevation where electricity will be generated.  This outstanding wind resource will enable Cape Wind to provide 75% of the electricity used on the Cape and Islands in average conditions.  The winds will be strong enough to cause the blades to rotate and the turbines to produce power about 88% of the time.

The site is also ideal for harnessing the summer ‘sea breeze,’ which means that Cape Wind will often produce above average power at the very times the electric grid needs the power the most—the mid to late afternoons during heat waves when electric demand reaches it peak.  This is in contrast to large land-based wind farms in remote or mountainous locations that are often not windy during these summer peak electric demand events.

‘Protected site’

Cape Wind’s site inside Nantucket Sound offers significant protection from open North Atlantic storm waves.  Typical wave heights are also smaller here than most other offshore locations that are a similar distance from shore.  This means that the site will be highly available to Cape Wind’s workers during both project construction and operations, which will help ensure that the project is optimally maintained and will be operating to the greatest extent possible.

Robust electric interconnect at a strategic grid location

Cape Wind’s power cables, submerged offshore and buried on land, will interconnect with the electric grid at the Barnstable substation, a robust electric hub that can accommodate Cape Wind’s substantial power supply.  Unlike many remote land-based wind sites that cannot reliably deliver power to the places that most need it, Cape Wind is perfectly situated to deliver its power to a portion of the electric grid that has high electric demand, where Cape Wind will deliver power to the homes, businesses, and schools of the Cape and Islands.

"Its [Cape Wind's] interconnection to the network comes on shore right in the middle of Cape Cod.  There's a lot of [electric] load there on Cape Cod, expecially during the summer.  So you can think of power being consumed in the local neighborhood where they interconnect, as opposed to some of the challenges we've been seeing in far northern Maine, northern Vermont northern New Hamphshire, where very few people live." -- Stephen Rourke, Vice President of System Planning, Independent System Operator New England (New England's electric grid manager).  This quote appeared on September 12, 2013 in a State House News Service article entitled, 'Grid Overseers Outline Choices About Power Flow, Sources'.

Ideal depth and seabed conditions


Horseshoe Shoal is a suitable location within Nantucket Sound because it is a shallow shoal outside of boating channels and flight paths. Horseshoe Shoal is a sandy bottom site, making it ideal for the installation of offshore wind foundations and turbines.

Ideal site based on technical review

The Cape Wind site is also widely recognized as an ideal offshore wind location by independent technical experts.  Researchers from Stanford University and the University of Delaware published a 2012 offshore wind study in Geophysical Research Letters that identified Cape Wind’s site as the best in the nation.

Ideal site based on academic review

The suitability of Horseshoe Shoal as the site of America’s first offshore wind farm has also been endorsed by James Manwell, the Director of the University of Massachusetts Amherst Wind Energy Center.  In the 1970s, Manwell was a student of Professor William Heronemus at the University of Massachusetts Amherst.  Professor Heronemus was the first person in the world to seriously explore the concept of offshore wind power.  Heronemus’ offshore wind designs were published in National Geographic Magazine in 1975 and served as an inspiration for some of the offshore wind pioneers in Europe in the early 1990s.

Ideal site overall

During the ten-year permitting review of Cape Wind, numerous alternative sites were evaluated and Horseshoe Shoal was identified as the best site.