The offshore wind industry is a newcomer to the use of the oceans and seabed when compared with historic maritime sectors such as fishing, shipping, and offshore hydrocarbon development. Only 30 years ago, Denmark led the world in building the first offshore wind farm, Vindeby—11 turbines located a mile offshore near the island of Lolland.
In 2020, the global leader in offshore wind-energy production was the United Kingdom, with the largest wind farm, Hornsea Project One, located off the northeast English coast. Notably, the farm is owned by Ørsted, a Danish multinational energy company and the world’s largest developer of offshore wind power. Hornsea One, with 174 turbine units, began supplying energy to the United Kingdom’s grid in February 2019. The first and only U.S. offshore farm (five turbines on monopiles) is located off Block Island, Rhode Island. Operating since December 2019, the farm generates enough electricity to power 17,000 homes and is estimated to reduce carbon dioxide emissions by 44,000 tons each year.
In addition to the United Kingdom, the top offshore wind nations by power capacity include: Germany, China, Denmark, Belgium, the Netherlands, Sweden, Taiwan, Vietnam, and Japan. Northern Europe remains the leader, but in recent years China’s offshore wind power capacity, now 23 percent of the world’s capacity, has increased more than that of any other nation.
As the costs for offshore wind development have decreased and technologies have advanced, Taiwan, Vietnam, and Japan have looked to renewable offshore wind power as a replacement for hydrocarbon imports. Construction began in 2020 on Japan’s first large commercial offshore wind project. Current U.S. commercial offshore wind developments are focused on two federal lease areas south of Martha’s Vineyard and Nantucket. The Coast Guard is reviewing navigation and waterway issues and cooperating with the Bureau of Ocean Energy Management, the federal agency responsible for offshore leasing and final project review.
The most influential driver of change for offshore wind has been the development of floating platforms. These will allow wind farms to be located farther from shore, where wind speeds are higher and more consistent. Fixed offshore wind structures—the mainstay of the industry—are limited to depths of less than 250 feet. The first operational farm since October 2017 with floating wind turbines is Hywind Scotland, off the northeast coast of Scotland in depths of 312 to 394 feet. A second farm (at a depth of 320 feet) off the Atlantic coast with larger floating turbines has been providing electricity to Portugal’s grid since January 2020. Floating platforms provide the promise for offshore wind power in the deeper waters off California, Japan, and South Korea.
Nation-states have the legal authority to build offshore wind farms in the coastal oceans consistent with the legal framework of the 1982 United Nations Convention on the Law of the Sea (UNCLOS). Two maritime zones defined by UNCLOS have relevance to offshore wind: the 12-nautical-mile (nm) territorial sea and the 200-nm exclusive economic zone (EEZ). Coastal states have sovereign jurisdiction over the territorial sea and thus have the same legal and regulatory powers in this zone as they do on land. Within a declared EEZ, coastal states do not have sovereignty but do enjoy specific sovereign rights over natural resources and the “production of energy from the water, currents and winds” (UNCLOS Article 56). Coastal states within their EEZs can regulate offshore wind farms and the subsea cables that connect them to land. However, the legal status of offshore wind facilities beyond EEZs in the high seas is not addressed by UNCLOS, and the introduction of floating platforms in deeper waters could lead to maritime disputes.
Offshore wind farms, especially in coastal waters with high marine traffic such as the U.S. Atlantic coast, European waters, and the Japanese and Chinese coasts, pose challenges to marine safety, environmental protection, and maritime mobility. Multiple marine uses of coastal waters overlap with offshore energy sites: fishing, commercial shipping, recreation, and naval–coast guard operations. Security and safety zones, some exclusionary, near wind farms may be necessary. Marine corridors in EEZs within and around the farms likely will be required and influenced by grid layouts to accommodate fishing and smaller vessels. The security of future wind farms may increase as they become more integrated with coastal state national grids. A new era of complex, coastal marine use has arrived.