After years of preparation, the offshore wind industry finally has a beachhead in the US. Development is accelerating rapidly. Spurred by sharp declines in European offshore wind costs that could soon be competitive in some wholesale markets and by prospects for local economic development and high-paying jobs, states like Massachusetts, New York, and Maryland have all passed supportive legislation to prime the offshore wind industry.
This push may be enough to usher a multi-gigawatt surge in US offshore wind development, led by the first commercial wind farm off Block Island, Rhode Island, commissioned in December 2016. With well-capitalized and experienced offshore wind developers such as Dong Energy, Statoil and Iberdrola eager to demonstrate their 15 years of European offshore wind know-how, it is likely that positive offshore wind market forces can be sustained in the US in the upcoming years.
According to a recent US Department of Energy Offshore Wind Technologies Market Report, there is a potential capacity for more than 14GW of offshore wind in sites already leased on the US outer continental shelf, which could spark investments of up to $50bn if fully developed. However, almost all of the current wind energy areas are located in the North Atlantic where strong winds, high population densities, and a relatively wide continental shelf provide favourable conditions that mimic the North Sea — where similar technology has already been proven.
An onlooker from the Gulf of Mexico may wonder how this is relevant to the southern states. Indeed, the Gulf of Mexico is different. For starters, annual average wind speeds are lower in the Gulf. Most sites achieve no better than eight meters per second (m/s) annual average, whereas 9-10m/s are common in the north. This could mean less energy and lower capacity factors. Another formidable challenge is the presence of tropical storms, with violent winds and sea states creating extreme forces that may exceed established design limits.
These lower average wind speeds and hurricane risks could compromise the performance of today’s North Sea wind turbines in many areas, but an economical, hurricane-resilient, low-wind-speed offshore turbine appears to be a viable technology pathway for future offshore wind technology.
As the wind industry learned in the evolution of land-based turbine designs (eg, low-wind-speed technology), technology must adapt to the site conditions. For parts of the Gulf, we envision possible “typhoon-class” turbines coupled with rugged, low-solidity, large-diameter rotors to capture the lighter winds. Substructures would follow the design methods established by the American Petroleum Institute that are already used to design oil and gas platforms in the Gulf and wind turbines in the Atlantic.
Aside from these site-driven engineering challenges, however, offshore wind in the Gulf of Mexico can claim major advantages that might offset technical and economic shortcomings. First, the quantity of the offshore wind resource technical potential in the Gulf States is enormous. In 2016, a National Renewable Energy Laboratory offshore wind energy resource study estimated that three out of four offshore wind states with the highest resource potential are in the Gulf of Mexico (Texas, Louisiana, and Florida).
The Gulf states possess 961 terawatt hours per year of offshore wind potential, almost one-third of the nation’s offshore shallow-water wind resources — and more than double the total US electricity consumption in 2015. As water depth is an important cost driver, the abundance of shallow water is likely to favourably impact the bottom line for substructures and construction activity. Gulf waters are also warmer than the North Atlantic and have smaller average wave heights, which can open construction and service operation windows, making turbines more accessible and further driving down cost.
Perhaps the biggest advantage for offshore wind in the Gulf states is their proximity to the massive oil & gas supply chains, ports, vessels and infrastructure that could be adapted to support large-scale offshore wind deployment. In fact, the nascent offshore wind industry leans heavily on decades of offshore oil exploration and extraction in the Gulf. For example, various Gulf coast companies were involved in the design, fabrication and installation of the Block Island wind farm. Therefore, it is no coincidence that many of the major offshore wind developers are oil companies, such as Dong, Statoil, and Shell.
In 2015, the US Department of Energy published the Wind Vision Report, which estimated that the Gulf states would contribute 10% of US offshore energy by 2050, or about 8.6GW of offshore wind. Although this commercial market for deployable offshore wind turbines in the Gulf could take several years to evolve, the US industry as a whole is gearing up for large-scale development today, and the Gulf states are well-positioned to thrive on this new energy industry.
Walt Musial is principal engineer at the National Renewable Energy Laboratory in Colorado