|Fig. 1: A) Annual Average Land and Offshore Wind Speeds ; B) Land Price per Acre ; C) Population Density  D) Change in Population  (Courtesy of the DOE, and the U.S. Department of Commerce. Other art work: V. Troutman.)|
This past summer, construction on the first offshore wind farm in the United States began in Rhode Island. This offshore wind farm will be connected to the grid at the end of 2016. This very new source of electricity for the United States is actually decades old for Europe, with the first offshore wind farm being installed in Denmark in 1991. With a goal to have 20% wind energy by 2030 in the United States, it is critical that offshore wind energy development is accelerated forward. Wind energy reduces harmful emissions, air pollution, and water consumption.  Offshore wind energy thrives within the combined constraints of wind speed, land availability, and energy demand.
The wind speed first must be high enough to move the blades (cut-in wind speed), but past that the power that can be extracted from the wind increases with the cube of wind speed. For example, on the coast of California, onshore the wind speed is on average 4 m/s, but offshore the wind speed is on average greater than 10 m/s (see Fig.1 A). This results in approximately 15 times as much extractable power. This can be increased further with the development of larger wind turbines as the power also is also proportional to the swept area of the rotor blades. 
The regions of the highest population are increasing at faster rates and generally correspond to the highest land prices in the United States (see Fig. 1 B-D). This creates the unique challenge of a higher energy demand in regions with scarce and expensive land. The highest wind speeds on land occur in the center of the country where land prices are 3-4 orders of magnitude less expensive, but long distance transmission is required to deliver the electricity to highly populated areas. This highlights the need for offshore wind energy. The coasts and the Great Lakes regions all have high population densities and high off-shore wind speeds (Fig. 1 A and C).
There are many additional challenges with offshore wind farms, which has led to the large delays in implementing this technology. The uncertain construction costs and need for specialized marine equipment have hindered progress, though the oil industry has already overcome many of these technological obstacles to build offshore oil rigs. There is also uncertainty in what type of policy support these offshore wind farms would receive from the government. The Department of Energy started an "Offshore Wind Strategic Initiative" in 2011 to support public and private research, with the main goal to deploy prototypes by 2017. Furthermore, the Bureau of Ocean Energy Management has grown and developed significant framework required for leasing coastal waters and approving projects. Despite environmental impact concerns, this is has been significantly studied and 40 environmental organizations including the National Wildlife Federation have endorsed offshore wind development. 
For wind farms to be installed in deeper waters, such as the Pacific Coast, floating structures are necessary to support the wind turbines offshore. Many different types of floating structures have been developed for offshore oil rigs, so it is not a question of if it is technologically possible, but a question of if we will make it a priority to develop. Wind farms installed at deep water depths will be even more expensive due to construction costs and rougher ocean and wind conditions.
For offshore wind energy to be viable, it is imperative that we support the early development of this technology. Comparatively, offshore wind energy is more expensive than energy from fossil fuels, but the environmental impact and the energy security of our future must be factored in as well. To continue to move forward and to get more offshore wind energy connected to our grid, projects will need long-term policies in place.
© Valerie Troutman. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 "Wind Vision: A New Era for Wind Power in the United States," U.S. Department of Energy, DOE/GO-102015-4557, April 2015.
 W. Larson, New Estimates of Value of Land of the United States, U.S. Bureau of Economic Analysis, April 2015.
 P. Mackun and S. Wilson, Population Distribution and Change: 2000 to 2010, U.S. Census Bureau, C2010BR-01, March 2011.