|A sailboat catches the wind off the Maine coast.|
Offshore wind presents a significant energy resource. The National Renewable Energy Laboratory has estimated that U.S. waters could host a gross wind power resource of 4,223 gigawatts -- about four times as much generating capacity as the current U.S. electric grid. If even a fraction of this can be developed in a cost-effective and environmentally friendly way, it could power a significant portion of our electricity needs.
While land-based wind projects represent a relatively established technology -- with over 60,000 megawatts installed in the U.S. by the end of 2012 -- and European waters are home to over 5,000 megawatts of offshore wind, no commercial offshore wind projects have been built in the U.S. The rigors of the ocean environment create engineering challenges for offshore wind, which drives costs up. Particularly in U.S. waters, the best wind resources are located in deeper waters farther offshore. This means that floating wind turbines may be the most cost-effective way to harness offshore winds.
While several prototype floating offshore wind systems have been deployed off Europe, no grid-connected projects have been deployed in U.S. waters. Using $12 million in funding from the U.S. Department of Energy, the University of Maine and its project partners have developed the VolturnUS prototype. This unit has several features that may lead to a breakthrough in the cost curve of floating offshore wind. While most models to date have relied on steel, the VolturnUS semi-submersible platform uses a concrete foundation and composite tower. While the prototype is just 65 feet tall, its design characteristics are hoped to lead to lower construction costs for larger-scale units closer to 500 feet tall.
The University of Maine is also planning a larger offshore wind demonstration called Aqua Ventus I. Using a separate $4 million Energy Department grant, the University is engineering and designing a pilot floating offshore wind farm with two 6-megawatt direct-drive turbines on concrete semi-submersible foundations near Monhegan Island. If selected for further funding in 2014, the Aqua Ventus I project could be constructed and installed in several years.