Improvements in offshore wind site characterization and technology advancement can reduce costs by increasing energy production and by reducing development timelines, capital costs, and operations and maintenance costs. With offshore wind just getting off the ground in the U.S., there is still a need for more extensive site assessments to better understand seafloor conditions as well as to inform the design and siting of offshore wind. This is one of the reasons why jacket foundations, which use a lattice structure to support the weight while using less steel, are becoming more common.
To support such a large turbine, the foundation needs to have a lot of mass, and therefore a lot of capital cost, under the water.
The newest class of offshore wind turbines being developed are 9–9.5 MW with a rotor diameter over 500 feet, similar to the height of the Washington Monument. Most turbines being installed offshore today are 5–6 megawatts (MW) in capacity (compared to 2 MW for land-based turbines). Offshore wind turbines are getting larger, complicating the use of monopile foundations. For example, monopiles are driven deep into the seabed using large pile driving hammers - a noisy process that can be harmful or annoying to marine animals, potentially leading to construction delays during seasonal migrations. conditions, including sandy seabeds, soil types that vary across small areas, and the need to comply with environmental regulations. However, there are several other fixed-bottom foundation types that may prove to be better options for U.S. offshore wind farm-used a “gulf-style” jacket foundation with an installation method adapted from the offshore oil and gas industry. Most offshore wind installations to date (accounting for 80% of installed capacity worldwide) have used monopile foundations, which are cylindrical structures driven into the seafloor and attached to the bottom of the wind turbine tower.Īs offshore wind projects move further from shore, jacket structures, which typically consist of four legs connected by braces, are becoming more common. offshore wind resource located where the water is less than 60 meters (100 feet) deep, foundations fixed to the seafloor are feasible in many locations. offshore wind development in deep waters, this blog examines innovations in fixed-bottom foundations.
While the first blog in this series focused on the floating foundations needed for U.S. This blog is part of a series that explores offshore wind technical challenges that are different in the U.S. Illustration by Josh Bauer, National Renewable Energy Laboratory (NREL)