Floating Offshore Wind
Offshore wind energy technologies harness kinetic energy from the wind to generate energy and transport that energy back to shore via a subsea export cable. The main advantage of offshore wind energy is access to stronger and more consistent winds, allowing for the use of larger turbines. The development of offshore wind in Europe and Asia has preceded development activities in other parts of the world; however, several projects in the United States are currently underway. Several floating offshore wind energy demonstrations exist throughout the world, but the technology is yet to be widely deployed.
Floating foundations are used at deep depths (40->1000m) and consist of a balanced floating substructure moored to the seabed with fixed cables. The substructure may be stabilized using buoyancy, mooring lines, or a ballast. Several designs for floating offshore wind substructures currently exist for various depth ranges, including barges, semi-submersibles, tension leg platforms, and single point anchorage buoys. These substructures are connected to one another via inter-array cables, which transport electricity generated from the turbine to floating offshore substations. High voltage export cables then transport the energy to shore.
The environmental concerns associated with offshore wind farms vary with foundation type. In general, collision risk with birds and bats is a major concern, though the impact is more difficult to quantify offshore because carcasses that provide evidence of collisions become lost at sea. As with all electricity generation, there is a slight concern that electromagnetic fields generated by power cables may affect animals that use Earth's natural magnetic field for orientation, navigation, and hunting. Although pile driving is one of the main concerns surrounding fixed offshore wind energy, floating projects can be constructed onshore and transported out to sea, reducing the impacts from construction-related noise and vessels. Floating foundation’s mooring lines may cause minor scouring or pose a risk of collision or entrapment, but the turbine foundation is mostly located in the upper layer of the water column where there tend to be less organisms.
Photo Credit: Joshua Bauer, NREL