Offshore Wind

Monopile Foundation

Monopile foundations are used in shallow depth applications (0-30 m) and consist of a pile being driven to varying depths into the seabed (10-40 m) depending on the soil conditions. The pile-driving construction process is an environmental concern as the noise produced is incredibly loud and propagates far in the water, even after mitigation strategies such as bubble shields, slow start, and acoustic cladding. As with land-based wind, collision risk with birds and bats is a major concern, though the impact is more difficult to quantify because carcasses become lost at sea. The footprint is relatively small, but may still cause scouring or artificial reefs. As with all electricity generation, there is a slight concern that electromagnetic fields generated by power cables and moving parts may affect animals that use Earth's natural magnetic field for orientation, navigation, and hunting. Likewise, chemicals such as anti-corrosion paint and small amounts of oils and greases may enter the waterbody during spills, though some turbine designs do not require lubrication. Artificial reefing is likely to occur around wind farms as the new hard substrate provides protection and attracts colonizing invertebrates.

Tripod Fixed Bottom

Tripod fixed bottom foundations are used in transitional depth applications (20-80 m) and consist of three legs connecting to a central shaft that supports the turbine base. Each leg has a pile driven into the seabed, though less depth is necessary because of the wide foundation. The environmental effects are very similar to monopiles, except that the footprint is a little larger.

Gravity Foundation

Gravity foundations are used in shallow depth applications (0-30 m) and consist of a large and heavy base constructed of steel or concrete to rest on the seabed. The footprint is relatively large and may cause scouring, artificial reefs, or physical destruction of habitat upon introduction. Otherwise, the environmental effects are similar to monopiles.

Gravity Tripod

Gravity tripod foundations are used in transitional depth applications (10-40 m) and consist of two heavy concrete structures connected by three legs, one structure sitting on the seabed while the other is above the water. Very few offshore windfarms are currently using this foundation. The environmental concerns are identical to those of gravity foundations, though the scouring effect may be less significant depending on the design.

Floating Structure

Floating structure foundations are used in deep depth applications (40-900 m) and consist of a balanced floating structure moored to the seabed with fixed cables. The floating structure may be stabilized using buoyancy, the mooring lines, or ballast. The mooring lines may cause minor scouring or a potential for collision, but the turbine foundation is mostly located in the upper layer of the water column where there tend to be less organisms.