are floating wind turbines the future?
Floating wind has the potential to be a cost-effective, secure and safe low-carbon energy source that is well positioned to make a significant long-term contribution to the world’s low carbon energy system. The UK has many high-energy offshore wind sites within 70 to 100km of the shoreline, but which sit at water depths in the range of 50-100m, beyond the depth at which existing foundation technologies are commercially viable. Floating turbines that are suitable for these deeper waters would enable the UK to make the most of the favourable (but currently unexploitable) wind energy resources around its coastline.
The first nation that look set to take advantage of this opportunity is Scotland, with a deal between the Scottish government and Norwegian oil company Statoil, to implement five wind turbines with a capacity of six megawatts each, set on floating structures 15 miles off the northeast coast of Scotland. The Hywind pilot park is claimed to be the first floating wind farm in the world, and will generate enough power for 20,000 homes with operations expected to start in late 2017. The 30-MW Hywind park will take advantage of average local North Sea wind speeds of around 19 knots and cover an area of around 1.5 sq mi (4 sq km) at a water depth of 310 to 395 ft (95-120 m).
The great advantage of floating wind turbines is that they can be placed away from the coast in deeper water as they don't need to be anchored to sea floor-mounted towers, which are typically limited to a water depth of up to 260 ft. The optimal water depth for fixed turbines is 65 to 165 ft (20-50 m), however two-thirds of North Sea waters are between 160 and 720 ft (49 and 220 m) in depth.
There are several advantages to locating away from shore, including reduced visual pollution – meaning they won't spoil anyone's view, which is a common complaint by some coastal residents. They can also reap the benefits of stronger and more consistent winds typically found farther out at sea since they aren't impeded by land features. Floating wind farms are also less likely to interfere with fishing or shipping activity, and by stringing the turbines together in a farm, they can share a common infrastructure, such as power cables and transmission facilities.
Whilst floating offshore wind technologies are capable of accessing previously inaccessible high wind resources in deeper water locations around the UK at affordable and competitive costs, the use of existing fixed foundation approaches in shallower water locations is still generally preferable to floating technologies in these situations. Therefore, the most affordable way of achieving substantial long-term offshore wind roll-out is likely to be delivered through a mix of fixed foundation systems in shallower waters and the deployment of a variety of new floating platform technologies in higher wind, deeper water locations.
v
“The UK has many high-energy offshore wind sites within 100km of the shoreline, but which sit at water depths of 50-100m, beyond the depth at which existing foundation technologies are commercially viable."