A floating wind turbine being towed into place at MHI Vestas' Windfloat site in Portugal
The North Sea between the UK and north-western Europe was the birthplace of the offshore wind industry and nations around the coast of the sea such as the UK, Denmark, Germany and the Netherlands, are the leading markets for the technology.
Offshore wind has a number of advantages over onshore projects – the wind out at sea is stronger and more reliable, and there is less visual intrusion so turbines can be bigger, enabling them to generate more power. The 13MW Haliade-X turbine made by GE, currently the world’s largest wind turbine, can generate enough electricity to power the average UK household for two days with each spin of its 220-metre rotor, for example. And turbines are continuing to grow, with Siemens Gamesa working on a 15MW device.
The North Sea is the epicentre of the sector for good reason – it is not just perennially windy, but shallow enough to enable turbine foundations to be fixed to the sea floor. There are many parts of the world that have wind resources as good as, if not better than, the North Sea and large cities to provide a market for their power but that currently cannot take advantage of this because the sea floor is too deep.
The industry has been working to overcome this by creating floating wind turbines but until recently the platforms could only support much smaller turbines than current projects. Industry sources say that floating wind is where bottom-fixed turbines were a decade ago – that is, at the very earliest stages of development.
But now floating wind has taken a giant step forward and looks set to see similar growth rates to fixed turbines, after MHI Vestas installed the largest and most powerful floating turbine at a project off the coast of Scotland.
Vestas is the world’s biggest turbine manufacturer and, through its joint venture with Mitsubishi Heavy Industries, it has now installed the most powerful turbine at a floating wind project, a 9.5MW device that is now in place at the Kincardine wind farm off the coast of Scotland – the first of five to be sited at the project that will have a blade tip height of 190 meters and provide enough power for around 35,000 homes.
It follows the commissioning in the summer of the 25MW WindFloat Atlantic floating offshore wind farm off the coast of Portugal, which features three MHI Vestas 8.4MW devices that were the previous largest floating turbines.
While fixed turbines sit on foundations around 15-30 meters deep, the water at the Kincardine array is 60-80m deep. Because they can be deployed in deeper water, the semi-submersible floating turbines can be used off coasts where there is no shallow seabed or further out at sea to take advantage of stronger and more consistent winds.
They are also easier to build, install and maintain. Fixed turbines have to be installed in place, requiring huge lift vessels to install the foundations and to transport and assemble parts onsite, as well as erecting the turbine. Floating turbines, by contrast, can be built on land, assembled in port and towed to their site using standard tugs, leading to significant cost savings. And when the devices need maintenance, they can simply be towed back to port where engineers can work on them in safe and hospitable conditions rather than having to carry out work hundreds of feet above the ocean, possibly in stormy weather.
Now that the industry is proving that it can build platforms to take larger turbines, floating wind is all set to become a key energy source for coastal cities around the world in the next decade.
