Governors' Wind Energy Coalition

The first offshore turbine ever to be installed without using heavy lift vessels, on its test run. Photo courtesy of Vestas

In the race for bigger offshore wind turbines, what’s under the water can be just as much trouble as what’s above.

Turbine makers are building giant machines that must withstand powerful storms in the inhospitable waters of the North Sea — but they will also need to spend money on sturdy foundations, specialized installations and ships that can nail the turbines to the ocean floor at depths of 115 feet.

But what if such turbines with rotors that sweep three football fields could just be towed out to sea and simply tethered to the bottom of the ocean at virtually any depth, kept steady amid the waves by a flotation device? As far-fetched as it may sound, giant floating wind turbines will carve their own niche in the offshore wind sector if they can provide access to locations with excellent wind conditions at cheaper prices, industry experts say.

Last month, the first offshore turbine ever to be installed without using heavy lift vessels gently floated away on a platform built at a shipyard in Portugal and was towed by a boat 217 miles to the coast of Aguçadoura for a year-long test. It’s a regular 2-megawatt turbine made by Denmark’s Vestas bolted on one of three columns of a triangular floating platform made by Seattle-based Principle Power.

“We are making a similar leap towards new energy resources as the oil and gas industry did in the 1970s when it began using floating structures,” said Alla Weinstein, CEO of Principle Power.

The first offshore turbine ever to be installed without using heavy lift vessels, on its test run. Photo courtesy of Vestas.

The floating technology allows turbines to be located in previously inaccessible locations where water depth exceeds 50 meters and wind resources are superior. Once in place, the platform is moored with four lines, two of which are connected to the column stabilizing the turbine, thus increasing stability and reducing motion, the manufacturer said. As the wind shifts direction and changes the loads on the turbine and foundation, pumps will shift ballast water between foundation chambers. The prototype, dubbed WindFloat, cost $30 million. It is now undergoing testing before completing the startup procedure. After early trials, it will gradually increase its power production to full capacity.

“The deep ocean is the next big energy frontier,” said Antonio Vidigal, CEO of EDP Inovação, which together with Principle Power, Vestas and other partners owns the joint venture WindPlus, which developed the project. “Deep offshore wind technology will allow us to harness stronger and more stable winds and in the medium term deliver sustainable energy into our electrical system.”

From Norway to Japan, experiments in the works

With northern Europe’s offshore wind market forecast to grow to €66 billion ($85.9 billion), turbine makers are eager for the floating technology to be validated so they can send even bigger machines out to deeper seas.

We have the 2-megawat turbine on a floating platform now, and with very few design changes it is possible to do it with the 7-megawatt turbine, as well,” Vestas executive Anders Bach Andersen said.

“It doesn’t really matter if it’s a big turbine or a small turbine, the floating technology is the same,” said Jesper Moller, an executive at Germany’s Siemens, which this year took the lion’s share of offshore wind turbine orders worldwide and is developing a 6 MW turbine to compete with Vestas.

Alstom, which has built a conventional 6 MW offshore turbine it hopes to sell in the North Sea, is also working on a floating prototype it hopes to have ready by 2014, said Cesar Muniz-Casais, an executive with the French power plant and high-speed train manufacturer’s wind division. Muniz-Casais declined to reveal the capacity of the planned floating turbine.

And opportunities may extend far away from the waters of the North Sea, as well. Japan plans to build a pilot floating wind farm with six 2 MW turbines at a cost of 10 billion to 20 billion yen. It will work with firms including Mitsubishi Heavy Industries and Fuji Heavy Industries during an evaluation phase due to be completed in 2016. After that, it plans to build as many as 80 floating wind turbines off Fukushima, the site of the nuclear accident, by 2020.

Norwegian oil company Statoil is also experimenting with floating wind turbines, currently testing its Hywind prototype in the North Sea. It plans to try out the design in a multi-turbine project off the coast of Scotland and, if successful, may use it to bid for business in Japan’s Fukushima project.

And Technical University of Denmark’s Risø National Laboratory for Sustainable Energy and 11 international partners started the four-year DeepWind program to create and test floating vertical axis wind turbines with capacities of up to 20 MW. Vertical axis turbines have the generator at the base instead of in the nacelle, with the rotor shaft installed vertically inside the tower.