A semi-submersible structure supporting a 2-MW wind turbine was towed nearly 350 kilometers (217.5 miles) to water depths of about 35 meters (114.8 feet) into open Atlantic waters and deployed off the coast of Aguçadoura, Portugal, last November (Figure 3). Though the WindFloat project joins a handful of similar projects under development, because it offers novel possibilities for offshore wind projects in regions with large and deep coastlines, it has been shoring up interest in the budding floating offshore wind sector.
|3. Floating an idea. Partners of the WindPlus Joint Venture—including Seattle-based Principle Power, Portuguese utility Energias de Portugal, and Danish wind firm Vestas—have towed and deployed a 2-MW floating wind turbine roughly 217 miles into open Atlantic waters. Courtesy: Energias de Portugal|
The WindFloat was developed by partners of the WindPlus Joint Venture, consisting of Seattle-based Principle Power, Energias de Portugal (EDP), A. Silva Matos, Vestas Wind Systems, InovCapital, and Fundo de Apoio à Inovação. More than 60 European vendors reportedly helped assemble, install, and precommission the system integrating a Vestas V80-2.0 MW wind turbine on land at the Lisnave facility, near Setubal, Portugal.
The system was then towed—without “the use of any heavy lift equipment offshore,” as Principle Power noted—217.5 miles in Atlantic waters. As of January, developers were commissioning, testing, and starting up the WindFloat, activities that include conducting trial operations and a phased ramp-up to full capacity.
The project isn’t the first floating wind turbine, nor the largest: In June 2009, Siemens Energy and Norway’s Statoil towed a 2.3-MW wind turbine 12 km (7.4 miles) to a water depth of about 722 feet at a North Sea location (for more information on this POWER Top Plant, see our December 2009 issue). That project continues to operate, and Statoil recently applied for a lease with the U.S. Bureau of Ocean Energy Management to test a pilot Hywind floating project in the Gulf of Maine.
What sets the WindFloat apart from Hywind and other floating wind projects is that, unlike the Hywind, which is essentially like a buoy (a spar moored on three lines) on which a turbine has been built, the WindFloat is a semi-submersible structure moored by four to six lines that almost acts like a tripod. The WindFloat is also distinct in that it can be towed out to sea fully commissioned and can also operate in shallower waters between 30 m (98 feet) and 50 m (164 feet).
The WindFloat is fitted with patented water entrapment plates at the base of each column, which dampens water turbulence effects. It also features a closed-loop hull trim system that mitigates wind-induced thrust forces—a system that provides the added benefit of better energy conversion efficiency in the event of a change in wind velocity and direction. The system is moored with conventional components, including chain and polyester lines, and pre-laid drag-embedded anchors. Challenges that could encumber development of the design include roller-coasting steel prices and grid connectivity issues.
Nevertheless, the simple, economic design could reinforce the world’s offshore wind industry, the structure’s developers say. “The (deep) ocean is the next big energy frontier,” said António Vidigal, CEO of EDP Inovação, the Portuguese firm that has called WindFloat “one of its more promising technologies.” “Deep offshore wind technology, in particular the WindFloat, will allow us to harness stronger and more stable winds, and in the medium term deliver sustainable energy into our electrical system. Now is the time for extensive testing and validation, moving forward in the development of this promising technology.”
—Sonal Patel is POWER’s senior writer.