If turbine manufacturer Vestas was hoping to make a big splash with its first turbine designed for the offshore wind market, then it certainly did not disappoint with its announcement that it is going to build a massive 7 MW turbine, which will stand 443 feet tall and have a rotor diameter of 164 meters.
Speaking from London, Vestas CEO Ditlev Engel told NAW that the new turbine will have more than twice the capacity of its V90 and V112 models. Before the company's announcement, industry watchers had been expecting Vestas to unveil a 6 MW turbine with a 150-meter rotor diameter.
According to Vestas, the new turbine will have a greater capacity to generate electricity than any rival offshore machine currently in operation. For example, REpower Systems sells a 6.15 MW turbine with a 126-meter rotor, while Areva sells a 5 MW offshore wind turbine.
Engel says that lowering the cost of energy for an offshore wind turbine was an important consideration. Some of the major stepping stones in achieving this are size and subsequent increased energy capture, which translates into a need for larger turbines that are specifically designed to operate in challenging offshore conditions, such as those in the North Sea.
For example, the machine will feature advanced sensors to predict the need for component maintenance, reducing the need for unscheduled replacement. Also, an intelligent control system can allow the turbine, in cases of a critical system error, to continue operating at a lower speed, for example, until the next scheduled service visit. This can ensure that lost production is minimized or avoided.
Vestas says production of prototypes of its 7 MW gear-driven machine is expected to begin in the fourth quarter of 2012. Serial production is set to begin in the first quarter of 2015, provided an order backlog is in place to justify the company's investment.
During the development phase, Vestas considered manufacturing a geared drive machine and a direct-drive machine using a permanent magnet generator, as some of its competitors, such as GE and Siemens, have done with recent offshore turbine offerings.
‘We kept all options open from the start, running two separate parallel research tracks,’ says Engel. ‘One that was focused on direct-drive and the other one on a geared solution.
‘We are not married to any technology,’ Engel continues, adding that during the research and design phase, Vestas considers, among other things, the availability of the materials needed.
One of the drawbacks associated with direct-drive machines is the availability of the rare-earth magnets, such as Neodymium, needed for the generator's configuration. Neodymium, one of 17 rare-earth metals, is found almost exclusively in China. In fact, the country controls more than 97% of rare-earth metal production.
‘Resources will come under pressure,’ Engel says. ‘The less the materials we have to rely on, the better. Besides, the gear-driven design is something we understand.’
While the offshore turbine is envisioned for the U.K. and European markets Engel, is quick to suggest the company could also make the turbine available for the U.S. or Chinese offshore wind markets.