GE Confirms Offshore Turbine Details

Speaking at the company’s ‘The future of alternative energy summit’, Stephan Ritter, GE Energy’s general manager for Renewable Energy Europe, confirmed a larger rotor diameter than the current 90.6 metre design and a power rating of some 4 MW. This compares with a 3.5 MW rating on the existing ScanWind models.

The variable pitch, direct drive machine will feature a permanent magnet generator, avoiding the use of a high speed gearbox. Ritter says the top head mass (THM) of around 250 tonnes is competitive with other manufacturers’ current designs.

Although still coy with regard to the exact name plate capacity, Ritter did acknowledge that the machine would be “a bit bigger”, than the existing design with an up-rated generator, “It’s going to be around 4 MW”, he said, observing: “More importantly, it’s going to have a bigger rotor.”

Ritter explained that the company intends to take proven elements of the existing ScanWind design, add GE technology proven on the company’s 1.5 MW and 2.5 MW machines “load controls, for example”, and combine them into a product that “we think is pretty compelling.”

ScanWind has an operational track record of more than six-years with the first 3 MW prototype erected during March 2003 in Nærøy on the Norwegian coast. Today some 15 machines in various configurations have been installed and are operating onshore, 11 of which feature generators supplied by Finnish company The Switch. Indeed, Ritter noted that this track record was one of the reasons why GE acquired the company, saying, “We didn’t just want to buy a design but we wanted to buy a track record with it.”

Testing of the larger rotor diameter version is due to begin this year with an onshore installation before the design is tested offshore in pre-commercial installations of perhaps two to four turbines. In a staged development, Ritter says the company plans further pre-commercial developments with 10 to 15 units and in 2013 the company expects to use the turbine in its first fully commercial offshore installation of the 50-100 turbine + scale.

The company’s move into offshore has long been anticipated and Ritter went some way to explaining the company’s previous reticence by pointing to the difference in maturity between the onshore (some 40 GW installed) and offshore (around 500 MW installed) wind sectors, saying that GE had focused on those areas which displayed the greatest growth, in this case the onshore wind sector in the US. But, he said, “Now is the time for investment in offshore.”

Emphasising the importance of reliability in the offshore wind arena, Ritter hinted at potential gearbox failure as a factor in its ScanWind decision, saying that direct drive technology was the way forward, particularly in the case of larger turbines of the type more typically associated with the offshore sector. Referring to its earlier foray into the offshore sector using a marinised version of its 3.6 MW onshore machine, seven of which were installed off Ireland’s Arklow bank in 2004, Ritter said that the company no longer intends to pursue development of that machine for offshore applications. Two key lessons had been learned by the company ahead of its decision to re-enter to the offshore market, Ritter said, “One is, don’t take an onshore turbine and put it offshore and the other one is ‘exceed on reliability’, and the belief is that the direct drive is going to rather exceed on reliability.”