EWEA 2015: Gamesa unveils medium-wind 3.3MW turbine

The G132-3.3MW is the first variant of a new turbine platform from the Spanish manufacturer.

The new modular platform builds mechanically and electrically on Gamesa’s 2.0-2.5MW range, featuring a high-speed drivetrain that comprises a main shaft with two bearings, a three-stage gearbox and a doubly-fed induction generator (DFIG).

"This drive concept has proven itself a reliable and efficient solution that has demonstrated its worth in over 10,000 2MW Gamesa turbines since 2002," said Gamesa chief technical officer José Antonio Malumbres, speaking exclusively to Windpower Monthly.

"We found that the DFIG-based solution remains well-suited to meet future grid demands in our main markets. A similar conclusion applies for concentrating the power converter, switchgear and MV-transformer inside the nacelle. The key benefits remain reduced cable power loss, optional factory pre-commissioning and, most importantly, superior levelised cost of energy (LCOE) performance compared with alternative configurations that have the power electronics in the tower base," said Malumbres.

Large rotors

The G132-3.3MW produces approximately 50% more energy than the G114-2.0MW, and around 30% more than the G114-2.5MW at Class II sites, according to the manufacturer. Referring to the new turbine’s large 132-metre rotor diameter, Malumbres pointed out that Gamesa has built up a comprehensive track record with 128-132-metre rotors from its 4.5/5.0MW series, launched five years ago.

"We are also rather unusual in having experience with both single-piece and segmented blades," he said. "The G132-3.3MW will initially be fitted with single-piece blades because today even 64.5-metre blades can be transported cost-effectively in our objective markets.

"However, we are prepared to offer segmented alternatives for future larger rotors," he added.

The blade design features proprietary Gamesa aerofoils. Technically, it builds upon the blades of the G114 models. This means a structural design based upon glass-fibre epoxy composite, and a vacuum-infusion process in a closed mould system. This avoids using carbon, which would complicate the manufacturing process and introduce higher quality risks.

"Our primary strategy is to offer the lowest benchmark levelised cost of energy in the 3-3.3MW class through maximising energy production and, in parallel, to minimise turbine head mass," Malumbres said. "Both rotor size and specific power rating are in our view very competitive in the medium- and high-wind 3MW sector."

Load reduction

The mechanical and electrical design of the new turbine are described by Malumbres as state-of-the-art. "We dedicated a large share of combined R&D efforts to developing a highly advanced load-control system. The main strategy was to substantially reduce incoming wind-induced rotor loads, which have a positive impact on the full load-path through the drivetrain, the load-carrying structure, tower and foundation," he said.

"Most important, loads reduction enables the use of lighter and cheaper materials, which reduces head mass and Capex. With the G132-3.3MW, we apply a combination of ‘conventional’ cyclic-pitch control — essentially a function of a blade’s position during each rotor revolution — plus a continuous measuring of actual blade root loads. This advanced load-control functional combination minimises rotor loads through the operation of the turbine."

The main drivetrain components — gearbox, generator and converter — are in-house developments that will be produced in Gamesa factories, but in markets without a local supply chain these will be procured from third-party suppliers.

Prototype schedule

The prototype is planned for mid-2016 with type certification by the year’s end, and series production to start in 2017. The turbine will be made available with three tubular steel tower options for a hub height of up to 114 metres, and a three concrete or concrete-steel hybrid tower choices for a hub height of up to 134 metres.