Close up - Nordex launches new low-wind machine

GERMANY: Nordex has launched a new 3MW N131/3000 low-wind IEC class IIIA model. The turbine is an addition to the 3MW/3.3MW Delta platform introduced earlier this year and features a 131-metre rotor, a new benchmark in the 3MW class segment.

Nordex's new 3MW turbine
Nordex's new 3MW turbine

In the first half of 2013, Nordex boosted its German 2013 market share from 3% to 11%, an achievement that was largely down to the N117/2400 turbine.

Speaking to Windpower Monthly, Jörg Scholle, Nordex head of engineering, said repeating a similar success story in the higher 3MW+ segment will not be as easy. "As key N131/3000 product-market strategy we again chose a conceptually similar 223W/m2 specific power rating to offer highly optimised efficiency," Scholle said.

"Also similar is a modest rotor blade-tip speed for low sound power performance (104.5 dB(A) enabling enhanced permitting and site integration. In the end, we combined the best of N117/2400 Gamma and Delta series technologies."

Technologically the N131/3000 builds upon the N117/3000 and N100/3300 Delta sister models and retains its high-speed modular drivetrain layout with double-fed induction generator and partial power-electronic converter. Scholle said this remains a proven economical solution offering the highest system efficiency. The gearbox had to be adapted for coping with a reduced rotor speed, resulting in a substantial higher torque level compared to the N117/3000.

The key new innovative component introduced in the N131/3000 is a slender 64.4-metre long in-house developed rotor blade called NR65.5. Structurally it builds upon the slender lightweight NR58.5 blade used for the N117/2400. This again means two "traditional" outer shells and the incorporation of carbon in the loads carrying structure (girders).

"What makes this new and substantially longer blade different is its very slender shape towards the tip, and a maximum chord (width) with 'flat-back' airfoil now extending further towards the blade root," Scholle said. "With this blade, energy capture could be maximised while simultaneously achieving a substantial loads limitation."

Tower choices for the N131/3000 include two tubular steel towers of 99 metres and 114-metres, as well as a hybrid-steel tower with 134-metre hub height. For the moment, this latter option is retained for the German market and, according Scholle, to a large degree dictated by road transport/logistical cost and, to a lesser extent, by height restrictions of a maximum 200-metre plus.

He said: "In addition, the market for high turbine towers is currently concentrated in Germany. For Scandinavian markets offering easy boat access, we are developing substantially higher towers with total installation tip heights of 210m. In the end, for each project a best match between the cost and benefits of tower height should be evaluated carefully to find an optimised solution that works."

At typical IEC class III sites with 6.5m/s average wind speed measured at hub height, a 24.8% higher annual yield has been calculated for the N131/3000 compared with the N117/2400. A prototype of the N131/3000 is envisaged for Q4 2014, followed by series production ramp-up in Q2-2015.

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