Nordex head of product-line management Jorg Scholle says: "Our product market focus is for inland sites with 6-6.5m/s average wind speed at hub height. Under these conditions, the N117/2400 achieves over 3,500 full-load hours - or a capacity factor of more than 40%."
He explains that the N117/2400 should be viewed as the latest extension of the current 2.5MW Gamma series. These in turn are part of an evolutionary upgrading and optimisation process that commenced in 2000 with the 2.5MW N80/2500 Alpha series and also incorporates N90/2500 and N100/2500 models. "Compared with the initial N80/2500, swept area has more than doubled. Mechanically and electrically the N117/2400 is similar to the previous largest diameter N100/2500 model," adds Scholle. "The main modification is the introduction of a larger capacity proven gearbox from established suppliers in order to accommodate higher nominal torque. The higher torque is induced by the new larger rotor diameter and reduced tip speed, which is one of the driving forces behind the N117/2400's low-noise behaviour."
The primary new feature is the NR58.5, a slender 57-metre in-house developed rotor blade with carbon fibres incorporated in the load-carrying main girders. The key benefits of carbon are enhanced stiffness combined with favourable mass characteristics.
However, this fibre material is also very costly, harder to process and less production-failure tolerant compared with fibreglass so Nordex minimised its use.
Nordex also applied glass fibre reinforced epoxy-resin composite right from the start instead of polyester-based material. Scholle said this resin, compared with polyester, has a number of benefits including a superior suitability for incorporating a glass fibre and carbon fibre mix.
The N117/2400 is available with a 91-metre hub height tubular steel tower, a 141-metre steel-hybrid tower or a newly developed 120-metre hub height tubular steel tower that comes in five sections and has a 4.27-metre tower foot diameter.
Last December, Nordex successfully completed static blade testing. A dynamic HALT-type fatigue test - aimed at simulating the full 20-year rotor blade lifecycle within a six-month period - is already under way.