Ongoing US wind market uncertainties led GE to establish a new organisation responsible for identifying dedicated products for onshore growth regions outside the US, von Bobart explained. "The first outcome of this was a low-wind turbine specifically focused on the German market, where dedicated products for inland regions have become a key technology-market driver," he said. "The new German coalition government favours a key role for onshore wind as part of the Energiewende [energy transition] effort, which underlines that we are on the right track with our 2.5-120."
The first GE 2.5-120 prototype was installed in the Netherlands, followed by a second atop a hybrid concrete-steel tower in September in Bavaria, southern Germany.
Von Bobart added that customer feedback had been very positive, resulting in several major projects already under construction across inland Germany. Countries in eastern Europe and Scandinavia could develop into substantial additional 2.5-120 markets.
The combination of 2.5MW nameplate capacity and a 120-metre rotor diameter results in specific power rating of 221W/m2, which is in line with competitor Nordex's N117/2400 and N131/3000 low-wind models (223W/m2).
Hybrid tower
For the hybrid towers, GE teamed up with German specialist Max Bögl, which also delivers other leading suppliers with its Max Bögl Hybrid Tower System. This comprises multiple pre-cast 3.8-metre high coning rings stapled atop each other by precision "dry joints", followed by post-tensioning to a structural single assembly by internal steel cables. The next steps involves tubular-steel section mounting nacelle and rotor installation.
GE's current hybrid tower with 139-metre hub height offers 199-metre total installation height, just below an informal 200-metre limit, as opposed to some competitors such as Enercon who will cross this barrier with the new E-115 (206.5 metres). Von Bobart said: "It is fact that German height restrictions are being relaxed, and everybody is looking into higher towers. We are evaluating both larger rotors and higher towers, together with expanding our supply chain for hybrid towers, as this is the only relevant solution for Germany. But a further cost of energy reduction remains our primary goal."
The slender, about 59-metre-long blades for the 2.5-120 do not contain carbon and were developed in cooperation with "a leading independent European blade supplier".
Evolution
Mechanically, the 2.5-120 builds on the 2.x series introduced in 2003. This evolved into the 2.5MW 2.5xl (2008), a 2.75-103 and, last year, into a 2.85-103 high-wind model. The drivetrain comprises a compact main shaft with twin bearings, incorporated into a cast housing that forms an integral part of a cast main carrier in two flanged sections. The main shaft is supported by a double-row tapered roller bearing facing the rotor and a cylindrical roller bearing behind. GE claimed the drivetrain lifetime-enhancing benefits include "pure" rotor torque transfer into the gearbox and full absorption of rotor-induced axial forces.
With the 2.85-103 GE switched back from a permanent magnet generator to doubly fed induction generator (DFIG), also for the 2.5-120 and latest 3.2-103 high-wind turbine model standard fitting.
A genuine wind industry novelty of both later turbine models is battery-type storage integrated in the power-electronic converter DC-bridge, an advanced feature for enhancing grid stability and voltage regulation capability. Additional industrial internet and built-in control features help manage the intermittency of the wind and offer predictability and higher reliability/availability.
Assembly
Germany is a major focus for GE's wind division. The Salzbergen assembly facilities are instrumental for its entire European wind portfolio. The assembley of the 2.5-120 turbines for all markets will take place here, at least in the near-term. "Having manufacturing locations closer to projects helps improve logistics costs for our customers and makes wind projects even more competitive," said Von Bobart. "The cumulative track record of all 2X model versions is now around 1,300 units, and we aim to have a significant number of 2.5-120 turbines in operation by the end of 2014."
