Fitting increasingly longer blades to low and medium-wind models is an ongoing industry trend, to both exploit previously uneconomic wind sites and to further drive down the cost of energy. Prominently displayed outside the event was the 64.4-metre long and slender Nordex NR 65.5 blade for the N131/3000 IEC IIIA turbine. The huge blade was mounted on a self-propelled multi-wheel "blade lifter" equipped with a pivotable blade adaptor, a high-tech development by German heavy transport specialist Scheuerle.
This second-generation vehicle is capable of lifting a blade up to a 70-degree angle, and rotating it around the longitude axis 110 degrees in a clockwise and anti-clockwise direction. This application is useful for blade transportation in forests and when negotiating complex road situations, including those with steep curves as found in the Alps.
Nordex blade
The NR 65.5 is today's second longest blade for onshore application - just short of the Gamesa blade with a 132-metre rotor diameter - and a huge step forward compared with blades of around 34 metres that were state-of-the art in 2000.
NR 65.5 design features include carbon fibres incorporated in the load-carrying girders and a specific outer section shape that helps to minimise sound level to 104.5 dB(A). This in turn allows turbine placement closer to noise-sensitive populated areas. It is destined for the N131 Delta turbine, due for installation later this year.
Siemens 3.3MW
Siemens presented a new version of its 3.2MW direct-drive model, increasing rating to 3.3MW and fitted with advanced aeroelastically tailored blades, which were initially developed for the 4MW SWT-4.0-130. The new blades have reduced mass. The SWT-3.3-130 has been developed specifically for the German market and is classed as an IEC IIA turbine.
The turbine incorporates a number of design modifications, including a switch from liquid generator cooling to an air-cooling system, now located inside the nacelle. Enhanced cooling capacity is necessary due to the bigger rotor and higher power rating. Structural modifications to accommodate the larger rotor diameter range from an upgraded hub and main bearing to a strengthened bed frame and increased yaw system capability. Generator design modifications include the fitting of stronger magnets that enable the higher output level.
The highest available hybrid tower for this model measures 142.5 metres at hub height and will be delivered by leading supplier Max Bogl group. The configuration offers a record 207.5-metre total installation height. The SWT-3.3-130 will become available in early 2017.
Journal bearings
German turbine design firm Wind to Energy (W2E) showed its new 2MW and 3.3MW Harvester series. Prototypes are planned for late 2015. The 2.0MW is an IEC IIIA turbine with 116-metre rotor diameter - a new record in this class.
The 3.3MW, also for IEC IIIA conditions, features a 130-metre rotor diameter and, like the 3MW model, is fitted with Winergy's semi-integrated HybridDrive medium-speed drivetrain, but an upgraded version with journal bearings. The latest W2E turbine licensee is Clean Ayr Energy, which is expected to start turbine production soon, with assembly facilities in the east-German city of Wismar.
There is growing interest in wind-turbine gearboxes incorporating journal bearings, not least due to the expectation that they will provide better gearbox reliability. Journal bearings are widely applied in many industrial applications and are known to combine compact size with a long service life and a high resistance to (static) impact loads.
Pioneer Winergy displayed a 3MW HybridDrive equipped with journal bearings in both gearbox and generator. A high-speed Winergy gearbox with journal bearings has been operating in a 2MW Vestas turbine in Scandinavia for more than 18 months despite cold-temperature start up and non-operating conditions (jiggling) being highly demanding and requiring extra measures to ensure sufficient lubrication performance.
Drivetrain choice in the market remains driven by hard facts and clear benefits as well as perceptions and individual preferences. Engineering consultancy Aerodyn announced the expansion of its AeroMaster turbine portfolio by introducing a 3MW IEC class IIIA platform called aM3.0/134. The licensed platform features a standard 134-metre rotor diameter in three different drivetrain concepts: conventional high-speed geared, HybridDrive or direct drive.
Zipper joint
German concrete tower specialist Drossler-Ventur unveiled a novel dry-bolted joint system for its octagonal-shape full concrete and concrete-steel hybrid towers. Previously Ventur vertical tower joints comprised interconnecting concrete block-type sections with a finishing grouting process. The new system consists of bolted connections described as a "zipper joint". Benefits include a much faster and cold-weather independent assembly process. Commercial introduction is planned for this year, said a Venture spokesperson. The towers are currently supplied to Nordex for the N117/2400 turbine and other turbine types, he said.
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