The 1.5MW turbine platform was originally developed by Friedrich Klinger at the Saarland University of Applied Sciences in Saarbrucken, south-west Germany.
At first glance the 1.5MW and 2.5/3MW platforms are technologically similar, yet there are substantial differences. One shared feature is the location of all power electronics, including the frequency converter and transformer, in the tower base.
Another is a toothed-belt blade pitch drive system. "All our permanent-magnet generators are in-house product developments, fully enclosed for maximum protection of sensitive coils and magnets against external environmental conditions," Rinck, a mechanical engineer who started his career as the first employee of Klinger's wind group in 2000, further explained the company's technology choices.
An outer-rotor configuration that has the magnets attached inside the generator rotor and rotates around the stator is common to all turbine platform and is claimed to offer superior cooling performance of the magnets.
Single rotor bearing
One major difference between the platforms is in the mechanical rotor support system. The 1.5MW series features a classic stationary main shaft (pin) solution with the rotor hub/generator rotor assembly supported by two main bearings. For the 2.5MW series, Vensys switched to a single rotor bearing solution, which offers simplified design and major head mass reduction potential.
Another major difference is in generator cooling systems choice. The 1.5MW generator incorporates a passive or natural air-cooling system, which offers reduced complexity by eliminating moving parts. The other side of the coin is that generator cooling performance depends on environmental factors, including especially ambient temperatures. The higher-rated 2.5/3MW Vensys generators incorporate an active air-cooling system, which includes electric fans and an air-to-air heat exchanger.
"The 3MW platform builds technologically upon our 2.5MW turbine design," Rinck said. "The generator is new, especially with respect to an increase in generator diameter and generator length. This was necessary in order to effectively cope with higher thermal loads due to a combination of 20% higher power rating and a larger maximum 120-metre rotor diameter. Several other components and systems had to be adapted as well, due to increased size-related loads."
The 1.5MW turbine has been produced since 2003, with additional 82-metre and 87-metre rotor diameters introduced at a later stage. A 2.5MW Vensys 100 prototype was installed in 2010 in Wagenfeld, Germany. Thecompany added 109-metre and 112-metre rotor diameters. These latter versions are offered with 140-metre concrete-steel hybrid towers supplied by Max Bögl for IEC class IIA and low-wind IIIA sites.
"The main markets for these high towers are Germany and Austria and, in future, perhaps Poland as well," Rinck said. "For China our 2.5MW series is fitted as standard with either 100-metre or 106-metre rotors. The latter size is explained by specific local supply-chain conditions, with the biggest rotor being increasingly preferred in line with general wind market trends."
More than 600 2.5MW turbines were operational by mid-February. The bulk of these are Goldwind machines in China, but another 17 2.5/112 turbines of this total operate in Germany and a small number of the Goldwind brand in North America and Australia. ReGen Powertech of India has acquired the second license for the 2.5MW series, although Rinck said a prototype of this had not been built.
A 3MW Vensys 120 IEC class IIIA prototype is envisaged before the end of 2014, and a medium speed IEC class IIA Vensys 112 sister model is also planned.