One of the German industry’s recognised strengths is mechanical and electrical engineering, so it is no surprise that numerous, often highly specialised firms, supply the global wind industry with a range of components and systems that are renowned for their quality.
The country exports gearboxes, generators, controls and drives, power converters, transformers, brakes, and (large) precision bearings.
Another recognised German success is the close cooperation between technical universities, technology research institutes and the wind industry, reinforced by a countrywide professional network comprising thousands of engineers, scientists and other specialists.
A major share of German turbine manufacturing is now concentrated in the north of the country, focused around a number of cities and coastal towns such as Bremerhaven, Emden, Cuxhaven, and Rostock.
Components manufacture by contrast is spread out over the country, even though many suppliers of large components choose production locations near their main customers or major export ports.
The port of Bremerhaven has become Germany’s main offshore wind industry production and logistics hub, attracting equipment providers, as well as offshore installation firms and dedicated service contractors.
Germany’s turbine suppliers feature several large players, such as Siemens Wind Power, with headquarters in Denmark, Enercon, Repower and Nordex.
Several smaller German and Germany-based suppliers include Bard, ENO energy, Fuhrländer, and PowerWind. Areva Wind (formerly Multibrid) and GE Wind Energy’s European onshore wind turbine facility are also based
Germany is perhaps the only country outside Asia to produce regular new wind industry entrants, with direct-drive turbines makers Avantis Energy and Schuler being recent examples.
TURBINE MANUFACTURE: PRODUCERS OF QUALITY
German companies boast a unique track record for design, operation and optimising of wind turbines. Enercon, Repower and Multibrid were the world’s first to introduce wind turbine models as large as 4.5–5MW from 2002.
Enercon’s direct-drive turbines achieved a reputation for quality, reliability and performance, while Repower, producing fast-speed geared models, also quickly earned a strong reputation. Both companies’ turbines can be seen worldwide.
Meanwhile, an innovative German medium-speed, hybrid wind technology known as Multibrid first appeared in 2001.
The concept, designed by Aerodyn Energiesysteme, aimed at combining the reliability of direct-drive with the lower weight of fast speed geared systems, and is now growing in popularity.
Founded in 2003 Bard, an integrated offshore developer, entered the wind market with its 5MW offshore turbine, designed again by Aerodyn, aiming at combining state of the art components with proven technologies.
The company earlier this year installed two second-generation 6.5MW prototypes, with a new design gearbox but with the same nacelle and weight.
Germany’s market leader Enercon is also recognised as a pioneer producer of in-house built components for its wind turbines, today as large as 7.5MW.
The company develops and manufactures ring generators of up to 12 metres in diameter for its direct-drive turbines, and designs its own power converters, turbine controls, and grid integration systems.
Its components are used only on Enercon turbines, which are installed across Europe and in other countries such as Canada, Turkey and Antarctica. Enercon’s direct-drive turbines, known for reliability and quality, are attracting strong interest across the world.
COMPONENTS PRECISION AND TECHNOLOGY
Engineering and design consultancies
A number of German engineering consultancy firms develop turbines for third-party clients.
Perhaps the best known is Aerodyn Energiesysteme, which in the mid-1990s developed an innovative 5MW offshore wind turbine with a medium-speed geared drive system called Multibrid.
Its distinct design features include a single-stage gearbox, a single rotor bearing and a medium-speed generator, all integrated into a single-cast main chassis.
The patented concept is a hybrid solution between conventional high-speed geared and direct-drive turbines.
This design focuses on the enhanced reliability of a less complex single-stage gearbox, minimising the risk of component misalignment due to the fully integrated housing, while eliminating weight penalties that were associated with direct-drive models at that time.
WinWinD of Finland and Areva Wind in its Bremerhaven facility manufacture Multibrid-type wind turbines (WinWind’s WWD-1 and WWD-3, and Areva’s M5000 Multibrid). The medium-speed drive system was slow to gain popularity but is now becoming a genuine industry trend.
Aerodyn has designed many wind turbines for German clients, including the 5MW Bard fast-speed geared turbine, as well as for foreign companies, especially in Asia. Other products from Aerodyn include rotor blades, electrical systems, and towers.
University development group
In 1990 German wind pioneer Professor Friedrich Klinger founded a wind turbine development group at the Saarbrücken University of Applied Sciences, resulting in turbine developments that have had a major impact on the global wind industry.
In 1995 they designed the Genesys, a 600kW direct-drive turbine with a permanent magnet generator (PMG), which had not been used in commercial wind turbines before. Permanent magnets allow a more compact design, plus a higher partial-load efficiency of the generator.
Industrial partners working with Professor Klinger together founded Vensys, producing a prototype of its first commercial wind turbine in 2003, the 1.2MW Vensys 62 with an unusual belt-driven pitch mechanism as well as the PMG with passive air-cooling. A technology licence was awarded to Goldwind that year.
In 2004 the 1.5MW Vensys 70/77 was developed. With an enlarged rotor diameter, and now also available with an 82-metre rotor size, it has become a huge commercial success.
More than 3,000 of these machines plus around six units of a new 2.5MW model have been installed by Goldwind, almost all in China.
KNOWLEDGE KEY CONCEPTS
Gearboxes, an essential component of most wind turbines, are typically sourced from third-party suppliers.
These precision components speed up low rotor revolutions to match the much higher generator speed. Winergy is the world’s largest supplier of gearboxes, providing many main turbine suppliers.
The company now makes custom-made gearboxes up to a 6.5MW power rating. Other well-known German gearbox suppliers include Eickhoff, Bosch-Rexroth, Renk, and new wind industry entrant ZF.
While direct-drive generators are often manufactured in-house by the turbine company, medium- and fast-speed generators are usually sourced from third-party suppliers.
One popular fast-speed generator principle is the so-called doubly-fed induction generator (DFIG).
In the early 1990s it was widely considered an obsolete technology but in 1996 German firm Tacke Windtechnik (now GE) integrated a DFIG into a 1.5MW pitch-controlled, variable speed, geared wind turbine.
A few years later DFIGs had become a wind industry standard and the concept is still widely applied today.
One main benefit of DFIG is that up to 75% of the power generated can be fed directly to the electricity grid, meaning the turbine only requires a relatively inexpensive partial converter for the remaining power produced. This represents substantial cost-saving.
Today, permanent magnet type synchronous generators are on the rise in geared and direct-drive turbines. Key German generator suppliers include Siemens and its associated firms Winergy and Loher, Partzsch, Weier, VEM Sachsenwerk, and SSB Duradrive.
The global wind industry sources a wide range of roller bearings from the German market. These include small and medium-size bearings that are among others used in gearboxes, generators, pitch-drives and yaw-drives.
Medium-size bearings are, among others, used to support rotor shafts, while yaw bearings, rotor blade pitch bearings and single rotor bearings are usually much larger.
One of the largest single rotor bearings in use is in the 5MW Areva Wind Multibrid M5000.
This precision component is delivered by the Schaeffler Group and measures 3.2 metres in diameter and 0.49 metres wide, and weighs 7,200kg.
Schaeffler like other German bearing suppliers including Rothe Erde, Liebherr and IMO, is known for its engineering and innovating capabilities and for series production of high quality precision components.
The nacelle main chassis of modern wind turbines is often a heavy-duty cast iron piece, while the rotor hub is always built as a cast component.
These castings for especially large 4.5—5MW turbines have become very heavy and bulky, some requiring a controlled cooling-down period of as long as six weeks.
When a new larger size of wind turbine emerges, at the initial stages there is usually only a limited number of suppliers capable of producing the matching castings.
With the arrival of the first generation 4.5-5MW size turbines for example, only few foundries in Germany such as Siempelkamp, MAN, and Friedrich Wilhelms-Hütte, were able to produce castings with component masses as heavy as 40 to 50 tonnes to the required quality standards.
But a common parallel trend is also that the number of foundries capable of delivering such complex heavy castings in the required numbers and of the right quality grows in parallel with wind industry advancement.
Now, more German foundries are capable of handling the even larger and heavier 6MW to 7.5MW turbine castings, including the 70-tonne main chassis for the BARD 5.0 and BARD 6.5 turbines.
Of the many different rotor blades developed by German wind turbine suppliers, two models stand out. The PowerBlade 61.5 metre is the longest to come out of Germany.
Made of glass-reinforced epoxy composite, it was developed by Repower and blade manufacturer SGL Rotec for Repower wind turbines.
The Enercon 57-metre segmented blade was the first of its kind. It is made with a fabricated steel inner section, and the outer shell made of glass-reinforced plastic composite.
This design allows it to be made in sections, greatly facilitating transportation.
Several specialised engineering consultancies, such as Aerodyn and Euros, also design rotor blades for third-party clients, and some blade developers such as SGL Rotec provide manufacturing facilities and services.