Spring Growth for Wind Turbines

A trend towards larger capacity turbines with longer blades and larger rotor diameters has been long established, with OEMs continuing to offer existing machines with a range of rotor diameters. But now, a new generation of still larger machines has been unveiled.

Among those companies unveiling new models REpower Systems AG, introduced its 3.2M114. Optimised for low-wind locations, the 3.2 MW turbine has a 143 metre hub height and a 114 metre rotor.

A hybrid tower made of concrete and steel is to be used. At the end of 2010, two 3 MW turbines were erected on 128 metre hybrid towers in Germany. A second 3.2M114 prototype, with a hub height of 93 metres and a steel tube tower is due to be erected late 2011.

Matthias Schubert, REpower Chief Technology Officer (CTO) says: “Especially in the European market, greater hub heights allow new sites to be developed. In southern Germany, for example, significant unexploited potential still exists in hilly terrain and forested areas.”

REpower majority-owners Suzlon, meanwhile, has also launched a low-wind version of an existing platform recently with its new S9X suite of machines.

An evolution of Suzlon’s platform, the upgrade is built around doubly fed induction generator-based technology. New blade designs with rotor diameters of 95 and 97 metres offer power production from moderate to low wind speeds, the company says, and tower heights of 90 or 100 metres are available for the 2 MW machine.

Serial production of the S95 turbine is scheduled to begin in Q2 of the 2011-2012 financial year, followed by the S97 in Q4.

Similarly, Alstom has revealed an upgrade to its existing 3 MW ECO 100 platform to specifically address low wind speed sites with a new (IEC Class III-A) turbine, the ECO 11X, with a larger rotor diameter. The exact rotor diameter, in the range of 115-125 metres, will be released in the second half of 2011, when the turbine will be offered for deliveries starting in 2013.

Earlier the company had announced a new partnership with French generator manufacturer Converteam in a move that will bring the company’s direct drive permanent magnet generator to Alstom’s under-development 6 MW offshore wind turbine.

Under the terms of the alliance, Converteam will supply Alstom with its Advanced High Density (AHD) direct drive PMG. Pierre Bastid, CEO of Converteam, commented: “The generator will have the largest torque of any PMG built to date, and with this project, we are making a big step in commercialising very large direct drive wind generators.”

The first two turbines are scheduled for installation off the coast of Belgium during the winter of 2011-2012 in collaboration with developers Belwind as part of a roughly 40 MW demonstrator project

Full commercialisation and series production of the turbine is anticipated in 2014. In January Alstom and EDF Energies Nouvelles (EDF-EN) announced that they would jointly bid using the 6 MW machine for projects under the recently launched French offshore wind tender for 6 GW by 2020.                                            

Converteam itself has recently been the subject of an acquisition by GE, which at the end of March announced that it had entered into a roughly US$3.2 billion agreement to acquire some 90% of the equity in Converteam from a controlling shareholder group.

GE’s announcement followed a similar move from American Superconductor Corporation (AMSC), which has signed an agreement to acquire Finland-based The Switch Engineering Oy.

Revealing the €190 million ($265 million) acquisition, AMSC said it expects The Switch’s background in advanced synchronous generators to help commercialise superconductor generators for its direct drive 10 MW SeaTitan turbine.

Direct Drive Systems

A number of new direct drive and hybrid systems have also been launched onto the market recently. For example, GE has introduced its 4.1-113 wind turbine, a 4 MW-class machine which it says is optimised for offshore use.

The company has signed a contract to supply one of the machines to Göteborg Energi for installation in Gothenburg harbour, Sweden, in the second half of 2011. The project is supported by the Swedish Energy Agency through its technology programme.

Earlier, in June 2010, GE revealed plans to install up to five offshore demonstration wind turbines through separate partnerships with Norwegian firms Statoil and Lyse and featuring a 4 MW machine with a 110 metre rotor diameter. Subject to successful completion of feasibility studies and the appropriate investment and funding decisions, the installation of the wind turbines is due to start in 2012.

This new machine builds on the 3.5 MW direct-drive design which GE obtained through its September 2009 acquisition of Norwegian firm ScanWind and which has been operating since 2005 on a coastal site in Norway.

A graphic showing Vestas’ 7 MW giant (Source: Vestas)

Siemens has also revealed its new direct drive gearless wind turbine for low to moderate wind speeds. The core features of the new SWT-2.3-113 wind turbine are its permanent magnet generator and a rotor diameter of 113 metres when fitted with the new Siemens B55 Quantum Blades. This new blade design is lighter than previous models but retains the strength of earlier generations, Siemens says. Each blade is 55 metres long and features a redesigned tip and root section. Meanwhile, the blade tip has also been redesigned to minimise loads and reduce noise levels to a claimed 105 dB, which Siemens says makes it one of the quietest on the market. The top head mass of the new machine is estimated at 114 tonnes, with the rotor comprising some 66,700 kg of that.

With a prototype of the new machine installed in the Netherlands in March, the SWT-2.3-113 is the second gearless wind turbine launched by Siemens following on from the SWT-3.0-101, the 3 MW direct drive wind turbine it launched in April 2010.

To date, Siemens has installed and commissioned a total of five direct drive SWT-3.0-101 wind turbines in Denmark and Norway with further projects planned in the US, Denmark and Germany.

“The first prototypes of our SWT-3.0-101 have been running for more than a year and fulfilling all expectations in terms of reliability and performance,” said Henrik Stiesdal, CTO of the Siemens Wind Power Business Unit.

“This year we’ll launch our 6 MW direct drive wind turbine, which will be particularly suitable for large offshore wind power plants,” he added.

Meanwhile, Northern Power Systems Inc has announced the introduction of a 2.3 MW permanent magnet direct drive wind turbine designed for the onshore market.

At the same time, the company said it had installed and commissioned its first prototype machine, owned by Heritage Sustainable Energy at the Stoney Corners wind farm in McBain, Michigan, in the US.

The prototype turbine, shipped from the new Northern Power factory in Saginaw, Michigan, is the largest such direct drive machine currently in commercial operation in North America, the company claims, adding that the Northern Power 2.3, features a superior power curve and a lower cut in speed than competing wind turbines.

New Entrants, New Technologies

A new entrant to the offshore sector, Doosan Power Systems, part of the Korean industrial conglomerate Doosan Heavy, has unveiled plans to develop a 6 MW offshore specific turbine. It plans to develop the turbine in order to enter the European market, where the company says it has identified a significant opportunity by 2020.

Furthermore, the company says that its clients have expressed an interest in seeing new competitive entrants to the offshore wind arena. It currently offers a geared 3 MW wind turbine product, first developed in 2004 and commercially launched towards the end of 2010, although currently this is mainly for its domestic market. In September 2009, Doosan installed a prototype machine in Gimnyeong, Jeju Island.

Doosan Heavy Industries & Construction also recently announced that it had acquired type certification for its 3 MW offshore wind turbine from DEWI-OCC in Germany.

Doosan says it has decided to aggressively step up its campaign to industrialise its wind power business. The company also says it plans to co-develop core parts, including blades, with local small and medium-sized enterprises.

While the conceptual specification of the new 6 MW machine is complete, Doosan says it is currently finalising both the technical details of the system as well as options for manufacturing and assembly — Scotland is one option being favourably considered with groundbreaking anticipated in 2012. Technical specifications — rotor diameter, and whether it is geared, hybrid or gearless — are due to be released as Wind Technology goes to press with the company still working with its design partners.

An on-site pilot prototype is due to be installed by the end of 2013 and this will be followed in 2014 by prototype and demonstration units offshore, likely comprising three to four machines. Currently, the company foresees commercial series production in 2015. However, it is also in discussion with its partners with a view to exploring an option to accelerate the development programme by a full year. In addition, it is open to the concept of jointly developing pilot schemes with utility partners, it says.

In a related move, the company has also said it expects to invest up to £170 million (around $255 million) in wind power in Scotland over the next decade.

Following positive discussions, Doosan and Scottish Enterprise have agreed to enter into a Memorandum of Understanding (MoU) that will likely see the company locate its R&D Centre of Excellence for Renewables at its current site at Westway in Renfrew, near Glasgow. A second phase will advance a further proposal for the establishment of assembly and manufacturing facilities in Scotland – now the company’s favoured location for wind turbine prototype-build and manufacturing.

Jean-Michel Aubertin, Doosan Power Systems’ CEO, said: “We hope to develop cutting-edge wind power technology that will enhance the role of renewables in the energy mix. This also is great news for Scotland’s economy in terms of jobs and inward investment. Doosan’s current wind power portfolio and position with the industry will continue to grow strongly over the coming years.”

Elsewhere, Germany’s Winergy presented a new 3 MW drive train concept in April 2011, the so-called ‘HybridDrive’, which combines the gearbox and generator in a single compact drive train concept. Winergy says that the HybridDrive uses only 20% of the quantity of rare earth elements required for direct driven wind turbines.

The new HybridDrive combines a two-stage gearbox with a permanent-magnet generator in a design that allows for a significant reduction of the nacelle size and minimisation of the overall weight, Winergy says. Direct connection of the gearbox to the generator enables the length of the drive train to be shortened by about 35%. Furthermore, Winergy says, its compact dimensions present various advantages for the design of a wind turbine.

For example, if the HybridDrive is used to replace an existing wind turbine design, it is possible to utilise the space that has been saved for the converter and transformer, instead of locating these in the tower. This choice of location for the transformers reduces the low-voltage cable losses, which subsequently improves efficiency, it says.

A modular design that allows assembly/disassembly of single elements through the internal service crane also represents an advantage over other existing integrated solutions, Winergy claims.

The company offers the HybridDrive optionally with journal bearings or conventional bearings for the planetary bearings. According to Winergy, the product distinguishes itself through its small product dimensions and the highest power density in the industry. Furthermore, the company adds, the concept can be easily implemented for the 6 to 7 MW power range of turbines.

Offshore Entries

Germany’s Nordex SE has revealed its new platform, the N150/6000, which has been developed specially for offshore. With a 150 metre rotor diameter, it has a nominal output of 6 MW and is a direct drive machine with a permanent magnet generator and a full power converter, a move the company says has enabled it to keep the, undisclosed, top head mass low. Nordex says it is currently engineering this drive train design in conjunction with its suppliers.

Explaining the move, Thomas Karst, CEO of the Offshore division, said: “Out at sea in particular, we must do everything we can to optimise the technical reliability of the turbine. With cost structures differing to those in the onshore market, we are able to implement a more complex drive system, namely a direct drive.”

Nordex has participated in a reference project in the German part of the Baltic Sea and says that up to 70 machines are to be installed in Germany from 2014-2015 onwards.

“Our strategy is being driven by the development of a competitive product. For this purpose, we are acting on the trend towards third-generation wind turbines, which are characterised by a substantially greater nominal output and lower specific weights,” said Thomas Richterich, Nordex CEO.

Nordex also recently launched its onshore 2.4 MW N117/2400 machine. The so-called Gamma Generation turbine has been specially developed for inland locations with a 117 metre rotor diameter and is the highest-yielding IEC III turbine in its class, with a capacity factor of 40%, its manufacturer claims. The N117/2400 is scheduled to enter series production in July 2012.

Nordex says it has also implemented a second efficiency package, which boosts the yield of its 2.5 MW series of turbines by 2.6% with its Nordex AP control module, which measures wind speed, direction and air density. Using this, the management system adjusts the generator to optimum effect, resulting in greater yields at low and medium wind speeds.

Vestas has also marked a new move back into offshore with a 7 MW machine boasting a massive 164 metre rotor diameter.

This new geared machine, at 7 MW, is significantly larger than previously announced plans for a 6 MW machine. The V164-7.0 MW features a swept area of more than 21,000 m².

Finn Strom Madsen, president of Vestas Technology R&D, explained the philosophy behind this particular design choice, saying: “We actually kept all options open from the start, running two separate parallel RD development tracks: one focusing on direct drive and one on a geared solution. It soon became clear that if we wanted to meet the customers’ expectations about lowest possible cost of energy and high business case certainty, we needed a perfect combination of innovation and proven technology and so the choice could only be to go for a medium-speed drive-train solution.”

Construction of the first V164-7.0 MW prototypes is expected in Q4 2012. Serial production is set to begin in Q1 2015, provided, Vestas says, a firm order backlog is in place to justify the substantial investment needed to pave the way for the V164-7.0 MW.

Commenting on the expected deployment of the machine, Anders See-Jensen, President of Vestas Offshore, said: “We expect the major part of offshore wind development to happen in the northern part of Europe, where the conditions at sea are particularly rough… we have specifically designed the V164-7.0 MW to provide the highest energy capture and the highest reliability in this rough and challenging environment.” Based on the potential market size, the business case for the machine is based on Europe and primarily the Northern European markets, Vestas says, though its adds that in due course it would take the machine to other regions, given demand.

DONG Energy and Vestas subsequently announced the signing of a letter of intent regarding testing of the new turbine. According to the letter of intent, DONG Energy will perform a design review of the V164-7.0 MW. Additionally, it is the intention that one or more could be installed at one of DONG Energy’s test sites for research and demonstration purposes. The companies are investigating the possibility of Vestas supplying a number of machines for DONG Energy’s Danish onshore Kappel test site, for example. The move could enable DONG to be one of the first to acquire this next generation turbine for a future commercial offshore project.

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