Husum 2007 Wind technology overview: 2007 at HusumWind

Wind turbine buyers are faced with serious equipment delivery periods of two years and longer. As a consequence, many suppliers seem so busy turning out their volume models in big numbers that the development of next generation wind turbines seems to have become second priority. Eize de Vries reports.

With around 640 exhibitors, and visitors from around the globe, HusumWind 2007 was again this year regarded as one of the world’s leading wind industry events. The renewable energy industry of host country Germany is in buoyant mood and booming. In his opening address federal environment minister Sigmar Gabriel said that the entire sector currently employs about 214,000 people, of which 70,000 are in the local, but internationally operating, wind industry. The ambition of the German government is to cover 30% of total energy demand by 2020 with renewable sources and up to 45% in 2030. Of this, a key role for repowering and offshore wind power is envisaged. Among the challenges ahead include generating huge amounts of wind power cost-effectively at demanding German North Sea sites – typically situated 40–50 km offshore in water depths of 40–50 metres. Gabriel stressed that achieving these impressive goals will not be at the expense of taxpayers. Each German citizen now contributes a compulsory €1 per month on top of their energy bill to finance the ongoing energy transition. This modest amount will in time rise to €1.40 per month as an ‘investment in the future of our children’ as Gabriel phrased it.

The Enercon E-126 – the 6 MW turbine has been installed on a prefabricated concrete tower in Emden, Germany jan oelker


New drive train solutions, but convention stays strong

Wind technology preferences on optimal drive train solutions continue to differ. Options range today from conventional geared drive, with around 85% of world market share, versus a gearbox with multiple generators such as Clipper, the slow-speed Multibrid type drive solution with a single-stage gearbox, and direct drive with no gearbox. Another ongoing wind industry debate focuses on the merits of heavy wind turbine concepts like some proven German 5–6 MW+ class designs set against prominent lightweight models like the Vestas V90-3 MW.

Multibrid moves

Among interesting recent wind technology innovations presented in Husum was a full-scale model of the novel SCD 2.5–3 MW wind turbine concept. SCD technology is the latest wind turbine development of the German engineering consultancy aerodyn Energiesysteme. The new concept further builds on the patented Multibrid technology the company developed over ten years ago, but the combination single main bearing and gearbox is different. The Multibrid technology is now applied successfully in three commercial products: Finnish WinWinD turbines of 1 MW and 3 MW, and the 5 MW Multibrid M5000 offshore turbine.

The Enercon E-126 being assembled jan oelker

Distinct features of the highly compact SCD drive train include a single main bearing, a two-stage planetary gearbox and a medium-speed generator. ‘The gearbox and generator feature an identical outside diameter and are flanged together by concentric joining surfaces, thereby eliminating any misalignment risks. The main bearing is flanged directly to the gearbox input shaft side. With this new design approach we achieved a SCD nacelle mass of 55 tonnes as compared to about 70 tonnes for a conventional 2 MW geared wind turbine. The nacelle length is only 7.4 metres as compared to around 14 metres for a conventional concept, while a nacelle cover could be eliminated,’ says aerodyn spokesperson Markus Rees, adding that aerodyn has not issued a SCD technology licence yet, but is talking to several interested parties.

Rotor blade family

Besides complete wind turbines, aerodyn is well known for numerous in-house developed rotor blade designs produced during the past decades for a series of equipment manufacturers. In the past, each rotor blade was custom designed for a specific client, explains Rees. However, a new strategy is to design an entire aeroBlade rotor blade family for respectively 1.5 MW, 2 MW and 2.5 MW class wind turbines, and with rotor diameters ranging from 70 metres to 103 metres. The bolt circle diameter for each power rating class has also been standardized in order to make the blades fully interchangeable with comparable rotor blade designs of other suppliers. A third new aerodyn wind technology development is the aeroControl wind turbine control system. Says Rees: ‘Our aim is to possess a capacity to offer a complete package deal to international clients. This ranges from a rotor blade technology licence to a complete wind turbine solution, including control system and all required production technology.’

cutting edge

LM Glasfiber of Denmark has been awarded the Product Prize 2007 by the Confederation of Danish Industries (DI). This was the 13th time the prize has been awarded, with the panel of judges reviewing 31 of the best new products in Denmark. LM Glasfiber received the award for developing the world’s longest rotor blade at 61.5 metres, successfully applied at the REpower 5M offshore wind turbine.

In its motivation for awarding this year’s product prize to LM Glasfiber, DI emphasized, among other things, that ‘on the basis of four years’ research and development efforts, LM Glasfiber has developed a whole new generation of blades that truly pushes the envelope in terms of materials and engineering.’

New wind entrants line up

One of the surprise developments in the global wind industry is the impressive renaissance of the sub-megawatt class and, more recently, capacities of about 1 MW to 1.3 MW.

Newcomer Unison Co. Ltd. of South Korea has developed a 750 kW pitch regulated direct drive turbine fitted with a water-cooled permanent magnet type generator (PMG) that has entered commercial production. The new turbine type is available with three different rotor diameters. The Unison U50 (IEC IA wind class) features a 50 metre rotor diameter and is the country’s first wind turbine development, realized with financial support of the Korean government. The two other sister models include the U54 (IEC IIA) and U57 (IEC IIIA). Design assistance was provided by aerodyn with design of machine structure and rotor blades, and wind turbine load calculations. The generator rotor is connected directly to a rotating main shaft supported on two main bearings. The PMG features 42 pole pairs, weighs 22 tonnes, and has a 3.8 metre diameter with a 1.2 metre depth. The drive train is housed in a compact spherical nacelle housing. A prototype was erected during the winter of 2005.

A variable pitch turbine hub from GE Energy on display at the show

In addition, Unison is working on a much larger 2 MW turbine, its U88 model. This variable-speed, pitch-regulated turbine type features an 88 metre three-blade rotor and a conventional geared drive train system that comprises a single main bearing, a three-stage gearbox and a PMG-type synchronous generator with full-converter. According to Unison CEO Doo-Hoon Kim, his company made the choice for a conventional 2 MW turbine in order to shorten development time. Similarly to the 750 kW unit, design assistance was again provided by aerodyn.

Besides aerodyn, a range of European and at least one US engineering consultancy are involved in the design of components and complete wind turbine concepts for Asian and other clients. For instance Windtec, a subsidiary of US-based American Semiconductor Corporation, develops customer-specific wind power systems from 750 kW to 5 MW for third parties via licencing or technology transfer agreements.

Emerging players and established giants

A second sub-megawatt class wind industry newcomer is Conergy of Germany. This rapidly growing renewable energy company already employs over 1500 staff and has a presence in more than 20 countries. Activities include photovoltaics, solar thermal energy, heat pumps, bio-energy and wind power. The Conergy PowerWind 56 is a newly designed 900 kW variable-speed, pitch-regulated turbine fitted with a 56 metre rotor diameter and a conventional drive train system. Among the technology features are a synchronous type PMG with full converter and a three-stage gearbox. With its new product, Conergy aims at meeting ‘the requirements and conditions of emerging wind markets.’ A prototype has been operating in Bremerhaven, Germany, since early summer 2007. Earlier Conergy acquired the existing design of a 6 kW four-blade turbine and renamed it the EasyWind 6 AC for grid-connected and EasyWind 6 DC for off-grid applications. The product has received a focus Energy Gold Award 2006 for product design and the Plus X Award 2007 for ecology friendly features.

Another wind industry entrant is Innovative Wind Power (IWP), a subsidiary of the Innovative Energy Group, headquartered in Dubai in the United Arab Emirates. IWP recently announced its new three-blade IWP-1250 Falcon 1.25 series. The company’s operational centre is in Germany, spread over Osnabrück for sales and project development, with wind turbine series manufacture in Bremerhaven. IWP’s first product is a gear driven variable-speed, pitch-controlled 1.25 MW turbine that will become available with three different rotor sizes: 62 metres, 64 metres, and 70 metres. Main features include an integrated modular-type drive system comprising a two-stage planetary type gearbox and a patented synchronous type generator composed as a single unit, says company sales representative Patrick Wurster. A prototype is planned for January/February 2008.

And, among multiple Chinese manufacturers that have emerged during the past years is Nantong Kailian. This company has developed a 2 MW geared variable-speed turbine that features a 82 metre three-blade rotor. According to a spokesperson at the company’s booth in Husum about 85% of all turbine components are locally made and a prototype is running.

Last June, French power engineering giant Alstom SA agreed to buy Spanish wind turbine manufacturer Ecotecnia for €350 million. Barcelona-based Ecotecnia operated as a co-operative and designs and assembles wind turbines up to 3 MW. Alstom’s range of power generation equipment and services serves the gas, coal, hydro, wind power, solar and nuclear industries. With the acquisition Alstom follows the example of competitors like Siemens and General Electric, which both entered the fast-growing renewable energy business years ago. The French firm is already a market leader in hydropower.

Big … and biggest

As a wind industry trend, the era of megawatt class stall-regulated wind turbines is gradually drawing to a close. Nonetheless, engineering consultancy Wind to Energy (W2E) of Germany has developed a new megawatt class turbine type for its licensee Fuhrländer AG. The mechanical concept of the FL 1250B builds on the robust 1 MW Fuhrländer FL 1000, but incorporates the latest design criteria. W2E mechanical design specialist Reinhard Grever observes: ‘In analogy to the FL 1000 the rotor is again bolted directly to the gearbox and the complete drive train is connected to the main chassis through elastomer elements aimed at both reducing vibrations and sound level.’ The new machine has a maximum output of 1.3 MW and is available with rotor diameters of 54 metres and 62 metres. A first 5 MW project with four turbines was recently completed 80 km north of Cape Town in South Africa, as part of the planned 30-turbine Darling Windfarm development.

A generator from SCD Technology dwarfs a young admirer at Husumwind 2007

The largest wind turbine nacelle on display in Husum was Fuhrländer’s 2.5 MW FL 2500, a W2E design that is available with rotor sizes of 80 metres, 90 metres, and 100 metres. A prototype with a 90 metre rotor was erected during the middle of September 2006 on a 160 metre lattice-type tower near the village of Laasow, 150 km south east of Berlin. According to Fuhrländer spokesperson Walter Lutz, the machine during the first year of operation generated 30% more electricity compared with a similar installation on a 100 metre tower. In common with multiple state-of-the-art wind turbine concepts, the FL 2500 comprises a single rotor bearing with no main shaft. A novel design feature is that gearbox and rotor bearing are assembled on separate flanges some distance apart. A so-called flexible shaft coupling connects the two mechanically, but prevents rotor-induced bending moments being transferred into the first planetary gearbox stage on the input side. The rotor-bending moments are instead transferred directly into the main chassis and only rotor torque is passed onto the gearbox input shaft by means of multiple elastomer type elements. The latter are known to effectively dampen drive train peak loads, and this in turn has a positive effect on gearbox lifetime. Fuhrländer, meanwhile, reports strong demand for its flagship wind turbine. In response it is building a new production location in the vicinity of the Siegerland regional airport and the A45 Dortmund to Frankfurt motorway. At over 200 metres in length, the new production halls offer sufficient capacity to build fifteen 2.5 MW class units every month. Around 200 employees, in addition to trainees, will work in the component and final assembly, testing and administrative sectors.

Nordex N100

In August, Nordex AG of Germany announced the launch of the 2.5 MW N100 developed for low and medium-speed inland sites (6.5–7.5 metres/second) as a further expansion of the N80/N90 multi-megawatt turbines. The initial 2.5 MW N80 (rotor diameter 80 metres) prototype was a pioneering product in its class and originates from 2001. A 2.3 MW N90 sister product was introduced in 2003, and the 2.5 MW N90 in 2005/06. The current track record of the N80/N90 series adds up to 400 turbines since 2001, with a further 370 under assembly. For the first turbines externally sourced 49 metre blades will be applied, said Nordex press spokesperson Felix Losada. Following an extension of the production facilities in Rostock at the end of 2007, N100 blades also will be produced in-house. As part of a near-miracle recovery since 2005, Nordex group revenues during the first half of 2007 increased by 28% to €323 million. Non-German business accounted for roughly 82% of total revenues. ‘With an order backlog of around €2.1 billion, our sales forecasts are secure beyond 2008,’ said CEO Thomas Richterich earlier this year. In 2008, Nordex wants to double its 2006 sales figure to more than €1 billion. Roughly 94% of total business originates from European markets and is handled by the company’s Rostock facilities.

By 2010 annual wind turbine production capacity will be expanded from 850 MW to 2000 MW. In-house rotor blade production is to be increased no less than threefold. Depending on capacity utilization levels, at least 300 new jobs are to be created in Rostock. Existing facilities in China will be extended too, while a production presence in the US is considered.

Besides Fuhrländer and Nordex, an increasing number of competitors already commercially offer, or envisage introducing, a 2.5 MW–3 MW model with rotor diameters up to 100 metres (see Table 1).

GE Energy commences series production of the long-awaited GE 2.5xl during the second half of 2008. Today’s workhorse is the GE 1.5 MW series. The 77 metre rotor machine is the main volume product and the overall track record of the 1.5 MW series now stands at nearly 7000 units, which is expected to grow to 10,000 by the end of 2008. The new GE 2.5xl has been well received in Europe, says the company’s Wind Energy Europe Managing Director Rainer Bröring: ‘Customers appreciate the large 100 metre rotor that ensures a high capacity factor, our rigorous design for reliability, product development strategy, and the multi-year operational track record of over a hundred turbines.’ With the GE 2.5xl turbine GE aims at recapturing a double-digit market share in Europe by 2009, while a 60 Hz version will be introduced in the US by 2010.

Hybrid technology

Finally direct drive pioneer Enercon regards wind turbines as a key technology, but not the only solution in an ongoing process towards a much greater role for renewable energy sources in the future power supply infrastructure. The German market leader has, therefore, during the past years gradually expanded its activities into additional power generation fields, energy efficiency and energy storage technologies. Enercon has already developed and commercialized a wind-powered seawater desalination system, and a wind-diesel system that runs up to 90% on wind energy. Recently the company entered the hydropower market with in-house developed technology comprising a slow rotating 5 MW gearless direct drive generator coupled to a Kaplan hydro turbine. The new hydropower plant is based on Enercon’s proven direct drive variable speed wind technology, and the company claims a 10% yield increase compared to ‘conventional’ hydropower conversion systems. Two units will be supplied to a 10 MW project in the river Weser near Bremen, and installation commissioning is planned for the end of 2009.

A second development is a hybrid power plant that operates 100% on renewable sources. This venture is a joint project of German companies Enercon with its wind turbines, Schmack Biogas and its biogas plants, and Solar World photovoltaic modules. The concept envisages each hybrid power plant comprising several distributed power generation units (wind, solar, biogas), a 1 MW pump storage ‘plant’, and an ‘intelligent’ central control unit. The latter is the heart of the hybrid power plant and among other functions analyzes short-term forecasts for wind and photovoltaic production. The biogas and pump storage systems provide the necessary system balancing capacity when wind and solar energy are not sufficient.

Enercon mans the main-brace

An innovative transport development is the E-Ship, Enercon’s 130 metre long, 22.5 metre beam freighter that is to enter active service from the end of 2008 for the shipment of wind turbines to export markets. The E-Ship, currently under construction at the Lindenau-Werft shipyard in the port of Kiel, will be fitted with a main diesel–electric propulsion system. A secondary propulsion source comprises four Enercon-designed cylindrical-shaped Flettner rotors, named after the German inventor Anton Flettner who developed the marine propulsion system in the 1920s.

Once operating in a wind flow, the 4 metre diameter and 27 metre high rotors are claimed to generate 10–14 times the propulsive force of a rectangular or trapezium shaped sail with identical area. The principle is based on the so-called Magnus-Effekt, a phenomenon named after the German scientist Heinrich Gustav Magnus. Enercon expects to achieve fuel savings of 30%–40% with the E-Ship compared to a conventional diesel powered vessel of the same size.

Erection of the E-126 with a 135 metre hub height on a prefabricated concrete tower composed of coning rings was completed during the first week of October, near Emden. The huge turbine features two section, segmented rotor blades with the company’s novel high-yielding airfoil design. The power rating is officially 6 MW, but is rumoured to be in the 7 MW+ range.

Storage technology

US-based General Compression (GC) plans to enter the wind market with a new innovative wind technology whereby the rotor does not drive a generator that produces electricity, but an air compressor instead.

The device effectively stores wind energy that can then be used for driving generators on demand, overcoming the variability problem attached to wind power generation. GC’s CEO Eric Ingersoll sees a number of distinct opportunities for the compressed air technology: ‘One option is to create internal system storage capacity by expanding existing wind projects with a number of our wind turbines. A second option is to provide peak power to a system on demand. A third possibility is to engage in dedicated wind projects as a main contractor.’

As a next step the young company plans to design a new 1.5 MW wind turbine with a 77 metre to 82 metre rotor featuring a novel variable-speed and variable-capacity air compressor. Ingersoll is already in a winning mood regarding market opportunities for GC’s new technology, reporting an ‘overwhelming’ response from big utilities in the US.

Offshore developments

Get connected
German utility E.ON Netz recently announced a €300 million investment in a high-voltage DC (HVDC) cable that will connect multiple future offshore wind farms in the Cluster Borkum 2 region to the national electricity network.

As part of the unique development each of the wind farms will be connected to E.ON’s offshore high voltage station by means of multi-socket connection and an individual sea cable. From there, a single export cable transports the power to shore, a much more cost-effective solution compared to the alternative whereby each wind farm is connected by its own export cable. ABB has been contracted to build cable connection over 100 km to the German north coast. The first phase involves a 400 MW line that is due to be operational in 2009. For the cable connection ABB will use its HVDC Light technology that it says enables efficient energy transport over long distances and a stable connection to the network onshore.

Floating on air
Norwegian energy company Hydro and Germany’s Siemens Power Generation (PG) have entered into an agreement to co-operate on technology to develop floating wind turbines based on Hydro’s Hywind concept.

Hydro already has a licence to place a floating demonstration turbine offshore near Karmøy, an island off the southwest coast of Norway, and Siemens is to deliver the first wind turbine for the proposed 2009 demonstration unit. The company is also considering the possibility of locating the wind turbine near an oil installation with the aim of supplying it with renewable energy.

Floating offshore turbines can generally be installed at sites with much greater water depths when compared to offshore installations on fixed foundation structures. Hydro expects to apply this technology in future on sites located 90 km–180 km offshore and in water depths up to 700 metres. Locating wind turbines far offshore has obvious advantages, such as reduced visual impact, reduced interference with bird migration and increased power production due to strong and stable wind conditions. The design by Hydro comprises a three-leg able tethered system similar to the concept used in oilrigs. It also includes a long submerged floating concrete cylinder that is ballasted.

Siemens has also announced that a partnership between Airtricity and Fluor has signed a reservation agreement that secures 140 of its 3.6 MW wind turbines for their proposed Greater Gabbard Offshore wind farm (GGOWF) off the British coast. The proposed 504 MW offshore development involves equipment delivery in 2009 and 2010.

Winergy AG of Germany has inaugurated its new 14 MW test rig for multi-megawatt class offshore wind turbine gear units. The record-breaking test rig follows only three years after a 7.5 MW device was put into operation. Today’s largest commercial gear driven turbines are in the 5 MW–6 MW class. Winergy is a Siemens company that claims to be the world’s only provider of complete geared drive systems for the wind power industry.

V90-3 MW withdrawal
Vestas Wind Systems of Denmark recently announced the withdrawal of its V90-3 MW flagship model from the offshore market, which is already employed in major offshore projects like Kentish Flats and Barrow (UK) and OWEZ (NL). According to industry sources the world’s largest wind turbine manufacturer is developing a ‘completely new’ offshore wind turbine model. The withdrawal action is said to be a response to multiple gearbox problems reported at several of its turbines operating offshore and onshore. Further details on the new/optimized/revised turbine model are not yet available.

Along with Siemens, REpower Systems AG and Multibrid Entwicklungsgesellschaft are the only two remaining offshore wind turbine suppliers. Both REpower and Multibrid have developed a 5 MW offshore wind turbine and each has operated its first land prototype since 2004. REpower operates several more land machines and two 5 MW offshore installations in a record depth of 44 metres of water off the Scottish coast. It will deliver another six of its so-called 5M units for the first phase of the Belgian Thornton Bank project and another six to the German Alpha Ventus (formerly Borkum-West) project. The companies have now entered the series production stage and each has established new manufacturing facilities in Bremerhaven. REpower spokesperson Dietmar Gosh confirmed in Husum that his company is working at an optimised 6 MW version of the current 5M giant. The successor turbine model will be named 6M but does feature the same LM 61.5P rotor blades, again resulting in a 126 metre rotor diameter.

Project developer Prokon Nord Energiesysteme acquired the Multibrid M5000 technology and all other rights in 2003 while the huge French nuclear power supplier Areva took over 51% of Multibrid Entwicklungsgesellschaft’s shares in mid-September. Earlier this year Areva lost the takeover battle for REpower with Suzlon Energy of India. Prokon Nord managing director Ingo de Buhr said in Husum that Areva wanted to step into the wind industry backed by a party with innovative technology, but in turn Areva brings in fresh capital to finance further growth. ‘Important for us is that one of the world’s biggest power engineering companies concluded that Multibrid means sound technology as a clear sign to the market and towards financial parties,’ said de Buhr. Before the end of the year, two 0-series land turbines will be erected on a land location at Bremerhaven, bringing the number of installations to four. In addition, thirteen steel Tripod foundations designed by Prokon Nord subsidiary OWT have been ordered. Six are destined for Alpha Ventus and the remaining seven units for the first 105 MW French offshore wind farm at Seine-Maritime.

Finally, according to experts the limited availability of wind turbine installation vessels might become a serious future bottleneck, considering the number of planned and approved offshore wind farm projects for development over the coming years. Rotterdam-based Smit Marine Projects seized the opportunity and has entered the market with the self-elevating barge ‘LISA.’ This extensively reconditioned and modified four-legged barge has an overall length of 72.65 metres and a 39.6 metre beam and is fitted with a 600 tonne ringer type crane. The deck payload is 800 tonnes–1600 tonnes and accommodation is provided for 40 persons. The first major contract for Smit involves the installation of 63 monopile foundations for the Robin Rigg (A + B) wind farm. However, ‘unfortunately the offshore activities commenced with a major drawback. Already on the first pile ramming location two of Lisa’s legs punched through the hard seabed top clay layer, causing the barge to tilt eight degrees. This incident occurred despite an expensive soil survey in the project area. As some damage may have been caused we towed the Lisa to Belfast for extensive damage assessment and necessary repairs,’ said Smit spokesperson Claudia van Andel.

Eize De Vries is Wind Technology Correspondent with Renewable Energy World

Small wind turbines

At the end of 2006, a group of private investors from the United Kingdom took over Gaia-Wind. The company manufactures unusual two-blade fixed-speed wind turbines featuring a non-integrated geared drive train, stall power output limitation and a downwind rotor orientation.

The free-yawing 11 kW wind turbine is put on either a tubular or a lattice-type tower with an 18.25 metre hub height. According to the company, the comparatively large 13 metre rotor ensures excellent yields at low- and medium-speed wind sites. The Gaia-Wind design originates from Denmark and during the past ten years over a hundred Gaia-Wind 11 kW units have been installed in Denmark and about another fifty abroad.

A highly advanced small wind turbine on display in Husum was the Skystream 3.7TM developed by US company SouthWest Windpower. This smart 1.8 kW downwind turbine with a 3.7 metre rotor diameter is characterized by its elegantly shaped compact nacelle and unusual curved blades. The clever rotor blade design feature aims at aerodynamic sound reduction that occurs when a blade passes behind the tower. The latter can typically provide a problem with downwind turbines when straight blades are applied. The Skystream can be regarded as a new-generation small turbine that is attractively priced at €3,800. During September 2007 the track record stood at nearly 1000 operational turbines.

Wind industry newcomer MARC Power Systems of Germany developed a series of visually attractive H-Darrieus type wind turbines in the 250W–5 kW range. A much bigger 50 kW turbine is also part of the plans. The smallest models feature a permanent magnet type direct drive generator and the 250 W turbine type as a design feature can operate in wind speeds up to 50 metres/second. So far, the company has manufactured six 250 W turbines and the 1 kW sister product is undergoing the certification process.


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