Last year saw exponential market growth in terms of installed wind turbines, coupled with continuing component shortages, which simultaneously put a brake on the maximum potential global wind market gain. The number of new wind markets is still expanding and some of these countries, particularly in Asia, have already become serious contenders for a place in the Top 10. Eize de Vries reports on key market and technology developments, trends, the companies and the main players in this still-growing sector.
The US became the world’s largest wind market in 2007, with US-based GE Energy by far the biggest equipment supplier to the sector. As Ryan Wiser and Mark Bolinger explain in detail on page 120, market analysts are generally positive about the fortunes of the US wind industry during the coming years. Yet, as we go to press, there remains a real danger that the US Production Tax Credit (PTC), which is vital to the continued growth of the US wind energy market, may fail in a bid to be extended at the end of 2008.
Failure to extend the PTC before late summer could risk 116,000 jobs and more than $19 billion in clean energy investment, warned the American Wind Energy Association (AWEA) in a 10 June letter to its members, urging them to put pressure on Senators for a positive vote on PTC extension. However, if they are successful in lobbying the government and their plans work out according to expectations, it is anticipated that the US will overtake Germany as the world’s wind energy market leader by the end of 2009, if not even earlier given ideal conditions.
While the US took the lead position, China ranked second and added some 3450 MW of new wind capacity during 2007. This impressive figure represents a market growth of some 156% over 2006 and the country now ranks fifth in the world in terms of installed capacity. With over 6000 MW of cumulative wind capacity installed by the end of 2007 and based on current growth rates, the Chinese Renewable Energy Industry Association (CREIA) forecasts a rise in cumulative installed capacity to around 50,000 MW by 2015.
In the wind market, GE relies heavily on its well proven 1.5 MW workhorse. This turbine has its technology roots in the mid-1990s and with the former Tacke Windtechnik of Germany. Having aqcuired the technology, worldwide GE now operates a record 8500 installations of its 1.5 MW machine. Furthermore, the company anticipates continuing strong demand for the 1.5 MW series in the years to come, possibly putting final cumulative numbers worldwide in the range of 30,000 wind turbines or more, an impressive 45 GW of capacity from a single turbine design.
Despite the success of its 1.5 MW machine, GE has continued to develop its wind turbine technology. For example, summer 2008 will see GE’s new 2.5 MW workhorse, the 2.5xl, go into commercial production. Among the features of this turbine are a new twin-bearing main shaft solution, a permanent magnet-type synchronous generator, and cyclic rotor blade pitching as a standard load-reducing control technology. This 2.5xl machine is further fitted with a 100-metre rotor (up from an initial diameter of 88 metres), a technology feature shared with a growing number of competing 2.5 MW machines.
The installed power/rotor swept area ratio (P/A = 0.32) is claimed by GE Energy to be highly suitable for around 80% of European wind sites. This ratio is closely comparable to the installed power/rotor swept area ratio (P/A = 0.32) of GE’s widely sold 1.5 MW turbine, which has a 77-metre rotor. With the 2.5xl, GE aims to regain the two-digit market share it lost years ago in the major European wind energy markets.
In another trend-setting development, early June saw Siemens Energy and the United States National Renewable Energy Laboratory (NREL) announce a co-operative research and development agreement. As part of the co-operation deal a new 2.3 MW pilot wind turbine model, with a record 101-metre rotor and a P/A ratio of 0.29, will be installed at the National Wind Technology Center south of Boulder, in Colorado. The current 2.3 MW Siemens volume model is fitted with a 93-metre rotor and therefore has a P/A of 0.34. Siemens will test basic installation characteristics and verify new performance-enhancing features and turbine reliability under severe weather conditions over a three-year minimum period of testing the installation at the Center.
Other competing models offering similar P/A-configurations to the GE 2.5xl include the Fuhrländer FL 2500 and the Nordex N100, while US-based Clipper Windpower plans a C-99 (rotor diameter 99 metres) sister version of the C-96 Liberty.
The 2.5 MW class itself is expected to expand further and thereby gradually succeed part of the volume market now dominated by 1.5 MW and 2 MW class wind turbines. But in all these three main power rating classes, and some sub-categories in between, new entrants continue to arrive.
In addition, during the past year several new state-of-the-art 3 MW-class wind turbine types have been introduced. And while 100-metre rotors continue to gain ground in the 2.5 MW class for yield-optimizing reasons, 3 MW rotor sizes announced now reach a record 116-metres (P/A = 0.28).
This trend for increasingly large rotors for given power ratings is a logical development – under almost all wind conditions additional swept area results in extra energy yield. Put another way, it leads to a superior capacity factor for a given wind installation. The trend towards fitting larger rotors on new and existing wind turbine types is by no means a new phenomenon, but is found in all capacity classes – see box.
3 MW entrants
Suppliers of recently introduced 3 MW turbines include Acciona of Spain, Alstom-Ecotécnia of France/Spain, and Enercon and REpower of Germany. Scanwind of Norway has been active in the 3 MW segment for a longer period. Table 1 provides an overview of wind turbine makes and types in the 2.3–3.6 MW class that are either under development, being tested, or already commercially available. A relatively wide product range is necessary as individual suppliers often do not fit into narrowly defined power rating categories.
Of the 3 MW newcomer list (status as of June 2008), Enercon has commenced building its share of the 264 MW Dutch Eemshaven project, which, once completed, will be the largest in the country. Vestas has already finished building 21 x V90-3.0 MW turbines at the combined site. Enercon will deliver the remaining 67 x 3 MW E-82s. These turbines are again fitted with the unusual ‘high-performance’ Enercon rotor blade design first introduced in 2003–4. According to industry sources, Enercon plans to run the 67 turbines for a prolonged period before commercial international sales start.
Acciona Windpower unveiled its 3 MW AW-3000 machine at AWEA’s June WINDPOWER 2008 Conference and Exhibition in Houston, Texas. The supplier is a division of the huge Acciona group, boasting commercial activities from real estate and urban and environmental services to water desalination, thermo-electric solar power and wind. With the new pitch-controlled variable-speed geared wind turbine, fast-growing Acciona Windpower is expanding its current 1.5 MW AW-1500 workhorse range into the multi-megawatt market segment.
The AW-3000 turbine is designed for wind classes IEC Ia, IEC IIa and IEC IIIa, and comes in three rotor diameter options: 100, 109 and 116 metres (IEC IIIa). The latter record rotor size represents a swept surface area of 10,568 m2. Electricity is generated at medium voltage (12 kV), which is claimed to reduce production losses and transformer costs. The main shaft is fitted onto a ‘double frame’, a design measure aimed at reducing gearbox loads and extending its operational life, the company explains.
The installation is further equipped with a number of intelligent control and monitoring systems, such as a control and power unit, and a condition monitoring system for certain key components. Additional systems include automatic lubrication for main shaft and generator bearings and blade bearings. The smart-looking AW-3000 wind turbine will become available on the market in 2009, with first deliveries expected for the second half of 2010. The turbine will finally be supplied with a concrete tower of either 100 or 120 metre hub height.
Alstom – Ecotècnia ECO100
Power engineering giant Alstom Power of France acquired wind industry pioneer Ecotècnia of Spain in 2007. Ecotècnia started out in 1981 as a wind co-operative society. Its current volume turbine is a pitch-controlled, variable-speed geared 2.0 MW ECO 80 (80-metre rotor), while the company itself is today a medium-sized wind industry player with 340 MW of new installations in 2007. The latest addition to the company’s product portfolio is the 3 MW Ecotècnia ECO100 (rotor diameter 100.8 metres) – a prototype with a standard 90-metre hub height has been operating since the end of March 2008.
Like previous wind turbine models, the ECO100 again features a clever modular geared drive concept. A key technology feature is the separation of rotor bending moments and rotor torque. Integral to this proven drive concept are two pre-stressed conical roller-type main bearings located inside the rotor hub, and a stationary axle pin that projects out in front of the cast mainframe.
Rotor bending moments are led directly into the cast mainframe via the hub, bearings and axle pin into the cast mainframe front section. From there, these bending moments are transferred into the tower via the yaw bearing. The rotor torque, by contrast, passes directly via a separate torque shaft from the hub into the gearbox, which, as a compact assembly, is located inside the cast mainframe.
The complete drivetrain assembly itself is supported at three points (two in the rear and one in front) in such a manner that the unit cannot be loaded by unavoidable elastic deformations of the mainframe. The ECO100 drive solution, in a combination with variable-speed and torque control, results in fewer drivetrain component breakdowns, according to the Spanish wind pioneer. This claim is not without importance as gearbox failures are still regarded as the single key breakdown cause in modern geared wind turbine drivetrains.
The nacelle housing is made up of three independent elements, one central section and left- and right-hand covers. This eases road transport and, according to ECO100 product information, also provides extra space for [servicing the] transformer, frequency converter and control cabinets. In addition, locating the transformer inside the nacelle is aimed at reducing internal electric power transport losses.
Type certification is planned for the end of 2008, followed by series production of 40 units in 2009. There are no plans for offshore at the moment, said the company’s Innovation and Reliability director Pep Prats Mustaros during an ECO100 product introduction presentation at EWEC 2008.
Since founding in 2001, REpower Systems AG of Germany has installed about 1200 wind turbines. If we include wind turbines manufactured by German and international licensees, this installation number is much higher, said REpower’s Christian Draheim when presenting the new 3.3 MW 3.3M wind turbine at EWEC 2008. REpower commenced early 2005 with a market analysis followed by a product definition and R&D started at the end of the same year. Main 3.3M product development targets included:
- the highest efficiency in the 3 MW class
- the largest possible onshore turbine
- similar transport logistics to the 2 MW REpower MM turbine series.
This new platform is envisaged to fill the gap between the 2 MW MM82/MM92 and the 5 MW REpower 5M offshore wind turbine. An up-scaling of the latter giant (prototype 9/2004) to 6 MW with a corresponding ‘6M’ nameplate was announced during September 2007. A first batch of three 6M prototypes will be erected later this year on land in Schleswig Holstein near the Danish border.
With the new 3.3M, REpower is focusing only on land-based applications and, like all other commercial wind turbines, the machine is being equipped with a doubly fed induction generator. The initial IEC IIa version will become available with a hub height of 78–80 metres and a rotor diameter of 104 metres. At a later stage additional 3.3M IEC WC Ia and IEC WC IIIa versions are planned, the latter with a 98–100 metre hub height.
The 3.3M will be fitted with a conventional drivetrain comprising a three-point gearbox support, and a non-integrated 4-pole doubly fed induction generator. Such a system is also applied in the 1.5 MW MD (phased out) and the 2 MW MM series, and in many competitor designs in excess of 4 MW. By contrast, the 5M features a geared drive solution whereby the main shaft is supported by twin main bearings, and the gearbox hangs at its rear. One of the reasons behind this design strategy is to isolate rotor-bending moments from the gearbox input side. Draheim said at EWEC that a primary 3.3M development objective was a service-friendly wind turbine design, whereby the gearbox has been sized according to REpower’s own gearbox design guidelines. Some years back, as a reliability-boosting measure, REpower increased the mass of its key drive components by 20%. Another reliability enhancement procedure is a check test run under up to 240% load. A 3.3M service feature is a special clamping device designed to keep the rotor in place during gearbox exchange.
During 2007 REpower and German rotor blade developer/manufacturer A&E Rotec founded the (51%–49%) joint-venture company PowerBlades GmbH for in-house offshore and onshore rotor blade production in Bremerhaven. Series manufacture of rotor blades developed by REpower is scheduled to start in mid-2008, and the location is close to the manufacturing facility for 5M offshore turbines. The 3.3M, the MM series and the 5M/6M turbines will, in future, be fitted with REpower design rotor blades. The 11-tonne 3.3M rotor blade is named RE50.8; no carbon fibres have been incorporated into the composite material.
Prototype erection is envisaged for the end of 2008, followed by a 0-series in 2009. Series production is to commence from late 2009.
Norwegian based ScanWind Group has been active for several years as an emerging producer of 3.0–3.5 MW pitch-controlled variable-speed turbines. The latest ScanWind 3500 DL with a directly driven permanent magnet generator has been designed for rough coastal IEC WC I wind conditions.
The company’s first demonstration unit was erected back in March 2003 at Nærøy on the Norwegian coast. This 3.0 MW unit was equipped with a (Siemens) directly driven permanent magnet-type generator.
A second demonstration unit was erected during the autumn of 2004, again a 3.0 MW onshore installation, but this time featuring an unusual variable-speed gearbox and a doubly fed induction generator combination.
The company says that, in total, fifteen 3.5 MW 3500 DL turbines are currently operational.
ScanWind’s assembly plant is located in Verdal, 90 km north of Trondheim, while the company is owned by Nord Trøndelag Elektrisitetsverk (NTE).
Sinovel, a subsidiary of the Chinese Dalian Group, acquired a 1.5 MW wind turbine licence from Austria-based engineering consultancy Windtec. The latter is a subsidiary of US-based American Superconductor Corporation. Sinovel claims that by the end of 2006 about 100 x 1.5 MW units had come off the assembly line, and about 500 turbines in 2007. Sinovel and Windtec are also working on 3 MW and 5 MW wind turbines. Sinovel engaged Germanischer Lloyd (GL) to certify its 3 MW wind turbine. GL is in charge of certifying the complete design of the 3 MW SL 3000, which will become available in an onshore as well as an offshore version. The German certification agency will carry out wind turbine design assessment, comprising all key components/systems including tower, rotor blades, mechanical as well as electrical components and safety systems.
2.5 MW Vensys 90/100
During EWEC 2008 Vensys Energy AG’s Stephan Jöckel presented a new 2.5 MW direct-drive Vensys 90 and Vensys 100, with rotor diameters of either 90 metres or 100 metres. The former is an IEC WC IIa turbine, while the Vensys 100 will be certified for IEC IIIa wind locations.
The German wind technology developer employs a staff of 30, 22 of whom are engineers. Vensys Energy is now 70% owned by Goldwind of China. Previously the Chinese acquired technology licences for the 1.2 MW Vensys 62/64 and 1.5 MW Vensys 70/77, and lately also the Vensys 90/100. The 1.5 MW turbine series is an optimization of the initial 1.2 MW model, while both feature a passive surface air-cooled permanent magnet type generator (see REW November–December 2007).
For the Vensys 90/100 the company developed a new generator. The outer diameter is again less than 5 metres, but generator mass has increased slightly from ‘less than’ 45 tonnes to ‘less than’ 55 tonnes. What really did change is the 2.5 MW cooling system, which is described as ‘active with air-to-air heat exchanger’.
There are other main differences too. The 1.2 MW/1.5 MW turbine drivetrain comprises a hollow stationary axle pin with twin bearings that carries both rotor and generator rotor assembly. This state-of-the-art system also appears in direct drive Enercon wind turbines (except for the 200/230 kW E30). The Vensys 90/100 series by contrast features a single, double-row, tapered roller bearing, a feature that appears in turbines such as the Vestas V90-3.0 MW turbine (over 600 operational). A single main bearing solution in combination with other design novelties has resulted in a top head mass (THM) that is superior to figures found for several 2.5/3.0 MW geared wind turbines, explains Jöckel.
Direct-drive turbines are normally at a THM disadvantage compared to geared equivalents, largely due to the high mass of annular generators. This phenomenon, whereby components increase in weight as size increases is known as the ‘square cube law’ or SQL. If, for instance, the dimensions of a solid cylinder double from 1 to 2, both volume and mass increase by a factor of 8 (23). Designers often succeed in curbing mass increase as a negative side-effect of up-scaling by applying alternative measures – such as adding spokes to an initial solid component. Lower THM translates directly into cost savings as less material input such as expensive steel and/or copper is required. Reduced dynamic loads in turn result in lighter and cheaper towers and foundations.
Table 2 compares Vensys 90/100 series THM with selected competing models. Jöckel draws the conclusion that ‘permanent magnet high-torque generators can be very light’! However, at the same time it should be remembered that THM is only one of multiple variables that together determine the total qualities of a given wind turbine concept. Most important is achieving the highest return on investment for the owner/operator, expressed in the lowest costs of energy (CoE; €/kWh/20y).
Current planning is to erect one Goldwind 90 and one Goldwind 100 in China during October, and one Vensys 100 (mother product) in November 2008.
No pause in innovations
The examples presented in this article clearly indicate that maximizing their output to meet strong market demand for wind turbines does not distract manufacturers and other technology providers from the process of innovation. On the contrary – several solutions presented have the potential to push wind technology advancement further, both in terms of increased cost-effectiveness and greater reliability.
In the emerging offshore wind market insufficient availability of installation vessels has been highlighted as a major bottleneck for the next few years. Nonetheless, the launch of construction of Hochtief’s Thor installation barge (see Miscellaneous developments) is a good example of how tight equipment supply can create fresh opportunities for others.
The unexpected decision (April 2008) from oil and gas giant Shell to pull out of the prestigious 1000 MW London Array project is not a cause for pessimism, say wind industry insiders. They do not expect any structural slowdown in overall offshore development progress, as other interested parties are expected take Shell’s place. On the wind turbine supply side, Vestas’ decision to release the V90-3.0 MW offshore wind turbine again for sale effective from 1 May 2008 will certainly provide some relief to developers in need for offshore turbines.
Talking about big numbers, offshore market leader Siemens alone has firm orders amounting to the supply of at least 249 x 3.6 MW turbines to be delivered in the coming years.
Additional positive news is that from this year onwards three new commercial suppliers of super class 5 MW offshore turbines (Multibrid, REpower, and Bard Engineering) will enter the market commercially. In the next few years each of these suppliers is expected to raise output gradually to about a hundred units a year.
Two of them, Bard and Multibrid, have already announced a substantial up-scaling of their turbine platforms by 20% or more. And all cumulative capacity that can be mobilized will indeed be needed in order to meet the latest European offshore wind objective of 40,000 MW by 2020.
Component supply will therefore continue to prove a major bottleneck in the next few years. In some areas, such as precision bearings, the global wind industry has to compete with equally strong demand from other booming industrial and related sectors.
Eize De Vries is Wind Technology Correspondent of Renewable Energy World magazine.
Historic AEOLUS II Turbine Decommissioned
The 80-metre AEOLUS II prototype had been in service for 15 years
On 13 February 2008 the AEOLUS II prototype was blasted in the Jade-Windpark near Wilhelmshaven, Germany. AEOLUS II, which entered into service in 1993, was perhaps the last remaining ‘large experimental prototype’ from an important wind technology development era that roughly encompassed the period 1978 to 1993.
The two-blade geared pitch-controlled AEOLUS II and its Swedish NÄSUDDEN II sister prototype were built following a multi-megawatt wind turbine research co-operation between Germany and Sweden. Their shared wind technology base was know-how gained during the design, operation, and testing of an earlier 2 MW class NÄSUDDEN I, a project covering the period 1978–1987. German aerospace company MBB developed and manufactured the new rotor blades, while mechanical engineering specialist Kvaerner Turbin AB was responsible for structural engineering, mechanical parts and delivery of the Swedish 3 MW turbine.
The turbine was erected on the Baltic Sea isle of Gotland. Among several distinct wind technology differences was that AEOLUS II operated with variable speed, while NÄSUDDEN II was a two-speed turbine with induction generator.
The AEOLUS II further featured a (now trendsetting) synchronous generator in a combination with full power converter. However, a main difference is that today’s preference is for a permanent magnet type synchronous generator due to superior partial-load performance. The AEOLUS II had a THM of 162 tonnes (nacelle 120 tonnes; rotor 42 tonnes) and a rotor diameter of 80 metres, while a pre-stressed concrete tower gave the turbine a hub height of 92 metres. AEOLUS II finally operated several years in the vicinity of three ill-fated single-blade 640 kW MBB Monopterus turbines. The latter installations were erected in 1990 and featured a 56-metre rotor diameter.
New research centre
Ingeteam of Spain is a leading company in a number of areas, including the design and manufacture of wind turbine control equipment and power electronics systems and solar PV inverters (REW March–April 2008). The company plans to invest €17 million in the first and only power electronics and high-power machine experimental research centre in southern Europe. Once operational it will house over 200 national and international top-level researchers. Today only four centres in the world are equipped to carry out this type of research, and are located in Germany, Japan and the US. The new laboratory, spread over two main locations, will validate the latest technologies in high power electronics and electric machines for power generation, rail transport, marine propulsion and steelmaking sectors. The High Power Electronics Laboratory, at the Zamudio Technology Park, will focus on studying medium-power converters through experiments involving inductive loads. The Electric Machine Laboratory in Beasain will concentrate at electric machines and machine-converter units involving the use of large electric machines of more than 30 MW.
Prior to installing a fist batch of six turbines offshore this year, Areva-owned Multibrid erected two further 5 MW M5000 wind turbines in Bremerhaven, north Germany. Turbine numbers 3 and 4 sit on 130-metre-high towers, comprising a steel-reinforced concrete base of about 60 metres and three tubular steel sections. Previously, two M5000 offshore wind turbines were erected onshore in Bremerhaven, a first prototype in 2004 and a second in 2006. All technological developments made over the past few years resulting from operational experiences have been incorporated into these latest turbines. The three rotor blades, each 56.5 metres long, were brought in by road from the in-house production plant in Stade to Bremerhaven, where Multibrid also assembles wind turbine since mid-2007.
Siemens global sourcing
Siemens Wind Power (SWP) wants to raise its annual output by 2011 to 4500 MW, compared with about 1400 MW in 2007. As a further step towards globalization, the manufacturer wants a stronger presence in the Asia-Pacific growth region. During an interview with Dow Jones Newswires in late 2007, chief executive Andreas Nauen outlined Siemens’s growth strategy for the next years. Part of this strategy is to commence sourcing components in China. Initially these components will be incorporated into wind turbines assembled at the Brande facilities in Denmark. A key aim is to test the quality of these components and bring them up to standard if necessary. In a parallel development, a wind turbine assembly facility will be built in China, explains Nauen. Assuming Chinese-made components prove satisfactory, from 2011 wind turbines will be built in the country using a mix of European and locally sourced components. The Chinese-made Siemens turbine supply will in time serve demand in the entire Asia-Pacific region, he concluded.
New jack-up type installation vessel Thor
Hellenic Shipyards of Greece has secured a contract from the huge building and civil engineering group Hochtief of Germany for the construction of a new large jack-up vessel named Thor. The barge is 70 metres in length, 40 metres wide, and has a 6-metre draft. Thor can operate in water depths up to 50 metres, while its crane hoisting capacity is 400-tonnes. The vessel can handle offshore wind turbines up to 5 MW. In addition the barge will be equipped with a dynamic positioning system operated by three Azipod drives. Delivery is scheduled for April 2009 and Thor will be employed for erecting offshore wind farms in the Baltic and North Sea, and worldwide. Classification is performed by Germanischer Lloyd.
Larger Rotors, Increasing Yield
The first pioneering 1.5 MW class wind turbine types (1995/1996) all featured rotor sizes of 60–66 metres, while today a 70–82.5 metre range is common. The first 2.5 MW Nordex N80 model, announced in 2001, featured an 80-metre rotor, while the latest 2.5 MW N100, announced in 2007, is fitted with a 100-metre rotor, giving a 56% increase in rotor swept area.
Back in 2001 a 70-metre diameter rotor was state-of-the-art, while 80 metres was about the largest the industry was capable of manufacturing at that time. Finally, the pioneering 3 MW Vestas V90-3.0 MW (prototype 2002) and WinWinD WWD-3 (prototype 2004) were initially both fitted with a ‘standard’ 90-metre rotor. WinWinD now offers an additional 100-metre rotor for low and medium wind-speed sites, while Vestas shelved a 2.75 MW V90-3.0 MW sister version with enlarged 100-metre rotor.
However, it should be mentioned that putting existing turbine types on higher towers is also a possible track towards further optimized energy yield. This yield-optimizing strategy is especially advantageous at low and medium wind-speed inland sites. At such locations, operating at higher altitudes offers not only substantially higher wind speeds, but the wind itself is generally also more stable and less turbulent. This potentially has positive effects in terms of reduced materials fatigue, and could therefore extend the operational lifetime of a wind turbine.