Vestas ‘Business Excellence as the Next Step!’

Amidst challenging times, the world’s largest wind turbine supplier, Vestas Wind Systems of Denmark, has ambitious expansion plans, aiming to deliver both business excellence and the highest level of customer satisfaction. 2009 has seen the launch of three new Vestas turbine models – this product range includes a prestigious 3-MW V112 turbine, while a V112 product variant specifically suited for offshore application is under evaluation.

Founded back in 1945 at Lem, in Denmark’s western Jutland, Vestas, now one of the world’s most experienced wind turbine pioneers, erected its first 33 kW V10 prototype, with a rotor diameter of 10 metres, in 1979. This tiny wind turbine, in common with a long line of its successors, featured a gearbox, although its V-belt driven generator solution — which had its roots in agricultural machinery — has long since been eliminated. The reconditioned and freshly painted nacelle now stands on display in the Vestas Test & Verification building in Aarhus. It is a genuine achievement that this prototype generated electricity for over two decades, a testament to the people of western Jutland, who are claimed to take pride in quality engineering and in making good machinery.

Headquarter Move

Vestas HQ has been based in Randers since 2004, but in 2011 it will be moved to one of Denmark’s largest (port) cities — Aarhus. In fact the Test & Verification facilities plus a Vestas Technology R&D Centre, Marketing and Nacelle, are already operational at several locations within the Aarhus city boundaries. Other main R&D facilities are located in Singapore and the US, together employing over 1200 engineers and scientists worldwide in R&D.

Being headquartered in a larger population centre offers many benefits, explains Christina Aabo, director of Product Management for Vestas Technology R&D at her new office location: ‘Easy access to the airport and other main transport facilities represents a real asset. Equally important is an attractive living environment to many international Vestas professionals — often based here temporarily — including the presence of schools, a university, leisure activities and cultural centres.’

As a vertically integrated supplier, for many years Vestas manufactured nacelles and rotor blades in house, largely in Ringkøbing and at Lem too. Indeed, despite a major international expansion, there are still many production and service facilities scattered in and around the Lem region. A former shipyard at nearby Ringkøbing, Vestas HQ between 1998 and 2004, is now a major nacelle assembly centre for V90-3.0 MW nacelles. This modern facility features two robots for tightening of pitch bearings, and a moving line system to optimize nacelle and rotor hub assembly.

Furthermore, Vestas manufactures a portion of its own tower demand in house, plus generators, controllers, power converters and castings.

In 2008 Vestas employed nearly 21,000 staff worldwide with production facilities spread through Denmark, China, Germany, Norway, Spain, Sweden, India, UK, Italy and the US. This April, due to reduced market demand in northern Europe, Vestas announced a major layoff plan involving 1900 of its employees, concentrated mainly in Denmark and the UK. The actual status is that approximately 1500 jobs will be lost as a number of employees have been repositioned in other jobs. A UK rotor blade facility at the Isle of Wight is now closing its doors with 425 job losses. Vestas says that the latter decision has been taken due to current unfavourable market conditions caused by the credit crunch, weak currencies and a lack of political support at a local level. A tower factory in Scotland was closed earlier.

‘It is one of Vestas’ main strategies to produce large components close to the main markets, and demand is shifting fast to the high-growth markets of the US and China’, Aabo explains. ‘Our long-term goal is to have an optimized supply chain and mainly supply: “North America from the USA”, “Europe from Europe”, and “Asia from Asia”. Even after the lay-offs, Vestas together with its suppliers, will still have factory capacity to manufacture, ship and install 10,000 MW in 2010.’

Global Product Platforms

The product portfolio includes 10 wind turbine models with power ratings from 850 kW to 3.0 MW, subdivided into five product platforms. These are all global platforms designed to fit local requirements, explains Aabo (see Table 1, below).

v52-850 kW Pitch-controlled variable speed operation
V60-850 kW New; for the Chinese market, among others
V82-1.65 MW Former NEG Micon product with Active Stall operation
V80-2.0 MW Pitch-controlled variable speed operation
V90-1.8 MW 2 MW mechanical and electrical design, sharing the same 44 metre blade as the V90-3.0 MW
V90-2.0 MW 2 MW platform mechanical and electrical design
V100-1.8 MW New; based on 2 MW platform design with V100 rotor blades
V90-3.0 MW Lightweight with compact semi-integrated drive system
V112-3.0 MW New; prototype phase

Until the early 1990s Vestas manufactured pitch-controlled, fixed-speed geared wind turbines with a non-integrated drive system. The V39-500 kW (1991) was the last product in this range. During 1994–1995 Vestas switched to (semi-) variable speed OptiSlip operation with the 600 kW V42/V44 series, later expanded with the V66-1.65 MW (1996), and V47-660 kW in 1997.

In 2000 Vestas switched to pitch-controlled, variable-speed operation. Today state-of-the-art wind technology, this was first applied in an upgraded V66-1.75 MW, and new V52-850 kW and V80-2.0 MW models. During 2002 Vestas erected a prototype of the lightweight V90-3.0 MW turbine model. This innovative turbine combines a number of distinct design features. A compact cast main chassis with a semi-integrated geared drive system, for instance, comprises a flange-on gearbox and a non-integrated doubly-fed induction generator. The gearbox itself is a compact 3-stage unit which (as an unusual design feature) forms a single assembly with a single rotor bearing, integrated with the gearbox housing. Rotor torque is directly transferred from the rotor hub to the main bearing and into the gearbox’s low-speed planetary stage. The traditional main shaft has been eliminated. This innovative gearbox was developed by a joint venture between Vestas and Hansen Transmissions of Belgium, which is now 61% owned by Vestas competitor Suzlon of India.

Wind Industry Product Example

Additional turbine features for the V90-3.0 MW include new slender, lightweight, rotor blades, and a top head mass (nacelle + rotor) of only 104 tonnes. The latter value is similar to the V80-2.0 MW top head mass, despite a 50% increase in power rating and a 27% growth in rotor swept area. A favourable top head mass enables the use of lighter installation cranes, and the application of lighter, and therefore cheaper, foundations. When the groundbreaking model was introduced at the 2003 international Husum wind industry fair, some enthusiastic wind turbine experts present said that competitors would have little choice than to follow this example. Others were more cautious, and some claimed that Vestas ’must have applied rather favourable load cases combined with minimized safety margins.’

Simultaneously with the V90-3.0 MW, Vestas introduced the V90-2.0 MW and V90-1.8 MW; both products are technically based upon the 2 MW platform.

All three of the latest new Vestas turbine models — the V60-850 kW, V100-1.8 MW and V112-3.0 MW — are fitted with a relatively large rotor compared to the nominal power level. This technical specification choice fits well into a wider wind industry trend aimed at offering dedicated turbines with optimized yield potential under most common wind conditions, including low and medium wind speed sites. The 850 kW and 1.8–2.0 MW series are further based on largely similar mechanical and electrical design principles. This includes a non-integrated geared drive system with a main shaft supported by two main bearings, a flange-on multi-stage gearbox, an intermediate shaft and doubly fed induction generator.

The V100-1.8 MW has now entered series production, with 50 turbines planned for 2009 and ramping up in 2010. The V100-1.8 MW rotor blade was previously developed for the envisaged V100-2.75 MW, a V90-3.0 MW sister model of which 12 pre-series units were erected before Vestas discontinued production. The V100-1.8 MW and V112-3.0 MW represent the first two Vestas models that feature the new cross-platform nacelle design layout with the characteristic CoolerTop cooling radiator.

‘Will to Win’

Vestas was first listed on the Copenhagen Stock Exchange in 1998. By that time it was also by far the world’s largest supplier and the only ‘true’ global wind industry player with a presence in all the main wind markets. That market-leader position had been achieved solely by organic growth, but in 2004 Vestas merged with one of its main competitors, NEG Micon of Denmark (see Vestas’ heritage sidebar, below).

‘New Vestas’ HQ was located at Randers, the former NEG Micon headquarters. During 2005 Vestas appointed a new CEO, Ditlev Engel, and the first corporate strategy was launched: ‘Will to win’. The latter reflects determination at improving business results and a return to profitability. Simultaneously Vestas aimed at maintaining a dominant long-term 1/3 world market share. In 2008 a new strategy with a new aim ‘No.1 in modern energy’ was launched, this time with a focus on achieving ‘Business Excellence and highest Customer Satisfaction’. According to Vestas, being No. 1 means being the best, not necessarily the biggest operator. Between 2004 and 2008 Vestas’ world market share, according to BTM Consult statistics, gradually declined from 34% in 2004, to 28.2% in 2006, 22.6% in 2007, and 19.8% in 2008. Simultaneously, several powerful competitors narrowed the gap with Vestas, though company annual sales more than doubled from 2784 MW in 2004 to 5580 MW in 2008.

Set against the 2004–2005 financial situation Vestas has in recent years enjoyed an impressive return to profitability, but also experienced a variety of technical and other issues negatively affecting product quality, and reliability. In addition, its company image was affected negatively by often-heard complaints about poor functioning of the service organization. Technology issues frequently pointed at include gearboxes, but also generators and pitch system hydraulics. Says Aabo: ‘We at Vestas R&D have a full picture of all the issues that have negatively impacted performance and reliability of the turbine fleet in the past, and the focus is on solving this in a fast and controlled manner.

And of course to avoid similar technical issues emerging again. A partial explanation and major contributing factor to some of the difficulties encountered is that during 2004–2007 Vestas employee numbers increased from 9600 to nearly 21,000. During 2007–2008 alone over 5500 new employees entered our company. For our organization this rapid growth path in many ways represented a critical phase. In such a situation serious errors can occur more easily due to a combination of inexperience and high stress levels for the existing staff. But this has given us now world-class internal training programmes and the ability to upgrade competences fast.’

Improving Product Quality

The first quarter 2009 interim financial report states: ‘Vestas should manufacture the best and most reliable turbines’ and ‘Vestas should maintain the best customer and supplier relations in the industry.’

To achieve these ambitious goals, sustained and dedicated efforts at all company levels seem essential. The Vestas mission statement: ‘Failure is not an option’ underlines organizational commitment to remedy failures by optimizing internal work processes, to safety and products and to a structured follow-up on all errors. Both Vestas and its key suppliers now apply a widely used Sigma quality management system within their organizations. ‘Level 4’, according to Vestas, represents the current status and ‘Level 5’ is the next target for the company and its main suppliers.

The success of a comprehensive quality management system is closely linked to an effective R&D organization, which in turn forms the basis for successful product development. For that purpose a number of interlinked disciplines have been brought together within Vestas Technology R&D. Specialist groups work in key dedicated technical fields such as drive systems, rotor blades, and control systems. Related ‘support’ areas include turbine diagnosis and monitoring, a materials testing lab, as well as a turbine and components test and verification centre. Unique for the wind industry is a ‘virtual nacelle’ that serves as an advanced product development support instrument and staff training tool (see page 26).

Vestas Technology R&D building, on the outskirts of Aarhus, impresses with its architecture. Inside, the nature of Vestas Technology R&D is emphasised by a full-scale, 44 metre rotor blade prominently on display in the spacious, open central area. This huge component has been sliced into multiple pieces, each individual cross-section providing a clear view of specific rotor blade details and structural design features. The main structural blade element is a central spar manufactured on special rotating machines in a semi-automated process. Composed of glass and carbon fibre-reinforced epoxy laminate, the anchoring spar is typical of Vestas rotor blades. The smallest square cross-section is at the blade tip. From there it gradually widens towards the blade foot, finally expanding into a circular shape with blade bolts to accommodate a pitch bearing. Both the upper and lower blade shell are laminated to the blade spar, together forming a structurally strong yet lightweight assembly. For its rotor blade manufacturing Vestas applies a so-called Prepreg® method, comprising of epoxy resin impregnated glass fibre sheets and carbon.

Continuous Improvement Management

Created initially as a remedying tool in response to various Vestas wind turbine technical and operational upkeep issues in the field, a Continuous Improvement Management (CIM) department was founded as part of Operations in Technology R&D and has operated for several years. Within CIM a dedicated Monitoring and Diagnostic Centre is responsible for collecting and statistically analysing data and recommending specific actions to the global service organization. This important task is performed by closely monitoring over 14,000 turbines spread over many wind farms operating in different geographical regions. Christina Aabo explains: ‘CIM is essentially a function of both costs and priority setting. Wind turbine wear and tear is, for instance, a function of micro-siting and upkeep strategy. As a method, CIM primarily focuses on finding correlations and analysing specific patterns.’

One of the turbine variables being monitored is the temperature level at critical spots in a component. These temperatures normally fluctuate within a certain range, and depend on variables such as ambient temperature and wind speed as a function of turbine output. If the component temperature of one turbine starts to differ from the other turbines within the same wind farm, it may be that the temperature deviations fit into a predefined operational range, in which case no action is required. However, if the temperature range is exceeded, pro-active maintenance becomes necessary.

Aabo continues: ‘Initially, our CIM focus was on monitoring and analysing turbines within a single wind power plant at individual component level. But with the huge fleet we are now at a level of much more advanced diagnostics that just a year ago, We have a very strong team of some very experienced wind turbine experts and young, very bright colleagues who make these ‘monitors’, which are like automated algorithms looking for deviation.’

Another area with the responsibility of Operations in Technology R&D is handling of serious incidents. No matter whether local service personnel are involved, or only turbine failure is reported, the dedicated organization handles the process. For example it could be a blade failing and causing the turbine to stand still. A first response is to preserve all possible relevant data, followed by a corrective action that includes communicating to the affected owner/operator. In parallel, as a major part of a systematic pattern search, a ‘root cause analysis’ is performed. Findings and conclusions result in a remedying action, based first upon priority-setting.

V90-3.0 MW Gearbox Project

Since 2003–4 Vestas has erected over 1116 of the V90-3.0 MW turbines, both onshore and offshore. However, since its commercial production start, the key turbine model has also undergone a series of improvements. One structural upgrade was to increase the number of yaw motors from four to six units, which required additional changes to the cast main chassis. And, early in 2007, Vestas withdrew the turbine from the offshore wind market after 72 of a total of 96 V90-3.0 MW turbines operating offshore (UK and the Netherlands) developed major gearbox problems. The V90-3.0 MW was released for offshore sales again from May 2008, and a recent order involves the delivery of 55 units for a 165 MW Belgian offshore project, Belwind.

Within CIM the Vestas Performance and Diagnostic Centre (VPDC) is responsible for V90-3.0 MW fleet handling, whereby a special

‘3 MW gear project group’ deals with the issue. Aabo says: ‘One of the main questions to be tackled first was finding out how many wind turbines were affected. The next questions were “what needs to be done?”, “who needs to participate?” and ‘what resources need to be allocated’? Finally, ‘are there any “Quick Fixes” available?’

Testing Times, Bending Moments

As part of the overall process this dedicated team closely follows V90-3.0 MW turbines in the field, focusing on installations that may develop a problem. Turbine visits typically include an internal gearbox inspection using a small video camera, or boroscope. Apart from close monitoring and inspections a major additional effort involved a number of focused activities such as modeling of structural loads and load simulations. Vestas also continues to hire new staff with a specialist background, such as automotive engineers or bearing specialists, in order to build in-house expertise at a level equal to its component suppliers. These staff in turn are also actively engaged in product development project groups.

Particularly impressive is a huge test installation, developed in house, at the Aarhus ‘Test and Verification’ facility, which enables highly accelerated gearbox testing. As part of a test a V90-3.0 MW drive system is driven at substantial overload by a much larger

5 MW geared installation. Testing with overload is necessary to achieve a required ‘wear acceleration factor’. An advanced feature is that the connecting intermediate shaft can be forced out of central position. This test aims at introducing simulated rotor-induced bending moments that correspond to actual operational loads.

Bending moments are infamous as a main contributing factor in causing premature wind turbine gearbox failure, which typically occurs within the low-speed planetary input gear stage. A V90-3.0 MW gearbox with an integrated main bearing solution has been designed to eliminate rotor-induced bending moments. While Vestas specialists discovered that the failures are concentrated at the low-speed planetary gear stage, a main outcome of the extensive gearbox analysis programme was that these failures are not linked to any single issue.

Aabo says that a complex issue has now been solved, and that a new validated design of the gearbox has been introduced for the V90-3.0 MW fleet. Meanwhile, the retrofit programme is not yet completed, and a number of turbines will need a second gearbox exchange in the future. This is because these, out of necessity, had been refitted with a current-generation gearbox, while awaiting the new solution. Aabo explains: ‘As part of an overall project approach we developed a gearbox exchange system that has reduced turbine downtime substantially – from 15–20 days initially to 6–7 days at the moment. An integral part of it is a gearbox repair loop at the repair facilities, where proactively changed gearboxes are brought in for reconditioning, and reconditioned units serve as their exchange replacement.’


V112-3.0MW product development commenced in early 2008 and a prototype is being erected in January 2010. A second prototype in Spain is planned for Q2 2010 and an eight-unit pilot series is envisaged in 2010, with series production due to begin in 2011. ‘Before commencing the wind turbine development, we first wanted to find out more about specific customers’ demands and asked professional clients to participate’, explains Aabo. ‘That resulted in a comprehensive list adding the clients’ wishes, with a clear focus on a reliable product, favourable costs of energy [€/kWh/20 years], timely turbine delivery, and design for easy transportation – just to mention some of the requirements. Our own turbine development focus was on a power plant perspective rather than wind turbine level as was usual in the past. In other words, what will be the best technology fit for a total wind power plant? Answering the latter question involves many different parameters, and includes determining physical and other boundaries.’

The V112-3.0 MW is an IEC wind class IIA/IIIA wind turbine and its drive system layout differs from the V90-3.0 MW ‘compact drive’ solution. As part of a concept study no fewer than 11 different drive-train system options were analysed, including non-integrated, semi-integrated, and fully integrated solutions. Reduced dependency on main suppliers and the application of easily obtainable components and spare parts was of high importance to Vestas too. Both factors offer the potential to contribute substantially towards enhancing reliability and ensuring high availability, Aabo explains one of several interesting findings: ‘If we were to use a single main bearing, a turbine of V112-3.0 MW size would require a bearing diameter of a size for which there are only two specialized steel mills in the world, and only one end supplier.’ That conflicts with a main

V112-3.0 MW development objective that there should be at least two different suppliers for all externally sourced main components such as gearboxes, generators, main shafts, or transformers.


The V112-3.0 MW features a conventional drive-train system with a 3-point gearbox support and, as a genuine novelty for Vestas, a permanent magnet (PM) type synchronous generator. This cutting edge drive system layout is a solution applied in a wide range of different geared wind turbine makes and models, including most former NEG Micon models. The modular nacelle of the V112-3.0 MW has been designed in such a manner that total mass of individually transportable assemblies such as gearbox + main shaft + main bearing does not exceed 70 tonnes. That is not without importance as for loads exceeding 70 tonnes or thereabouts, special heavy-duty road trailers are required, and these have only limited availability. The approximately 180 tonnes V112-3.0 MW top head mass is a state-of-the-art value for geared wind turbines with comparable power rating and rotor swept area.

The choice of a PM generator with full converter fits a wind industry trend. Compared with doubly fed generators, this solution offers greater flexibility with regard to grid frequency (50 Hz or 60 Hz), superior partial load efficiency, and easier compliance to future grid feed-in codes. Aabo adds: ‘Another main advantage of PM generators compared with doubly fed generators is that the mechanical drive system remains untouched by grid voltage backlashes. That, in turn, (depending on the total number of grid failure related incidents) has a highly positive effect on turbine design life.’

As a further novelty, the V112-3.0 MW is fitted with a modular Vestas-design electronic power converter; one of the key design parameters was a built-in capability for drivetrain load control. And, as part of an overall effort to create a safe and easy maintenance environment, the converter is integrated into the nacelle floor.

Compared with a V90-3.0 MW, characterized by a rather cramped nacelle, V112-3.0 MW main component exchange – including gearbox overhaul – is a lot easier and substantially faster. All the main components, including those located in the hub, can, for instance, be hoisted down with the aid of an on-board crane. In the event that a gearbox has to be completely exchanged, the rotor does not need to be removed, as Vestas engineers have developed a special main shaft clamping system. And, for sites with limited accessibility, Vestas has developed an innovative tower crane, which eliminates the need for expensive mobile cranes. The device, at a prototype stage, is fitted with a kind a tower-gripping system that enables it to mechanically move up and down the tower.


The converter, generator and gearbox are all liquid cooled, where a CoolerTop arrangement with large radiator is aimed at both saving energy and ensuring noise reduction. That is achieved by reducing the number of moving components and electrical components. This cooling system is also used for pre-heating purposes, preventing condensation. In a ‘cold temperature’ version, for operation in temperatures down to minus 30oC, cooling water is heated up with the aid of electric heaters.

For the V112-3.0 MW, Vestas developed a new 54.6 metre rotor blade, which offers 55% more swept area compared with the V90-3.0 MW with its similar power rating. The slender blades, with a 4 metre chord (maximum width), are composed of glass-fibre reinforced epoxy composite. With the blade development a design focus was on high power output, noise control, load reduction, and intelligent pitching. A lot of design effort was also put into developing an airfoil with reduced sensitivity to dirt built-up (sand, insects etc). Aabo elaborates: ‘The cyclic pitching mode is only applied when necessary, which is in practice mainly at high wind shear and/or high turbulence conditions. The main background behind this strategy is that continuous pitch mechanism movements contribute to accelerated pitch system wear and tear. Then you would like to balance this and have the most optimal operation of the single turbine at the single location at the site.’

Another issue for the developers was the maximum blade length that can still be transported in one piece by road. Vestas therefore mapped the available road infrastructure in all main European markets and the US, and if necessary applied additional measures such as physical checks too.

Finally, the V112-3.0 MW is a first new product from the new product platform. The new turbine concept appears well positioned for the global onshore wind market, not least due to its large swept area. In the offshore wind market Vestas now competes with a V90-3.0 MW model against several suppliers, all offering larger turbine models from 3.6–6 MW. A dedicated V112 offshore model with increased power rating to benefit from above-average offshore wind speeds could therefore represent a logical platform expansion choice for Vestas.

When asked about the relevance of such an idea Aabo says: ‘A V112 offshore version is under evaluation!’ Well informed wind industry insiders are already more explicit on the likelihood of such a platform expansion, and claim that a V112 offshore version is to be launched soon.

Eize de Vries is Wind Technology Correspondent for Renewable Energy World magazine.

Eize de Vries and Jackie Jones of Renewable Energy World magazine sincerely wish to thank Christina Aabo for enabling our two-day Vestas visit to Aarhus, Lem and Ringkøbing. We would also like to thank the more than 14 Vestas experts who contributed their time, and shared ideas with us during many open and frank discussions. Their efforts provided much valuable information as a background for writing this article.

For reasons of readability, all quotes have been attributed to Christina Aabo, though a number of these in reality originated from other Vestas experts.

 Sidebar: Virtually real

In one of the R&D building corners a full-scale but “empty” V90-3.0 MW nacelle has been “converted” into a “virtual nacelle”. Vestas is according to the specialists responsible for the project, almost with certainty the only wind turbine supplier in the world that currently has (in-house) developed such a unique advanced virtual tool.

A large screen in the front section displays a 3D image of a complete drive system plus with additional components and systems, and physically dominates the virtual nacelle inside. The image on the screen visualises physical boundaries like the nacelle sides, working platforms, the top cover with manhole, and all components in their real full-size shape and colour scheme.

In order to operate and become an integral part of the virtual system a person can either wear special 3D spectacles, or a helmet with 3D glasses combined with a joystick. These devices provide an amazing capability to virtually explore the nacelle, including ‘walking around’ and viewing individual components like the gearbox, generator, main shaft, hub, control cabinets and transformer. The potential is enormous. Engineers can, for instance, study the overall impact of a new gearbox torque support design applied in 2 MW platform turbines, or service personnel can check the accessibility of a new oil filtering system position.

The helmet offers even more advanced possibilities as the accompanying joystick is functionally attached to a virtual hand, which can be operated for conducting specific tasks like the opening or closing of a generator hatch. Another powerful feature is that it can display any drive system with all other internals of different Vestas turbine models on demand.

With the virtual nacelle project development in its completion stage, Vestas design and manufacturing engineers will become a key user group. Familiarizing new service staff with different Vestas turbine platforms is another envisaged future main application. Aabo says that the new technology-learning environment offers great potential for substantial time and cost savings compared with conducting the same activities inside a real nacelle in the field.

Sidebar: Vestas heritage

‘New Vestas’ emerged from a 2004 combination of Danish companies ‘Old Vestas’ and former NEG Micon. The latter a product of a 1997 merger between two other former Danish wind pioneers, Nordtank Energy Group and Micon. During 1998 NEG Micon acquired a number of competitors including former NedWind (NL), Wind World (DK), and Wind Energy Group (UK). It also acquired former Aerolaminates (UK), a specialist in wood-epoxy based rotor blade technology. NEG Micon subsequently built a new manufacturing facility for wood & carbon reinforced epoxy composite blades (W&CRE) at the Isle of Wight. In 2001 the company switched to pitch-controlled variable speed operation based upon a doubly fed induction generator solution. It was applied in two (semi-) commercial sister models of 2.75 MW (2002) and 4.2 MW (2003) each. The latter NM110/4200 turbine was in the combined turbine range and was to be further developed into a 4.5 MW Vestas V120-4.5 MW with enlarged 120 metre rotor, W&CRE blades and a top head mass of only 210 tonnes. Product market launch was set for 2005, delayed to 2009 and finally shelved. The only remaining former NEG Micon product is the two-speed active stall Vestas V82-1.65 MW turbine with over 2100 units erected worldwide.

Sidebar: Materials and EMC Lab tests

In the new advanced Materials Lab Vestas test engineers apply a so-called Highly Accelerated Life Testing (HALT) method to greatly reduce normal 20–25 year operational wear and tear to a few days or weeks. ‘Vestas makes increasingly applies accelerated testing for a wide variety of components and even full systems’, says Aabo. ‘In climate chambers, for instance, fatigue life of electronic board soldering connections can be simulated by rapidly varying temperature level in a predetermined test cycle. Materials degradation on the other hand can be simulated by vibration testing, or in combination with rapid temperature variations. We also conduct comparative parallel component tests with different material grades taken as a main variable. These tests – partly in the Test and Verification facilities – provide valuable knowledge and improved understanding on issues like catastrophic component failure set against slow materials degradation.’

An electro-magnetic current (EMC) lab is also used for Vestas wind turbine high power electronics equipment with interference effects as one of the focus test areas. Wind turbine controller electronics can potentially affect external electronic sources, but external interfering electronic sources can also interfere with wind turbine functioning. ‘It is very important that we set targets and aim at reducing all potential “emission” from wind power. That can be audible noise, EMC, or radar, bat or bird interference. A wind power plant is in the environment for at least 20 years and should not cause any downside to the surroundings’, adds Aabo.

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