Issue 01 • 2012energıze                                                            GL Group            www.gl-group.come n...
Renewable energy consultantsGL Garrad HassanEXPERIENCE MATTERSHELPING CLIENTS NAVIGATE THEIR PROJECTS FOR DECADESDUE DILIG...
editorial                             To Our Readers                             A year ago the Fukushima disaster shook u...
con t e n t s 01/ 2 0 12                                                                                             CFD  ...
prof i le                        i n br ief                            in Brief:                            gl group’s ren...
Photo: Dreamstime/Erikdegraaf6                                                      marketenergıze renewables
With experience gained over almost three                 decades, GL Garrad Hassan has an                unsurpassed techn...
m a r k e t pr ic ing                               As growth in wind deployment in Europe and        However, the maxim “...
The maxim ‘if                                            something appears                         As auction designers st...
m a r k e t supply ch a i nsupply chain. Following years of uncertainty, new growth perspectives are giving confidence to ...
now comparable to the UK’s, albeit set in a very different       ture. The long lead time of new cable factories means tha...
m a r k e t f ina nci n gstimulus. Germany’s KfW is providing a credit volume of up to five billion euros for projects suc...
20                                                                                                                        ...
m a r k e t insur a n ce                             “You can charter a ship in a minute, because         But the offshore...
the                                                                                                                       ...
software16         energıze renewables
GL Garrad Hassan is acknowledged for its technical rigour. This is reflected in its multiple industry standard software pa...
sof t w a re w ind fa rme r                                             Effective Tools for                               ...
VisualisationVisualisation. Maps and diagramshelp planners understand thespecific operating conditionsat the proposed site...
sof t w a re w ind fa rme r     Farmer makes use of this information to automaticallyadjust the turbine wake development a...
extracting momentum from the atmosphere. As a result,            gime on site. These uncertainties are then used to derive...
sof t w a re onlin e d a ta ma n a g e m e n tMaximisingthe PotentialMonitoring and analysis of on-siteresource measuremen...
munication and support cases. With the new support tool,             service. theenquiries can be handled in a timely, tra...
sof t w a re c omp u ta ti o n a l fl u i d d yn a mi csRosa’s Windy Plateausharp ridges, steep slopes and rocky plateaus....
Rough          Conditions          WinD FLoWinG over the edge of          Rosa’s plateau and impinging on a          propo...
sof t w a re c omp u ta ti o n a l fl u i d d yn a mi cs                                       calculation. Long before co...
Photos: Dreamstime/Antikainen/Wojphotopreparation. Wind flows inmountainous areas represent a challenge indesigning and co...
certification28          energıze renewables
Certification of wind                           farms, turbines and their                           components is state of...
cer t i f i c a t i o n o ffs h o re                                           FINO1. The research                        ...
Turbulence Models                                                 under Scrutiny                                          ...
cer t i f i c a t i o n o ffs h o re                                  wind fields show a higher probability of extreme win...
cer t i f i cat i on fa t igue                                                                                            ...
GL Group Energize Renewable Magazine
GL Group Energize Renewable Magazine
GL Group Energize Renewable Magazine
GL Group Energize Renewable Magazine
GL Group Energize Renewable Magazine
GL Group Energize Renewable Magazine
GL Group Energize Renewable Magazine
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GL Group Energize Renewable Magazine

  1. 1. Issue 01 • 2012energıze GL Group www.gl-group.come n e r g y. e f f i c i e n c y. e n g i n e e r i n g . re n e w a b le sGreenAspirationsmarket No Barrier to Growthsoftware Managing Rough Conditionscertification Modelling Turbulences
  2. 2. Renewable energy consultantsGL Garrad HassanEXPERIENCE MATTERSHELPING CLIENTS NAVIGATE THEIR PROJECTS FOR DECADESDUE DILIGENCE PROJECT DEVELOPMENT PARTNER TURBINE CONSULTINGCONSTRUCTION MONITORING SITE FEASIBILITY ASSET MANAGEMENT & OPTIMISATIONENERGY ASSESSMENT MEASUREMENT SERVICES SHORT-TERM FORECASTINGINTERCONNECTION LAYOUT DESIGN TRAINING COURSESINSPECTIONS & AUDITS ENVIRONMENTAL & PERMITTING SOFTWARE PRODUCTS
  3. 3. editorial To Our Readers A year ago the Fukushima disaster shook up the world, raising new questions about the feasibility of nuclear power. Renewable energy is moving centre stage. We are a young, fast-growing industry, but we still have to overcome numerous technical, political and financial challenges before the world can fully rely on us. Always at the forefront of this evolutionary process, energize renewables is acutely aware of the essential questions that must be resolved to take renewable energy to the next level. We are not afraid of bringing up sensitive issues such as “Are tenders creating unsustainably low prices?”. A close look at emerging wind energy markets such as Brazil and South Africa highlights the urgency of this topic (page 8). Critical evaluation of current wind field models is the subject of a study on offshore wind turbulence conducted by GL Renewables Certification (summarised on page 30). Dr Andrew Garrad As the market evolves, so does the supply infrastructure. “No Barrier to Growth” (page 10) asks whether the supply chain is still the bottleneck of offshore wind projects. This was one of the topics addressed by the Hamburg Offshore Wind Conference, hosted by GL Garrad Hassan in February 2012. Other items on the agen- da included the current role of banks in financing offshore wind parks (page 12), and the targets insurance companies are setting for the offshore wind industry (page 14). Crucial technical and environmental considerations for planners of wind farms are discussed in “Effective Tools for Pre-Construction Energy Assessment” (page 18), and “Maximising the Potential” (page 22) explains key aspects of monitoring and analysing measurements. This is a multi-faceted issue indeed, and I believe it clearly shows our industry is heading in the right direction. Renewable energy is a dynamic, fast-growing, inspiring global industry with a bright future. I hope you enjoy reading this issue of energize! Yours sincerely, Dr Andrew Garrad President of GL Garrad Hassan01/2012 3
  4. 4. con t e n t s 01/ 2 0 12 CFD The new Computational Fluid Dynamics capacity 24 08 10 12 14 18 22PriCing suPPly Chain FinanCing insuranCE WinDFarMEr ODMPower supply no barrier to Offshore Clear targets Tools for pre- Ensuringcontracts in growth and eco- projects: Banks for the offshore construction accurate dataemerging markets nomic viability back in the ring wind industry assessments collection4 energıze renewables
  5. 5. prof i le i n br ief in Brief: gl group’s renewables Business segment gl garraD hassan is one of the world’s largest renewable energy consultancies. It offers a unique level of service expertise and global presence across the whole project lifecycle with approximately 950 members of staff in 42 locations, across 24 countries. Its technical scope covers all relevant aspects of onshore wind, offshore wind, marine re- newables, and solar energy. It addresses the requirements of manufac- turers, operators, investors, project developers authorities, and the sup- ply industry with regard to all technical aspects of renewable energy applications. Given the current focus on wind energy, GL Garrad Hassan is able to provide a comprehensive set of services including the optimal design of wind farms, improvement in the performance of existing wind farms, measurement projects (wind resource, wind turbine performance and structural behaviour), inspection services, a large array of software products and turbine design services. In addition, GL Garrad Hassan has gained substantial experience in tidal and wave power generation and is involved in various solar projects. gl rEnEWaBlEs CErTiFiCaTiOn is a leading certification body primarily focused on the certification of wind farms, wind turbines and their com- ponents as well as marine renewable energy. At the forefront of know- how in renewables technology, it is abreast of all the necessary stan- 30 dards and requirements and takes a harmonised approach in ensuring that these are met. Manufacturers, banks and insurers around siMulaTiOn Turbulence the world rely on the state-of-the-art service provided by GL Renewables models under Certification. scrutiny Together, gl garraD hassan anD gl rEnEWaBlEs CErTiFiCaTiOn form the Renewables business segment of the GL Group. gl grOuP is a technical assurance and consulting company for the 33 energy industries and also a leading classification society. GL Group employs almost 6,900 engineers, surveyors, experts and administrative DEsign how to predict staff. Its global network consists of more than 200 stations in 80 components countries. fatigue life01/2012 5
  6. 6. Photo: Dreamstime/Erikdegraaf6 marketenergıze renewables
  7. 7. With experience gained over almost three decades, GL Garrad Hassan has an unsurpassed technical, political and economic understanding of renewable energy technologies, projects and markets.01/2012 7
  8. 8. m a r k e t pr ic ing As growth in wind deployment in Europe and However, the maxim “if something appears too good to the US slows, the baton has firmly been passed be true – it probably is” seems pertinent. Electricity cost- to emerging markets such as Brazil and South ing US$ 63/MWh from wind farms is lower than has been Africa. Surging demand for electricity in these markets sees achieved in almost any other market and gives natural gas state-dominated electricity sectors struggling to keep pace. a run for its money. The response has been to attract private capital by award- How are these extraordinary prices achievable in ing contracts through competitive tendering of power pur- Brazil? Indeed, are these prices sustainable at all? The ab- chase agreements (PPAs). sence from recent tenders of EDP, IPR-GDF, Iberdrola and Cut-throat Competition: When Will Reality Strike? In the face of soaring energy needs, emerging markets resort to competitive tendering of power supply contracts. Experts are frowning at the results The ambition is remarkable. Brazil plans to install at Petrobras is indicative of the view of some leading regional least two gigawatts of additional capacity per year until players. 2020, and South Africa’s revised integrated resource plan The cost of delivering wind projects in Brazil does not seeks to bring the share of wind to the grid to nine per appear sufficiently favourable to drive prices to the levels cent by 2030.If the sole intention of awarding contracts by observed. However, the onshore wind resource in parts of auction is to foster competition, the Brazilian example must Brazil compares favourably with any region on earth. Ca- be viewed as a roaring success. Fierce competition between pacity factors of 50 per cent are thought to be achievable 240 participants in the August 2011 tender round saw 20- by upscaling turbine rotors and the development of new year contracts awarded to 44 projects. Prices sank as low products for the unique conditions. Illustrations: Dreamstime/Alan_smithee/Filograph as US$ 63/MWh for contracts start- abstract Placing Low Bids ing in 2014. Emerging economies have ambitious goals for their Discovering the true cost of sup- In a competitive process like that employed in Brazil, a renewable energy future. plying a good or service through small number of projects with overestimated energy yield Bidders are eager to win power generation contracts competition is widely used to reduce can significantly influence the prices of contracts awarded Fierce competition leads to prices and the desire of governments to all projects. Bidders are forced to place uncomfortably yield and price expectations to secure low-cost energy supplies low bids to win a contract or risk forfeiting the costs of de- that may be unsustainable vital to any economy is laudable. veloping the project and participating in the auction. There8 energıze renewables
  9. 9. The maxim ‘if something appears As auction designers strive to accommodate the unique characteristics of wind power the process becomes ever too good to be more unwieldy. In South Africa, the challenge of designing a true it probably is’ successful auction is seen by the absence of much develop- develop seems pertinent. mental wind capacity from a recent tender round. An oner- oner ous prequalification process muted competition and just 634 Oscar FItch-rOy Senior Policy Consultant at MW was contracted. More than 1 GW remains available for GL Garrad Hassan a second round in March. Pent-up demand and sufficient time for developers to prepare compliant bids presages an over-subscribed auction and cut-throat pricing here, too. Two Decades of Progress Recent history is littered with examples of sub-optimal out- out comes from wind-power auctions. The UK’s non-fossil fuel obligation tenders saw only a fraction of contracted plants ever completed. Denmark’s 2009 offshore wind tender at- at tracted just one participant. Policymakers seeking to unlock the potential of markets like Brazil and South Africa face a dilemma. If administratively set tariffs risk over-rewarding and competitive processes risk unsustainable pricing, how are no direct parallels with this uncertainty for conventional should they respond? Is there a compromise? Means of ac- ac generation, which can enter into long-term fuel supply con- commodating the uncertainties inherent in the costs and tracts to mitigate market risk. revenues of wind power should be sought. Mechanisms that An alternative explanation is that a frenzy of interest allow the tweaking of tariffs as the understanding of costs in the auction led to “winner’s curse”, which defies the develops between contract award and project completion assumption that all participants are able to make pure- would go some way to addressing this information gap. POtEntIal . ly rational decisions based on the information Important lessons about the role of competition have Brazil plans to available. Empirical studies suggest that in com- been learned over two decades of progress. Emerging install at least petitive situations players systematically over- countries planning to harness the power of markets to re- 2 GW of additional estimate the value of what is being sold. This veal prices could do worse than to heed words attributed capacity per might be shown by commitments to generate to Mark Twain: “History may not repeat itself, but it does year until 2020. electricity at unfeasibly low prices. It could be rhyme.” OF This article was first published in Windpower Monthly magazine. the case that a structural oversupply of global turbine- manufacturing capacity means developers’ costs are tem- GL GROuP ExPERT: Oscar Fitch-roy porarily low. But this raises questions about the long-term senior Policy consultant sustainability of the prices once the supply chain rebal- Phone: +44 117 972 98 78 ances. E-Mail: oscar.fitch-roy@gl-garradhassan.com01/2012 9
  10. 10. m a r k e t supply ch a i nsupply chain. Following years of uncertainty, new growth perspectives are giving confidence to the offshore wind industry. No Barrier to Growth The long-held assumption that supply chain bottlenecks will limit the growth and economic viability of the offshore wind sector in Europe is no longer valid The history of the offshore wind sector has factors, combined with a lack of market certainty and the been a roller-coaster ride on many levels. Over global financial crisis, culminated in the “choking” of the the last decade, the supply chain for this in- sector in the period 2008–10. A few projects still went dustry has veered from early optimism and healthy levels of ahead, but with eye-watering capital costs and significant competition through to market withdrawal and scepticism. programme risks. In fact until recently, it has never had a truly dedicated sup- ply chain, with goods and services being begged and bor- Decoupling at Last rowed from parallel industries: most notably onshore wind, The announcement of the UK “Round 3” lease awards in oil & gas and coastal engineering. During boom times in early 2010 was a game changer for the supply chain. It pro- these competing sectors, this “entanglement” has dogged vided a clear and significant market (33 gigawatts), over a the sector with diverted produc- relatively extended time frame (to 2020). It has since be- absTracT tion capacity and resources leading come clear that such a target is a stretch not only for the The last decade has been to spiralling costs. In addition, early supply chain but for grid connection and finance. This has challenging for suppliers to participants had their fingers burnt led to a more realistic perception of Round 3 as a two-dec- the offshore wind industry Tough conditions in competing by overly optimistic pricing, a poor ade endeavour, as underlined by recent government pro- sectors are diverting investor’s understanding of the cost-base and nouncements which envisage just 18 gigawatts to be in attention to offshore wind inappropriate risk allocation. These place by 2020. Germany’s ambitions for offshore wind are10 energıze renewables
  11. 11. now comparable to the UK’s, albeit set in a very different ture. The long lead time of new cable factories means that regulatory framework. And despite the waning of political investment decisions need to be made this year to avoid support for the technology in the Netherlands and Sweden, a supply crunch in the middle of the decade. These argu- the recent (re-)emergence of French ambition has served ments are supported by the EWEA Report “Wind in our to bolster supplier confidence. Ultimately, this needs to Sails – The coming of Europe’s offshore wind EWEa . be translated into investment in the required facilities and energy industry” as authored by the GL Garrad The “Wind products. We are starting to see this happen with the help Hassan Strategy & Policy team and launched at in our Sails” report is of funding and support from governments keen to exploit the EWEA conference in Amsterdam. available for the jobs potential of the sector. download at Commitment from both incumbent and new entrant Forecast: Sunny with Showers Later ewea.org supply chain players has never been higher. Established For the first time we are seeing a trend towards wind turbine suppliers see offshore wind as a source of a dedicated supply chain for offshore wind, fuelled by weak growth to pick up the slack in their orderbooks created conditions in other sectors and an increasing shift towards from the maturation of key onshore markets, whilst indus- technology specialisation as designs are better tailored to trial majors from China, Korea and Japan are drooling over meet market requirements. Such decoupling goes hand in the potential to bring their heavy engineering and manu- hand with creating healthy supply chain competition. This facturing capability to the party. Installation vessel availa- will help unlock desperately needed cost reductions. JP bility remains stretched in the short term, but several new- build offerings are due to hit the market in the next 12–24 GL GrouP ExPErt: months, easing this much-hyped pinch point. High-voltage Joe Phillips Global Head of Practice, strategy & Policy subsea cables are the clear exception to this general trend, Phone: +44 117 9729900 with production capacity stretched for the foreseeable fu- E-Mail: joseph.phillips@gl-garradhassan.com Momentum. Change the Record! regulatory uncertainty in the uK must be rEGulaTory uncErTainTy in the UK and other adressed markets has the potential to undermine the urgently to confidence of the supply chain to invest and securePhotos: Dreamstime/Toft, Seaports of Niedersachsen investment. greater clarity is urgently needed to avoid a loss of momentum. Yet overall the outlook is one of supply meeting demand. The nuclear lobby and other vested interest groups must be challenged if they continue to use perceived supply chain inadequacies as a weapon of choice. 01/2012 11
  12. 12. m a r k e t f ina nci n gstimulus. Germany’s KfW is providing a credit volume of up to five billion euros for projects such as Global Tech I (l.) and Borkum West II (r.). Banks Back in the Ring Clear signs of change at the Hamburg Offshore Wind Conference 2012: banks are becoming increasingly open-minded towards offshore wind projects The investments required for offshore wind en- their reservations, but are even signalling their readiness ergy farms are high – and they are fraught with for cooperation. greater risks than comparable land-based in- stallations. Small wonder that banks have approached new New Money, New Investors projects only with caution in recent years. One of the reasons for this reversal in mood is the new Off- But now the situation has changed. Thanks to the new shore Wind Energy programme of KfW, which is providing development framework set in place by the German Gov- a credit volume of up to five billion euros for ten offshore ernment at the beginning of the year, the business mod- wind farms in the Baltic and North Sea. This has smoothed el of renewable energy sources has also regained its at- the waters, since individual banks usually only wish to be in- tractiveness in the offshore sector. Clear indications of this volved with tickets of around 50 million euros. For projects were to be seen at the Hamburg Offshore Wind Confer- in which over a billion euros have to be funded in total, this ence 2012 organised by GL Gar- stake is simply too small. Peter Schäfer, Head of the Renew- abstraCt rad Hassan. There is a robust spirit able Energies Department at KfW, listed the mega-projects Thanks to state incentives, of open-mindedness in the market which have been launched with the aid of his institute: C- offshore wind farms are gaining in interest for banks – despite the risks, which still exist Power II, Borkum West II and Global Tech I, amongst oth- and investors as much as before. The offshore ers. A total of 23 banks were involved in these projects: 16 Complex contractual structures business model is picking up speed alone with Global Tech I, a joint project by utility companies. remain challenging again; banks are not only displaying For this project, KfW took on the lion’s share with 330 mil- 12 energıze renewables
  13. 13. 20 Consented 18 lion euros through its subsidiary KfW IPEX-Bank. The inten- 16 derstand, and time-consuming contract negotiations. As tion is to realise large projects of this kind more easily in fu- a compromise, Atvars suggested EPCI (Engineering, Pro- ture with the aid of the KfW offshore programme. 14 curement, Construction and Installation) contracts. One of the financial players that is becoming increasingly This viewpoint was shared by Dirk Mous, Vice Presi- active in the German market is Green Giraffe Energy Bankers 12 dent Infrastructure & Renewables at NIBC Bank. In the (GGEB). Based in Paris, the financial advisor holds interests in current phase of the industry, the prevailing multi-con- Borkum West II, Meerwind, Global Tech I and others. Global 10 tracting system means that the partner who should Tech I alone boasts a funding volume of over a billion euros. shoulder the financial risks is the one who is best able Under construction Accomplishing the financing of these projects was difficult, 8 to. Each risk must be identified, defined and regulated says the Managing Director of GGEB, Jérôme Guillet. One by contract. Dirk Mous also emphasised: “The earlier the thing, however, has been shown: “There is enough money in 6 banks are included in technical matters and legislatory the market for good projects.” One of the main prerequisites requirements, the better. It is essential not only to con- Online 4 sult financial advisors but also to call upon legal counsel”. At the conference, it became evident that the market offshore market. projects online, under 2 of the offshore wind industry is, from the vantage point construction and consented (in GW) and share of consented offshore capacity (MW). Norway 2% Latvia & Italy 1% each Capacity. German share in consented projects is enormous – and UK, Belgium & Finland 5% each Denmark 0% accordingly the financing demand. for this, however, is early involvement of the banks of the banks, undergoing major change at and their advisors in the discussions, the setting of present. Although the industry is still fair- guarantees and the planning of the logistics, espe- Sweden 6% Germany 45% ly small in terms of volume, the banking cially of the installation vessels. For him, the key is- institutions see it as increasingly attrac- Estonia 7% sue is: “How much influence can the banks have in tive – with some caveats. Michael Sup- Ireland the contract negotiations?” pan, Vice President at Deutsche Bank, be- 11% Netherlands 12% lieves that the sector has definitely become Many partners, Many Contracts more interesting for investors. Offshore wind Sou rce: EW EA (Jan. 2012) Eriks Atvars, Managing Director at UniCredit, sees further is now viewed as a promising field. The current challenges ahead. He characterised the position by referring trend: “There has been a repricing of risks across the to the contracts: “We most appreciate EPC contracts. But whole spectrum,” as Suppan observed. There can be no these are not available in the offshore market. Why is that?” doubt about it: The market is on the move. HS His answer: “The situation is too complex and there are tooPhotos: Global Tech I, Trianel many risks for one owner/operator to take on the turn-key construction of a project all by himself.” Instead, multi-con- GL GRoup ExpERT: Dr Helmut Klug tracting is predominant in the offshore wind industry, with Managing Director CEMa all the attendant drawbacks – many partners, many differ- Phone: +49 441 36116 880 ent contracts, a web of relationships that is difficult to un- E-Mail: helmut.klug@gl-garradhassan.com 01/2012 13
  14. 14. m a r k e t insur a n ce “You can charter a ship in a minute, because But the offshore sector is still far from achieving this the owner and the charterer know on what blissful state, as the example of Munich’s municipal utility, conditions they want to finalise. But in off- Stadtwerke München (SWM), shows. By 2025, the third- shore wind, you negotiate for six months, discussing largest city in Germany aims to cover the complete energy clauses up and down. This cannot continue in the long requirements of all private households as well as industrial run.” With these words, Dr Patrick Wendisch, Managing and commercial consumers from renewable energy sources. Partner of Nordwest Assekuranz, With today’s share of renewables in the energy mix stand- abstract zeroed in on one of the prime ob- ing at 4.7 per cent, this is certainly an ambitious – if not The risks of offshore wind turbines demand clearly worded jectives of his industry. “This new extremely bold – objective. SWM is already participating insurance contracts up-and-coming industry should and in three large offshore projects – Global Tech I, Dan Tysk The industry is working towards must arrive at standard contracts and Gwynt y Môr. The three projects differ considerably, a sensible distribution of risk and standard clauses.” as Dr Thomas Meerpohl, SWM Head of Project Develop- “No Risk No Fun” w in d in du st ry. et s fo r th e offs ho re es s is se tti ng cle ar ta rg th e in su ra nc e bu sin s st an da rd co nt ra ct s Fir st th in gs fir st : th e in du st ry ne ed ment, stressed during the Offshore Wind Conference of GL Garrad Hassan. There are different partners and there are different contractual provisions, each with a different dis- tribution of risks. What is more, the projects differ to some extent also in terms of the logistics concept, the selected type of turbines, and the foundations. But which concept and what contracts are the best? Nobody knows. Dr Meerpohl sees the positive side – the opportunity to gain a wealth of experience. The time frame may be tight, but the core message is clear enough. All three projects reflect the new strategy of regional energy providers: the municipal utilities want to, and indeed must, produce their energy themselves to a large degree in future. Who would quibble about the few years by which such an important goal might be delayed? Good Contracts, Bad Weather Gaining Experience. Munich-based SWM is already Over the past few years, underwriters, corporate law firms participating in three large offshore projects. and banks have built up expert teams that are exclusively14 energıze renewables
  15. 15. the ins tal lat ion . one of danger of worst traps is the bad weather. confusing ice with focused on projects for offshore wind energy. For example, insurance clause, he is missing the “knock-for-knock” prin- Hogan Lovells International with a team of a dozen law- ciple. “Why don’t we see that more frequently?” yers in Hamburg. One of them is Dr Christian Knütel. He “Knock-for-knock” is not very popular, however. “Every- referred to a few of the largest pitfalls to avoid in the off- body wants to ‘pass the hot potatoes’ on to somebody shore wind business. Many partners come from the world else,” remarked Dr Patrick Wendisch of the Bremen-based of shipping or the onshore industry and, for want of expe- insurance broker Nordwest Assekuranz. “No- spEcialists . rience in the new sector, tend to underestimate the risks. body wants to keep them in his own pock- Underwriters, Unfortunately, it is not possible to insure against any “lack et.” The hottest potatoes for him include the corporate law firms and banks in claim management”. His simple advice is therefore that weather risk, the manufacturer and subcontrac- have built up contracts are meant to be read: “You can lose as much tor guarantees, contractual penalties and the expert teams money with the bad execution of a good contract as with logistical costs. “Risk of weather is a special focused on offshore projects. a bad contract.” cover – it’s very complicated, but in the end One of the worst traps is taking onboard too much we generally find a good solution. The insurance industry bad weather risk, or failing to define this risk precisely. In is very much in the process of learning its lessons.” His ad- autumn, the installation ships are not always able to oper- vice to all involved: Risks have to be accepted – “No risk, ate, so that one would have to ask: “Who forced the ship no fun!” HS into a bad weather period?” As a fundamental rule, he ad-Photos: AlphaVentus, SWM vises against taking on the entire weather hazard, because follow-on risks are associated with it. “What do you do if GL GRoup ExpERt: peter Frohböse a vessel needs to be exchanged and the new vessel has a Offshore Germany different wind class?” His recommendation: Each contrac- phone: +49 40 36149-2748 tual partner should bearthe risk he can manage. Regarding E-Mail: peter.frohboese@gl-group.com 01/2012 15
  16. 16. software16 energıze renewables
  17. 17. GL Garrad Hassan is acknowledged for its technical rigour. This is reflected in its multiple industry standard software packages which are relied upon by professionals around the world. Illustration: iStockphoto/instamatics01/2012 17
  18. 18. sof t w a re w ind fa rme r Effective Tools for Pre-Construction Energy Assessments A multitude of interrelated technical and environmental factors must be considered before a wind power project can be planned and implemented. Backed by decades of experience, GL Garrad Hassan’s proven software WindFarmer helps planners to manage the complexity Wind farm design and energy assessment WindFarmer software developed by GL Garrad Hassan as within the wind industry are complex pro­ a platform for discussion. cesses that vary greatly depending upon the constraints and challenges of each wind farm site. Stake­ Energy Calculations holders such as developers, utilities, and financiers must Calculated energy production values for a wind farm re­ technically evaluate a project to determine its profitabil­ quire several inputs in order to properly evaluate the esti­ ity and feasibility in the market. A software package that mated energy generation of a site. The topography for a can model the performance wind farm and the boundaries of the site may be loaded ABstrAct of all types of farms is es­ into the software as ESRI shape files. The wind flow on the The ability to reliably predict the sential in the wind industry. site should be characterised by on­site measurements and energy yield of a proposed wind farm is crucial for all stakeholders Some of the key features extrapolated out to the rest of the site, and the historical Sophisticated modelling and and models needed in such air density on the site must be evaluated. analytics software is needed to a wind farm design soft­ The efficiencies and loss factors specific to the sitePhoto: Dreamstime/Kasto80 account for all influential factors WindFarmer is a proven, highly ware package are highlight­ should be understood, and a turbine layout and power flexible wind farm design tool ed here, using the latest curve must be selected. Once this basic site information 18 energıze renewables
  19. 19. VisualisationVisualisation. Maps and diagramshelp planners understand thespecific operating conditionsat the proposed site. Wind Farm Wake Modelling The Eddy Viscosity Wake Model is a CFD model that has been developed, refined, and validated using operational wind farm data for many years and has proven to be a suc­ cessful wake modelling algorithm in a wide variety of stand­has been entered, the type of analysis method chosen to ard situations. WindFarmer also includes several modifica­calculate energy is dependent upon the characteristics of tions to this base model for wind farms that fall outside ofthe wind farm being assessed. the normal operational envelope of the model. With these The energy production of a farm is greatly influenced adjustments, the exceptional characteristics of regions withby the wake effects from upwind turbines, and the use such observed wind regimes can be taken into account.of an accurate wake model is key to making an accurateestimate. WindFarmer has several different wake models Wind Farm Wakes in Complex Terrainavailable to take into account the specific challenges of the Environmental parameters such as air density and turbu­broad range of wind farms in development and in opera­ lence levels as well as the development of the wake itselftion within the industry. are a function of the underlying topography. Wind­01/2012 19
  20. 20. sof t w a re w ind fa rme r Farmer makes use of this information to automaticallyadjust the turbine wake development and energy calculat­ed, based on the turbine’s position in the terrain.Closely Spaced Wind Farm LayoutsThe closely spaced wake model allows for wake modellingto be completed on wind farms that are built for uni­ or bi­directional wind regimes, as these types of wind farms havetheir own unique challenges. Such regimes lend themselvesto turbine layouts that are positioned closely together inone direction to maximise electricity generation per giv­en area. Turbine wakes in such a layout do not propagateindependently and as such, must be modelled differently.WindFarmer’s Eddy Viscosity Model for Closely Spaced Tur­ complexity Made simple. WindFarmer structures andbines effectively models the wakes propagated for this type correlates the site-specific information to provide reliable information for decision-making.of wind farm by altering the classic Eddy Viscosity modeland allowing velocity deficits caused by the wake effects tobe added cumulatively. deep. The Large Wind Farm Wake Model has been devel­ oped to model the increased wakes generated at theseLarge Wind Farm Model large­scale wind farms. The model works by taking intoAs the wind industry has developed, the size of wind farms account several characteristics specific to large wind farms,has increased both on­ and offshore to include farms that the most important being the alterations to the boundaryare greater than 100 megawatts in size and many rows layer caused by the presence of a large number of turbines20 energıze renewables
  21. 21. extracting momentum from the atmosphere. As a result, gime on site. These uncertainties are then used to derive thethe wind profile varies across the farm, analogous to an relevant exceedance levels so that stress cases can be runincrease in surface roughness length. Within WindFarmer, and debt service coverage ratios can be converted into cur­this highly technical and crucial feature is in the form of a rency for pro forma preparation.check box where the software performs the overall analysis WAKE . Eachof upstream turbines to derive the added wake losses due Efficient Wind Farm Design wind turbineto the large wind farm wake effect. The Large Wind Farm Wind farm design software packages offer a causes a wakeWake Model has been tested and validated with data from range of tools to support the engineer in design­ that will affect other turbinesoffshore and onshore wind farms in operation. Furthermore ing an efficient wind farm layout. These tools locatedthe speed of the energy yield calculation, typically 10–15 include aids for automatic generation of both downwind.minutes for a 100­turbine array, enables wind farm design­ random and symmetric layouts with high energyers to explore many different layout options within a very yield. Using these advanced tools in the design of a windreasonable time frame. farm can help to mitigate project deficiencies found later in the detailed energy assessment. As wind farms becomeUncertainty Analysis larger and more complex, scientific research is increasingOnce the estimated energy production calculations for a site the understanding of how wakes behave within such aare completed, the uncertainty associated with these results complex environment. A software package such as Wind­must be quantified. Uncertainty calculations are essential Farmer is essential to leverage this knowledge and produceto quantify and assess the asset’s viability and profitability reliable estimates of electrical power production. SHin order to raise project financing. As such, WindFarmer in­corporates uncertainty analyses into its results to provide an GL GroUP ExPErT: sarah Hermanevaluation of the many sources of uncertainty present with­ Photo: Dreamstime/Visdia team Leader Energy Groupin the development process, such as data collection sensors, Phone: +1 512 469 6096 115topographic modelling, and yearly variation of the wind re­ E-Mail: sarah.herman@gl-garradhassan.com01/2012 21
  22. 22. sof t w a re onlin e d a ta ma n a g e m e n tMaximisingthe PotentialMonitoring and analysis of on-siteresource measurements increases thevalue of the data for assessments. It canbe challenging to quickly identify andresolve problems relating to equipment Since its initial release in spring 2010, the GL Photo: iStockphoto/Jeannot Olivet Garrad Hassan Online Data Management (ODM) Measurement. service has continued growing and is currently Ensuring accurateused by clients in 26 countries worldwide with more than and continuous500 met masts under management. The data collected with- data collection is important.in each project allows developers of wind farms to maximisethe value of their wind resource measurement investment viastable, accurate and continuous data collection and review. Working with wind means rapidly changing conditionsMeet Conditions, Implement Improvements and equipment pushed to its limits. The ODM service of-One of the clients that use this service is Wind Capital fers a 24/7 fully secure, password protected online accessGroup. The company is developing utility-scale wind farm to quality-controlled data for managing and maximisingprojects all across the central US and has offices in St. Louis, the potential of measurement campaigns. “GL Garrad Has-Missouri, St. Augustine, Florida and Chicago, Illinois. Com- san’s ODM service enables us to turn around internal en-bining community relationships with experience and vision, ergy assessments at a much quicker rate since cleaned dataWind Capital Group has developed wind farms – currently is readily available to download,” said Rachel Redburn ofoperating or under construction – producing nearly 1,000 Wind Capital Group. “We have also noticed that GL GarradMW of economically viable, clean, renewable electric- Hassan’s energy assessments tend to have a quicker turna- ity. Its current projects round time because the cleaned data is available to them, abstract have the potential to as is all the mast documentation.” Online Data Management produce enough wind To further improve the ODM service, GL Garrad Has- allows developers to maximise energy to power more san released a new Customer Relationship Management the value of their investment in on-site measurements than 300,000 homes, (CRM) component to its service at the end of 2011. The GL Garrad Hassan offers offsetting more than new CRM functionality offers a complete, centralised view an industry-leading data 1.6 million tonnes of of all issues regarding measurement equipment under man- management service carbon each year. agement, and a full history of all associated electronic com-22 energıze renewables
  23. 23. munication and support cases. With the new support tool, service. theenquiries can be handled in a timely, transparent and trace- ODM home page summarises theable manner, as the full history of communication with the headline mea-GL Garrad Hassan ODM team is tracked, ensuring a direct surement results.and personalised service. Having a comprehensive overviewof the status of all the monitoring systems enables ODM have arisen. Routine data checking ensures that challengesusers to schedule maintenance and repair programmes to with equipment are quickly identified and resolved, there-provide maximum value and benefit in the site data. fore increasing the value of the data for subsequent use in formal, bankable assessments. “The ODM service hasAccess to Summary Statistics proved to be a handy tool for internal analyses as it is niceThe service is designed to help developers minimise fre- to be a few clicks away from wind roses, time series plots,quent and detailed investigation of on-site resource mea- and correlations among sensors on a single mast,” ex-surements while maximising the value associated with plained Wind Capital Group’s Rachel Redburn.stable, accurate and continuous data collection. Data are The quality control of data provided by the ODM servicephysically located at a secure server farm, fully backed up is based on GL Garrad Hassan’s years of experience pro-with multiple levels of redundancy. The service allows ac- viding energy assessment services. The addition of a newcess to summary statistics including energy estimates and client support tool and enhanced alerting system providesother critical information pertinent to the early stages of developers and investors with a highly responsive and de-project development. As on-site data measurements are tailed monitoring service. CEtransmitted, received and processed by this automatedservice, the cleaned data are checked weekly by an experi- GL GrouP ExPErt: caroline Evansenced analyst and a full set of statistics for all instruments Project Manager Online Data Managementon each mast are presented on the website, alongside a Phone: +1 604 602 2399full history of the measurement equipment and issues that E-Mail: caroline.evans@gl-garradhassan.comKey Features of the Service Instant access to quality-controlled data as well as full maintenance records stored Storage of mast photos and documents, and monitoring equipment at any time. in one location. for example calibration certificates and Modern and user-friendly interface, incor- Broad range of statistics and graphical maintenance records.  porating Google TM Earth. analyses derived from the data available Estimated energy and capacity calculations Raw and cleaned data can be downloaded at a click, including interactive graphical based on selectable project characteristics. for multiple masts and projects. tools for time series, shadow plots and 24/7 fully secure and password-protected PDF summary data reports as downloads. correlations. online access (https). Detailed log of all data exclusions, for ex- Detailed mounting configuration of cur- Robust and secure server infrastructure ample from icing, instrument malfunction, rent and historic instruments. with multiple levels of redundancy.01/2012 23
  24. 24. sof t w a re c omp u ta ti o n a l fl u i d d yn a mi csRosa’s Windy Plateausharp ridges, steep slopes and rocky plateaus. Modelling the wind flow in this kindof terrain is no walk in the park. GL Garrad Hassan’s brand-new, state-of-the-artcomputational Fluid Dynamics capacity leads such demanding projects to success “Most definitely not!” exclaimed Rosa, my cli- standing at the foot of the hill, which is why you ent, almost laughing. We were planning a visit would put a wind turbine at the top. Now imagine to the site of a wind farm proposed by Rosa’s that you can “pump up” the hill, as you would a employer, a growing developer. Fifteen turbines would be balloon. The traditional wind flow models that have placed on a barren, rocky plateau that rose almost a hun- been a staple of wind energy assessments since the dred metres above its surroundings. My job was to pre- 1980s are known as “linear” models. They assume that dict the turbines’ energy production by modelling the wind if a hill doubles in height, then the effect that the hill has flow at their locations, so I had to see the site in person. on the wind flow around it, notably the abstract“We’re not walking up to the top, it’s way too steep,” she speed-up experienced at the hilltop, Traditional linear wind flow said. “Let’s get a helicopter.” I thought, “So steep we need also doubles. This linear scaling actual- models cannot predict a helicopter?” Well, then, traditional wind flow modelling ly works fine in simple terrain with shal- wind conditions in complex terrain with sufficient methods would not be of much use. We would have to low slopes. accuracy and detail bring out non-linear computational fluid dynamics (CFD). Now, continue pumping. For CFD, while requiring a while, everything goes well. massive computing Beyond Tradition resources, can help avoid But as you pump the hill up fur- costly mistakes when Imagine the wind blowing on a very shallow hill. Standing ther and the slopes become steep- choosing the locations for individual turbines at the top of the hill, you feel a stronger wind than when er, new things start to happen.24 energıze renewables
  25. 25. Rough Conditions WinD FLoWinG over the edge of Rosa’s plateau and impinging on a proposed turbine located in a slight local depression. The circle illus- trates the turbine’s rotor area, 90 metres in diameter. The streamlines show the direction and speed of the cFD-siMuLateD FLoW (blue is low speed, yellow and red are high speed). tHe FLoW DetacHes in tHe Lee oF tHe pLateau’s eDGe, causing recircu- lation (shown as spirals), low wind speeds, and intense turbulence. A turbine placed in such uneven flow would not only have a poor poWer output, it would be subject to a lot of wear and tear, thus raisinG Maintenance costs anD DoWn- tiMe. To remedy this, the proposed turbine was relocated toward the lower right of the image where the flow is nice and regular.01/2012 25
  26. 26. sof t w a re c omp u ta ti o n a l fl u i d d yn a mi cs calculation. Long before commencing construction works on a new wind farm, the wind flow conditions at the site must be modelled using advanced techniques, such as CFD. The speed-up at the top still increases, but not as culation over many processors. In January 2011, GL Garrad much. As the slopes pass the 30 per cent mark, the flow Hassan gave a home to a cluster that currently allows the behind the hill detaches – the air no longer flows parallel to CFD calculations for one wind farm site to be completed the ground surface. This massively reduces the wind speed within two days. there, while turbulent eddies are shed onto the other hills The more subtle trade-off, however, is the level of care, downwind. engineering judgment and expertise needed to do CFD All of these effects have very real impacts on turbines properly. There are many choices to be made at every step located in complex terrain. But traditional, linear models when setting up and interpreting the results of a CFD sim- cannot account for them. This means reduced accuracy and ulation (meshing strategy, boundary conditions, represent- increased uncertainty. ing different wind directions, etc.). One mistake can lead to inconsistent results, or worse, results that look plausible New Tool in the Arsenal but are misleading. Unfortunately, awareness of this key CFD does not make the same assumption of linearity as tra- difference between CFD and linear models has not yet be- ditional models do, which in principle makes it better suited come universal in the wind industry and some practition- to model the wind flow in complex terrain. However, there ers of CFD may be falling into some of the many traps that are two significant trade-offs that have “don’t do this at exist in CFD. home” written all over them. GL Garrad Hassan has several years of experience in the CFD is way, way heavier than linear models, computa- application of various CFD models to wind farm sites. Since tionally speaking, which means that you need a very large January 2011, GL Garrad Hassan has settled on a com- and expensive computer in order to get the level of spatial mercial, state-of-the-art, multi-purpose engineering physics detail needed and to run the model in a reasonable amount simulation package as a calculation engine. To ensure con- of time. The latter is usually done by parallelising the cal- sistency and reduce sensitivity to user input to a minimum,26 energıze renewables
  27. 27. Photos: Dreamstime/Antikainen/Wojphotopreparation. Wind flows inmountainous areas represent a challenge indesigning and constructing of wind farms.a method was developed and parameters were set up that Mistakes Avertedcan be applied uniformly to a majority of complex-terrain As it turned out, the CFD simulations worked like a charmsites, without site-specific tuning. on Rosa’s rocky plateau, providing critical insight into the wind flow patterns there. GL Garrad Hassan cFD .Validation Exercise was able to determine that two of the fif- ComputationalTo verify the soundness of this CFD method, it was applied teen proposed turbine locations would be so fluid dynamics uses powerfulto a dozen complex-terrain sites, each equipped with two or severely affected by adverse flow conditions computers tomore masts from which quality-assured measurements were that this would lead to low production lev- analyse andavailable (70 mast pairs in total). This allowed performing els as well as increased wear and tear, hence simulate thecross-predictions between masts using CFD and comparing high maintenance costs. The planned turbine behaviour of complex liquidthese wind speed predictions to the actual measurements. locations were moved by two hundred metres, or gas flows.Furthermore, a traditional linear model was run for compari- where the flow would be more regular and theson. CFD provided two important benefits when compared wind speeds higher. Thanks to advanced flow modelling,to the linear model: the deviation from measurements was the output of the client’s project could be substantiallygenerally reduced by one third, and very large deviations improved, and its expected lifetime extended. Now thiswere much less frequent. The linear model occasionally re- certainly did please Rosa. jFCsulted in very large errors (up to 20 per cent on the meanwind speed) but this was not observed for CFD. The fullresults of this validation exercise are documented in a pa- GL GRouP ExPERT: Dr Jean-François corbettper presented at EWEA 2012 in Copenhagen. Based on this Head of cFDevidence, CFD methodology can consistently reduce uncer- phone: +45 33 377139tainty in the context of wind resource assessments. e-Mail: jean-francois.corbett@gl-garradhassan.com01/2012 27
  28. 28. certification28 energıze renewables
  29. 29. Certification of wind farms, turbines and their components is state of the art and a must around the world. GL RenewablesPhoto: Dreamstime/Pdkx77 Certification offers project and type certification. 01/2012 29
  30. 30. cer t i f i c a t i o n o ffs h o re FINO1. The research platform was erected in Photo: Wilhelm Heckmann the North Sea in 2003, and provides the highest continuous wind meas- urement in the offshore sector worldwide.30 energıze renewables
  31. 31. Turbulence Models under Scrutiny Wind turbine designers use a variety of simulation tools to predict the wind loads at the proposed site as accurately as possible. But how can the tools chosen be further improved without reducing safety level? corded in samples of 10 minutes with a frequency of 10 Hz, were analysed for the study. From the data pool, only sam- ples with appropriate wind speeds and turbulence intensities were used for analysis. The statistical properties were calculated and compared with the theoretical values commonly used in standard wind field models. Synthetic wind fields were generated All simulation tools used in wind turbine de- using the wind field generation tool of GL Garrad Hassan’s sign require a simulated wind field as input. To Bladed software. The parameters for the turbulence mod- obtain reliable results from a numerical wind els were chosen to match the analysed characteristics of turbine model, the wind field model used to analyse tur- the FINO1 data. bulences must be realistic. In a recent study on offshore wind turbulence, GL Group experts examined the validity Detailed Insight of current wind field models by benchmarking them against The study showed that wind profiles as well as the distri- wind time measurement series taken at the FINO1 offshore bution of wind speed fluctuations are captured very well research platform located in the North Sea. by the commonly used wind field models. These models Preliminary investigations had shown that the various assume the wind speed fluctuations to be Gaussian distrib- models used to describe turbulent wind according to the uted. The analysis of conditioned FINO1 data confirmed this GL Guideline or the IEC standard can result in significant dif- assumption on the basis of 10 minutes-time series which ferences regarding wind turbine loads. did not include meteorological trends on larger time scales. aBstract The applicability of these models and The analysis of the highly time-resolved FINO1 wind speed Wind profiles and the distribu- tion of wind speed fluctua- of deviations in load analyses have measurements with the statistics of increments showed the tions are captured very well by been the subject of discussion among intermittent characteristics of atmospheric wind fields. This the commonly used models design experts. The aim is to reduce feature is pronounced over a broad range of time scales. The relations between stan- dard deviations of the wind margins without compromising safety. Standard wind field models do not reproduce this behaviour speed components differ from Approximately two years of FINO1 of atmospheric wind fields. That means, in comparison with the Kaimal and Mann model data from three different heights, re- the standard IEC or ESDU models the atmospheric01/2012 31
  32. 32. cer t i f i c a t i o n o ffs h o re wind fields show a higher probability of extreme wind Wake effects in large wind farms aggravate turbulences. speed changes on small time scales. The consequence is a Load analyses based on effective turbulence revealed strik- probable underestimation of extreme gusts and their rising ing differences with respect to the chosen model. Interest- time. The intermittency is known to result in additional loads ingly, the Kaimal spectrum produced higher fatigue loads as well as in intermittent power fluctuations. in this case than the ESDU spectrum. For cases with lower The relations between the standard deviations of the turbulence the study yielded the opposite result. Neverthe- wind speed components coincide with the ESDU model but less, the Kaimal model showed good agreement with the differ significantly from the Kaimal and Mann model. How- results of the extreme load simulations for large wind farms. ever, these results should be compared to other offshore Future research projects will investigate these important BLadEd . measurements to exclude influences originating influences on loads of neighbouring wind turbines in great- GL Garrad Hassan’s from the mast and the measurement devices. er detail. Further investigation is needed to improve the integrated software wind models used in wind turbine load analyses. The Mann package for the A Few Surprises model, in particular, will be subject to further investigation. design and certification of The length scales of turbulence were calculat- The GL study, while not a complete review of current onshore and ed for the FINO1 data and compared to those wind modelling techniques, provides a good basis for fur- offshore turbines. given in the relevant standards. Synthetic time ther discussion within the IEC TC 88 committees regarding series were generated with the calculated properties using the continued development of the IEC 61400-1 and IEC Bladed. Some significant differences from the assumptions 61400-3 standards. TM were found to exist. A load analysis of simulations for some key parameters showed striking differences in the result- ing loads. Unfortunately, real-load measurements were not GL GrOuP ExPErT: available for comparison. Nevertheless, the ESDU spectrum tanja Mücke was found to describe the atmospheric spectral probability GL rc, Onshore Loads densities measured on FINO1 better than the other stand- Phone: +49 40 36149-8720 ard models. E-Mail: tanja.muecke@gl-group.com Figure 3. Probability density function ofFigure 1. Turbulence intensity of the FINO1 Figure 2. Distribution of turbulence inten- wind velocity increments normalised todata in the selected wind direction sector. sities for u10 = 16±1 m/s at 81.5 m height. a standard deviation of σ=1 32 energıze renewables
  33. 33. cer t i f i cat i on fa t igue Will it last? the design lifetime of a wind turbine is very long, and the components in thePhoto: iStockphoto/Teun van den Dries main load path are huge and expensive. to predict component fatigue life, Loads. design engineers rely on sophisticated Components, long life, simulation tools complexity: Everything is huge in a wind turbine. Modern megawatt-class wind turbines are ex- planet carrier – are mostly made of large, complex-shaped posed to high and complex loads. Larger com- castings or steel materials. Since wind turbines are often ponents entail increasing cost and the demand located in remote areas where access for inspection is diffi- for a sturdy substructure able to carry the deadweight and cult and repair is costly, their design must be based on reli- the aerodynamic loads. At the same time, lightweight and able safety assumptions, in particular a long crack initiation optimised structures are important design objectives to re- phase. But more importantly, the prediction of component duce material consumption and cost, and to improve com- life prior to crack initiation is what designers of these heav- petitiveness. ily loaded structural components are most interested in. A Considering the large-size components and the long current GL study is investigating new ways of improving the design lifetime, full-component fatigue tests are not com- accuracy of fatigue resistance predictions. mon practice in the wind industry. Hence simulation of glo- bal loads and component fatigue behaviour is vital. Since Design Loads failure of large parts can be an economic disaster, simula- The simulation models commonly used to verify the tion accuracy is essential. strength of key components typically account for the ro- tor blades and tower in much detail, whereas the dynamic Wind Turbine Components properties of the drive train, the structural components and The load-bearing structural components of a wind turbine other crucial elements are barely con- – in particular, the hub, main shaft, main bearing sidered. Design loads for a wind turbine abstract housings, machine frame, torque arm and are thus only available within certain Understanding component fatigue behaviour in wind predefined coordinate systems of the turbines is crucial and complex Gear box. wind turbine, e.g. its blade root, hub To optimise design safety and Conventional centre or the tip of the tower. Compo- economic efficiency, current three-point models require further refinement suspension. nent loads must be extrapolated 01/2012 33

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