In Berlin for the European Offshore Wind Conference & Exhibition in December, Eize de Vries reports on Europe’s goal of having 40,000 MW of offshore wind power by 2020, and on the technologies and businesses planning to deliver that goal.If Europe wants to meet its binding target for a 20% renewable energy share by 2020, EU countries must inevitably accelerate offshore wind development. Two concrete steps towards large-scale deployment of offshore wind were taken on one day in December – the European Commission announced an offshore action plan for 2008, and regional co-operation was promoted through the signing of a trilateral offshore research agreement by Germany, Sweden and Denmark.The agreement covers technical, environmental as well as additional research topics and other European countries were explicitly invited to join in. It replaces a 2005 joint document by Germany and Denmark that served as an open instrument for enhanced co-operation on offshore wind power issues.
The 20% by 2020 renewable energy target translates into the equivalent of 34% of electricity to be provided by renewable sources, according to the European Commission. The 20% to 34% ratio is explained by the fact that cumulative energy use encompasses multiple heat applications, use as transportation fuels, in agriculture, industry and such like, in addition to use in energy-to-electricity conversion. And unfortunately a huge share of total energy use is still being thrown away unused.Among other processes, this happens as waste heat during large-scale centralized electricity generation, heat and power transport losses, as part of industrial processes, and due to heat losses. Largely unknown is also the fact that about 5% of the world’s overall energy is used for the production of mineral fertilizers that are applied in modern agriculture.
Wind energy could produce an estimated 12% of total electricity supply – equivalent to more than a third of the 34% renewable electricity by 2020 target – but only if offshore wind power is developed at a much faster pace than currently. LESS RISKY
Back in 2003, the European Wind Energy Association (EWEA) published a scenario for wind energy, including an offshore wind target of 70,000 MW by 2020. For various reasons, including a booming and less risky global onshore market, that offshore target will now be reached later. However, in response to the new 2020 target, the wind industry has put together a series of policy recommendations for large-scale deployment of offshore wind in the coming 13 years. EWEA launched this new publication, entitled ‘Delivering Offshore Wind Power in Europe,’ at the opening session of the European Offshore Wind Conference & Exhibition, in Berlin in December. One key recommendation is the call for a European action plan for offshore wind (confirmed by the Commission). Other parts of the plan include establishing stable, long-term markets for offshore wind, increasing research and technological development, improving grid integration and facilitating efficient planning procedures.
EWEA’s report estimates that, if barriers are effectively removed, up to 40 GW of offshore wind energy could be operating in the European Union by 2020, supplying 4% of Europe’s electricity, subsequently the UK government announced ambitions to produce 33 GW by 2020 – see article, page 74. At the end of 2007 the European (i.e. world) cumulative total offshore wind capacity, installed between 1991 and 2007 added up to about 1.1 GW.
The bulk of offshore wind turbines installed today fit into the 2-3 MW class, which means 300-500 new installations are required for each additional 1000 MW added. In order to achieve the ambitious 40,000 MW target by 2020 the pace of annual installations will need to be stepped up to 3 GW on average during the next 13 years.
However, during the coming years the average power rating of new offshore installations is expected to rise steadily, and this in turn reduces the total number of wind installations required. This anticipated development is mainly due to a gradual introduction of new turbine makes and models in the 5-6 MW+ class. Future application of bigger offshore wind turbines may therefore reduce the cumulative number of installations required, but the challenges to meet still remain formidable nonetheless.
GERMANY’S BALTIC I
Nordex AG of Germany announced during a press conference at the Berlin conference that it will deliver 21 of its 2.5 MW N90/2500 series turbines for what it calls the first commercial offshore wind farm in Germany. The construction permit required for this project was issued in April 2006, but its planning history dates back much longer.
The developer and operating party is the German global developer and marketer of renewable energy projects wpd think energy.The first turbines in the 52.5 MW Baltic I project are scheduled for installation in May 2009 and the wind farm is to go into operation the same year.
The site is located roughly 13 km to the north of the peninsula of Darss, where the Baltic Sea has a depth of 15 to 19 metres.The turbines will be placed on monopiles and are each expected to yield about 10 MWh annually. So far, though, Nordex has only limited experience offshore. The company installed a first 2.3 MW N90/2300 turbine in the ‘Kattegat’ near Frederikshavn, Denmark during 2003. A second machine, this time a 2.5 MW N90/2500, became operational early 2006 in the German port Rostock and again this was put into relatively shallow water.
Baltic I received support of the state government of Mecklenburg-West Pomerania, where Nordex turbines are being assembled at the company’s key manufacturing base near the port of Rostock.
Nordex Chief Executive Officer Thomas Richterich pointed out at the Berlin press conference that: ‘With the Baltic I project, we are able to gain further crucial experience to prepare for offshore business, which will put us a good position once this market starts growing in importance in a few years time.’
In his address Richterich also stressed that Nordex at the moment is not planning a massive entry in the offshore wind market, but instead chooses a gradual step-by-step approach.To stress the point he showed BTM Consult 2007 figures indicating a 1.2% offshore wind share in the cumulative market total until the end of 2006, a share that is expected to grow to 5.2% by the end of 2011.
However, Nordex has already commenced on a concept study for a new 3-5 MW wind turbine with what it describes as ‘offshore features.’ A prototype is envisaged for 2010 and production of the 0-series turbines is planned to begin by 2011 or 2012.
A near shore wind entrant is WinWinD of Finland that during the second half of 2007 began installing the first of ten of its 3 MW WWD-3 Multibrid-type wind turbines at the Kemi Ajos Harbour wind farm.WinWinD is a small company but was one of the first wind suppliers to introduce a commercial 3 MW class turbine. Three of these turbines were now installed on artificial islands in the sea close to the shore.The installations being delivered have a hub height of 88 metres and a rotor diameter of 100 metres, and each turbine is expected to generate 7500 MWh of electricity per year.
Both 2008 and 2009 are set to become offshore wind boom years in Europe with a planned total volume of 1507.5 MW of new installations coming online. Of this total, the UK is likely to account for no less than 800 MW, while leading supplier Siemens Wind Power plans to complete four new wind farms with a combined capacity of 578 MW. The period 2008 and 2009 will also mark the commercial offshore entry of three different 5 MW turbine designs in a French 105 MW project, a 60 MW development and part of a 400 MW project in Germany, plus 30 MW in Belgium.This is a genuine milestone as currently only two 5 MW REPower turbines operate offshore in the challenging Beatrice project, with a record 44metre water depth. By the end of 2010 a cumulative European offshore capacity of 3-4 GW is expected to be operational, according to the EWEA report.
Another major trend is seeing offshore projects getting bigger. The 166 MW Nysted project off Denmark is still the world’s largest offshore wind farm on a megawatt basis, but the 180 MW Robin Rigg project in the UK is in progress, and Denmark’s 200 MW Horns Rev extension is planned for 2009. And late in 2007 Siemens Wind Power signed a Reservation Agreement aimed at the delivery of 140 x 3.6 MW turbines for the UK’s 504 MW Greater Gabbard wind farm due in 2009-2010. Permits have now also been granted in the UK for a project almost twice that size – the 1000 MW London Array planned outside the Thames estuary.
In view of the number of large projects currently on the starting blocks, one concern – in the short-term at least – is the turbine supply situation. Until recently only two major players – Vestas of Denmark and Siemens Wind Power of Germany – have supplied the bulk of the offshore market, with Vestas holding a cumulative operational offshore market share of about 60%. However, the fact that the world market leader withdrew its 3 MW V90-3 MW flagship from the offshore market during 2007 potentially leaves a supply gap for the immediate future. At this stage it is uncertain when and with what product(s) Vestas will make its planned offshore market re-entry.Aside from the V90-3 MW offshore market withdrawal issue, the fate of the 4.5 MW V120-4.5 MW – an up-scaled former NEG Micon 4.2 MW offshore turbine – remains unclear. The latter product raised high expectations in the offshore wind market and was originally due to be launched commercially in 2009.
As a result of these developments Siemens, and to a lesser extent GE Energy, for the moment remains the sole volume supplier that can deliver substantial offshore turbine quantities while also boasting a considerable offshore track record.
During 2008 both REpower and Multibrid should relieve some of the supply pressure as they launch series production of their 5 MW offshore turbines. The two companies have now established new production facilities at the port of Bremerhaven, in northern Germany. According to industry sources, each of them is projecting the manufacture of up to 100 turbines a year by the end of the decade. While such numbers may seem modest at a first glance, establishing a robust supply chain for custom-developed components such as complex rotor hubs, or main chassis with masses up to 70 tonnes is by no means easy.The very size of the huge bearings, generators, gear systems and so on required is a challenge.
Like the 1.5 MW class, commercially introduced in the late 1990s, the initial stages of the 5-6 MW product cycle will again be characterized by a handful of qualified suppliers. These dedicated and risk-sharing suppliers often directly participate in the wind turbine development process and as a prime requirement should be capable of delivering on time, with the right qualities and in the required quantities.
Late in 2007, Bremen-based newcomer Bard Engineering installed the first of two 5 MW VM prototypes in the port of Emden following a two-year product development and prototype construction period. A third prototype is planned during the second half of 2008 at a location in the river Jade, close to the port of Wilhelmshaven.This turbine will be put on the company’s patented Tripile offshore foundation structure, as a final trial run before heading offshore.Wind turbine series production for Bard’s first 400 MW Bard Offshore 1 North Sea wind farm will begin in 2008, with a planned 20 turbines. Production volume is planned to double in 2009, again designated to the project, and will increase further to 50-60 units in 2010.Twenty units of that latter batch will complete BARD Offshore 1. The remaining installations manufactured that year will either flow into one of the developer’s next offshore projects or enter the global marketplace.
Some wind industry insiders believe that some of the first- generation 4.5-5 MW concepts possess substantial built-in design reserves that could enable system up-scaling as manufacturers gain experience. REpower announced a 20% capacity increase from 5 MW to 6 MW in 2007, but says it will initially maintain the 126 metre rotor size. And last year Bard founder Argnolt Becker in the company’s magazine Bard Magazin said:’In the foreseeable future we will reach 6 MW installed capacity. My aim is ‘7 + x MW,’ which gives us still a lot of work to do.’
As a rule of thumb, fitting a larger generator makes economic sense if the available wind can provide a substantial number of full-load hours at the upgraded output level.Average wind speed at hub height is the determining factor here, as wind power is a function of its speed cubed.
Adding a bigger rotor nearly always pays off in terms of increased total energy yield, but it also raises dynamic rotor loads that are, in turn, transferred into the drive train and the entire structure. Furthermore, a bigger rotor requires the maximum rotor speed to be reduced because of noise and other reasons, increasing drive-train torque and thus requiring larger and more costly components.
Siemens installed the first 25 of its 3.6 MW flagship machines at the Burbo Bank wind farm in the UK in 2007. By the end of the year Siemens had installed 434 MW of offshore wind since 1991, originally as Bonus. The power-engineering giant is now planning to install 54 of its 3.6 MW units in 2008, and a further 55 in 2009. Siemens is also expected to introduce a substantially bigger offshore unit during the next few years, which may be an up-scaling of the SWT-3.6-107 flagship model.
US-based companies Clipper Windpower and General Electric are also both working on an offshore wind turbine in the 5-7 MW class. Finally, Gamesa of Spain has announced a 4.5 MW G-128 offshore turbine that will feature, at 128 metres, the world’s largest rotor diameter.The current status of these three ambitious projects is unknown.
Late in December 2007 offshore wind industry newcomer DarWinD of the Netherlands announced the completion of the design phase of its 4.7 MW direct drive DD115 turbine (rotor diameter 115 metres).The company is now part of the fast-growing Dutch sustainable technology concern Econcern, based in Utrecht, which currently employs a staff of about 900 in 19 countries.With its direct drive permanent magnet (PM) type generator, the DD115 differs completely from the three above-mentioned German 5 MW turbines in terms of its drive train. The REpower 5M and the Bard VM are ‘conventional’ geared concepts, while the Multibrid M5000 features a highly compact integrated drive train with a single- speed gearbox and slow speed generator. The DarWinD turbine – like the M5000 and VM – features a single rotor bearing, and it also has three rotor blades. The new concept builds on experiences gained with the former 2 MW Zephyros, a project that was conducted under leadership of former Lagerwey.
Initially the design team opted for a two-blade rotor as this offers several advantages, including during offshore installation. For instance, complete nacelles plus the assembled rotor can be transported on the deck of a barge/vessel and hoisted onto the foundation structure in one piece. However, this two-blade concept was later abandoned for system dynamics reasons, explains DarWind’s managing director Vincent van den Brekel.A key feature of the DD115 is a barrel- shaped generator with an outer stator diameter of only 5.25m. This stator outer surface is exposed directly to the passing ambient air. He further says that the air-cooled generator, a design from electric power engineering specialist Converteam SAS, headquartered in France, exchanges about 80% of its heat to the passing airflow: ‘The remaining 20% of cumulative cooling demand is provided by air drawn from inside the tubular steel tower, which is fed through the generator coils. These coils are sealed off completely from the saline outside air.’ A visual clue to the secondary cooling system are the two exposed air circulation pipes fitted on top of the nacelle that can be seen in the righthand image on page 38.
DarWinD plans to erect the first two prototypes on land by Q1 of 2009, one being destined for ECN’s multi-megawatt class wind turbine test field. Van den Brekel comments: ‘Series manufacture will commence in 2011 with a planned 60 turbines, which includes two 0-series units. From that initial level we plan to increase production step-wise to 120 turbines in 2012, 220 in 2013, 300 in 2014, and up to an output of 350 installations by 2015.’ He adds that he is fully aware of risks involved in jump-starting from two prototypes straight into series production of sixty turbines and the teething problems that might surface in multiple turbines operating offshore.Van den Brekel says:’A careful evaluation of risks and opportunities forms the basis of our decision to move fast. If DarWinD as an alternative waits until 2013 with a commercial offshore wind market entry, we face the risk of having lost the necessary momentum definitively to international competitors.’ One asset DarWinD can draw upon is that sister company Econcern and project developer Evelop already have a portfolio of several offshore projects collectively totalling thousands of megawatts.
Another issue Van den Brekel elaborates on is where DarWinD will establish its wind turbine manufacturing facilities. This new infrastructure is to be supplemented at a later stage by an in-house rotor blade production plant.’We do plan a production facility somewhere along Europe’s North Sea shores, together with the building of a local logistics chain that comprises key component suppliers for the turbine. This decision on where to build DarWinD’s production capacity is expected for Q1 of 2008,’ he continues.’The newly established group of industrial companies together will provide great opportunities in terms of employment creation and innovation within the entire supply chain. For instance, Converteam has already agreed to build a generator manufacturing plant next door to our wind turbine assembly facility. Being a company of Dutch origin is not an automatic guarantee that our production facilities will also be established in the Netherlands. This especially because, compared with ambitious European countries like the UK and Germany, the Dutch government clearly lags behind in ambition together with its lack of long- term support for offshore wind power.’ In other words, a country that proves to take offshore wind development seriously is likely to benefit both directly and indirectly from DarWinD’s long-term industrial development plans.’
Speculation continues meanwhile on Enercon’s medium to long-term plans regarding the offshore wind market. The German market and technology leader and direct drive pioneer recently erected a first 6 MW E-126 prototype at the port of Emden.This second-generation E-126 features among others an enlarged 127 metre rotor with the new blade design and a fully closed nacelle. The giant replaces the 4.5-6 MW E-112 of which nine units in total are operational. One of these 6 MW units operates near Emden at a ‘wet feet’ location in the water just behind a dyke. During 2005 an attempt to install an E-112 with a rotor diameter of 114 metres with a tubular steel tower on top of a so-called suction bucket foundation in shallow water off the coast of Hooksiel,Wilhelmshaven, failed. Bucket- foundation technology itself is not new but the sheer size of the E-112 foundation represented a genuine wind industry record. The foundation principle is based upon a cylindrical steel structure with an open bottom that is ‘pushed’ into the soft seabed when the air inside is removed with the aid of suction pumps.The friction between subsoil and bucket wall ensures long-term stability after installation. The decision to cancel sinking operations was taken after mechanical deformations in the cylindrical part were detected. During a presentation in Berlin, Soren Nielsen of MBD Offshore Power (DK) Denmark, said that the failure cause was likely an impact by the Giant 4 installation barge colliding with the bucket.The impact left a dent of about 80 mm in the skirt, causing structural instability that developed into the foundation failure later. Enercon plans to install a total of eight E-126 turbines by the end of 2008, one of which is planned at the DEWI-OCC offshore test field in Cuxhaven.
… AND OTHER FOUNDATIONS
In general the so-far limited cumulative offshore wind track makes offshore foundations an issue that still raises much debate among specialists.
The majority of today’s offshore wind turbines are mounted on a monopole-type foundation, comprising the actual pile with, sliding over its top, a transition piece or TP. By contrast a minority of wind farms built in shallow water feature gravity-based concrete foundations. A third option is a jacket-type foundation, like the concept applied at the Beatrice wind farm.A fourth foundation alternative developed among others by Multibrid for its 5 MW turbine is a welded steel tripod. A fifth alternative is Bard Engineering’s ‘Tripile’ that comprises three relatively small vertical piles and an interlinking transition piece on top. TP functions here are to provide necessary rigidity to the assembly, while a central flange enables the top head mounting for the wind turbine. Belgian project developer C-Power has chosen a 40 metre high gravity- based concrete foundation for its 300 MW Thornton Bank project, which will finally comprise sixty 5 MW REpower turbines. The project comprises three building phases until completion in 2012. Phase I encompasses six turbines, Phase II is for 18, and the final phase is for 36 of the giant 5M units.The foundation base width is no less than 21 metres while the total foundation mass is about 21,000 tonnes. The proposed wind farm is situated about 28 km off the Belgian coastline by Zeebrugge, and will be built in water depths ranging from 12 to 27.5 metres.
These foundation examples show that today’s offshore wind projects are not only characterized by various degrees of complexity, but also by widely differing individual developer perceptions on optimal foundation technology solutions.
FOUNDATION MASS VERSUS COSTS
The Dutch TU Delft DUWIND institute presented a poster in Berlin showing a comparison of three offshore foundation alternatives for 30-50 metre water depths.The research was on foundation mass in relation to total costs and focused towards future projects in the Dutch section of the North Sea. Other participating Dutch project partners besides TU Delft were offshore contractor Heerema, and the Energy Research Centre (ECN). A 5.5 MW GE offshore wind turbine was used as a reference installation as part of the research project. However, GE itself has not yet made public such information on the proposed new product. The research project compared a monopile foundation with a steel tripod foundation and a steel jacket-type foundation as shown in Table 1, right.
A key conclusion is that despite high steel prices, monopole-type foundations should not be written off as a potential solution for deep-water North Sea locations.A second major conclusion is that fabrication costs for manufacturing the multiple steel main joints of the tripod and jacket emerge as a key cost driver.
However, in addition, the researchers claim that the labour- intensive fabrication process for such foundations itself requires substantial investments in shipyard or other heavy industrial capacity.
BANKING ON EXPERIENCE
Besides the challenges of wind turbines and foundations, several presentations in Berlin dealt with novel installation methods and the urgent need to speed up the efficiency of the installation work offshore. Vestas offshore manager Albert Winnemueller said two installation days per turbine is now state-of-the-art, and bringing this requirement down to one and a half days will ultimately prove to be a large improvement. He also predicted an installation vessel or barge shortage for the next five years. This under-capacity might occur as soon in 2009. In addition,Winnemueller pointed at cable installation as a critical path activity during offshore wind farm construction, and said that finding experienced contractors with a sufficiently robust financial and technical track record is currently difficult.
Another issue raised in Berlin is the need for know-how in banking and the insufficient attention this has been given in the industry.The concensus is that experiences gained in one project should serve as a structural learning tool and be made available for the benefit of following projects. However, multiple wind industry experts claim this is often not the case in practice, and that new projects sometimes seem to start from scratch. Under-utilizing potential learning curve benefits in turn may raise overall project investment costs. This can result in wasted time and resources, avoidable failures during installation and higher lifetime operational costs.
The fact is that the offshore wind industry, in facing an increasing demand for vessels, barges and qualified staff, has to compete with the booming global oil and gas industry. The latter sector makes use of the same marine equipment suppliers, and has by definition much larger budgets available for comparable jobs. But while there are unmistakable signs of pending equipment shortages, several initiatives have been announced to counteract this potential bottleneck situation. For instance, Jack-up Barge BV; Worldwide Marine Services of the Netherlands recently ordered ia total of nine jack-up barges in three different sizes and capacities.These barges are a design from the Dutch marine equipment specialist GustoMSC. During 2008 the first series of four barges, each with a 300tonne crane, will be delivered to the company.’One of these has already been rented to A2SEA of Denmark for the UK’s Robin Rigg project, where it will be employed to install the top heads. Two other jack-ups on order are bigger in size and feature a 500-tonne crane, while the remaining four barges are smaller than the 300-tonne crane barge version,’ explains sales manager Jacques van Mill. Jack-up Barge rents these, including crew, and other barges in its fleet to third parties.The smallest versions are also well suited for turbine upkeep, he concludes.
Finally, taking all current and future challenges facing the offshore wind industry into account, the steps required to deliver during the next thirteen years are formidable. The industry will need to do its part by speeding up production and by increasing overall reliability of the installations, including optimizing efficiency in the entire project cycle.
An equally – or more – important task lies in the hands of national European governments. They are not only future partners in offshore wind, but also the key facilitators.
Eize de Vries is Wind Technology Correspondent for Renewable Energy World e-mail: email@example.com
Maud Olofsson, Swedish Minister for Enterprise and Energy and Communications, talked about her government’s recent proposal for a new ‘ambitious level of 2500-3000 MW of offshore wind by 2016. The current total is 135 MW. Connie Hedegaard, newly appointed Danish Minister for Climate and Energy, said that her government will double the amount of renewable energy in Denmark. The aim is to achieve at least a 30% share of renewable energy sources in total energy consumption by 2025. Offshore wind power is likely to be a major contributor. Michael Mueller, Parliamentary State Secretary, German Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany, said that ‘no other topic will have its mark on the 21st century as energy will do.’ He talked of the changes Germany has recently implemented to support offshore wind power, such as increasing the feed-in tariff, and said that infrastructure will be built to enable easier grid access. Germany’s latest offshore goal is the addition of ‘25,000 MW of offshore wind power by 2030, which will cover 15% of Germany’s energy demand.’ Malcolm Wicks, UK Energy Minister, said ‘energy security is becoming a key component of national security when you look at current geopolitical risks.’ He named climate change and energy security as two key challenges. Minister Wicks also stated: ‘25,000 MW of offshore wind capacity has been consented in the last 12 months in the UK,’ and added that his country was set to ‘overtake Denmark in terms of offshore installed capacity in 2008.’