James Lawson, Contributor
January 10, 2013 | 6 Comments
Reliability is the key attribute of a turbine today, particularly offshore. There are many other important measures of wind turbine performance, notably the cost per unit of electricity generated, but they count for little if a turbine breaks down. And how do you investigate reliability? Test, test some more – and then test again.
Capable of exerting forces of up to 84 MNm, WTTC offers the full suite of certification tests along with the latest blade prototype development methodologies, R&D partnerships, blade repair capabilities and hands-on workforce training. Fatigue tests employ the National Renewable Energy Lab’s (NREL) patented resonant test system technology. As well as the WTTC, NREL’s smaller-scale National Wind Technology Center still offers blade, drivetrain and many other types of testing, research and development for turbines up to 5 MW. The WTTC also proves that test centres can act as hubs for further investment: TPI Composites has opened a blade R&D centre and prototyping factory 74 km south of Charlestown. TPI will be a WTTC customer, and cited it as key to its decision to set up shop in Massachusetts.
Another new wind turbine blade-testing facility is planned for Clarkson University, based in Potsdam, New York, this time focusing on smaller blades in the 12-15 metre range. The Center for Evaluation of Clean Energy Technology will be built and run in conjunction with other partners by London-based Intertek plc, using a $4.2 million grant from the New York State Energy Research and Development Authority.
Still on the East Coast, Poseidon Atlantic in Northampton, Virginia, will offer sites for turbine prototype testing, infrastructure, wind measurements and wind turbine testing and certification services. The site is planned to hold between five and ten turbines, with a maximum size of around 5 MW. The owners expect to start construction in late 2013, with the first turbines online before the end of that year.
Asia’s only independent test centre is SGS Wind Energy Technology Center (WETC) in Tianjin, China. Opened in June last year, this focuses on full-scale blade testing for blades up to 70 metres long. The centre offers natural frequency, static, fatigue and ultimate static tests as well as a full range of other consultancy and solutions such as blade-specific non-destructive testing and composite technology training.
As befits the current world leader in both installed wind capacity and turbine manufacturing, Europe has the largest spread of test facilities both in operation and under development. Germany’s Fraunhofer Institute opened its new Competence Centre Rotor Blades testing facility in Bremerhaven last year. As well as several beam test rigs and material climate chambers, the centre’s two test rigs can handle blades up to 70 metres and 90 metres respectively. The 90 metre rig – a giant 1000 tonne block of steel – can load blades along their length to a maximum of 1800 kN and bend them by up to 30 metres. Uniquely, it allows the blade to be tilted too. To cope with demand, another test rig for 50 metre blades will go into operation this year.
The latest development here is the DyNaLab (Dynamic Nacelle Laboratory). When active in 2014, it will have a drive output of 10 MW and will be used to test complete nacelles ranging from 2 MW to 7.5 MW. A 40MVA artificial grid will allow complete electrical certification of test turbines, and the institute is currently working to scope the test stand’s final specification. There are also plans for a new lab for foundations and support structures at Fraunhofer’s Hannover location. ‘This facility gives us the possibility to test the dynamic behaviour of the complete structure with near-realistic simulation of soil/seabed-support structure interactions,’ says Dr Jan Wenske. A medium voltage lab, a pitch-system test bench and a mainshaft lifetime test bench are also under development, he adds.
Fraunhofer is looking to build further turbine test sites, he says. Germany already has the DEWI test site near Wilhelmshaven, currently holding ten prototypes totalling over 19 MW, while a new site in Janneby, Schleswig-Holstein, will open at the end of this year. Developed by GL Garrad Hassan and two partners, Janneby will have eight test locations suitable for turbines up to 150 metres in height. Users will be able to access services that include wind, acoustic, power performance, load, power quality and LVRT measurements. A LiDAR test site is also planned.
The Netherlands hosts Europe’s largest testing site in Lelystad, where the first turbine started operations in June last year. Operated by Ecofys, Lelystad can service ten turbines with tip heights up to 200 metres. The main Dutch testing facility is Knowledge Centre WMC. Able to test blades up to 60 metres long, it has operated since 2003.
Spain’s CENER was the world’s largest independent turbine testing facility when it opened in 2008. Under one roof, it hosts a full range of static and fatigue tests for blades up to 100 metres, and can test drivetrains of 2-6 MW. To complement lab work, CENER hosts many other electrical testing, design and analysis services, and also runs a test wind farm offering high-speed and high-density (Class 1) winds that can take turbines up to 6 MW. ‘The drivetrain lab offers a six-degrees-of-freedom drivetrain testing bench, a torque-only nacelle test bed and a generator test bench,’ says Pablo Ayesa Pascual, director of CENER’s Wind Energy Department. ‘The first two are capable of applying a torque of 6 MNm and all have been dimensioned for 8 MW of main actuation. We see a 12 MW power test bench in the near future, however we have no formalised plan as yet.’
Over in the UK, an investment in the region of £150 million ($240 million) means the National Renewable Energy Centre (Narec) will soon rank among the top global independent testers. Joining the existing 50 metre test facility, the new 100 metre blade-testing centre will be the world’s largest and should be ready for commissioning by September 2012. The 130 metre-long building will house a single Moog hydraulic blade-testing rig. There will also be 3 MW and 15 MW drivetrain testers; the former is intended primarily for tidal turbines, but could be used for wind too. The 3 MW centre is close to completion while the 15 MW facility is slated for completion by August 2013. The centre already offers a broad spread of services including a dry dock, subsea and electrical testing, and a cold chamber that can drop down to -20C. Narec is also planning an offshore turbine test site at Blyth, Northumberland, for 2014. ‘Our USP will be the ability to test on- and offshore at the same time,’ says Steve Abbott, Narec’s marketing and communications manager. ‘We’re geared to large offshore turbines and marine facilities, and will have the ability to replay extreme events onshore. Our customers – manufacturers and project developers – want to demonstrate turbines in UK sea and seabed conditions, with learnings that translate to other North Sea locations.’
Turbine testing development in Denmark is focused on the Lindoe Offshore Renewables Center (LORC) in Odense. Still at the planning stage, it will include facilities for welding research, foundation testing and other mechanical testing for lubricants, gears, bearings and oil filters. Innovative ‘helicopter testing’ will evaluate how blade coatings cope with mechanical strain, UV exposure and chemical resistance, as well as tip and leading edge erosion.
The other big development in Denmark is Risø DTU’s new turbine testing field at Østerild in northern Jutland. With space for seven turbines up to 20 MW and 250 metres high, Østerild augments the Høvsøre test centre, which can hold five turbines with a maximum height of 165 metres. Turbulence at Østerild gives manufacturers a wider range of test wind conditions, measured more accurately by 250 metre-high met masts. Advanced grid connection technology will allow greater experimentation, such as checking turbine tolerance to varying grid frequency. Østerild’s infrastructure is nearing completion, with two test sites already available and it will host the second prototype of Siemens’ 6 MW offshore turbine later this year.
With this rapid expansion of test facilities, manufacturers and developers have more choice in where to develop prototypes and prove new designs. Though centres often form long-term partnerships with manufacturers, a mixture of knowledge sharing and competition between independent providers can only help to raise test standards, and so improve turbine reliability and performance.
‘Companies need effective testing to prevent silly mistakes that cost money and affect the industry’s reputation,’ says MassCEC’s Rahul Yarala. ‘Of course, there’s only so much business out there and every lab needs revenue. That’s a good thing: it improves test timing, methods and cost effectiveness.’
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