creating wind turbines
Lloyd WindEnergie (to which GL Garrad Hassan is also a part), and it has been approved for the evaluation of turbines in Europe – often a requirement before building and deploying a wind turbine.
Current research topics With his overview of the industry, Jonkman easily lists a number of current research topics in wind energy. One deals with wind farm array effects – in other words, how wind turbines interact with each other due to wakes and turbulence. Next, while the size of turbines on land won’t increase much more with an upper bound of roughly three MW today, offshore turbines can reach five, 10 or even 20 MW. However, we need a better understanding of wind variations over large turbines, and structural models will have to include nonlinear responses. Jonkman adds that there are developments
in offshore structures. Today, they are typically monopoles anchored in the sea bed. But, as water depths increase, they need multiple legs with jackets or tripods, and in deeper water floating turbines will become cost effective. But each support structure needs a different modelling approach. Yet another area of study is the gear
box, which at the moment is the top of the list of failure mechanisms for wind turbines. Considerable research is going on to determine why they tend to fail. In this regard, Romax Technology (Nottingham, UK) specialises in the development of wind- turbine drive train systems. It uses its own specialist software, RomaxWind, coupled with Dassault Systems’ CATIA V5 and ENOVIA SmarTeam PLM capability. David Reetham, senior project engineer,
explains some of the complexity of ensuring maximum efficiency: ‘Equal load sharing between planetary or epicyclic gears is crucial to ensure reliability and low vibration. By taking into account the effects of structural deflections, mounting conditions, gravity, assembly and manufacturing tolerances, we use software simulations to predict load sharing through each planet gear. Add this to gear-contact patterns, durability calculations, phasing calculations and noise minimisation, and the complexities increase. ‘Once we’ve optimised the drive train
specification and features, CATIA is deployed to develop and refine the concept and bring it to a manufacturable state. CATIA is also used to evolve the initial design so that production will be as closely related to the 3D digital model as possible.’ At the gearbox design stage, there is a requirement to analyse the interactions of
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Massachusetts. They would be essentially invisible from shore, while also being located in areas that provide greater wind power potential. Large sea areas, with stronger and steadier winds, are available for wind farm development. All of Europe’s offshore turbines are
Analysis of a wind-turbine gearbox done at Romax Technology using CATIA
many components, and this analysis requires many meshes to be done for different purposes. Thus, according to Paul J. Gibbs, team leader for analysis and verification, Romax uses Altair’s HyperWorks to create meshes to calculate the strength of gearbox housings and internal components. ‘Weight
currently mounted on fixed-bottom, foundation-based towers in coastal shallow waters, not more than 130 feet deep. However, the world’s first deep-water floating turbine, capable of generating 2.3 MW, is currently being tested off the coast of Norway. Olinger’s research is assessing the
potential for developing offshore wind farms consisting of up to 100 floating turbines, each rated at five MW (more than 60 per cent larger than typical land-based turbines). While the potential is immense, the obstacles
THE RENEWABLE ENERGY INDUSTRY IS FRAUGHT WITH ENGINEERING CHALLENGES DUE TO A WIDE RANGE OF VARIABLES THAT GO WELL BEYOND COMPONENT DESIGN
is an important design consideration, and Hyperworks optimisation tools allow us to get the maximum performance out of components that are also heavily space- constrained,’ he comments.
Getting into deep water Concerning offshore wind turbines, there are often considerable objections to their erection and operation with regard to environmental and aesthetic concerns. Floating wind turbines, located far from land, would solve problems associated with placing turbines near attractive natural beaches and coastal environments, explains David Olinger, a principal investigator at Worcester Polytechnic Institute in
associated with placing turbines weighing up to 15 million pounds on towers as tall as 300 feet, in deep ocean waters, are significant. ‘How should they be transported to installation sites? What combination of platform and buoy designs, together with mooring solutions, will best stand up to major storms and large wave heights? How will environmental conditions vary from one ocean site to another?’ he asks. To address such questions, Olinger
and his team are combining computer simulations with experimental modelling. ‘While computational modelling does a good job of handling forces associated with moderate waves and wind, nonlinear responses that will arise in storm conditions require physical modelling,’ he notes. These platforms are tethered by flexible moving cables, which have a small diameter compared to the platforms. This results in multiscale models using custom codes which he and his team are developing. His first models are focusing on wave
WindModeller streamlines just above the ground for a site in Snowdonia, north Wales
loading; already, the team has examined towing and transportation conditions. The impact of severe wave conditions on the scale models will be tested next. In a later stage, wind loading will be coupled in, and here he might draw on some commercial packages. When the entire project is complete, Olinger aims to have a computer simulation program capable of testing a wide range of design types and potential environmental conditions.
FEBRUARY/MARCH 2011 33
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