Engineers from the University of Glasgow have used sophisticated computer simulations of bladeless wind turbines (BWTs) to identify for the first time how future generations of the technology could be built for maximum efficiency. The findings could help the renewables industry take BWTs, which are still at an early stage of research and development, from small-scale field experiments to practical forms of power generation for national electricity grids.
BWTs generate power through a process called vortex-induced vibration. They take the form of slim cylindrical structures that sway in the wind, like lampposts in inclement weather. As the wind blows against them, BWTs create vortices – alternating swirls of air that rock the entire structure back and forth. When the frequency of the rocking matches the structure’s natural tendency to vibrate, the motion is amplified significantly, and the increased motion is converted into electricity.
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The team’s simulations of the performance of thousands of variations of BWT design cast valuable new light on the interplay between mast dimension, power output and structural safety in winds between 32 km/h and 112 km/h.
Their key finding is that there is an optimal design for BWTs that creates a ‘sweet spot’ where power generation is maximised against structural strength. The ideal design, which finely balances power generation against sturdiness, is an 80-centimetre mast that is 65 centimetres in diameter. That design could safely deliver a maximum of 460 watts of power, the team found, significantly outpacing the best performance of even the best-performing real-world prototypes built to date, which have delivered a maximum of 100 watts.
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Their model also demonstrated the limits of other designs, which could potentially generate more power. They showed how different designs of BWTs could, in theory, generate up to 600 watts, but at the cost of structural integrity – in real-world conditions, they would quickly fail.
According to the team, their methodology could provide the foundation for scaling up BWTs to utility-grade systems generating one kilowatt and beyond, making them much more practical for use by renewable energy providers.
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‘What this study shows for the first time is that, counterintuitively, the structure with the highest efficiency for extracting energy is not in fact the structure that gives the highest power output, said Wrik Mallik of the James Watt School of Engineering. ‘Instead, we have identified the ideal midpoint between the design variables to maximise the ability of BWTs to generate power while maintaining their structural strength.
‘In the future, BWTs could play an invaluable role in generating wind power in urban environments, where conventional wind turbines are less useful,’ he continued. ‘BWTs are quieter than wind turbines, take up less space, pose less of a threat to wildlife, and have fewer moving parts, so they should require less regular maintenance.’
‘We hope that this research will help spur industry to develop new prototypes of BWT designs by clearly demonstrating the most efficient design,’ said Professor Sondipon Adhikari. ‘Removing some of the guesswork involved in refining prototypes could help bring BWTs closer to becoming a more useful part of the world’s toolbox for achieving net-zero through renewables.
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‘We plan to continue refining our understanding of BWT design and how the technology can be scaled up to provide power across a wide range of applications,’ he continued. ‘We’re also keen to explore how metamaterials – specially designed materials that have been finely tuned to imbue them with properties not found in nature – could boost BWTs’ effectiveness in the years to come.’
The research has been published in Renewable Energy.