Technology
Up to the challenge
A team at Oxford Brookes University has shown that wind farms could perform more effi ciently by substituting traditional propeller-type designs for compact vertical axis wind turbines (VAWTs). When
arranged in grid formation, these turbines can increase each other’s performance. Elly Earls speaks to two of the researchers behind the study, professor of engineering materials Dr Iakovos Tzanakis and former master’s student Joachim Toftegaard Hansen, to fi nd out how to help speed the green transition.
I
n 2019, Joachim Toftegaard Hansen was in the final year of his mechanical engineering degree at Oxford Brookes University. He was casting around for a suitable dissertation topic, when Ørsted, the world’s leading developer and operator of offshore wind farms, downgraded their anticipated rate of return for several projects in Europe and Taiwan from 7.5–8.5% to 7–8%. As the wind approaches the front row of turbines in a modern wind farm, turbulence is generated downstream, which is detrimental to the performance of the subsequent rows. And while the industry’s standard measurement model allows for this to some extent, Ørsted realised that wake turbulence had a higher negative effect on production than earlier models had suggested. Half a percentage point may not sound like much, but it added up to billions of pounds. Not only did the announcement lead to a fall in the company’s shares, the management stressed this discovery could affect the entire industry. Hansen was intrigued. Was there a way to organise wind farms to
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minimise this effect and increase the amount of energy generated by each row? Or could a different turbine design be the answer? Most wind farms today are made up of horizontal axis wind turbines (HAWTs) – the standard three-blade ‘pinwheel’ design. But what about vertical axis wind turbines (VAWTs), which spin around an axis perpendicular to the ground and, unlike HAWTs, can capture wind from any direction?
VAWT or not The biggest VAWT that has been built to date is the 110m tall, 3.8MW EOLE turbine in Quebec, Canada, which was put out of service in 1993 when its rotor bearing failed under the 880t weight it had to support. Since then, funding has largely been channelled into HAWTs, which have grown to 16MW offshore, positioning them as the clear favourite in the choice for wind power installations. But could the industry be missing a trick? Hansen consulted with his supervisor, Dr Iakovos Tzanakis, a professor in engineering
World Wind Technology /
www.worldwind-technology.com
Oxford Brookes University
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