Research highlights 'major flaw' in conventional wind farms – and a promising solution

The now-familiar sight of conventional propeller-style wind turbines could – and perhaps should – be replaced by farms of more compact and efficient vertical axis turbines in future, a team of researchers has said.

The engineers at Oxford Brookes University carried out research that found the vertical turbine design is “far more efficient” than traditional turbines in large scale wind farms, and when set in pairs the vertical turbines increase each other's performance by up to 15%.

The team from the School of Engineering, Computing and Mathematics (ECM), led by Professor Iakovos Tzanakis, conducted an in-depth study using more than 11,500 hours of computer simulation to show that wind farms can perform more efficiently by substituting the propeller-type Horizontal Axis Wind Turbines (HAWTs), for Vertical Axis Wind Turbines (VAWTs).

“The research demonstrates for the first time, at a realistic scale, the potential of large scale VAWTs to outcompete current HAWT wind farm turbines,” a research announcement said.

VAWTs spin around an axis vertical to the ground. The research found they exhibit an opposite behaviour to HAWTs – when arranged in grid formations, they increase each other’s performance. Positioning wind turbines to maximise output is critical to wind farm design.

Professor Tzanakis said: “This study evidences that the future of wind farms should be vertical. Vertical axis wind farm turbines can be designed to be much closer together, increasing their efficiency and ultimately lowering the prices of electricity. In the long run, VAWTs can help accelerate the green transition of our energy systems, so that more clean and sustainable energy comes from renewable sources.”

With the UK's wind energy capacity expected to almost double by 2030, the findings could be a stepping stone towards more efficient wind farms, understanding large-scale wind energy harvesting techniques, and ultimately improving renewable energy technology to replace fossil fuels more quickly.

According to the Global Wind Report 2021, the world needs to install wind power three-times faster over the next decade to meet ‘net zero’ targets and avoid the worst impacts of climate change.

Lead author of the Brookes report Joachim Toftegaard Hansen said: “Modern wind farms are one of the most efficient ways to generate green energy.

“However, they have one major flaw – as the wind approaches the front row of turbines, turbulence will be generated downstream. The turbulence is detrimental to the performance of the subsequent rows.

“In other words, the front row will convert about half the kinetic energy of the wind into electricity, whereas for the back row, that number is down to 25-30%. Each turbine costs more than £2m/MW. As an engineer, it naturally occurred to me that there must be a more cost-effective way.”

Co-author and senior lecturer Dr Mahak said: “The importance of using computational methods in understanding flow physics can't be underestimated. These types of design and enhancement studies are a fraction of the cost compared to the huge experimental test facilities. This is particularly important at the initial design phase and is extremely useful for the industries trying to achieve maximum design efficiency and power output.”

The research was published in International Journal of Renewable Energy.

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