Vertical turbines far more efficient in large-scale wind farms

The research suggests that the now-familiar sight of traditional propeller wind turbines may be eventually replaced by the sight of wind farms containing more compact and efficient vertical turbines.

Vertical Axis Wind Turbines (VAWTs) spin around an axis vertical to the ground, spinning like a giant weathervane and exhibiting the opposite behaviour of horizontal turbines. Although vertical turbines have been experimented with and improved in recent years, they are not yet used on an industrial scale as horizontal turbines are.

A team of researchers from Oxford Brookes school of engineering, computing, and mathematics conducted a study into VAWTs using more than 11,500 hours of computer simulations to demonstrate that wind farms can perform more efficiently using vertical turbines. The research found that VAWTs increase each other’s performance when arranged in grid formations; positioning turbines to maximise output is critical to the design of wind farms.

The Renewable Energy study – the first to analyse so many aspects of wind turbine performance – found that, when set in pairs, vertical turbines boost each other’s performance by up to 15 per cent.

“This study evidences that the future of wind farms should be vertical,” said Professor Iakovos Tzanakis. “[VAWTs] 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.”

The UK is particularly well positioned to exploit wind energy for electricity generation, and its wind energy capacity is expected to nearly double by 2030. The government aims to deliver a third of total energy supply from wind by the end of the decade. The findings are a step towards designing more efficient wind farms and ultimately replacing fossil fuels as energy sources.

Joachim Toftegaard, a graduate and lead author of the report, commented: “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 per cent. Each turbine costs more than £2m/MW. As an engineer, it naturally occurred to me that there must be a more cost-effective way.”

Dr M Mahak, a lecturer and co-author of the study, added: “The importance of using computational methods in understanding flow physics can't be overestimated. 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.”