Vertical turbines more efficient in large scale wind farms – Oxford Brookes University

New research from Oxford Brookes University has found that Vertical Axis Wind Turbines (VAWTs) are far more efficient in large scale (offshore) wind farms than the traditional Horizontal Axis Wind Turbines (HAWTs).

Spinning around an axis vertical to the ground, VAWTs exhibit the opposite behaviour of the traditional horizontal propeller design and increase each other’s performance when arranged in grid formations. When set in pairs, the vertical turbines increase each other’s performance by up to 15 per cent, according to the study.

A research team from the School of Engineering, Computing and Mathematics (ECM) at Oxford Brookes 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 traditional HAWT propeller type for compact VAWTs. 

The study is the first to comprehensively analyse many aspects of wind turbine performance, with regards to array angle, direction of rotation, turbine spacing, and number of rotors. It is also the first research to investigate whether the performance improvements hold true for three VAWT turbines set in a series.

“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”, Professor Iakovos Tzanakis said. “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”. 

According to lead author of the report and Bachelor of Engineering graduate Joachim Toftegaard Hansen, modern wind farms – while one of the most efficient ways to generate green energy – have one major flaw: a downstream generated turbulence. As the wind approaches the front row of turbines, turbulence will be generated downstream, which 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 £2 million/MW. As an engineer, it naturally occurred to me that there must be a more cost-effective way”, said Joachim Toftegaard Hansen.

The research, Numerical modelling and optimization of vertical axis wind turbine pairs: A scale up approach, was published in the International Journal of Renewable Energy (ELSEVIER).