Cross axis wind turbine: Pushing the limit of wind turbine technology with complementary design

In unfavourable wind conditions, factors such as low wind speed, high turbulence, and constant wind direction change can reduce the power production of a horizontal axis wind turbine. Certain vertical axis wind turbine design principles perform well under these harsh operating conditions; but, these wind rotors typically have low power coefficients. To overcome the problems above, a novel cross axis wind turbine has been conceptualised to maximise wind energy generation. This is achieved via harnessing the wind energy from both the horizontal and vertical components of the oncoming wind. The cross axis wind turbine comprises three vertical blades and six horizontal blades arranged in a cross axis orientation. Initial testing using deflectors to guide the oncoming airflow upward showed that the cross axis wind turbine produced significant improvements in power output and rotational speed performance compared to a conventional straight-bladed vertical axis wind turbine. In particular, it was found that the cross axis wind turbine integrated with a 45 degrees deflector produced a power coefficient 2.8 times higher than the vertical axis wind turbine. The rotor rotational speed was increased by 70% with well-improved starting behaviour. Initial computational fluid dynamics analysis was done to illustrate the flow field of the deflected air stream by an omni-directional shroud. The simulation showed that the approaching air is deflected upwards by the guide-vane, which would interact with the horizontal blades and produce additional torque. The cross axis wind turbine is applicable in many locations, creating significant opportunities for wind energy devices and therefore reducing dependencies on fossil fuel. (C) 2017 Elsevier Ltd. All rights reserved.