A new breed of massive vertical-axis wind turbines could eventually replace the current crop of deep-sea wind farms being built around the UK. This will address many of the limitations of using horizontal-axis turbines in deep water.
Details of the new design are published in the latest issue (166 EN1) of the ICE Energy journal.
Limitations of horizontal axis wind turbines
When it comes to offshore operations, particularly in deep water, horizontal axis wind turbines have certain limitations. Andrew Shires of Cranfield University gives some examples:
‘…scalability restrictions, the necessity for high-lift installations offshore, high gravitational and aerodynamic moments on the support structure and the need to maintain rotary equipment at heights typically over 60-80 m’.
Benefits of the new design
Conversely, he says vertical access turbines with a V-shaped rotor mounted directly on a floating base offer significant advantages, including ‘scalability, low over-turning moments and better accessibility to drive train components’.
The paper describes the aerodynamic optimisation of a novel 10 MW vertical axis wind turbine, in which the potentially unlimited-size rotor looks like the paired, winged seeds of a sycamore tree and can be mounted just above water level.
Shire says the so-called Aerogenerator design has 'significantly lower over-turning moments' than conventional horizontal and vertical axis turbines, leading to reduced loads on the supporting structure. It also does not suffer from 'cyclic gravitational loading' – which is currently limiting further growth in horizontal turbine blade size.