The "X-Rotor offshore wind turbine" is a Vertical Axis Wind Turbine (VAWT)/Horizontal Axis Wind Turbine (HAWT) hybrid. The X-rotor concept directly targets cost of energy reduction and addresses scalability of wind turbines through a combination of the following key innovations:

1) Large reductions in the cost of drive-trains through an easily scalable approach to power take-off that does not require a gearbox or a multi-pole generator, whilst still achieving comparable efficiency levels in power conversion.

2) Large reductions in Operation and Maintenance (O&M) costs through no heavy components or machinery being situated at a great height above sea-level, and through general simplification of the turbine.

My PhD aims to address the new challenges in operations and maintenance strategies. There are three work packages that aim to conclude the lowest operational cost for each problem. Firstly, the control implementation of utilising the turbine if one of the secondary (HAWT) rotors is not functioning will allow there to still be energy extraction, but is the increased loading on the turbine worth this? Additionally, the maintenance method for the secondary turbines has several options, such as modular rotors which can be maintained onshore, or alternatively more conventional offshore maintenance. And finally, the rotational speed of the secondary rotors is going to be much greater than conventional turbines, hence my investigation into the maintenance method and composition of the blades.