Reliable, low-cost offshore wind turbines

Moving into greater water depths with larger turbines represents the next big step for offshore wind power generation. Its installed capacity was 5 gigawatt at the end of 2012, and this could be 8 times higher by 2020, meeting 4 % of European electricity demand. However, more challenging environmental conditions call for an alternative to conventional designs to ensure reliability and cost effectiveness.

In the EU-funded project 'Innovative wind conversion systems (10-20MW) for offshore applications' (INNWIND.EU), partners are investigating and demonstrating new designs for 10-20 MW and their components. Furthermore, they are developing new methodologies for assessing innovative subsystem and turbine system designs.

To achieve progress beyond the state of the art, INNWIND.EU places focus on adaptive lightweight rotors that combine active and passive flow control and new structural concepts. Another field of focus is a standard mass-produced integrated tower and a substructure simplifying and unifying turbine structural dynamic characteristics at different water depths. INNWIND.EU is also turning away from conventional direct-drive generators, hinging on new designs that reduce weight.

So far, project members have defined a 10 MW reference wind turbine that forms the basis for assessing all innovations related to the turbine and its components. Proper key performance indicators should guide their development by striving to decrease the cost of energy.

The team has evaluated new aerodynamic rotor concepts for offshore operation. These include blades with a high tip speed ratio and two- and three-bladed rotors with low solidity along with low induction design variants.

Suitable designs of superconducting direct-drive and magnetic pseudo direct-drive generators have been proposed for integration into 10 MW wind turbine architecture. These lightweight direct-drive generators will be validated through prototypes. The team is also currently evaluating a four-legged steel jacket support structure and floating structure designs.

INNWIND.EU should deliver significant insight into the development of large-scale offshore wind farms in deep waters. Project findings will pave the way for significantly higher installed capacities and greater electricity penetration than those anticipated with current technology.