In the X-Energy sub-project X-Zweiblatt Floating, floating two-bladed 20 MW wind turbines were examined in order to further expand the potential of offshore wind turbines.
Around 80 percent of the world's usable offshore wind potential lies in waters deeper than 50 metres. However, this makes them unprofitable for wind turbines that are anchored to the seabed. Large floating wind turbines offer the opportunity to install wind turbines in deeper and windier waters and thus further increase the amount of green electricity required. Various pilot projects with floating turbines have already been realised, but so far mostly with standard three-bladed turbines from ground-based systems. The use of just two rotor blades could however offer major advantages for floating turbines in particular:
- A low tower head weight, which reduces the inertial forces in fluctuating systems and, thanks to a lower centre of gravity, reduces the amount of material required to stabilise the floating platform.
- The special option for pendulum hubs, which decouples the tower movement and the rotor surface and results in less stress due to swell.
- Fewer parts (one less blade including blade bearing and actuator) and therefore lower failure rates and less effort in maintenance, manufacture, erection and dismantling of the turbine.
However, two-blade systems are typically characterised by their smoother running, i.e. they run more unevenly than a three-blade system due to the poorer distribution of aerodynamic forces and their rotor geometry.
Results
To quantify these advantages and disadvantages compared to conventional three-bladed turbines, high-resolution servo-aero-hydro-elastic simulations of floating two-bladed and three-bladed turbines were carried out and the results compared in the project X-Zweiblatt Floating. These simulations are so precise that they are used in the industry for the certification of wind turbines. At the same time, a cost estimate for the reduction of the manufacturing, maintenance, installation and dismantling effort for floating two-blade turbines compared to floating three-blade turbines was carried out.
The results of the completed sub-project X-Rotor Zweiblatt were utilised and continued for the sub-project X-Zweiblatt Floating.
