Two-bladed, yaw controlled wind turbines – lowering the offshore cost of energy.

Company / Unternehmen: Condor Wind Energy
Speaker / Referent: Martin Jakubowski

Three-bladed turbines currently dominate the market for wind turbines both onshore and offshore. They are easy to build and over the last two decades, their manufacture has grown from a cottage industry into a substantial multinational industrial sector.

Two-bladed turbines have been neglected – yet for the US Department of Energy and NASA in the 1970s to 1990s, two-bladed turbines were seen as the best prospect for economic utility-scale wind turbines, as the laws of physics dictate that two-bladed turbines are lighter than three-bladed turbines and therefore less costly to manufacture. The reasons for this are two-fold – engineering and political. Two-bladed turbines present considerable engineering challenges, including dealing with unbalanced wind loads on the rotor and aerodynamic stability issues. There have been some concerns over aesthetics and noise levels – as two-bladed turbines rotate faster than three-bladed turbines.

Condor Wind Energy has developed a two-bladed turbine for the offshore wind market, where noise level and aesthetics are less of an issue. Two- bladed wind turbines are cheaper to build, install, operate and maintain than three-bladed turbines – and will bring the price of electricity down to the point where subsidies will no longer be needed.

Condor overcomes aerodynamic unbalancing by using an elastomeric teetering hinge, which filters out almost all asymmetric loads coming from the wind. At the same time, the teetering hinge enables gyroscopic forces to be overcome, thereby allowing the power output of the turbine to be controlled by yawing the turbine out of the wind for power control and breaking, rather than by using a blade pitch control mechanism. This provides a unique and elegant engineering solution, combining simplicity with robustness, as well as eliminating a leading cause of turbine failures – the blade pitch mechanism.