Chiu P.K., Roth-Johnson P.M., Wirz R.E., “Optimal structural design of biplane wind turbine blades,” Renewable Energy, Vol. 147, 2019, https://doi.org/10.1016/j.renene.2019.08.143

Biplane wind turbine blades have been shown to have improved structural performance, aerodynamic performance, and reduced aerodynamic loads compared to conventional blade designs. Here, the impact of these factors on blade mass is quantified for the first time. The objectives of this work are to quantify the mass of biplane wind turbine blades which have been designed for realistic loads, and to understand the mass-driving constraints for such blades. A numerical optimization approach is used to design the internal structure of biplane wind turbine blades, minimizing blade mass subject to a number of design requirements which are imposed as constraints. The mass reductions are significant, showing that the optimal biplane blades are more than 45% lighter than a similarly-optimized monoplane blade. This is primarily due to the improved resistance to flapwise deflection when compared to the monoplane blades, which allows for considerably less spar cap material to be used in the biplanes. Biplane blades are also shown to have improved resistance to edgewise fatigue damage, requiring less trailing edge reinforcement. Given such large mass reductions, some criticality is required, and the limitations of the present approach are discussed. The results of the optimization present strong evidence that biplane wind turbine blades may be an enabling concept for the next generation of lighter, larger, and more cost-effective wind turbine blades.