ABSTRACT
Several mathematical models exist that explain the functioning of rotors. In order to design a small wind turbine, one can employ a complete but simplified theory that has been validated experimentally by several authors. The aerodynamic performance of curved plates at low Re and infinite wingspan is slightly better than that of an airfoil specially designed for fast wind turbines, like the NREL series, at the same ideal conditions. A rotor with a high number of very thin blades has potentially a high aerodynamic performance at low Re, but it presents several drawbacks. The drawbacks are: heavy construction and consequently higher material cost; higher mechanical loads in strong winds—and consequently more cost for reinforced structures; the shape of the blades is optimized for λ = 1, but the best theoretical coefficient of power (CP) can be attained in the interval 3 < λ < 4.
