Using the petiole of the miriti palm for the core of a small wind turbine blade

Abstract

In many small wind turbine blades, the interior space between laminate skins is filled by a material core. The mechanical properties of the core are much less important than its density, which must be low to reduce the moment of inertia as high inertia increases both the starting time of the turbine and the gyroscopic loads on the blades. In this paper, we use, for the first time, the petiole of the miriti palm (PMP) as the core of four small blades, in order to analyze its effect on turbine starting performance. PMP is abundant in the Amazon region and harvesting it does not destroy the palm because the petiole regrows; therefore, harvesting is fully sustainable and may well have a major role in increasing the sustainability on wind turbine manufacturing. We consider the benefits of using the easily worked petiole for the core in terms of manufacturing, as demonstrated by the construction of a 0.598 m blade. PMP is less dense on average than alternative materials, such as expanded polystyrene and balsa wood. The starting performance is an important issue for small wind turbines. It is evaluated using a quasi-steady model, in which blade element momentum theory is coupled to Newton's Second Law. The low density of the small blade made using petiole of the miriti reduces the starting time by 10% when compared with expanded polystyrene and 42% when compared to balsa wood.