HTYPE WIND TURBINE PERFORMANCE PREDICTIONS BY A LOW COMPUTATIONAL EFFORT ALGORITHM

Resumo

The use of vertical axis wind turbines (VAWTs) has been increasing in recent years. H-type
wind turbines may be a good alternative to horizontal axis wind turbines (HAWTs) at places with low
space availability, as occurs in cities, low wind velocity and disturbed wind streams, as occurs in areas
of mountainous reliefs. Hence, methods of wind turbine performance prediction have become even more
important, in wind energy potential studies. They may reduce the number of experimental trials or field
tests needed. However, the wind stream behavior on a vertical axis wind turbine is usually complex and
hard to predict. A low computational effort algorithm for H-type wind turbine performance prediction
was conceived and tested in a regular home computer. At H-type wind turbine simulation, some inputs
are the airfoil, air density and dynamic viscosity, chord length or solidity, rotor height and radius, free
stream velocity, tip speed ratio range for a constant number of blades (also an input), initial guess and
stop criteria of axial induction factor and maximum number of iterations within the stop criteria. For
non-Joukowski airfoils, the lift and drag coefficients are given in input tables, changing with the angle
of attack and azimuthal angle, from π/180 (1o) to 2π rad (360o) and step value of π/180 rad (1o). Each
table refers to a specific Reynolds number. The tables are previously analyzed, and missing or
non-integer angle values of angles of attack with their coefficients are filled-in by linear interpolation.
For Joukowski airfoils, the circle parameters are inputs. The resultant profile and lift coefficients are
analytically calculated. The variation of power coefficient with tip speed ratio curves are similar to the
literature findings. The predicted power coefficient is 2% higher than the maximum value of
experimental results (same tip speed ratio), in a simulation that lasted 34 seconds to run.