New site typologies characterized by non-standard air density have been recently considered for wind energy exploitation. The work attempts to assess the effect of air density on turbine performance, whether with variable or fixed speed. Since the power density of the sites with non-standard density is intrinsically different, it is impossible to reach the standard rated power at the standard rated speed. Three scenarios are possible (i) to keep the standard rated speed of the turbine by changing the size of the electric generator; (ii) to change the rated speed of the turbine by adopting a different pitch angel setting; (iii) adoption of extendeders to the blades can also help in restraining the standard rated power at the standard rated speed for p less than pst. The power curves for the three turbine configurations, each in three different air density conformations, have been calculated running BEM simulations. A tentative correlation between the length of extenders and decrease of air density is finally proposed.
Wind Engineering, 2005, Vol 29, Issue 2, p. 115-129