Fluid Mechanics and Thermodynamics of Turbomachinery, 5e

328 Fluid Mechanics, Thermodynamics of Turbomachinery
FIG. 10.4. (a) First General Electric baseline HAWT, 3.6MW, 104m
diameter, operating at Barrax, Spain, since 2002. (Courtesy U.S. Department
of Energy.)
range of operation. Commercial turbines range in capacity from a few hundred kilowatts
to more than 3MW. The crucial parameter is the diameter of the rotor blades, the
longer the blades, the greater is the “swept” area and the greater the possible power
output. Rotor diameters now range to over 100m. The trend is towards larger machines
as they can produce electricity at a lower price. Most wind turbines of European origin
are made to operate upwind of the tower, i.e. they face into the wind with the nacelle
and tower downstream. However, there are also wind turbines of downwind design,
where the wind passes the tower before reaching the rotor blades. Advantages of the
upwind design are that there is little or no tower “shadow” effect and lower noise level
than the downwind design.