Page 141 - Sustainable Cities and Communities Design Handbook

118 Sustainable Cities and Communities Design Handbook

The conversion of wind to electrical power is generated by a wind turbine.
The modern wind power technology (such as the wind turbine) has been
perfected over the last decade. The wind turbine power plant typically gen-
erates electricity in much the same way (through electromagnetic induction) as
an alternator in a car. As shown in Fig. 6.4A and B, a wind power station is
usually positioned such that its rotor always faces the wind. The power engine
has a drivetrain system that often includes a gearbox. There is a wealth of
information about wind power. Interested readers are referred to the literature
(Wealth of Information, 2009).
Wind power depends on three variables: (1) wind velocity, (2) radius of
generator, and (3) temperature, which determines the air density. The
following is a simplified summary of the aforementioned relationship about
the operational state of the wind turbine.
l First, the power increases with the cube of the velocity (e.g., a twofold
increase of velocity leads to an eightfold increase of power output).
l Second, the power increases with the square of the radius (e.g., a twofold
increase of velocity leads to a fourfold increase of power output).

FIGURE 6.4 (A) Power is generated by a wind turbine. Turbines have increasing capacity rating
from left to right in (A). The dashed line is 50 m in height. (B) The power is related to the
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following factors: sweep area (in the rotor radius squared), the wind velocity (v ), and the tem-
perature variation that affects air density.