Environmental Engineering Reference
In-Depth Information
8
8
Wind Power Systems -
Electricity from Thin Air
With all the different renewable energies available today, wind power is considered
a model technology because it has transformed from something of a cottage industry
to a billion dollar business within just a few years. During the mid-1980s wind
power was still viewed as relatively unimportant, yet by 1994 there were already
several thousand installations offering a total output of more than 3500 megawatts.
By 2008, wind wheels turning worldwide were providing an impressive output of
more than 121 000 megawatts. The result was the creation of more than 440 000
new jobs worldwide.
Yet the use of wind power is actually old hat and dates back many centuries. Years
before the birth of Christ simple windmills were being used in the East for irrigation
purposes.
Wind power was not exploited in Europe until much later. In the twelfth century
post mills started to become popular for milling grain in Europe (Figure 8.1). These
had to be rotated towards the wind, either manually or with the help of a donkey.
In addition to milling grain, millers in those days also had the diffi cult job of man-
aging the mill. When a storm approached, millers had to stop the mill in time so
that they could remove the canvas from the vanes to prevent the power of the wind
from destroying the mill. Wooden block brakes were used to stop the mechanism
but these were not without their own dangers. In their hurry to stop the vanes of the
windmill from turning, millers would sometimes apply the brakes too hard and start
a fi re because of the heat that developed on the wooden brake blocks. This is why
so many windmills burned down at the time. Long periods with no wind were
another problem for millers.
In the centuries that followed, mills underwent considerable technical change, as
the Dutch windmill shows. In addition to milling grain, they were now also used to
pump water and carry out other power-driven tasks. Technically sophisticated mills
