Page 294 - Alternative Energy Systems in Building Design

268 WIND ENERGY TECHNOLOGIES

In the United States, the use of water-pumping windmills contributed significantly
to the development of farming and ranching in the vast expanses of the American and
Canadian Midwest and West. In the early days of railroad transport, windmills were
used throughout the world to pump water from wells to supply the water needs of
steam locomotives. The modern wind turbines used today were developed as recently
as the early 1980s.

Wind Power Generation

In essence, wind power generation results from the conversion of wind kinetic energy
into electricity through the use of specially designed wind turbines. As mentioned ear-
lier, wind power also can be used as to pump water or grind grain.
Wind circulation or convection results from an uneven distribution of solar heat.
Owing to earth’s 23.5-degree axial tilt, solar energy is absorbed unevenly at the poles
and equator, which results in a heat differential that causes hot and cold air circulation,
or convection, between the equator and the poles. Moreover, dry lands on the crust of
the earth heat up and cool down more quickly than do the seas. This results in a
differential heat distribution that causes a global atmospheric convection system with-
in the earth’s surface and spanning through its stratosphere.
A significant portion of wind dynamic energy occurs at high altitudes, where wind
speeds exceed 100 mi/h. A large portion of the wind energy is converted into heat
through friction with the earth’s surface and particulates in the atmosphere. It is esti-
mated that the stored power potential of wind energy exceeds 72,000 GW, which could
be harvested for commercial use.
At the end of 2007, worldwide capacity for wind-powered generators was 94.1 GW.
At present, wind produces about 1 percent of the world’s electricity. According to the
World Wind Energy Association’s 2007 report, wind energy represents 19 percent of
electricity production in Denmark, 9 percent in Spain and Portugal, and 6 percent in
Germany and the Republic of Ireland.
Wind energy is one of the most abundant forms of renewable energy and could be
harvested throughout the globe, reduce dependency on fossil fuels, and decrease green-
house gas emissions. Owing to the intermittency of wind, power produced by wind tur-
bines lacks stability and consistency. In order to stabilize and regulate electrical power
production, wind power farms make use of special energy storage devices and supple-
mental power-cogeneration and energy-storage technology in order to harmonize power
production.

Wind Power Management

In order to make wind energy a reliable source of electric power, a number of challenges,
such as power-production intermittency, energy storage, and power-output regulation,