Wind power is the second largest renewable non-green house gas producing energy source.
Surpassed only by hydro-electricity.
Denmark produces over twenty percent of its electricity from wind turbines.
In California, the wind installation at Altamont Pass near San Francisco has more than 5000
wind turbines.
And those at Tehachapi and Palm Springs have over 3000 each.
These California sites have a large range of turbines, from small units that generate
as little as 100 kilowatts, to some with 90 meter blades that generate 1.5 megawatts.
Many countries are rapidly adding capacity.
And within a few decades, wind power should provide at least four percent of global electricity.
As much as 72,000 giga-watts of wind power might be commercially feasible worldwide,
many times the current totaled energy demand.
Winds derive from temperature differences between the tropics and the poles, Between
land and sea and between Earth's surface and upper atmosphere.
Electric power generated from wind is proportional to its speed to the third power.
Winds near ground level encounter many impediments and the velocities approach zero, velocities
increase markedly with height above ground but decrease with surface roughness.
Because of power that can be extracted from wind increases with wind velocity to the third
power, a hub height of large turbines are usually placed 40 to 80 meters above ground.
Evaluations of potential sites for wind turbines are based on average wind speeds at 50 meters
above ground.
Most of these sites are located just off shore, where land sea temperature differentials drives
winds, and where open water presents few impediments.
Modern wind turbines benefit from a, improvement in materials such as carbon composites and
aluminum alloys that reduce weight and increase durability B more sophisticated designs in
which the angles of blades change with wind velocity.
C, gearboxes that translate slow turbine speeds into fast spinning generator shafts.
And d, dynamic loading and breaking that keeps the turbines from spinning too fast in high
winds.
Noise from a wind turbine increases with the fifth power of the speed of the blade tips,
And so gearing and breaking keeps the turbines from becoming a greater nuisance.
The intermittent nature of wind makes it an unpredictable energy source.
Worse yet, demand for electricity may not coincide with periods of high winds.
For instance, Texas is a state in the United States that generates the most wind power.
The hottest days in Texas, which have the peak demands for electricity to power air
conditioning, tend to be those with the least wind.
As such the success of wind power depends on integration into a large energy grid with
high capacities for energy storage, such as hydroelectric power.
Danish wind farms, for example, export almost half of their electricity to neighboring countries
such as Sweden and Norway that have large hydroelectric power storage.
On the positive side, the cost of wind power has diminished to where it is competitive
with other energy sources.
Wind power, like hydroelectric, has negligible fuel cost and relatively low maintenance cost.
Most of the cost are for construction and transmission.
Ecological concerns about wind turbines center largely on injuries to animals that's lying
to turbine blades.
Collisions with existing wind turbines kill 20,000 to 37,000 birds a year.
By comparison, annual bird fatalities from collisions with buildings are between 97 and
976 million with high tension lines between 130 and a thousand million.
With communication towers between four and 50 million, and with vehicles somewhere around
80 million.
Therefore, wind turbines are responsible for a minute fraction, less than.003 percent of
bird deaths from collisions with human structures.
Wind farms also face opposition if their turbines obstruct scenic views.
To improve their aesthetics new installations have more widely spaced turbines, which look
less cluttered then old installations.
And offshore installations are located further out to sea.
For example a 420 megawatt wind farm proposed for Nantucket Sound would place 130 turbines
each 75 meters tall eight to fifteen kilometers from the beaches of Cape Cod, Nantucket, and
Martha's Vineyard.
None the less the turbines would still appear prominent on the horizon this project has
been embroiled in controversy since 2001.
In summary, number one, fears of major accidents have stalled the use of nuclear power Number
two, most of the best locations for hydroelectric power are already in use.
Number three, wind power's expanding despite difficulties in site selection.