One immutable fact is that the wind
doesn't blow all the time. That can never be changed. Another
is that 25 to 60 percent of the time the wind is blowing, it is at a
rate less than the maximum efficiency for the turbine. As a
result, windmills operate at only around 33 to 40 percent of maximum
production level, compared to 90 percent for coal and 95% for nuclear
power.
Turbines start producing power with
winds at about 8 mph and operate most efficiently with winds about 30
mph. Though higher wind speeds have more energy, turbines
become less efficient at collecting it. And the machines must be shut
down when a cut-off speed is reached, beyond which high winds
could cause rotor blades to fly off or vibration that can shake the
turbine into pieces. Turbines must not operate in wind speeds
over 56 mph, and typically the cut-off speed is set at 50 mph.
They also have a cut-in speed, usually 7 to 10 mph, below
which the blades will not produce usable power. A
complete wind energy system includes rotor, transmission, generator,
storage and other devices, which all consume energy.
Wind turbines
are—and always will be—unable to achieve high efficiency even
under the most favorable conditions. To attain 100 percent
efficiency would mean all the kinetic energy had been captured and
the blades would stop rotating. The best efficiency achieved is
about 47 percent, which is about as good as it can get because of a
physical law known as the Betz Limit. This has been known for a
hundred years. It was independently discovered by three
scientists in three different countries: Albert Betz (1919) in
Germany, Frederick Lanchester (1915) in Great Britain, and Nicolay
Zhukowsky (1920) in Russia. Their discovery applies to all
Newtonian fluids and identifies the maximum amount of kinetic energy
that can be captured by windmills as 59.3 percent. But the
advocates of wind power are either ignorant of this or
willfully ignore it to make wind power seem feasible for achieving
their goals. Wind turbines may be useful in remote locations
with adequate winds where more efficient energy sources are
unavailable, but they will never achieve widespread displacement of
more economic energy without the waste from government subsidies
and/or artificially high electricity rates for consumers.
As wind terminals proliferate, the most
favorable wind locations are taken, and more and more are located in
less favorable locations, with necessarily lower efficiency and
higher costs. Also, the best wind locations are generally located in
areas remote from the cities where most of the electricity is used.
This necessitates construction of extensive distribution networks
that make wind power even more uneconomic. The uneconomic realities
are hidden in a labyrinth of subsidies, regulations, tax credits,
consumer electricity rates, taxpayer costs, and political
considerations that camouflage the true costs. In a free market—where
government could not create some winners by forcing losses on
others—wind power would be noncompetitive with coal, natural gas
and nuclear power.
No comments:
Post a Comment