Re: Why Not....
- From: "Ouroboros_Rex" <its@xxxxxxxxxx>
- Date: Wed, 6 Aug 2008 12:50:08 -0500
Amused wrote:
My S-I-L asked, "Why wouldn't we just build a wind generator and get
our electricity for nothing."
And it got me to wondering...why not?
First off. Wind generators are B-I-G. The newest models are 250'
feet tall to the hub. Each blade is 130 feet long. Those towers are
subject to immense stresses. Therefore the bases for the towers
aren't just a couple of legs stuck in the ground. They are highly
engineered and must be anchored to some type of bedrock, in some way,
(or some damn deep pillars).
The blades start spinning with wind speeds somewhere around 9 miles
per hour. Now, 9 mph is not all that fast, BUT calculations show
that the average wind speed needs to be about 15 mph over a year, to
get the 9 mph most of the time. The eastern half of Kansas (which
exceptions) doesn't measure up. However, the western half does
achieve the 15 mph minimum.
It has been calculated that a wind farm covering 100 square miles
could actually produce all the power necessary for Kansas plus some
additional power for the national grid...MOST of the time.
Wind turbulence is the next consideration. Turbulence is a major
consideration. Again. Remember that in creditable amounts of torque
and stress are placed on the blades. Turbulence can actually cause
one blade to be pressing in one direction while a blade on the
opposite side is pressing in the opposite direction. Theoretically,
it's possible to have a wind generator standing tall in a 15 mph
wind, and the blades are not turning, at all.
Wind studies for potential sites take at least a year, and normally
two years, and they're not only measuring wind speed, they're
measuring wind direction AND the comparing the wind direction across
the entire grid of the potential farm.
High speed, straight line winds are much less of a worry, than medium
speed swirling winds. It's theoretically possible for swirling
winds, plus the immense torque generated to twist a wind tower right
off it's base. (Never happened, AFAIK).
Most wind plants shut off completely when wind speeds exceed 45 mph.
Apparently the vibration and the harmonics of a 260' propeller
spinning at ultra high speeds scare the bejesus out of the most
ardent engineers.
(If I was going to bet on a 250' tower standing up to a tornado, I'd
bet on the tornado)
The highest draw on electricity is always in the summer. In too many
areas, even with 15 mph average speeds, the summertime wind speed is
too low to even turn the blades.
-> Therefore, full capacity backup generation capability is required.
There are actually very, very few places in America where a wind farm
could actually meet 100% requirements year-round.
-> Just because a wind generator cannot meet 100% of requirements,
doesn't mean it's not economical or desirable, BUT it's a big cost
factor.
A single wind tower is expensive. It's expensive to buy, it's
expensive to install, and there is an ongoing maintenance requirement.
Remember that 10 mile by 10 mile wind farm? It's been estimated that
it would create 3,000 new jobs just to keep it in operation. Of
course, THAT'S not necessarily a bad thing, but it is a cost factor.
It takes many hours and sometimes days to fire up big generating
plants. Therefore, most of the time, a standard plant is normally up
and running EVEN if there is very little draw on actual power
generated. (Happens almost every night). What wind generators can
do is to reduce the use of other fuels in the back up generation
sector in the "off months". Fixed generators can be shut down, and
fossil fuel requirements reduced. Therefore, the total fuel
expenditure for a year is reduced, (sometimes significantly) but it's
almost never eliminated.
-> Basically, most of the time, a wind farm can significantly reduce
the need for additional future power generation facilities to some
degree, AS long as the existing facilities can "gear up" to handle
peak loads. This is where the national grid can be of immense help
in leveling out the peaks and valleys.
Therefore, bottom line...wind generation is NOT an alternative
method, it's a supplemental method of power generation.
Now, consider a separate observation. Just when wind generation is
dropping towards zero (in the summer), solar power generation would
be reaching it's peak efficiency. Again, this would allow for
smaller backup plants.
In a perfect world, a combination of wind-solar-nuclear, thoroughly
integrated over a wide area would be the most optimal arrangement.
Connection to high capacity, cross-country transmission lines is a
major consideration. In even, low-density population areas,
constructing such lines can reach a million dollars a mile.
There is initially, a high impact on wildlife populations, especially
birds. BUT! 100 square miles is not a very big area, and quite
quickly, the birds learn to go around...(or they die).
There are other "hidden" costs, to be considered. As it happens, the
best places for wind farms tend to be in very remote locations. This
is good and bad. For instance, in building the 100 square mile farm,
you'd have to build a frigging town just to house and support the
construction crews. (Estimated temporary jobs....24,000) not to
mention temporary cement plants and highways good enough to handle
very heavy truck traffic.
Hang 'em from big black blimps. =)
.
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- From: Amused
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