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Storing wind-generated energy as gravitational potential energy? - Page 30

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Posted by Neon John on December 10, 2008, 10:02 am
 


By "Better" do you mean larger or more reliable?  The largest US wind turbine
that I've read about is 5 MW.  I have some photos of the blades being
transported.  Each blade requires an extended, custom-built semi trailer,
complete with escort cars front and back and special licensing in each state.
IOW, each blade is about as complicated to transport as a nuclear steam
generator or load of fuel.


Again, according to US trade rags, the US is doing better, probably because we
have vastly more land area from which to choose sites.


OH, that's easy.  A typical twin unit reservation is 500 acres.  Each unit is
good for 1000 mw (1200, uprating to 1400 at Sequoyah) and there are 2 units.

2000/500 = 4 megawatts per acre.

Now I could cheat and use Browns Ferry.  3 1100 MW units on a 500 acre
reservation.  6.6 megawatts per acre.  Oh.  Wait a minute.  That's not
cheating by Greenpiss standards.  In that world, it's OK to quote the absolute
maximum possible (or impossible) theoretical output as the norm, isn't it?

Here's an interesting press release from TVA concerning BFNP that will give
you some talking numbers.

http://www.tva.gov/news/releases/0402bfrecord.htm

Frankly, I was impressed, especially at the Brunswick run.  Over 2 years
without a scram.  They must have already converted to high burn-up fuel.

I should also note that much of the land on a 500 acre site is wasted.
"Security clearance" and stuff like that.  I don't recall the size but the
island that Three Mile Island is on is considerably smaller.  300 acres is
sticking in my mind but don't quote that.

The actual plant probably covers only 5 acres.  Add in a few more for the
cooling towers and the cooling water channels and it's still probably under
20.  If you're really interested, I can dig out the exact coordinates for
Sequoyah and you can use google Earth to see the plant and figure that out.
The image is excellent and the sun is at a good angle for shadows.  I know the
height and diameter of some of the structures casting shadows so one can
calculate scale from that.

Here is something that is vitally important to understand about nuclear
plants.  Their capacity is limited by regulation and not physics or design.
Sequoyah, for example, was designed to produce around 1200 MW.  When I say
"designed" I mean that this is the regulatory limit set in the design
documents and the FSAR (final safety analysis report).  It is not the wide
open throttle limit.

Sequoyah has received generator and turbine upgrades that has allowed it to
change its regulatory limit to 1400 megawatts.  Most nuke plants in this
country are planning, have executed or will be executing similar "up-ratings".

I'm trying to recall the number that we discussed once during training but
seems to me like the "all knobs to the right" limit of Sequoyah is about 1600
MW.  That is, with the plant running at the thermal limit of the fuel rods.

 On the Link simulator, which faithfully duplicates the behavior of the plant,
right down to vibrating the floor when one fscks up :-), I have pushed over
1600 MW.  I probably damaged some "fuel" in the process - the computer didn't
tell me that.  All it takes is flipping a few controls to "manual", blocking
the neutron monitoring over-power trip signal, grabbing the joy stick and
pullin' rods.


That's 60,702 watts per acre or 0.0000607 megawatts per acre, to match the
units I used in the nuke calculation above.

Even that figure gives me heartburn, as NREL (National Renewable Energy
Laboratory), which publishes insolation data for the US, quotes an average
insolation rate of only 1 watt per square foot.  That's only about 11 watts/sq
meter.  How are they going to make more power than what the sun provides?
Seems like 1.5 watts/sq ft is what NASA uses when figuring solar cell capacity
for space use so the desert can't be THAT much better than the global average,
can it?



Like the old saying goes, "those who fail to do the maths are doomed to look
silly".  Or something like that :-)

Actually, it's not just the maths, it is the concept of scale.  Few people
outside the scientific and engineering ranks have any concept of the term
"order of magnitude".  The best thing that ever happened to me was going
through school in the pre-calculator days when we had to use slide rules.

That forced us to know scientific notation, to be able to estimate the order
of magnitude of the answer before computing it and to realize when the answer
was off by an order either way.  Calculators rob the student of that learning
opportunity.  I still use my slide rule regularly just to keep those skills
sharp.

Like I said in an earlier post in this thread, Nukes look so small relative to
other large factories and power sources such as hydro dams.  They can't make
THAT much power, can they?  Well yes... yes they can.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
I don't speak Stupid so do speak slowly.


Posted by The Natural Philosopher on December 10, 2008, 12:22 pm
 
Neon John wrote:

Right. an acre is about 4000 sq meters, so thats about a kilowatt per
square meter.

somewhere between 100 and a thousand times better use of land area than
a 'renewable' plant.



Well in the context I want, that of a small crowded overpoulated island
(1/5 of the USA in about  the size of california) its meaningful.

Our total energy use (peak) I estimate at 350GW. so thats 350 million
square meters, or 350 square kilometers. abot 20x20 kilomters  Compared
with an area the size of Wales for renewables.


Ok, I really appreciate your knowledge here.

I was working on 3.5GW from a twin reactor/turbine site as being
realistic with modern sets. Sounds like its realistic.

current UK electricity generation is IIRC about 75GW peak.



I think its similar. you can angle your mirrors at the sun, so get a bit
more capture surface per unit land area as it were.. if you like your
shadow is bigger than the land usage.


same here.


Even so, it takes about 50 tons of refined uranium a year to keep a
rector going.
Thats 5,000 tones of fissile material thats would be need for my 350GW
peak island scenario.

and at 1% extraction from the ore..thats a lot of ore..

Posted by Neon John on December 11, 2008, 12:24 am
 


(caution: I'm getting into an area that I don't know that much about.)  I
believe that your 50 tons is of fuel ready to load.  Remember, though, that
even with high burn-up cores, only less than 5% of the available uranium is
used.  More typical is about 3.5%.  The rest, at least in the US under the
current political climate, is sitting there wasted in spent fuel casks.

Then there are the breeders that can use the depleted U-238 that currently
can't be given away to make more fuel than consumed.  Once breeding technology
enters the fuel cycle, very little new U will have to be refined for a LONG
time.

Finally, there is the recovered Pu from all the bombs that we've (all the
major nuclear powers) have dismantled.  I'm afraid to quote a number for how
long the current inventory of US plants can be operated on the available PU
once MOX fuel is adopted but it is a large number of years.  I'm thinking
nearly 100 but that could be wildly wrong.  And we haven't even mentioned the
thorium cycle.

Plenty of fuel for farther than I dare risk peering into the future.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
Why the US is losing its competitivve edge:"It used to be that the USA was
pretty good at
producing stuff teenaged boys could lose a finger or two playing with."-James
Niccol


Posted by dennis@home on December 11, 2008, 10:58 pm
 



Some of the UK reactors are running on Plutonium oxide.


Posted by Andy Dingley on December 12, 2008, 12:20 pm
 
No they aren't.  We have some small use of MOX (far less than planned)
but I don't know of anything using PuO alone.


As an aside, MOX fuel is intended to use _civilian_ Pu rather than
military Pu. There's about 5 times as much of it available and it's
relatively low cost (having few other uses).  Military Pu isn't really
that big a problem anyway, as it's so difficult to engineer a weapon
from. The proliferation hazard is military HEU (bombs or submarine
fuel) which _is_ easy to weaponeer. In an ideal world we'd be burning
this stockpile ASAP in simple HEU reactors (Triga-like for the most
simple example, but probably PWRs similar to existing submarine
designs) as it's an easy piece of reactor design, massively simplified
by the effort already invested in the enrichment. However fear and
inertia means we've barely started even this little.


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