Superconducting Power Grid Launches In New York 264
EmagGeek writes "IEEE is running a story about a new superconducting power grid that was energized in April in New York State. The lines operate at 138kV and are cooled to 65-75K to maintain superconductivity. These lines are run underground and can carry 150 times more electricity than copper lines of the same cross section. The project is funded with taxpayer dollars through the Department of Energy."
A related story at MarketWatch indicates that this is part of a large-scale effort to upgrade aging infrastructure.
I'd contribute funds to that... (Score:5, Funny)
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Superconductors = almost no heat (Score:5, Informative)
how much energy does it cost to keep them so cool?
Not as much as you may think.
The whole point of using super conductors is that their resistance is incredibly low, almost 0 ohm. They are thus highly efficient and don't lose much energy into heat through Joule effect, compared to classical conductors used in regular power lines. They will naturally stay cool.
So it costs some significant amount of power to cool them down to their working temperature, but once there, the super conductors keep their temperature almost for free, you only have to make up for what is lost because of the insulation.
Similar superconductors are used in the high-field super-magnet inside medial MRI machines. And those machine doesn't need a whole nuclear plant's worth of energy to keep them cool.
Re:Superconductors = almost no heat (Score:4, Informative)
The whole point of using super conductors is that their resistance is incredibly low, almost 0 ohm.
No, the whole point of using super conductors is that the resistance is EXACTLY 0 ohm, not incredibly near. There is no resistance, at all.
Re:Superconductors = almost no heat (Score:5, Informative)
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Superconductors break down if you put AC through them, so yes. AC might have been the right choice when Tesla was around, but not anymore.
Re:Superconductors = almost no heat (Score:4, Informative)
You don't have inductive losses; you have losses due to skin effect [wikipedia.org] -- basically alternating current in a conductor tends to travel along the outer surface of the conductor, rather than through it. The higher the frequency, the less of the conductor is used to actually carry current. All major transmission lines run DC for this very reason (and also to facilitate synchronization of different generation "zones").
Re:Superconductors = almost no heat (Score:5, Informative)
You use the right words for an electircal engineer, but your conclusions are inaccurate.
Skin effect doesn't reduce inductive losses. It just means you generally increase resistive losses bceause your effective cross section is reduced. High voltage AC transmission lines are famously inductive, such that transmission line workers where metal mesh in their suits so they don't get the weird feeling of the oscilating magnetic field through their bodies.
And, no, long distance transmission lines are most decidedly NOT DC in the U.S. Now, in Brasil and China, yes, long haul DC transmission lines exist [wikipedia.org]. But they have to pay a huge cost in terms of equipment for this. It's balanced out due to the decreased construction cost and resistive losses. Long haul DC lines are only economical when you have a massive distance between your power generation and utilization, or you're trying to balance load over a rather massive area.
In the area of my ignorance, though, I don't know if inductive losses would ever be significant for a superconductor. One of the defining characteristics of superconductivity is that external magnetic fields only penetrate a tiny distance (~100 nanometers) into the superconductor. I don't know if there might be a similar oddity which prevents them from generating a magnetic field outside of the conductor and coupling with other conductors.
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And, no, long distance transmission lines are most decidedly NOT DC in the U.S.
I think you're wrong about this--maybe not the majority of the lines, but there ARE some HVDC lines in the US. Example:
http://www.abb.com/cawp/seitp202/A4CA486DE1BF9C18C1257368002B05E1.aspx [abb.com]
Re:Superconductors = almost no heat (Score:4, Informative)
In the area of my ignorance, though, I don't know if inductive losses would ever be significant for a superconductor. One of the defining characteristics of superconductivity is that external magnetic fields only penetrate a tiny distance (~100 nanometers) into the superconductor. I don't know if there might be a similar oddity which prevents them from generating a magnetic field outside of the conductor and coupling with other conductors.
No, there's nothing that keeps superconductors from making external fields. In fact, one of the most common applications of superconductors is as electromagnets.
The GP post is just completely incorrect about all transmission lines being DC. You are right, they're normally AC. However, the reasons they're AC might not apply to superconductors. The reason AC became the standard way to transmit electric power was that AC can be put through a transformer, and with a transformer you can step up the voltage for long-distance transmission, then step it back down again at the end. The higher voltage gives smaller ohmic power losses. With a superconductor, you don't have to worry about ohmic power losses, and that might make it more practical to transmit power using DC. The advantage would be that you'd have no inductive losses. The disadvantage would be that you'd need an inverter at the end in order to convert to AC, since the user's building is full of AC devices. Inverters are not perfectly efficient, and they're also not cheap, so maybe that's worse than just accepting the inductive losses.
Trying to imagine an application where you'd really want to use superconducting power transmission with DC, one that occurs to me is if you have a big photovoltaic farm in Arizona, and you want to send all that energy to Los Angeles. The photovoltaics produce DC, so somewhere, somehow you've got to have an inverter. Maybe you'd put the inverter at the LA end, and avoid inductive losses. But it would be a huge engineering project to lay a trench from Arizona to LA and fill it with liquid nitrogen.
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They can feel the magnetic field? (Score:5, Interesting)
High voltage AC transmission lines are famously inductive, such that transmission line workers where metal mesh in their suits so they don't get the weird feeling of the oscilating magnetic field through their bodies.
That's wild... it is news to me that humans are able to directly perceive even very strong magnetic fields. For example, I don't think patients feel anything when undergoing an MRI [wikipedia.org] procedure. Can you cite a source for this information? Thanks
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And, no, long distance transmission lines are most decidedly NOT DC in the U.S. Now,
There is an exception..
On the West Coast is one of the longest DC transmission lines. It runs from near The Dalls Oregon on the Columbia River to within about 60 Miles of Los Angeles in Southern California. It is 846 miles long
http://en.wikipedia.org/wiki/Pacific_DC_Intertie [wikipedia.org]
"A 1,362 kilometer (846 mile) overhead transmission line consisting of two uninsulated conductors 1,171 mm2 containing a steel wire core for strength."
C
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In a class of superconductors known as Type II superconductors, including all known high-temperature superconductors, an extremely small amount of resistivity appears at temperatures not too far below the nominal superconducting transition when an electrical current is applied in conjunction with a strong magnetic field, which may be caused by the electrical current. This is due to the motion
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So if I turned off my freezer all I'd have to do to keep the low temperature would be to "top up" the cooling agent to maintain heat lost through the insulation? Isn't that what refrigerators do already?
Do you have any clue how cold it has to be for superconducting? "M
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At least with this stuff you can use liquid nitrogen instead of liquid helium.
Re:Superconductors = almost no heat (Score:5, Insightful)
Comment removed (Score:5, Insightful)
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I'm from the area (very close to said power plant) so I figured I could clarify on why Long Island is the NIMBY capital of the world:
There are very few rivers and streams on Long Island, and most of them are in located in parks or protected woodlands. This means that almost all the drinking water for LI residents comes from ground water - most of it is contained in large underground aquifers.
Nuclear catastrophes usually involve radioactive material finding its way into the ground - and eventually the ground
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No free Lunch (Score:3, Informative)
Even though the conductors may contribute zero heat energy, it still costs a lot to keep them cooled.
A cable is a long thin tube buried under ground. It has a tremendous surface area. Heat leaks in from the ambient surroundings.
The article mentions the cost of cooling, but it did not give a figure. It is possible, that the energy consumed for cooling exceeds the energy losses in a non-superconducting cable of the same capacity.
Also, with a superconducting cable, one must include the cooling system's fail
Re:Heat from environment (Score:5, Funny)
The hotter the environment, the worse the thermal insulation
They run it through New York state to take advantage of the Hillary Cooling Effect.
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Presumably less than they were losing on thermal losses before, though I can't find any decent numbers, nor do i have enough details (length, gauge, current) to calculate a guesstimate.
Re:I'd contribute funds to that... (Score:4, Funny)
The article SHOULD have said that the wires were about 1/1000th the diameter of an African male elephant, and carry about 12 Library of Congresses worth of current - for a total of a mind-boggling 23 Senate chambers' worth of hot air.
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Cool! (Score:5, Funny)
Hmmm... (Score:5, Interesting)
Besides economics, another advantage the company is touting is that the cables can prevent fault currents, surges that are caused by grid-scale short circuits. Superconductors have an inherent current-limiting ability in that if the current increases past a certain threshold, they lose their superconducting abilities and become normally resistive, damping the current.
Hmm, interesting, but there's more. simply follow the links in TFA and you'll come to these:
"So there's been a stir over the disclosure that AMSC is under investigation by the office of Representative John Dingell, a Democratic congressman from Michigan, one of the most influential U.S. legislators, and an aggressive inquisitor."
"The incident that aroused Dingell's suspicions was the award in 2006 by the U.S. Department of Homeland Security of a multi-million dollar no-bid contract to AMSC to develop and test what it's calling Secure Super Grids in New York City. Working with the local utility Consolidated Edison Co., AMSC plans to develop and install superconducting cables that would connect substations in a much tighter mesh, so that if stations or feeder cables fail, power can be instantly rerouted. Feeder cable failures were implicated in the 1999 and 2006 New York City neighborhood blackouts."
Wow, I didn't know the DHS was responsible for awarding no-bid contracts to energy interests. There ain't no business like no-bidness!
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The Department of Homeland Security is just amazing. I admit I haven't been paying as much attention as I could have, but, so far, I have only heard about _one_ thing they did that I thought would actually...improve homeland security. For the rest, they have embarked on numerous projects that range from interesting to horrible, but that are all very expensive and do little to improve security.
On the one hand, I am glad to see a large portion of the money that DHS gets goes to interesting projects, rather th
Re:Hmmm... (Score:4, Insightful)
In regard to projects like this, you have it all wrong. Let's think for a minute.
New York City and its tri-state metro area is the largest in the country, and essentially the world's financial capital. Its arguably one of the most important areas in the country.
For a variety of reasons like NIMBY, the dysfunction of NY state government and rapidly increasing demand, an increasing proportion of the electricity supply is coming from places hundreds of miles away in Upstate NY and Quebec. The geography of NYC and Long Island (and the high cost of land) makes it very difficult to add transmission lines, and makes it relatively easy to attack the existing lines.
So, if a technology like superconducting transmission lines would allow you to increase capacity and better protect these lines by burying them, it seems like a valid security measure to me.
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I dunno - having John Dingell investigate someone for government fraud is like Typhoid Mary accusing someone of not covering their mouth when they sneeze.
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Is there an in-print or online version of the Paranoia game rules around anywhere? Apparantly Hacknoia turned out to be more like Top Secret than Paranoia.
Wow, !vaporware? (Score:5, Insightful)
With the influx of superconducting [slashdot.org] articles [slashdot.org] I got a pretty good feel of "hight temperature" superconducting being vaporware. It's cool that we're seeing real world applications now. TFA even tries to trick you into not believing the summary by saying they were "commissioned", but if I read correctly they mean "was put on the power grid" by commissioned, not "was approved to be built."
Re:Wow, !vaporware? (Score:5, Funny)
It's cool that we're seeing real world applications now.
Superconducters are way cool man.
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"I got a pretty good feel of "high temperature" superconducting being vaporware."
You might want to ask anyone who's ever been in a MRI why the dang thing works at all without it's superconducting super magnets.
by 'high temperature' right now we mean somewhere around 90-110K prior to 1986 high temperature meant 'below 22K'
http://en.wikipedia.org/wiki/BSCCO [wikipedia.org] BSCCO is the most common superconductor, at least for lines, http://en.wikipedia.org/wiki/YBCO [wikipedia.org] YBCO is better for super conducting super magnets. at leas
Re:Wow, !vaporware? (Score:4, Interesting)
You might want to ask anyone who's ever been in a MRI why the dang thing works at all without it's superconducting super magnets.
According to Wikipedia [wikipedia.org] and your information, MRIs generally use Liquid helium to cool things down to 4K. That's not a high temperature even in the superconductor world.
oh hey, and what about the maglev train in japan, or various ones in germany?? do you honestly think that doing magleg based on normal electromagnets would be energy efficient?
Only one major Maglev line [wikipedia.org], the JR-Maglev, uses high temperature superconductors. JR-Maglev [wikipedia.org] is not commercial; it's just research. Currently, there are two major commercial Maglevs [wikipedia.org], neither of which use high temperature superconductors (let alone any superconducting at all).
These are the reasons I felt that high temperature superconducting is vaporware. It gets a lot of research and demos, but not much real world application. The Japan demo maglev is close, but it was never put in large scale or commercial use. The power grid in TFA seems to be one of the first mass commercial uses of superconducting used. YMMV, someone point out my fail if there have been more uses of high temperature superconductivity in the public space.
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What I remember from school was that the now-old high-temp superconducting materials were brittle, and therefore difficult to make power lines from. However, that's just an engineering problem, and for buried power lines inside presumably rigid pipes carrying the coolant, perhaps that's not even a difficult problem.
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MRIs are usually built with what are called high-Tc superconductors. Here Tc stands for critical temperature, and means the temperature at which it possibly still superconducts.
But another factor needs to be taken into account: high magnetic fields destroy superconductity, just as high temperature does. So there is also a critical magnetic field (called Hc).
The catch is, that the critical magnetic field depends on temperature: the lower the temperature, the higher a magnetic field is allowed. This is of
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In Canada in a place called crowleys ridge I came upon a truck sized super conductor based stabilizer used to connect the wind farm at that location to the power grid.
Not exactly mass market but definitely an application of superconduction.
still a problem though (Score:2)
Saving Energy (Score:5, Interesting)
Maybe the US will now leapfrog from an antiquated power distribution system to the most advanced in the world. Maybe. One positive aspect of this is the reduction of energy loss due to the superconductivity. This may also allow long distance lines to be run (even though the cooling will be a problem) which might help balance out the grid when needed.
According to Wikipedia, super conducting cables will use roughly half the energy saved for cooling, but since losses are around 7%, that's still a rather high amount of energy saved.
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Am I saying that t
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One positive aspect of this is the reduction of energy loss due to the superconductivity. This may also allow long distance lines to be run (even though the cooling will be a problem) which might help balance out the grid when needed.
Cooling is indeed a problem, but it's a problem for normal underground power cables too. Yes, normal cables don't need to be so cold, but they also generate a lot more heat that needs to be got rid of. What's interesting is that overall switching to superconducting cables is still a win (they wouldn't be rolling it into production if they didn't think that) even after considering increased capital costs, and that they can push those sorts of voltages and currents through high-temperature superconductors. Ne
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This is a pretty good write up of what is involved in an underground cable:
http://jwz.livejournal.com/94645.html [livejournal.com]
Wild stuff.
How long is it? (Score:3, Informative)
reliability ? (Score:3, Insightful)
To a large extent good old passive wires make for quite a robust system.
However with the addition of all the support equipment necessary for LN2, doesn't this make for a step
backward in terms of reliability ?
Decentralized power production, e.g., solar, still seems like a more worthwhile idea to me.
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Re:reliability ? (Score:4, Informative)
You might be surprised how little different it would be to have power lines running superconducting in parts of NYC. With the vastly complex infrastructure already in place, doing these lines might not be all that big a deal in some ways.
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Unfortunately your theory is silly. Liquid nitrogen is quite expensive and effectively insulating a system such as you imagine is, well, impractical and not affordable.
You might be surprised how little different it would be to have power lines running superconducting in parts of NYC. With the vastly complex infrastructure alread
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I guess that depends how you define expensive. I see prices for LN from $0.50 to $3 per gallon depending on location, though I have no idea how much is used for this kind of thing.
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In cold boxes (which feature pretty complex, closely-packed piping) we'd use at least 12" of perlite insulation from exterior heat sources. For critical individual lines you're talking about vacuum jacketing with at least a 1" vacuum annular space and special shielding, which is what those "high-tech", stainless steel containers are (sort of). These containers an
Okay, one last time. (Score:3, Insightful)
It looks like my impression of what those tanks were for was wrong. Kinda. We've seen enough references in this thread to cooling systems for power lines, and especially to the emergency cooling problems when something goes wrong, that I suspect that this is part of what I was hearing about.
But, of course, I always made it clear that I wasn't sure. You know, like when I wrote: Because, iirc, many of the . .
I never
Re:reliability ? (Score:5, Informative)
One of the characteristic sights on New York City streets is big tanks of liquid nitrogen standing on the sidewalk, steaming away, with lines running from them down a manhole. Why? Because, iirc, many of the telephone company switching systems already run supercooled and when a repair needs to be done they need supplementary chilling.
Those nitrogen tanks are used by Verizon to pressurize underground telephone cables and keep moisture out:
http://gothamist.com/2008/01/31/nitrogen_tanks.php [gothamist.com]
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No, those N2 tanks are used to push water out of phone lines to prevent shorts. All wiring in the city is buried, and a lot of that is below the natural water table. The N2 keeps certain otherwise problematic lines dry by building pressure and pushing out the water.
-molo
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(Solar heaters are so efficient, they're even used in Wales, not a country known for masses of sunlight.)
I used to have a solar water heater in Melbourne at 37 degrees south. In the winter it would deliver warm water at best. In the winter in the UK I doubt it would be any good at all.
Lastly, there's one small issue I have with these superconducting cables. 77K? There are superconductors that operate at something like 2-2.5 times that temperature! Are these guys wanting to prove it can't be done?
High temperature superconductors tend to lose their conductivity in the presence of a magnetic field, which limits their current handling ability. Also the materials are quite brittle.
Just the thing we need, 150x power usage (Score:2, Insightful)
These will go perfect with a 150x increase in power plant construction!
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Forget wires (Score:2, Insightful)
We need to move towards generating electricity locally, instead of trying to generate it all in one place and then move it to where needed.
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You mean apart from the kilowatts available on every electrical outlet in the house?
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One could always siphon off power right now with an antenna if they're close enough to a power line, making for a dangerous situation, though that would be illegal. I do not condone it, but I doubt the electric company would notice, since it's power they write off as the result of transmission. Essentially, it's illegal to harvest power that's being wasted via leakage from the lines. I guess it's sort of like "dumpster diving."
"Hey, we're throwing this away, but no, you can't have it; it's our garbage, not
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it's illegal to harvest power that's being wasted via leakage from the lines
Actually, it does cost the electric company more when you leech power in this way - you are basically setting up a huge air gap transformer, with the overhead electrical line as the primary and your leeching loop as the secondary.
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The only thing I can think of that might be different is solar, where bigger or more panels don't seem to up efficiency that much.
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For places with high-density population such as Manhattan, generating locally isn't feasible for now, and won't be for a long time to come. Improving the grid here is worthwhile.
Re:Forget wires (Score:5, Insightful)
This is only a 150 metre prototype, but if the technology scales then it will have a major effect on the economics of power distribution.
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what's the cooling method ? (Score:2)
in the lab you get things cold by pouring liquid nitrogen on them; that doesn't seem feasible w/ miles of line, so what's the method ? peltiers ?
Real world apps, geeky nerdy physicists (Score:2)
And in further news (Score:3, Interesting)
ConEd (NYC's electric supplier) got approvale for a 23% rate increase yesterday
Fremont without powerlines (Score:2)
What would happen if the Fremont power line nest was replaced by 3 underground superconductors? 1000 houses would suddenly appear from under the wires & jump to $5 million. For the first time in 50 years, Automall Pkwy residents could see the sky.
If you like the concept of solar in the desert (Score:2)
How does it have voltage if it's superconducting? (Score:2)
I must misunderstand something. Wikipedia (http://en.wikipedia.org/wiki/Superconductor) says
"The simplest method to measure the electrical resistance of a sample of some material is to place it in an electrical circuit in series with a current source I and measure the resulting voltage V across the sample. The resistance of the sample is given by Ohm's law as R = V/I. If the voltage is zero, this means that the resistance is zero and that the sample is in the superconducting state."
So, no voltage implies n
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So, no voltage implies no resistance implies superconductivity. But the reverse isn't true? We have a cable that has superconductivity yet still has voltage?
There is a potential difference between the cable and ground because the cable is insulated from ground, ie, there is no superconductor to ground.
There is no potential difference along the cable because it has no resistance.
Dumb question (Score:2)
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Being near high tension lines tend to cause interference in radio signals. More static, etc. This has almost zero resistance. So, does that mean less interference?
No. The transmission line will still radiate an AC electromagnetic field at 60Hz, but the cable housing around it may prevent that from creating interference.
In addition, by putting "receivers" close to high-tension lines, you can take energy from it. What is interesting is that it causes local heating on the lines. So, can somebody use some copper coils to do the same to these? If so, then it could be used to increase local heat to the point of causing a cascade loss; i.e. here is a way to bring down a line, and causes a massive release of energy. Is this true?
An external field can induce current in the superconducting line but that won't cause heating because the line has no resistance. Superconductors can lose their superconductivity in the presence of a magnetic field so I suppose it is possible to bring the line down in a way similar to the one you describe.
New York's Next Project... (Score:3, Funny)
Supercooled water mains!
Wait...
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How about operating cost? (Score:2)
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Re:OK - 150x capacity, BUT: (Score:4, Interesting)
In a standard copper line the value is zero: we don't cool them
Conventional underground transmission lines are oil cooled. Superconducting transmission lines have almost zero resistance and should require less cooling once they reach working temperature.
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Correct on all accounts.
And additionally, oil cooling of traditional powerlines is nasty business, because these lines get hot, and sometimes so hot that the oil boils and/or hydrolizes, and when THAT happens, you have carbon - which is conductive - and then, well, you got yourself a blackout.
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Re:Possible new 'Terrorism' target? (Score:5, Interesting)
There are many, many ways to build a system to manage loss of coolant, nuclear reactor scrambles being obvious extreme versions. Some of these approaches could be used in a case like this. But we're dealing with Con Ed here, the guys who neglected maintenance such that we ended up having three major blackouts in ten years. So I'm not optimistic. The only thing that we should remember is that at least in theory such problems are somewhat addressable, not least by just the kind of rerouting that this system is supposed to make much easier and faster.
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WTH is a "nuclear reactor scramble"? Wikipedia sheds no light, and not even Google was my friend. In fact, your /. post is the only Google hit for that exact phrase.
Try scram [wikipedia.org] instead.
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What happens when a 'Terrorist' finds a way to purge/rupture the coolant? *POOF*
What happens if lightning directly strikes the conductor's coolant jacket? Could that cause a coolant jacket leak?
It's liquid nitrogen. I doubt that much would happen besides it evaporating and the power line failing.
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Erm. Underground?
I'd like to see lightning hit down there.
Re:Possible new 'Terrorism' target? (Score:5, Informative)
Underground power cables are struck by lightning amazingly often - I think more often than high-tension lines. Lighting strikes originate quite deep - given they cross 8 km of air gap, several meters of damp earth should come as no surprise.
Re:Possible new 'Terrorism' target? (Score:4, Interesting)
Re:Possible new 'Terrorism' target? (Score:4, Funny)
The Germans arrested him early in 1942, but let him go for lack of evidence.
That's where they nazis lost it. They should have just rounded up all suspects and put them in a freedom camp or something.
Re:Possible new 'Terrorism' target? (Score:5, Insightful)
I wish that was funny and not depressing.
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These are *superconductor* (Score:3, Informative)
The added logistical complexity to keep the low temperature on the whole network will do it all for you.
As I said a couple of threads above [slashdot.org], the whole point of using superconductors is that they have almost 0 ohm resistance. They can't heat up through Joule effect. They keep cool for free.
You only have to make up for whats lost through the insulation. That's it.
Re:Possible new 'Terrorism' target? (Score:4, Informative)
Of course, a terrorist could blow up any sort of power line with a big enough bomb, but so what - there are far higher-value targets.
Aside from bombs, a coolant leak would be easily stopped in the short term by a water jacket. Do you know how you insulate liquid helium pipes in a lab? You pump liquid helium through them, and a 4 inch thick layer of ice forms in a few minutes, insulating the pipes just fine. At higher temperatures you'd want to provide the water, but I'd bet liquid nitrogen escaping through a layer of water would self-seal very quickly.
Lightning strikes are a problem for all buried power cables, but it's a well-solved engineering problem.
Re:Possible new 'Terrorism' target? (Score:4, Insightful)
- Liquid nitrogen is cheap. The more of it you need, hence the larger your machinery for making it, the cheaper it gets.
- We're talking about a hundred million dollar system here, just in construction and maintenence costs. Not to mention the billions of dollars worth of services that would depend on it.
- If your insulation is at all effective, the amount of liquid nitrogen required to cool a given stretch of cable is pretty small, since the whole cross-section of cable is something like two centimeters, including part of the cladding.
This being the case, maybe it would be cheaper all around to just keep two or three hundred liters of "extra" liquid nitrogen in tanks connected to the system every mile or so. If the system is leaky, who cares? As long as you're making liquid nitrogen faster than you're leaking it and you are keeping the stuff flowing effectively to the leak, it's just not that big a deal. Keep in mind that at retail prices "two or three hundred liters" is about four hundred bucks worth. Maybe. Relative to the cost and importance of a system like this, a few hundred bucks, even the cost of the equipment to make that liquid nitrogen, is a rounding error.
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Why is the voltage so high ?
Surely, if there is zero resistance, then there is no need to reduce the current to save on energy loss, so why still transmit at such a high voltage with the superconductor ?
TIA