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Superconducting Power Cable in Detroit
mgarraha writes: "According to a
Washington Post article, this summer
Detroit Edison
will lay 1200 feet of superconducting power cable near their
Frisbie substation, which serves 14,000 customers in downtown Detroit.
The cable, made by American Superconductor and Pirelli, consists of
silver-clad HTS ceramic ribbons woven around a pipe for liquid nitrogen." We've mentioned this particular project before. It's not room-temperature, but still interesting to see superconductors coming into large-scale, common use.
But you can't keep it pressurized. Like all refrigeration systems, it works by compressing the refrigerant into a liquid (where it will give off heat, like at the back of your fridge) then releasing it into a low pressure area (known as an evaporator) where it will evaportate. The process of evaporation requires heat, and it will take it from its surroundings, therefore leaving its surroundings cooler. That's how refrigeration works, so keeping it pressurized doesn't do anything until you allow it to depressurize and evaporate.
Unfortunately, you're not going to see these brittle ceramic superconductors dangling in the wind from cheap steel towers. That means huge expenses incurred creating an entirely new underground long-distance power infrastructure. The real question is, will that expense be recovered?
Superconducting Niobium alloys (of the traditional Liquid Helium temp variety so as to avoid quenching in high fields) have been in use for more than 20 years now. Do you know of a major North American metro area that does not have an MRI imaging facility? No? That means superconductors have been in widespread use in routine clinical NMR-MRI imaging for all sorts of medical conditions (heart patients, epileptics and brain imaging, etc.). None of the liquid nitro temp ceramic compounds has the magnetic quench resistance that the niobium alloys do. A typical MRI coil needs to maintain a uniform field of 1.5 Tesla across the body parts being imaged - including whole body NMR scanners.
I think that in this case supercritical refers to a fluid that has been heated behond its boiling point, but has not undergone a phase transition. The liquid will undergo a phase change as soon as a nucleation site for bubble formation is introduced. Once bubbles start to form the liquid can boil explosively.
This is one of the reasons why chemists wear goggles.
You can do this one at home: Get a *clean* pan (glass is best), and fill it with water. Gently heat to boiling point.
Allow it to cool slightly, then heating *very* gently. If there are no jaggy bits in the pan, bits of dirt in there etc you should be able to superheat the liquid. If you want to test this then stand back and throw in a pinch of salt, bit of sand, pet gerbil, whatever.
Ice formation also needs to start somewhere - it is possible to supercool liquids. I believe that some arctic fish exist in a supercooled state during winter - stick a pin in them and they freeze solid in a couple of seconds.
Koff-koff-koff OH man it's been a while.
Still, I wouldn't want to be too close then the 1200 foot long fuse blows...
"There is such a thing as a supercritical fluid, but that is way beyond the scope of this discussion."
Hi, I'm not a ChemE, just a mathematician. But what little I know about supercritical fluids pertains to their use as solvents -- which sounds like a bad idea for underground cabling. However, I'm glad you mentioned them. This is the first time I've seen mention of supercritical fluids since the summer of 1991.
There was a question above about the environmental impact of the nitrogen line breaking. Using supercritical fluids, for instance supercritical nitrogen, to replace nasty organic solvents has great environmental benefits. And just as funny as the worry about releasing nitrogen into the air, was that you could (jokingly) negate any greenhouse effects from supercritical carbon dioxide by putting a plant where this solvent was exhausted.
-Paul Komarek
environmentally-friendly aspects of replacing traditional organic solvents with supercritical carbon dioxide,
Indeed if one had to dump something in the atmosphere this would be most folks #1 choice followed by pure water.
The biggest danger would be freezing something important like a bodypart from extended immersion. However since liquid Nitrogen behaves like most liguids and doesn't do anything funny it's not hard to understand/predict & it does evaporate easily.
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
Liquid Nitrogen is used in LOTS of processes and has a well established production infrasructure. Indeed if you were to call a local distributer you'd find they likely deliver to most of the research, manufacturing & medical facilities around you; those they don't likely have on-site production.
If liquid-Nitrogen cooling cables takes off you'll likely see sales of modular production facilities increase but I doubt the overall economics will change: This is pretty basic & well established stuff.
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
I poured it all over my hand, and hit it with a banana - my hand shattered into several pieces. Just had to hold them in place until they thawed and everything was as good as new!
(I am so full of shit. You ever call anyone a 'this'? It means 'mixed up piece of shit' - same letters, just mixed up. *snork*)
Better yet, hold the base of the bulb in one hand, and piss into the toilet with the other!
Hey, it's time to winnow out the Slashdot crowd. Evolution in action...
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This wasn't about transmission losses.
I'm pretty sure this is about not digging up the streets. Read the article.
They're only running 1200 feet of cable. That's not enough for transmission to be a problem. But it is a helluva problem to expand the system: the old conduits were laid down a looooong time ago, and are at capacity.
The new cabling allows them to triple the capacity without digging new trenches.
I'm pretty sure that's what this is about: expanding inner-city capacity without the expense and trouble of laying new conduits.
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Switching those wires to superconductors would take care of the loss due to resistance in the wires, but it would not prevent the inductive transfer of power to other conductors (like the "capture coil" and florescent light you mention).
So, it sounds like a good idea, but what is the environmental impact of a break in that pipe with that liquid nitrogen in it? Ain't it going to go liquid to gas awful damn fast?
7 November 2006: The day Americans realized corruption and incompetence weren't addressing 11 September 2001
These only look feasable for a few miles-
i.e. putting those high tension wires underground
in an urban area. Still need a power plant to
generate electricity.
I expect the problems causing the power outages in California are due to management decisions, not lossy transmission. New transmission technology, coupled with the new lossless cables, will just result in the same brownouts. The management, in their race to make as much profit for the shareholders as possible, will just shutdown the 20% extra generation that they no longer need.
And perhaps read the article? The wire itself isn't made of poisonous material. And if the enclosing pipe breaks it'll release Nitrogen into the atmosphere. You know, the same atmosphere we breath...which is a bit over 75% Nitrogen.
Watch that knee!
Blar.
I hope all the engineers working on this project have thought of this! Quick, what's the number for their offices so I can warn them!
Blar.
Yes, but this would be useless for superconducting applications. The whole point is for it to be cold, or else the superconductor won't work.
Also, superconductors that conduct at lN2 temperatures do so not because they are surrounded by lN2, but because they are at or below the boiling temperature of lN2 under standard pressure. Even if you could keep the lN2 liquid at a higher temperature by pressurizing it, the superconductor would still cease to superconduct the moment it's threshold temperature is reached. The good news is the superconductors produce no heat so all that's needed to keep the lN2 around is good insulation.
Finally, both gas and steam are gasses.
If anyone is interested, I just looked up the critical point for nitrogen at webelements.com. It's 126.2K [or -146.9 C (-232.4 F)]. Regardless of the pressure, it is not possible to liquify nitrogen (or keep it liquid) above this temperature.
Yeah, but there's not _much_ value in that. You still have to wrap the wire around rigid pipes. and once the system is in place and operating at supercooled temperatures it's going to be relatively brittle anyway --- probably not earthquake proof in any event.
Yes, you would see a localized increase of nitrogen. Just as you see a localized decrease at the facility where the nitrogen is extracted from the atmosphere. It's not proof - but this has been going on for decades. It's not as if they're MAKING nitrogen - they're only moving it from one part of the world to another. That's just got to be harmless.
1. Liquid Nitrogen is cheaper than beer.
That's not much help. Cheaper than what beer? Chimay runs about $9.00US/liter around these parts.
Of course, it's worth it!
There's still a good reason to use AC:
Transformers are a heck of a lot cheaper than DC-DC or DC-AC converters, and can be made about as efficient as a solid state converter. When you're dealing with such high voltages, high currents, or both, you'll find the solid state converters are significantly more expensive.
-Adam
Honk if you've... Oh, nevermind. ***WHOOOSH***
This sig 80% recycled bits, 20% post user.
Actually, there are two ways energy is lost, only one of which is inductively. You can harness the magnetic field generated by the power line with a coil (inductive), but you can also harness the electrostatic force generated by the line. This is what happens when you bring a flourescent light close to a high tension line.
Given that a high tension line is, say, 40ft in the air (for good reason), and is at 40kV, then there is 1000V per foot between the line and the ground. The air has a very high resistance, but a few pico or nano amps does flow from the wire to the ground. This is not enough to be felt by the human body, but will light a flourescent bulb (not full brightness, but close). As the lines get close to the ground (as when coming to a substation) they put fencing around it because the voltage can get as high as 10kV per foot, generating more current, more ozone, and a more hazardous place for the human body.
At any rate, I mention this because the superconductor will have very little electrostatic energy (underground cables are insulated better than just with air), but will create a greater magnetic field. This inductive energy is only lost when there are ferrous materials (or conducting loops) within its field. If they engineer it well, they can even limit those losses significantly.
-Adam
Root. It does the body good.
This sig 80% recycled bits, 20% post user.
No, he is right. I don't know where you took your thermodynamics classes, but you were misled. All materials have a "critical point" above which there is no liquid state. To be more precise, there is no liquid-gas phase transition -- in fact what you get at high pressures is a mush that transforms smoothly from "mostly liquid like" to "mostly gas like", but there is never any 2 phase seperation.
For N2, the critical point is below room temperature.
I suspect that there was at the very least a pressure release valve somewhere on your ln2 tank.
Finally, I suppose they could use N2 based vapor cooling along the length of this pipe, but they would have to be screwed in the head to want to. You would have to build the whole system to withstand several thousands of psi with controlled bleed valves the whole way. It is much, much simpler to pump low temperature lN2 the whole way where your equipment only has to handle a small pressure over 1 atm.
Well, like any electric line, the person who cut it is in a world of hurt. Presumably the lN2 system has some sort of safety shutoff the prevents it from pumping too much lN2 out of a rupture, but even so, there could be enough cold nitrogen gas in the area to suffocate someone nearby.
It sounds from the article like this isn't likely to be a problem in their location: They are doing this because it is so hard to dig there.
The cool thing about MgB2 is that people are hoping they can "tweak" it to superconduct above the magic 77K (the cupric oxide semiconductors were also discovered with a Tc around 40K, and quickly improved), while still being easier to work with than ceramic superconductors and more importantly, it points to new areas of research that might improve our understanding of superconductors in general, possibly leading to mugh higher temperature supercondutors
Actually, it should be substantially cheaper. High power underground lines, including these ones, are usually oil cooled. Oil cooling is pretty expensive, since you have to somewhere dissipage quite a bit of heat. Liquid nitrogen is cheaper than water, and the superconductor doesn't produce any heat.
People are also looking at using this kind of wire in high power electric motors and transformers for the same reason -- not efficiency, but size and cost.
OK, maybe this is covered in other material, but it wasn't in the article. What happens if the cable breaks? I realize that once the liquid nitrogen gets out of the pipe, it will evaporate pretty quickly. But it's still a hazard, over and above the electrical current.
-Todd
---
"The details of my life are quite inconsequential..."
They do if they work for NASA :0
Actually, this isn't right. The general scheme is to use an earth return to the power plant. Even if there is a conductor running as a return it shouldn't be carrying any current. You can demonstrate how this works pretty easily with a cheap 2 prong extension cord and a lightbulb.
- Cut the extension cord so that you have a length of cord attached to the end that plugs into the wall. You may discard the end which you'd plug lamps into.
- Cut the wider prong off of the plug end.
- Remove the side of the cord associated with the removed prong.
- Strip a small amount of the insulation from the end of the remaining wire.
- solder this to the threaded part of a lightbulb.
- Plug your modified plug into the wall and touch the base of the bulb to a faucet or other grounded metal object.
- If the bulb doesn't light, turn the plug over and try again.
- BE VERY CAREFUL NOT TO TOUCH THE SHINY METAL PARTS WHEN PLUGGED IN. IT WILL HURT A LOT.
This works because one line in your home sockets is always held at ground potential while the other one varies between -120 and +120 volts (If you live in the US or another place with a 120V household supply). This page does a little bit of explaining on how all of this works. You might also want to check out this article at the always informative howstuffworks.com site.________________________
I don't want free as in beer. I just want free beer.
It's lossy enough that California can't easily buy power from other states or countries which have the power. Ontario is going to bring back Bruce B nuclear power plant (more than enough to power a few small cities). Not because we need it now, but we may in another decade or so. I'm sure British Energy is willing to sell the power being generated to the south. Good luck getting it there though.
Rod Taylor
Liquid N2 is very cheap (a gallon of LN2 is cheaper than a gallon of milk in most places). Also, if you keep it presurized, then you don't have to worry about keeping it cold since it can't expand.
Mark Duell
However, you're wrong about the attraction. If you have a chunk of ferromagnetic material, it will feel a force pulling it toward the area of stronger B field. This happens to be toward the conductor. The gradient isn't as strong near a linear conductor (1/r) as it is near a solenoid (1/r), but it is an attractive force nevertheless.
The superconducting cables are all but certainly set up as coax (DC) or twisted triplets (3-phase AC). The field from these will be mostly self-cancelling due to the balanced currents.
That remark was just too ironic for this US-born and -educated geek to resist quoting.--
Time is Nature's way of keeping everything from happening at once... the bitch.
Maybe you should stick to grammar.
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Time is Nature's way of keeping everything from happening at once... the bitch.
Notice the words "carrying capacity" in what you just quoted? That means they can ramp up the amount of power carried by the lines which risking burning them UP!
120 characters isn't enough to explain it.
Now, now, don't jump down his throat too soon. Current environmentalist dogma is that no new technology should be deployed until it is absolutely proven safe (the "precautionary principle"). Can any of you actually *prove* there are not adverse environmental effects of increased nitrogen levels? Saying, "any idiot can see that there aren't", while true, still isn't absolute *proof*.
We ran this story in February in Future Energies (which in turn we picked up on from Salt Lake Tribune), and we were also excited about the possible power savings. We know that in conventional grid it's around 20%. When carrying the AC current there will be losses by motion of magnetic flux though the superconductor. Can anyone tell us what the losses will be through the superconducting cable?
Phillip.
Property for sale in Nice, France
Ya, thats why its +60% of the air we breath is Nitrogen.
If it was said on slashdot, it MUST be true!
Actually, transmission lines already have very little loss due to the extremely high voltage they operate at. Superconducting cables could reduce loss in distribution systems considerably, but there is still the loss in transformers and low voltage wiring, which is considerable.
The real killer here is the initial cost, although a 57MVA (I think) cable is very impressive, I'd bet it's still 10 times the cost of the aluminium-plastic cables currently used. Another thing against it is that smaller capacity cables are often good - if you have 5 normal cables and one has a fault, you're OK but if you're supplying a large area with one of these babies and it goes, it will take a long time and a lot of money to fix.
And considering the current price of electricity (even in California), I suspect this is not going to be economically justifiable for a long time.
As others have pointed out, LN2 (liquid nitrogen) is very cheap, but that's not the issue. It merely has to be cheaper than doing it the conventional way.
// TODO: fix sig
If the nitrogen is kept at the right pressure, then it doesn't even have to be kept cold.
Well, the whole point of having liquid nitrogen is to keep the supraconductor cold... There's no point in having liquid nitrogen at room temperature.
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Where are you from anyway? I'm assuming it's the US based on the sorry state of education there.
Hey, don't judge us all based on the comments of a few idiots..... oh wait, nevermind.
----
Do you even know anything about perl? -- AC Replying to Tom Christiansen post.
From the American Superconductor site link I wasn't able to determine any details of the actual manufacturing process. It does indicate that the there are "oxide compounds" involved - but..!
I also couldn't find any indication of the life of this. How long until it begins to breakdown, and when it does what compounds will be released into the ground? And what does the manufacturing process put into the atmosphere in the way of by-product gases and other exhaust? If I understand correctly there is a stream of coolant (liquid nitrogen!) inside the pipe bundle - what happens if the pipe breaks? And of course - what are they going to do with all that cable that was ripped out..
Sounds like a neat idea, but not enough info for me to decide if they really thought this through..
Using liquid nitrogen, while expensive, will certainly save money. Our current power grid can lose twenty percent or more power in transit. Keeping a constant flow of liquid nitrogen is pittances compared to the enormous savings of a 25% increase in power distribution. That's a LOT of power. Granted, we won't reap the benefits of this until after much of the United States has better power cabling, but this is just a start. |JH|
It sounds pretty expensive - will the extra efficiency be worth all the money spent on liquid nitrogen? Anybody have any stats about this?
Yes... But this time there's more details. Think of it as "followup", which is sorely lacking in virtually all other "news" media.
Temkin
Of course, if you are a Chem E and you I am wrong, then please enlighten us!!
uh? Are you the grammar nazi or not? Second post with a second gramatical error.
Tsk tsk tsk
~~~Please pass the salt, I hate unsalted MD5s
Heh, if you happen to have a steel plate in your head, better make sure you don't walk over that underground superconducting cable, else your head could get glued to the ground.
That will be funny. Also, imagine all the lose coins that this thingy will collect...
~~~Please pass the salt, I hate unsalted MD5s
Informative? Perhaps. Wrong? You bet!
The gas that escapes is actually hotter than the rest of the liquid, and takes energy away from it. Thus the liquid becomes colder. You have to apply energy to remove the vapor, so overall you lose energy. (Otherwise you would have a perpetuum mobile.)
How can a cable get cold from contact with liquid which is at room temperature? Think about it for a second.
Inductive coupling is not a "loss". If you remove that coil you're not "losing" anything anymore. It's just a way of transferring energy via EM fields. Oh, you thought that the energy actually travel inside the wires? Not so. Go read up on your EM theory.
1. Liquid Nitrogen is cheaper than beer.
2. Because superconductors offer zero resistance, they also do not become hot. The only gain of heat (and need for more liquid nitrogen) come from losses to the air (conduction, radiation).
If it wasn't cheaper, they wouldn't do it.
I'm sorry, I doubt this project will ever pay for itself. for 1500 ft. they would have been far better off using another low loss system, like UHV or something.
Treatment, not tyranny. End the drug war and free our American POWs.
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See my user info for links.
Can you propose some mechanism where the nitrogen gas would "slurp up enough energy to cover it's (sic) latent heat of condensation" that didn't involve what we commonly think of as a temperature differential?
I didn't pay nearly enough attention in my PChem class, but I did pay some attention in the diff. eq., and I don't remember many situations where a cold material would transfer heat to a warm material. Can you elaborate on this?
Slashdot is jumping the shark. I'm just driving the boat.
Ok... so what you're proposing is that they compress the nitrogen (which would heat it), then allow heat to escape (to bring the nitrogen back down to ambient temperature), and then decompress the nitrogen (which would make the decompressed nitrogen extremely cold).
That's a pretty damned good idea. Maybe they could catch this cold nitrogen, and repeat the cycle many, many times, and make it even colder. In fact, perhaps they could cool and catch all the nitrogen this way, and avoid having to deal with highly pressurized nitrogen. Then, it would all be cold, but they would be able to keep it at a much lower temperature, and much less of it would escape as a gas and waste energy. Then only stuff above room temperature would be the stuff in the isolated compressor!
Wow! I should get a patent on this "refridgeration" method! I'll make a billion dollars!
Slashdot is jumping the shark. I'm just driving the boat.
" this summer Detroit Edison will lay 1200 feet of superconducting power cable near their Frisbie "
Uhmmm, I dunno about you, but that's gonna be one hell of a frisbie to throw.
--- Metamoderating abusive downgraders since my 300th post.
In my opinion, any one worrying about the environmental impact of releasing nitrogen gas should be shot in the head immediately.
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Yes, I'm sure the city of Detroit hasn't done any estimation or analysis, and has no idea how much this will actually cost, unlike some random slashdot poster who must clearly be some kind of electrical infrastructure idiot savant.
Of course you must be right, what was I thinking. I mean, you have so much support to go a long with your opinion. Christ, how the hell did a fucking idiot like you get +2?
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"and dear god does this website suck now." -- CmdrTaco
The magnetic fields around an electrical conductor actually rotate around the core, rather then attract it; counterclockwise, if you were facing the current flow. A coil will produce a nice directed magnetic flow, though.
Also, coins do not contain ferromagnetic elements.
Where are you from anyway? I'm assuming it's the US based on the sorry state of education there.
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"and dear god does this website suck now." -- CmdrTaco
According to the second law of thermodynamics the amount of energy needed to cool all that wire cannot, according to the law, be less than the energy saved by the reduction in resistance, because that would decrease entropy, which is impossible.
That isn't even remotely True. It wouldn't decrease entropy; it would just bring the rate of entropy creation down to zero (or near zero). Or are you saying everything has an equal amount of efficiency?
God, why are so many people so stupid!
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"and dear god does this website suck now." -- CmdrTaco
Nitrogen gas is not a hazard unless it can displace all of the oxygen in the aria.
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But they recover this heat, and use it to power a steam turbine at the liquid nitrogen producing plant, which means that it is far more efficent than a regular air conditioner, where all the heat is pumped away into the air. I seem to remember a figure of 75% of the energy used in the compression is recoverd from the heat.
This repetition is getting old...
You'd better think a little more slowly next time.
The pipes that carry the nitrogen and wire will be buried, and any escaping liquid would quickly evaporate.
Also, nitrogen isn't flammable. It's the major componant of our atmosphere.
--
Soma: because a gramme is better than a damn.
Of course, the homeless are going to be plenty pissed because they can't tap it for free juice, and they can't rip it out and sell it to the local scrap dealer.
Help save the critically endangered Blue Iguana
Superconductors conduct heat as well as electricity near perfectly.
so the temperature will be evenly distributed
'There is a Light that never goes out.'
I don't understand how they can have the constant flow of liquid nitrogen...won't this send the price of the whole operation up really high? does anyone have any information on how they plan on implementing the liquid nitrogen?
:)
I think it is pretty cool that superconducting is actually gonna be used for something bigger than laboratory tests.
The anti-salmon
I can see the newscast now Two men frozen to death while digging in their back yards, power to the city is out until the liquid nitrogen pipe can be fixed
I love the concept of superconductors, but I kind of wonder about the feasability of mag-lev and power lines and the like without high Tc Superconductors.
Ok, people, look at your refridgirator, air conditioner, or something please. How do they work? The "coolant" is cooled by being highly presurized (squeezing heat out) and then quickly depresurized, causing it to absorb a great deal of heat. Any student of thermodynamics would be able to tell you that. So, what they will do with the liquid nitrogen is exactly what they do in your air conditioner, except capable of cooling to levels which the freon or amonia (some ac's) would freeze solid. Why do you think this liquid nitrogen will ever exist at room temperature after it is initially cooled. Refrigerant/ac systems use internally cycled refrigerant, which always stays cold. Better performing AC's use a method observed in fish's gills increase O2 intake, running un-oxygenated and oxygenated blood in oposite directions through the gills. The same could be done with liquid nitrogen, running it both ways through a bi-layered pipe, or a pipe composed of woven tubes.
Spring is here. Don't believe me, look outside!
While supercooling my overclocked toaster?
"It'll flash fry a buffalo in 30 seconds..."
"Aww, but I want it now!"
Tom.
Oh arse
"If at first you don't succeed, lower your standards."
Perhaps the nice folks at DTE should work on actually providing reliable energy. Weeklong power outages are routine after any kind of storm. And they have the absolute chutzva to claim that burying cable wouldn't reduce outages, only make them more expensive to fix. So tell me, how does hail, wind, rain, ice, or tornadoes effect underground cables?
-- I Am Not A Terrorist.
what happens if it's cut? anyone have any idea? just curious
"A door is what a dog is perpetually the wrong side of" - Ogden Nask
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
Consruvatation of energy has nothing to do with the energy to obtain or maintain superconducting. That is why room temp superconductors would be so good.
So I wonder (not having read the article, flame if you must) how often these 14,000 residents will have to deal with reduced power due to refrigerated nitrogen problems. What fraction of full power do you figure the unrefrigerated cables can carry? Complicated feats of engineering often precede complicated problems.
To everyone who has responded that liquid nitrogen is harmless, I believe the question was more about what if something sparked and ignited this stuff? I do know from my limited experience with using it for shipping (don't ask) that it is generally pretty safe stuff, but still... Anyone have a good answer to this?
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If the insulation is sufficient, then only a very small amount of nitrogen would be necessary for the entire system because the superconductors themselves will not be contributing any I^2*R heating. Except for a larger amount of nitrogen consumed during the initial cooling-down process, the nitrogen cost during steady-state operation is directly proportional to the heat energy getting through your insulation. The insulation's heat conductivity can be made arbitrarily close to zero (although the better it gets, the more expensive it is). I would imagine that to reduce nitrogen costs they would use a structure analogous to a Dewar flask along the entire length of the line. If they did, then they would only need a slow trickle of liquid nitrogen along the entire length of the line.
When you compress nitrogen, it gives off heat.
When you let it expand, it sucks in heat, giving off cold, at a certain equilibrium temperature if you mix the liquid and gas phases adequately.
But it takes power to compress nitrogen; i.e., power roughly equal to the heat it gives off.
The net effect is, you might as well build a big air-conditioner and use that to cool the pipes, because even if you put canisters and a ride in a truck in the middle, that's all you're getting.
You're heating up Flint to cool down a tube in Detroit.
The question is, how much power is needed to compress air, remove the oxygen (you don't want the cable blowing up if it sparks), and transport the product to the head end of this cable? Is it less than the power lost in an ordinary cable? You're kidding.
--Blair
With superconductors allowing small, powerful, efficient electric motors... I would bet on electric cars taking over all else in my lifetime.
Heck, maybe these new motors will let people drive their 2050 Ford Monster-SUV with a clear conscious.
I posted and all I got was this stupid sig
Ok, so you have liquid nitrogen in a pipe. You have to expend energy to make gaseous nitrogen (read: air) into LIQUID nitrogen. In fact, it takes a lot of energy, because it has to be compressed, and cooled at the same time. There's your cooling oil, or some such. Also, you burn fossil fuels or whatever. But, you say, you take energy out to make it into a liquid. Again, as it is compressed and heats up,. you bleed this heat/energy by running another liquid on the outside of the reaction chamber. The hot nitrogen gives its energy to the relatively cool fluid, whatever that may be. That energy is usually not recovered. Then, you have to pipe the nitrogen around. Usually this is done with insulated pipes so the nitrogen doesn't get hot in transit. But, of course, if you did that here the superconductor would not be chilled efficiently. Ok, so you have liquid nitrogen in thin metal pipes that are good heat conductors. Now, most metals I know of become REALLY brittle at low temperature. That means that any kind of geological stress, like a minor earthquake or a heavy truck passing by on the road overhead, could possible shatter or just crack the pipe, allowing a leak to develop. If the pressure on that leak built up it could possibly explode, although with a nonreactive material like nitrogen this is not that likely. And anyway, I'm sure they're only doing this because they happened to have a need for N2 nearby and decided to piggyback this superconducting thing onto it. We'll see in the next few years if this whole thing was really worth it.
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Take a physics class out of petty cash and try again.
Thermodynamics only requires that energy in exceed energy out. While it does take more energy to make the liquid nitrogen than the LN will take out of the cable in the form of heat there is no one-to-one relationship between the power taken to do the N to LN conversion and the energy transmitted by the LN cooled conductor. (There *is* a relationship but it is the intersection graph of several curves.)
Since there is a big bucket of energetic electrons being poored into the system at one end "simple" applications of Thermodynamics do not apply.
Complex, system-wide annalysis only requires that the energy cost of manufacturing the LN be less than the total energy "gain" of the power *not* lost in carrying the electrons through the cooled material.
Consider (metaphorically and super over-simplifiedly 8-) that as energetic electrons are pushed through a material they must "leap" from molicule to molicule. Those molicules are moving around and represent hard-to-hit targets. When you cool the materials you line up the molicules and pack them closer together making that jump easier. The molicules themselves are also more still so the little arcs of the electrons as they pass through them are smoother and so less of the energetic state of the electron is burned up maintaining orbit. OF course the leaping and orbiting itself applies forces to the atoms and "wants" to move the molicules, which is why the passing current makes heat.
Your initial question is more about the heat-engine principles of the state change of the Nitrogen. Were the Nitrogen to be used as the energy transmission device (like water in a nuclear power plant), like if the source energy was used to make the LN and then a turbine was used at the receiving end, spun by the expanding Nitrogen gas, you would end up with a serious loss to Thermodynamics that made the process unworkable.
Ok that was a little off... Consider the cost to manufacture a rubber ducky. Lots of oil and energy. Now consider shipping a lot of rubber duckies across town. If you were to put postage on each duckie and mail it you would loose a lot of duckies and piss off a lot of postal workers. There is a considerable cost to putting the duckies in boxes, the boxes on paleets, the palletts on trucks, and driving those trucks across town. That cost of orderly shiping is significant but it is still far lower than individually mailing them. The bigger the palletts, the bigger the trucks, and the tigher you can pack the duckies into each box, the cheaper per-duckie cost of shipping. You also lose fewer duckes because the individual postal workers wont be ditching the individual duckies and only a large-scale thief will take a pallet of the things. What normal/honest warehouse worker needs a whole pallet of bathroom toys? This model happens all the time in every form of industry, it's called "the economy of scale".
The duckies are electrons and the shipping infrastructure is the wire. Cooling the superconductor is basically bribing the union reps not to strike. 8-)
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I wonder how this will affect the Gauss tank the army was working on . Has anyone heard about that lately??
I know nothing...It is Ok because I am from Barcelona!
You're effectively doing the same thing. By heating the water the vapor pressure of the water overcomes the pressure that the air is putting on the water and the water boils. A vacuum removes the air pressure so that the vapor pressure of the water is higher and it boils. I'm sure you already knew that though; from high school.
I'm not a chemist, rather a former high school chemistry student. Somewhere back in the confines of my limited memory I find something about curves and temperature and pressure. I.E. you can boil water at room temperature if you create a vacuum or something. Is the idea to keep the pressure in the pipe high enough so the Nitrogen doesn't convert to gas? Is that an issue? They're referring to -380 degrees farenheit as a high temperature. Wow. Anyway the potential here sounds absolutely incredible. This is really cool.
:)
Peace, and stay cool! hehe
My Karma was at 49, then they switched to words. All that work for nothing!
After looking at the pictures of the Refrigeration Building, I really have to wonder why they need to refrigerate anything. It looks damn cold as it is!
As far as pipe breakage goes, I think that nitrogen is going to stay a liquid with those temperatures.
Superconducting cables are great in a protected area. The amount of energy carried by those cables will be such that it can really blow up better half of the city. Because you can not see electricity does not mean it is not there. This country need Electrical Engineers ... why
1. 110V, 60Hz Distribution system. Eats more copper and generators got to run faster.
2. Power outlets without any switch ! I can't imagine that. If you want to see the the real power plugs, check what Brits did - the got more senses in that are at least.
3. Power cables without ground--another sin, all two pin cables must be banned.
4. Power shortage in CA ??!! Talk about bad planning and middle management/politicians running the infrastructure.
But, who am I to say, everybody is busy making money in the DOT-COM ... no real engineers needed anymore just sit down and code and have some stupid guys keep the cities running.