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.
How long is it? (Score:3, Informative)
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.
Re:Cost? (Score:1, Informative)
Who says you have to make motors out of copper?
Alluminum is a great conductor, and we already make engine blocks out it. No shortage there.
Re:OK - 150x capacity, BUT: (Score:3, Informative)
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.
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.
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:Wow, !vaporware? (Score:2, Informative)
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 course quite important if you are building large electromagnets, as in MRI-scanners.
The reason high-Tc superconductors are used for MRIs is that their higher critical temperature is related to the high critical field allowed at low temperatures.
Aside: the reason that only now superconductors are getting to be used in power applications, such as the one mentioned in TFA, is that it is still very expensive, and that large scale production of quality superconducting material is still hard (it is very brittle).
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:Just the thing we need, 150x power usage (Score:3, Informative)
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: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)
Re:"nuclear reactor scramble"? (Score:3, Informative)
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.
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]
Re:Saving Energy (Score:3, Informative)
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. Neat stuff!
I don't think this is competitive with above ground cables yet; they're enormously cheaper IIRC both to build and maintain (but can't be used everywhere). As such, most of the world's power infrastructure won't change for a while.
Re:Saving Energy (Score:3, Informative)
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.
Re:Forget wires (Score:3, Informative)
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.
Re:Superconductors = almost no heat (Score:3, Informative)
At least with this stuff you can use liquid nitrogen instead of liquid helium.
Re:Superconductors = almost no heat (Score:3, Informative)
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:reliability ? (Score:3, Informative)
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
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 failure rate and the failure rate of the cooling system's power supply in reliability calculations. The power supply, of course, does not run at 138 KV.
Re:Superconductors = almost no heat (Score:2, Informative)
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:Saving Energy (Score:2, Informative)
You're missing the point. The real benefit here isn't that they're 4% more efficient, it's that they use 1/150th of the copper.
Re:reliability ? (Score:1, Informative)
Solar heaters are still very efficient, even if they only "deliver warm water at best". They're very simple, plus you don't need rare materials or lots of energy to make a solar heater. If yours doesn't deliver a high enough temperature on its own in your area, feed the warm water into your regular heating system and save the energy that it would take to get cold water up to that temperature.
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.
Re:Superconductors = almost no heat (Score:3, Informative)
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.
Re:Superconductors = almost no heat (Score:3, Informative)
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."
China has the US beat with over 7KM of DC lines.