Real World High-Temperature Superconductor Engine

wes33 writes "An amazing technological achievement deploying high-temperature superconductors is reported in Space Daily. American Superconductor Corporation (nice scifi-ish name) has built a 5MW electric ship motor using high-temp. superconductor technology. The Queen Elizabeth's 44 MW engines weigh 400 tons each (and she has two); a single comparable HST motor (36.5 MW) will weigh 75 tons!"

Comments

what about the generators?

[tmacc]

As far as i know, they use diesel generators to provide the power usually. Using HTS in the generator would/could provide a drastic improvement in the effciency, and would be a much more exciting development in my opinion.

disappointing article...

[nusratt]

...says virtually nothing about the actual HTS technology, which seems to be the only really novel aspect of this equipment.

Re:disappointing article...

[tmacc]

http://www.amsuper.com/products/htsWire/ Here is a link that has some good specs on the wire they use.

Re:disappointing article...

[grumpygrodyguy]

AMSC's first generation HTS wire, based on a multi-filamentary composite architecture, is capable of carrying over 140 times the

power of copper wires of the same dimensions.

Umm, not to go overboard here or anything, but isn't this like one of the most significant engineering breakthroughs in the last 100 years or so?

How about a new microprocessor fab process using this material?

More Power?

[the darn]

Since they've made one that's comperable in power but much smaller in size, would it make sense to make one comparable in size and of much greater power as a replacement for use in existing vessels? Or are there other limiting factors in the amount of power that is useable in such circumstances?

Re:More Power?

[tmacc]

For retrofitting, you wouldn't want to put an engine of much greater power in there, it would destroy the other parts. It would be like putting an 800 hp engine in a car designed for an 180hp one.

Re:More Power?

[Timber_Z]

Thats note the point. The point is that is FAR more effient then current technologies. The exact implemention is trival. Every so often technology makes a huge jump in performance that has a major impact on an industray. (Like moving from Hand Saws to Chain Saws for lumber: for example) This looks like it might be one of those times.

Re:More Power?

[Cecil]

Or are there other limiting factors in the amount of power that is useable in such circumstances?

For a boat? Sure, cavitation. Propeller blades can only spin so fast (that is, push a certain amount of fluid) before they begin to create destructive turbulence in the fluid that cripples their pushing power. The same basic problem exists in aviation, which is why propeller-engine planes can only go so fast regardless of how big and numerous the engines and blades are. Jet engines, rockets, or some other form of propulsion are needed to go any faster.

No, more efficiency.

[the_twisted_pair]

It's all about efficiency, and therefore running cost. Optimum cruising speed is set by considerations of wave drag for a given hull - there's a sharp curve, whereby faster cruises become *incredibly* inefficient. Big marine diesels providing this motive effort are far and away the most efficient prime movers on the planet, because economies of scale and the singular nature of the task lends itself very well to such optimisation - which the owners take advantage of.

The bottom line is that every single %age point gained represents a huge saving to the owners in fuel cost. If it can be done with a lighter/more efficient propulsion package, so much the better - that's extra cargo that's free to carry, but the prime incentive is fuel cost - you may not realise we're talking *thousands* of tons for oil bunkers on big ships...

I'm not at all surprised that marine propulsion is the first major application of high-temp superconductors in this regard.

Generators aren't critical... yet.

[Engineer-Poet]

The Navy doesn't like diesels because they're too noisy for vehicles which chase submarines. The alternative is a gas turbine, which spins fast enough that you can make an acceptably small and light alternator without going to extreme materials; only when you need to drive a low-speed propellor do you really need the high-current capabilities of superconductors.

The technical explanation is that you can transfer a lot of power with a small, rapidly-varying magnetic field (like the itty-bitty toroid in your computer's power supply, running at 100 KHz instead of the 60 Hz power line frequency), but to transfer the same amount of power with a slowly-varying field needs a much bigger field, bigger currents and bigger losses. Superconductors get rid of the losses and can sustain bigger fields in a smaller package.

Re:Generators aren't critical... yet.

[Euler]

After reading the arcticle, the reason why these motors can achieve higher density is because the thermal dissapation issues are reduced when you don't have DC losses in your coil windings.

You are right as far as lower freqencies needing more core material. But, I can't see how superconductors would change that equation at all. Even if the superconductor carries more current, the magnetic material has the same basic flux energy storage capacity. Ships tend to use higher frequencies anyway, such as 400Hz, so frequency probably isn't the problem. In a propulsion system, the design engineers are probably allowed to choose any frequency they want. Also, superconductors don't eliminate all loses. Core losses are still going to be an issue unless the motor design is significantly different than anything seen before, or uses superconducting mu-metal.

You can always make a slower, higher torque high-frequency direct-drive sync motor by adding more poles. But you can't make a low-freq motor faster. i.e. top speed for a 2-pole 60Hz sync motor is 3600 RPM.

Also, from what I remember, superconductors tend to lose superconductivity in strong magnetic fields. Hopefully, they have worked around that problem.

what temp?

[klossner]

The article is silent on exactly which temperature this high-temperature superconductor requires. Are we still at liquid-nitrogen temperatures or have we gone higher?

Re:what temp?

[SurG]

The link to their website [amsuper.com], mentioned earlier, has some really nice technical papers. For one type of the wire they use some complicated compound with Tc =110 K. Didn't find Tc for the second type of wire (Y123). I'm pretty sure, however, that even if Tc is higher than 77 K, they still run it on 77 K, since other parameters like Ic should be better than around Tc. And nitrogent is pretty much standart cryoagent anyway. Their critical current for those wires looks pretty impressive (> 100 A )

Re:what temp?

[merlin_jim]

Why does everyone say with superconducting wire in the power grid that the cooling is the hard task?

That's not it, it's raw current carrying capability. Superconductors break down at high currents. Cooling a superconducting wire isn't as hard as you might think.

Superconductors conduct heat as well as electricity. The Newtonian description of the heat of a superconductor is the net average of all the temperature deltas it's exposed to integrated over the area of exposure. A superconducting wire is (in a non-relative universe) always the exact same temperature throughout.

Make the wires thin (don't need thick wires if you're super conducting), they're probably brittle so you'll have to clad it in a fairly rigid material... and just make that material a pretty good insulator. With a thin enough wire you can have practically zero surface area. And your cladding will probably be cheaper than high tension cable. You'll have to bury it because superconductors have a catastrophic failure mode; if a high temperature event happens, the entire wire will stop superconducting immediately, and all that electricity in the wire converts to thermal/kinetic energy, as the electric field damping generates a huge magnetic field and basically turns the entire wire into a railgun pointed radially outwards.

At both ends, have a heatsink of superconductor material embedded in liquid nitrogen. As long as any liquid nitrogen remains, the entire wire will be at the temperature of the liquid nitrogen. The only reason you need a heatsink is to spread out the area of contact so you don't boil the liquid nitrogen so fast that large air bubbles form on the surface of the heatsink.

The more insulation you have the less liquid nitrogen you'll need on an ongoing basis to replenish the system. But compressing liquid nitrogen out of the air is a relatively cheap activity in terms of energy expenditure. Especially if you have superconducting wire to make the compressor out of. No reason not to just submerge it in the liquid nitrogen with the power distribution wires.

Though you might want some of the motors to be a more traditional design... startup on a system like this is a bitch. The wire doesn't go superconducting all at once, there's a travelling wavefront that moves along it, speed dictated by the rate of heat conduction at the interface. In the case of a blackout, you'd have to have traditional compressors with backup generators (or just big power storage caps) in the mix just to get the whole system back online as quickly as possible, otherwise you're stuck waiting for the heat to travel through the system, building up reservoirs of liquid nitrogen and removing progressively more heat as each distribution station comes back online.

Yes, hull shape

[leonbrooks]

are there other limiting factors in the amount of power that is useable in such circumstances?

At a certain velocity dependent upon the shape, the hull changes from slicing through the water more towards trying to push against it, once you cross this knee, you need to add bucketloads of power for a very small improvement (basically, until you get your aquatic beastie to plane).

Modulo propellor cavitation, hull collapse and other stuff which becomes dominant at those power levels, it would be quite a joy to see an ocean liner scudding friskily from wavetop to wavetop.