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

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: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 )