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

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:disappointing article...

[tmacc]

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

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: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.