Electric Energy Storage at Superconducting Temperatures?

[Aero2]

Is it Theoretically possible to build a superconducting motor/generator/energy storage device all at superconducting temperatures? The device needs to operate in vacuum, accelerate and decelerate with only field energies exiting the vacuum chamber.
I don't have much faith in batteries at 4^oK temperature but perhaps ultracapacitors would work to store the regenerated energy.

 

[MATLABdude]

These guys claim to be able to do most of those individually (American Superconductor):
http://www.amsc.com/products/motorsgenerators/index.html [Broken]

I don't think you'd need every part of the system to be super cooled, as long as you could pass your current out of the cryogenic parts. You could have high efficiency superconducting generators charging low(er) efficiency batteries at room temperature, and those batteries could then be used to power super conducting high efficiency motors.

 

[Aero2]

Thanks, but you see, the constraint is that only field energies exit the vacuum chamber. No power cables, nothing but minimal plumbing to keep things cold. I forgot to mention that the complete vacuum chamber is held at superconducting temperatures. It is. Including any control electronics.

 

[Bob S]

I think the preferred superconducting energy storage device is a superconducting inductance; E = (1/2) L I². It has no moving parts. Motors and generators are mechanical devices for converting electrical energy to and from mechanical energy.

see
http://www.accel.de/pages/2_mj_superconducting_magnetic_energy_storage_smes.html [Broken]
http://en.wikipedia.org/wiki/Superconducting_magnetic_energy_storage

 

[Aero2]

Thanks Bob S., but wouldn't that cause a relatively large magnetic field to exit the vacuum chamber? I'm concerned that such a field would interfere with my purpose as well as mask my signals.

 

[MATLABdude]

Maybe we're dancing around the issue here; Aero2 what is it you seek to accomplish? We may be able to better help you if you attach some more detail (e.g. the motors and generators I posted are big--and so probably would any others--and would not fit in anything other than a large web sputtering machine or purpose built large vacuum room).

BTW, an incidental property of superconducting superconductors is the Meisner effect; they exclude magnetic waves, and anything on the inside of a superconducting shell would probably be protected from any external EMF. Or so I seem to recall from my condensed matter class however many years ago it was.

EDIT: Or in space, I suppose.

 

[Bob S]

Thanks Bob S., but wouldn't that cause a relatively large magnetic field to exit the vacuum chamber? I'm concerned that such a field would interfere with my purpose as well as mask my signals.

The big MRI machines hospitals use are iron-free and are running at about 1.5 Tesla (15,000 Gauss), and they do have some external field, but it is manageable. I'll bet those machines have a lot of stored magnetic energy. 1 cubic meter of air at 1 Tesla is 397,887 Joules = 110 watt-hours. Is that enough? How much energy do you need to store, and why?

 

[Aero2]

I've been reluctant to introduce the theory motivating my question because I fear readers will get hung up on the question of the validity of the theory. My question is motivated by a desire to estimate how much energy the device will consume each day whether it operates as the theory hopes, or simply sits and spins. Of course I have assumed a design to minimize energy consumption that may or may not be optimal.
The device is outlined starting on page 14 of the paper linked here:
http://www.hpcc-space.com/publications/documents/AIAA5595JCP2007DarkAbbreviated.pdf" [Broken]
The first 14 pages are justification and background, the device is outlined at the end of the paper. If an application is needed, then I am thinking of a fixed wing aircraft application.

 

[Bob S]

BTW, an incidental property of superconducting superconductors is the Meisner effect; they exclude magnetic waves, and anything on the inside of a superconducting shell would probably be protected from any external EMF. Or so I seem to recall from my condensed matter class however many years ago it was.

EDIT: Or in space, I suppose.

I worked on a series of large superconducting dipole magnets for the Fermilab Tevatron. At room temperature, the inductance was about 49 mH (millihenrys) (measured with a few milliamps of current), but as soon as they cooled below about 9 kelvin, the inductance dropped to about 45 mH. The difference is due to the Meisner effect excluding the B field from the coil itself. But at high current (say over 1000 amps), the field fully penetrates the superconductor. None of this had any effect on the roughly 4 Tesla of peak field in the aperture.

 

[Bob S]

Suppose we had a superconducting coil, 1 meter diameter and 2 meters long, that could produce a field of about 1 Tesla inside the coil. Very roughly this represents 1.5 cubic meters of 1 tesla field, or 1.2 megajoules joules of stored energy. The H field required is about 800,000 amp-turns per meter. Now we double the size of the coil, thus increasing the volume of stored energy by a factor of eight, to about 10 megajoules. It still requires only 800,000 amp turns per meter to produce 1 tesla, but the length of the superconducting cable increases by a factor of four (twice the diameter and twice the length). So bigger is better. But the forces on the coil (Lorentz forces) have to be evaluated.

For comparison, the CMS (compact muon solenoid) build for the CERN LHC (large Hadron Collider) experiment is 5.9 meters diameter, 13 meters long, runs at 4 tesla, and stores 2.6 gigajoules of energy.