milo@ndmath.UUCP (Greg Corson) (05/23/87)
A simple question for all you superconductivity experts out there. Given the
current superconductors available out there:
How much energy could you store in a superconductive device roughly the
size of a Lantern Battery? (ie: how many amp/hours or KWatt hours)
Greg Corson
{pur-ee,seismo}!iuvax!ndmath!milomwtilden@orchid.UUCP (05/25/87)
In article <226@ndmath.UUCP> milo@ndmath.UUCP (Greg Corson) writes: >How much energy could you store in a superconductive device roughly the >size of a Lantern Battery? (ie: how many amp/hours or KWatt hours) > Hmmmm. Of course the initial question would be just what sort of energy storing devices would become super efficient under superconductor technology. Let's assume for the moment that we have the following to work with: - ambient temperature (or better) SC wire with copper type flexibility capable of carrying the maxi-megaampheres of sci-fi dreams. - An ideal ferrite-core substance to allow for concentrated, directed magnetic core windings. This should do much to reduce the size of our storage device so that concentrated magnetic fields can exist in an atmostphere without ionizing the gas and loosing energy. - Finally, something just as difficult to conceive, a perfect insulator of infinite thinness so that coils can be tightly compact and capacitors have a perfect dialectric seperator. With these assumptions a device immediately comes to mind: a Tank Oscillator. This circuit is a classic in electronic theory. It is composed of hooking a capacitor and a coil in parallel. Charge in the capacitor discharges into the coil producing a magnetic field. When the charge is depleted the current flow stops and the magnetic field collapses back onto the coil producing a back electro-motive force (EMF) which charges the capacitor and the cycle repeats. The current flow is a perfect sinusoidal voltage/current curve. Inherant losses in the coil efficiency and the connecting wire usually slow this process to a stop. A device of this type made with superconductors would be both useful, small and explosive. Properly designed it would be the perfect AC battery. Plug it into the wall (through a resistor so you don't blow every fuse in the house) and it would charge to the optimal electron density possible ( Anybody got any figures for this? how many electorns can be comfortably stuffed into a battery-sized volume before saturation occurs?). I'm guessing that such a battery would be capable of delivering a 1 amp @ 120 VAC for about 10 minutes, making it around .72 Kwatt/hours. Of course there are some major problems to be considered. The shelf life of such a device would be in severe question not to mention internal voltage stability. And if the battery was damaged when it contained a full charge, I think there would be a lot of scorched earth in the immediate vicinity. Anyway, it's worth thinking about. So the question is, what other devices could support such a charge reliably and secondly, does anybody have any information on how close such a device is to reality? I know that the current hit-and-miss work going on with ceramic superconductors has yet to get even a proper defining theory to explain the effect, and that current densities have yet to exceed the microamp range. So how about it? Let's get some talk going. -- Mark Tilden: _-_-_-__--__--_ /(glitch!) M.F.C.F Hardware Design Lab. -_-___ | \ /\/ Un. of Waterloo. Canada, N2L-3G1 |__-_-_-| \/ work: (519)-885-1211 ext.2457, "MY OPINIONS, YOU HEAR!? MINE! MINE! MINE! MINE! MINE! AH HAHAHAHAHAHAHAHAHA!!"
cmcmanis%pepper@Sun.COM (Chuck McManis) (05/26/87)
One of the things that was not stated in all the hoopla about high
temperature superconducters was that the current density of the
devices is relatively small. The number I hear was something on the
order of 10 to 15 mA. Which is not all that usefull in generating
huge magnetic fields. The current is limited by a lack of free
electrons in the ceramic material. Any attempt to increace the
current causes some of the 'non-free' electrons to get involved and
the material heats up and stops super conducting. The paper in
Sunnyvale had an article on one person seeing super conducting
effects at dry ice temperatures although they couldn't isolate the
the material and reproduce it.
--Chuck McManis
uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.don@gitpyr.UUCP (05/26/87)
In article <19635@sun.uucp> cmcmanis@sun.UUCP (Chuck McManis) writes: >One of the things that was not stated in all the hoopla about high >temperature superconducters was that the current density of the >devices is relatively small. The number I hear was something on the >order of 10 to 15 mA. Which is not all that usefull in generating >huge magnetic fields. A recent article in "The New York Times" claimed that IBM has recently made breakthroughs in the new oxide-type superconductors yielding huge current densities. I can't remember the exact figure, but I think it was in the hundereds of thousands of amps. The article commented that superconductors with small current densities weren't extremely useful and that the IBM development was a major breakthrough. In fact, I've been kind of surprised at all the attention that superconductor research has been getting in the "Times". There have been at least 5 front-page articles about superconductors in the past 3 months. The most recent article (last Tuesday, I think) claimed that new materials superconduct at dry ice temperatures and that these same materials exhibit small amounts of superconductivity at room temperature! -- D.L. Deal, Office of Computing Services, Georgia Tech, Atlanta GA, 30332-0275 Phone: (404) 894-4660 ARPA: don@pyr.ocs.gatech.edu BITNET: cc100dd@gitvm1 uucp: ...!{akgua,allegra,amd,hplabs,ihnp4,masscomp,ut-ngp}!gatech!gitpyr!don
henry@utzoo.UUCP (Henry Spencer) (05/26/87)
> With these assumptions a device immediately comes to mind: a > Tank Oscillator. Uh, don't forget that superconductors are not loss-free for AC, as I understand it. -- "The average nutritional value Henry Spencer @ U of Toronto Zoology of promises is roughly zero." {allegra,ihnp4,decvax,pyramid}!utzoo!henry
agn@unh.cs.cmu.edu (Andreas Nowatzyk) (05/26/87)
The low current density of the new materials (order of 1000 A/cm^2)
is already history. Samples of the new material that were created by
vacum deposition techniques showed current densities arround
10^5 A/cm^2 at 77K. This is similar/better than the values for conventional
superconductors. In addition, critical current densities of up to
5*10^6 A/cm^2 were reported for the new material when cooled to 4K.
A superconducting energy storage device is simply a coil with a
superconducting switch. The stored energy is 0.5*I^2*L, were L is the
inductivity of the coil. Using ferromagnetic materials for the coil
is useless because their permeability decreases to 1 at high magnetic
fields. The real problem is to prevent the coil from destintegration due
to the high mechanical forces on the current carrying wire.
The inductivity of a cylindrical air coil is roughly
L = N^2*r^2/(9r+10l) *10^-6 Henry (l,r are in inches here)
You see that the stored energy for a fixed size coil does not depend on N
(the number of turns). Assuming a D-cell sized coil (50% conductor, rest
mechanical support and current switch): l=2", r=0.5", N=1 => L=10nH
This coil uses about 5cm^2 to carry the current => I=500KA
Total eneregy storage would be 1250 Ws. A normal NiCd rechargeable battery
of the same size has roughly 18000 Ws!
On a larger scale, things look better for SC energy storage but the large
magnetic stray field might be unacceptable.
-- Andreasjeff@gatech.UUCP (05/29/87)
I had wondered what would happen to a superconducting device that was
carrying, ... say 10000 amps at a few volts and something went wrong
with the coolant. A previous posting mentioned something about some scorched
earth and they weren't talking about anything close to 100000 watts.
If they take the temperature all the way up to room temperature, these
devices have the potential to fail in a truly catastrophic way.
--
Jeff Lee
CSNet: Jeff @ GATech ARPA: Jeff%GATech.CSNet @ CSNet-Relay.ARPA
uucp: ...!{akgua,allegra,hplabs,ihnp4,linus,seismo,ulysses}!gatech!jeffphil@amdcad.UUCP (05/29/87)
In article <15644@gatech.gatech.edu> jeff@gatech.UUCP (Jeff Lee) writes:
<I had wondered what would happen to a superconducting device that was
<carrying, ... say 10000 amps at a few volts and something went wrong
<with the coolant. A previous posting mentioned something about some scorched
<earth and they weren't talking about anything close to 100000 watts.
<If they take the temperature all the way up to room temperature, these
<devices have the potential to fail in a truly catastrophic way.
Of course the military will be VERY interested in such applications.
--
Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or amdcad!phil@decwrl.dec.comhenkp@nikhefk.UUCP (Henk Peek) (05/29/87)
In article <15644@gatech.gatech.edu> jeff@gatech.UUCP (Jeff Lee) writes:
->I had wondered what would happen to a superconducting device that was
->carrying, ... say 10000 amps at a few volts and something went wrong
->with the coolant. A previous posting mentioned something about some scorched
->earth and they weren't talking about anything close to 100000 watts.
->If they take the temperature all the way up to room temperature, these
->devices have the potential to fail in a truly catastrophic way.
Superconducting coils are made out of very thin (100 micro meter)
superconducting wires. Those superconducting wires are interdented
in a Cu wire. When it goes out of superconducting the current pass
through the Cu. The energy must be very fast (~1 sec) removed.
Bij connecting resistors to the coil, the most of the energie is
disipated in the resistors. During such event the superconducting
wire going very fast to room temperature.
henk peek ..!seismo!mcvax!nikhefk!henkpblarson@castor.usc.edu (Bob Larson) (05/29/87)
In article <15644@gatech.gatech.edu> jeff@gatech.UUCP (Jeff Lee) writes: >I had wondered what would happen to a superconducting device that was >carrying, ... say 10000 amps at a few volts and something went wrong >with the coolant. What happens when you replace a perfect conductor with a resistor? Probably nothing much exciting. (There is NO voltage across a superconductor.) Any energy storage in a superconductor is in the surrounding magnetic field, which for power transmission would probably be minimised as much as practical. -- Bob Larson Arpa: Blarson@Usc-Ecl.Arpa Uucp: (several backbone sites)!sdcrdcf!usc-oberon!castor.usc.edu!blarson seismo!cit-vax!usc-oberon!castor.usc.edu!blarson
henry@utzoo.UUCP (Henry Spencer) (05/31/87)
> I had wondered what would happen to a superconducting device that was > carrying, ... say 10000 amps at a few volts and something went wrong > with the coolant... Current superconducting magnets, as I recall, tend to imbed the s.c. wire in something like copper precisely for this reason. The copper doesn't have to carry the full current for any length of time, it just has to be able to dissipate the stored energy without melting. -- "There is only one spacefaring Henry Spencer @ U of Toronto Zoology nation on Earth today, comrade." {allegra,ihnp4,decvax,pyramid}!utzoo!henry