What would happen if an energy storage device failed?

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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mdeminico
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What would happen if an energy storage device failed?

Postby mdeminico » Wed Nov 02, 2011 4:42 pm

So, semi-hypothetical question here...

Neglecting farads and such at the moment to (I think) simplify things... Let's say you have a capacitor that is capable of storing essentially the equivalent of 10 MJ of energy. That's about 2.5 kilos of TNT equivalent energy.

If that capacitor suddenly fails catastrophically, what happens? Is the energy equivalent of 2.5 kilos of TNT suddenly released, causing a massive explosion?

Same story for 100MJ, etc...?

Is there any way to prevent this massive explosion once the release is imminent?

Skipjack
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Postby Skipjack » Wed Nov 02, 2011 4:48 pm

If that capacitor suddenly fails catastrophically, what happens? Is the energy equivalent of 2.5 kilos of TNT suddenly released, causing a massive explosion?

I have seen speculation on this board that it would and would be really dangerous. I do wonder though whether it is possible to have some sort of savety mechanism. E.g. split things up into multiple smaller capacitors that can not all be discharged at once because they are physically separated and on separate circuits, etc.
I am not an engineer, but I am pretty sure that you could think up a solution.

mdeminico
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Postby mdeminico » Wed Nov 02, 2011 6:14 pm

Dangit, why did I post this in news... sorry guys, I meant to put it in General, can someone move it?

mvanwink5
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Postby mvanwink5 » Wed Nov 02, 2011 6:16 pm

I have seen a metal ruler fall out of a person's pocket onto battery terminals. The battery literally blew up (may have been hydrogen gas igniting though, we did not retest). Internal resistance in the case of the battery would be the limiter. When busbars short, devastating explosions are the norm with the copper busbars vaporizing. People have died in such explosions. I would fully expect an unfused capacitor would do the same. In fact, small capacitors on circuit boards that fail have been know to make a nice pop.
Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

ladajo
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Postby ladajo » Wed Nov 02, 2011 7:23 pm

Yes, capacitors can and do suffer catastrophic failures. They will split/rupture and "explode". This has been discussed before here, and in fact, if you poke around you may find photos of the old EMC2 lab with water tubs for caps.
I have blown large caps, large SCRs, large IGBTs, and vaporized some fairly heavy bus bars in my past. Good fun, but, it does give you a measure of respect and safety conciousness in the designs and initial power sequences. When you are messing with kit hooked up to 4160, 12470 or 25KV feeds, you quickly realize that there is a whole lot of nut behind it to make nice plasma balls in free air. After about two or so, "I didn't see that comings" you learn to permanently adapt and adjust your methodologies. Failure to do so tends to lead to terminally short and spectacular "careers".

mdeminico
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Postby mdeminico » Wed Nov 02, 2011 8:23 pm

So it would probably be unwise for ultracapacitors with massive amounts of energy stored in them to be integrated into a transportation vehicle (car), in the event that an accident or some other catastrophic event happened, it would be even more catastrophic.

ladajo
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Postby ladajo » Wed Nov 02, 2011 8:37 pm

This has been a question wrestled with for Green vehicles for a while. A buddy of mine at MIT worked on a flywheel storage system targeted for vehilce use, but was eventually thought unviable due to the energy densities involved and the potential results of a catastrophic failure to the vehilce occupants. This same issue has been batted around by the battery crowd. I can tell you with certainty that, Li-ion packs can fail spectacularly and lethally. At the end of the day, the energy required to move a sizeable mass a alrge distance, say 400 miles, remains a large number. To safely stuff that into a can or box and draw on it in a repsonsible manner is the challenge, and one of the reasons that we have stuck with petro based systems. We have good experience engineering machines with liquid tanks that more or less do not pop instantly during normal operations and use. Now if you go outside the box, yes you surely can make them go pop. And occasionaly, a bad design surfaces, ala Ford Pinto. but the are fixed quickly with minimal hoo-haa.

Skipjack
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Postby Skipjack » Wed Nov 02, 2011 11:49 pm

Of course a gas tank can explode just as violently and catastrophically and I am sure that a battery can be built in a way to not cause a big huge explosion.
That said, it is true that you need to pay extra attention in the design of these systems. The thing with capacitors though is that you could in theory have a small one and just charge it every 50 miles within just a few seconds... Not a problem in a densly populated Europe. Could be more of an issue in the US.

ladajo
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Postby ladajo » Thu Nov 03, 2011 12:07 am

I am still waiting for the first Hybrid mini-volcano, where the battery pack cooks off. More than likely it will be in a highway wreck. Existing conventional car batteries are small enough, and designed such that if they get ka-smooshed the typically bleed out and don't cook off a fire. however, that said, occasionally, they do get dead shorted and start a fire. Imagine a Prius pack getting dead shorted in a crunched wreck. Could be cool to see, as long as you are not in it.

D Tibbets
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Postby D Tibbets » Thu Nov 03, 2011 1:02 am

High density energy storage can and do fail spectacurly. As noted above. Superconducting magnets are an example of this . The large powerful super conducting magnets in the ITER tokamac could make an impressive explosion if the supetconducter quenches. Apparently there are safty measures - very quick switching through robust busses into a large heat sink (like a lake). This has been discussed on this board before. A Polywell with as strong but smaller superconducting magnets is to a degree less forbidding. I wonder if a quench in this case might do ~ the same amount of damage as did the failure of a magnet in the LHC a couple of years ago.

Lithium ion batteries can be a problem as illustrated by many notebook computer fires. A large lithium ion battery pack could be more impressive when it fails. Tesla Motors handles this by placing a few batteries in a resistant container, and then hooking a bunch of these sub assemblies together to run their roadster.

Dan Tibbets
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ladajo
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Postby ladajo » Thu Nov 03, 2011 1:26 am

If you want to see a really cool Li-ion pack failure, make a hole in the case and toss one off a dock into salt water. Stepping back may be prudent depending on size of the pack and your ability to toss.

DeltaV
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Postby DeltaV » Thu Nov 03, 2011 4:12 am


MSimon
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Postby MSimon » Thu Nov 03, 2011 4:40 am

Skipjack wrote:
If that capacitor suddenly fails catastrophically, what happens? Is the energy equivalent of 2.5 kilos of TNT suddenly released, causing a massive explosion?

I have seen speculation on this board that it would and would be really dangerous. I do wonder though whether it is possible to have some sort of savety mechanism. E.g. split things up into multiple smaller capacitors that can not all be discharged at once because they are physically separated and on separate circuits, etc.
I am not an engineer, but I am pretty sure that you could think up a solution.


The problem is that to do such a thing the volume (and thus costs) go up.
Engineering is the art of making what you want from what you can get at a profit.

Joseph Chikva
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Re: What would happen if an energy storage device failed?

Postby Joseph Chikva » Thu Nov 03, 2011 7:12 am

mdeminico wrote:If that capacitor suddenly fails catastrophically, what happens? Is the energy equivalent of 2.5 kilos of TNT suddenly released, causing a massive explosion?

Same story for 100MJ, etc...?

Nothing dangerous if capacitor bank is designed correctly. From time to time every capacitor will breakdowned as every has limited lifetime (charge-discharge cycle). Depends on ration between working and allowed voltage, operating temperature, discharge current, etc.
But large capacitor bank should be divided on separate segments and after proper grounding you can approach and to change damaged on new. If not grounding residual charge can kill when approaching.

Joseph Chikva
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Postby Joseph Chikva » Thu Nov 03, 2011 7:35 am

D Tibbets wrote:High density energy storage can and do fail spectacurly. As noted above. Superconducting magnets are an example of this . The large powerful super conducting magnets in the ITER tokamac could make an impressive explosion if the supetconducter quenches. Apparently there are safty measures - very quick switching through robust busses into a large heat sink (like a lake). This has been discussed on this board before. A Polywell with as strong but smaller superconducting magnets is to a degree less forbidding. I wonder if a quench in this case might do ~ the same amount of damage as did the failure of a magnet in the LHC a couple of years ago.

I do not know what here has been discussed but fast switching off of large inductance would damage some components of circuit (may be melt down because of self-induction). That's all.

At LHC as I know (may be not correctly) as result of failure very powerful beam hit wall and burnt out the hole.


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