While you describe gasoline as ‘highly volatile’, it is actually very safe, we routinely put 25 pounds of the stuff in ordinary plastic jugs that you can just put anywhere you want. Gasoline burns, but can only burn as fast as the oxygen supply allows, which is pretty limited in an uncontrolled situation. If you spill 20 gallons of gas and light it, it will take quite some time to burn up, and will release that energy over a wide area.
Contrast that with a substance that doesn’t need an outside element to combust, like TNT or nitroglycerine. A small fraction of the energy that 1 gallon of gasoline contains is enough to blow your car to smithereens.
That is my issue with supercaps, they don’t have any inherent limiting factor to the energy release, all the energy is available in a fraction of a second. The same amount of energy that can bring your car up to 100mph (enough energy to spectacularly crush it against a wall) a dozen times will be released all at once if the containment is breached.
But as pointed out I think, it would make using natural gas to generate electricity even more attractive … the point made by Stranger that the source to generate the electricity is fungible … and the fact that a power plant to battery to motive power is much more efficient per unit natural gas well to wheel than CNG is by far. The electricity infrastructure for daily commuters is also already in place. The use for CNG will be for trucks and other vehicles that require the range that a battery cannot easily provide.
There are segments where it makes some sense, but mass use in vehicles probably isn’t one of them. I was told something long ago that can put it in perspective: H2 is not a “fuel” - it’s an energy transmission system. The hydrogen is more a mechanical “battery” than a fuel like gasoline. But yes, it’s got tremendous energy losses from source to wheel and is thus suitable only for a narrow range of specialty purposes.
It’s “very safe” because we have 100 years of established infrastructure and experience with it. In road-going vehicles, I don’t see it as any safer or less safe than any other energy-dense system that can cause a localized fire or explosion.
It’s not like a supercap battery in a Prius XVIII is going to level a city block.
It’s very safe because the energy release is limited by the underlying chemistry. You can put a gallon of gas in an open bucket, throw in a match, and you won’t die in a horrible explosion, despite the fact that the gas has as much energy as 30 pounds of dynamite.
If you have a supercap that has the energy equivalent of 1 gallon of gas, and the containment fails, the energy is going to be released, all at once. It’s not going to spill on the ground and release slowly as oxygen is fed to the reaction, it’s going to go, because nothing is holding it in anymore. It doesn’t have to level a block, it just has to level your car, with you in it.
Okay. As cars explode into fireballs with their occupants inside pretty much every day of the year, I still don’t see a technically “more volatile” energy source being any worse. Yes, it’s a hazard. Yes, accidents happen. No, I don’t think it’s impossible to engineer the overall safety to match what we expect with liquid-fuel cars. No, I don’t think it’s a good net argument against supercaps as high-efficiency vehicle ‘batteries.’
When the national speed limit was raised, a very, very bright co-worker (CalTech, with honors) ranted and swore that vehicle fatalities were going to go up 18%. He was correct in the narrowest possible technical sense, but that it’s a more complex situation than the kinetic energy in vehicles at highway speeds simply didn’t occur to him. He paid for lunch six months later, when (as I predicted) fatalities actually fell a measurable degree.
Allee samee here. That some kinds of batteries and supercaps are more volatile and self-contained explosive sources does not necessarily translate to any higher risk overall.
Cheesesteak, I’m trying to understand your concern; When a capacitor discharges or “quacks” it is all electrical energy which goes to ground, in the case of a mangled car, probably through whatever part of the frame offers the best path. If you don’t have anything to ignite, like 25 gallons of gasoline, you have a flash, a quack and it’s done.
You don’t have batteries catching fire like Li-ion batts on the Dreamliner, releasing fumes or like gasoline. Stranger, as usual, is likely right but supercaps do have their uses; especially in short term release like storing regenerative braking or replacing batteries in present day cars.
We are in the process of replacing some diesel gensets at work and they use 500 farad supercaps in place of the start battery. Zero maintenance, 20 yr life, operates from -40 to 65 C.
And about 0.2% of those resulted in a fatality. My feeling is that a 100 mile capacity supercap is going to go off like a car bomb if the structure fails. That supercap will have the same energy capacity as 50lbs of TNT. It gets cracked by a hard collision, the energy has to go somewhere, and it’s not going to go there in nice orderly fashion.
Perhaps, overall, it could be made safer than what we have today. Me, I’d rather stick with batteries.
Energy doesn’t “go to ground” (or rather, some of it inevitably does, but not in the way you’re thinking). Current does “go to ground”, but that’s not what we’re worried about here. The danger of a breached capacitor isn’t electrocution; it’s explosion. The energy has to go somewhere, and where it goes will be heat. Pile that much heat together in a small space, and things go boom. The only sense in which energy is “going to ground” is in that you’re leaving a crater.
Is this a problem? Absolutely. Do I know how to solve it? No, I’m a physicist, not an engineer. But I’m sure that by the time we have capacitors potent enough for this to be an issue, the engineers will have come up with some way or another to solve it.
We have, however, established that some posters have no sense of humor.
That aside, are you contending that with about 33,000 vehicular accidents a year, with around 3,000 immediate fatalities, that there’s any day of any year that one of those ten fatalities and thousand accidents didn’t involve fire? —and all that in just the US, leaving out countries like India and China where a prevalence of tonka-toy cars on overcrowded and unsafe roads have much higher overall numbers?
Let’s hop back out of Absurdistan and to topic. No, I don’t think any form of vehicle power source or plant under current serious consideration represents any greater net danger than gasoline/IC. Despite any individual characteristics of how each power source might fail. None are going to go up in a block- or city-leveling mushroom cloud, now that we’ve decided not to built 30-foot Impalas with nuclear reactors.
I’m not contending anything of the sort. Don’t put words in my mouth just because your attempt at “humor” didn’t work.
you said something stupid, then boffking blindly linked to something about the number of vehicle fires. Vehicle fires have numerous causes- long term oil leaks on the engine which ignite (not gasoline fed,) electrical (not gasoline fed,) fuel leaks underhood (gasoline fed,) engine/transmission overheating (not gasoline fed,) fuel leak after collision (gasoline fed.) None of those involve “exploding,” gasoline doesn’t explode.
They won’t level a block, but an explosive failure that releases the same energy as is stored in a gallon of gas will make your car look like it was hit with a Hellfire Missile.
As someone who has personally watched a car explode, Michael Bay-style, and seen footage of similar Rapid Vehicle Disassemblies, I’m pretty much done attempting to humor you or play high-school debate.
No compact source of vehicle power is completely safe, including gas. It’s all about risk to value assessment, not physics experiments.