Comment by trollbridge
10 hours ago
I can - it’s called a bomb. Some of the problems with batteries are heat dissipation (one of those problems that superconductors would mostly solve), fire safety, and end of life disposal. Higher energy density makes it even worse.
A good place to start would be a BMS on individual cells that monitors them for general degradation, unexpected discharge, unexpected temperature changes, and can remove a failing cell from the array.
Gasoline has 10x the energy (MJ/Kg) than TNT, but it's not a "bomb". Being a "bomb" is about energy release rate. A battery is still controlled by its chemistry.
Liquid gasoline does not have anywhere near the energy of TNT, or even a battery for that matter. It contains basically zero releasable energy. It needs oxygen or another oxidizer to react with to actually release any energy. TNT and batteries' energy density calculations include the oxidizer and the oxidizer is in close proximity to the fuel (molecularly so in the case of TNT). If you 10x the "energy content" of gasoline it's still rate limited by access to oxygen. If you 10x the energy density of a battery (the type with the oxidizer contained within the battery, not a fuel cell or metal air battery) you've got 10x the energy ready to be released quickly if oxidizer and fuel mix in unfortunate ways
It's an interesting discussion, because if you assume access to atmospheric oxygen, gasoline is MUCH more energy dense.
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Energy capacity vs. energy release rate, or energy vs. power, tends to follow an inverse relationship, at least within similar domains.
The fuels which afford the highest rates of storage tend to release it more slowly. Chemical explosives typically have about 1/10 the energy storage capacity (by mass) of fuels, as several people have pointed out.
Similar relationships exist for other forms of energy storage. For electricity, fuel cells, chemical cells ("batteries"), flywheel / reaction storage, and capacitors tend to offer a trade-off between total storage capacity and reaction time. Capacitors can react at intra-phase rates (that is, within a single 60Hz power cycle), whilst batteries and flywheels can take longer to come online.
See for example: "Battery Parameters" <https://www.monolithicpower.com/en/learning/mpscholar/batter...>.
"Liquid gasoline does not have anywhere near the energy of TNT,"
Energy density of gasoline is approximately 44 to 45 megajoules per kilogram.
Energy density of TNT is approximately 4.184 megajoules per kilogram.
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One of the problems with gasoline is its explosive nature, which the fuel storage and delivery system of a car attempts to mitigate. It has a better profile for burning off than a battery though since it will spill out and burn away from the vehicle.
Gasoline isn't that explosive. You can shoot up a gas tank and it will just burn. What you see on TV is movie magic. Gasoline vapor can explode, but you need the right air to fuel ratio and a spark.
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"Fast X: why cars don’t really explode when they crash"
"Petrol and diesel can only explode when under pressure and mixed with air and in the case of petrol, have a small amount of energy added in the form of a spark or a flame. Engines pressurise the fuel/air mixture in the cylinder and so produce small, confined explosions which turn a crankshaft and drive the wheels."
"When cars are involved in collisions, fuel lines are often torn and petrol leaks out onto a hot engine. Liquid petrol can catch fire in the presence of air. But it can’t explode because it’s not under pressure and is in the liquid phase rather than a vapour."
https://theconversation.com/fast-x-why-cars-dont-really-expl...
> Gasoline ... it's not a "bomb"
My teen years would beg to differ, when some neighborhood friends and I decided to experiment with gas and bleach. The neighborhood residents, fire department and local police also had an opinion, too. (We all got into BIG trouble. Definitely one of the dumber things I did as a teen.)
Bleach? What does that do?
My high-school crowd stopped just short of building a multistage FAE device. I left early for college and everybody else was short of cash, and that was the end of our neighborhood R&D program. All pre-9/11, needless to say. It's a lot less fun when the possible punishment goes from detention at lunch to waterboarding in Gitmo.
Poorly stored gasoline can spontaneously combust, though. So more like a firebomb.
No it can't. To combust it needs ~ 500F. If you left it out uncovered in the open and allowed the it to vaporize with a spark nearby, it might explode, but thats not spontaneous combustion. Gasoline sitting in a sealed container wont spontaneously combust.
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Gasoline doesn't do that. Perhaps you're thinking of the following?
What it does do is slowly polymerize, becoming useless as an ICE fuel in time, typically in a year or two. This is why backup generators should run on propane, which has no degradation mechanism.
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Some heavier elements have hilariously high energy densities and aren't bombs (on their own), but the catch is the energy release is a trickle. Point is it's not an automatic follow that high density = high discharge.
Have a look at Electric impedance spectroscopy- https://en.wikipedia.org/wiki/Dielectric_spectroscopy
Theres a handfull of Tier 1 BMS chips that support it already. though, half of them are meant for traction/EV packs instead of BESS.
Making it require air (or some other kinetic / transport process) would help with that. E.g. zinc-air battery.