Car powered by compressed air?

The gravimetric energy density of hydrogen per kilogram is MUCH lower than gasoline when the mass of the CONTAINMENT STRUCTURE is included.

Finding ANY substance with a better energy density per kilogram than gasoline for automotive uses is totally pointless. It might make a 30 pound difference in vehicle weight. Hydrogen is certainly NOT a candidate in any way, shape, or form.

The volumetric energy density of hydrogen per liter is ludicrously low, even when liquified.

Yup, agreed.

Best regards, Spehro Pefhany

Isn't that a matter of scale? After all, large liquid-fueled rockets used LH2, though some used kerosene, too.

Probably more likely that we'll (as in 50 years from now) be using a synthetic hydrocarbon fuel of some kind, at least where batteries and electrics prove to be inadequate. It's hard to imagine an A380 operated off of batteries.

And the mass energy density of liquid hydrogen is actually WAY higher than gasoline, but dealing with cryogens is not inexpensive, let alone cryogens that gas off stuff that tends to explode when mixed with air.

Best regards, Spehro Pefhany

Hey, I've got an idea! Let's put one of those in DimBulb's garage!

Oh, the humanity!

Best regards, Spehro Pefhany

A popular misconception and a dead wrong OUTRIGHT LIE.

The CONTAINED mass energy density of hydrogen is actually WAY lower than gasoline when used in any automotive app. And gets ridiculously worse as the container empties.

Further, the mass energy density is utterly and totally meaningless for automotive apps, as voluumetric density utterly and totally dominates.

Even in those apps when mass energy density is crucial, twenty out of twenty X-prize candidates used something else instead.

The volumetric density of hydrogen is ludicrously low. Even when you throw cyrogenics or high pressures into the mix. Neither of which should EVER be allowed even remotely near the general public.

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My son did a report on this subject, several years ago, and his literature search and study (using only official gov't sources and reputable, scientific sources) showed exactly this conclusion, too. Whether by volume OR by mass, whether cryogenic or high pressure (5000 psi) or any other way that even remotely might be used in a car (metalic hydrogen, obviously not doable), gasoline/kerosine always stored more energy per unit.

I do remember seeing something on the TV recently, about chicken feathers burned to a crisp in some 'special fashion,' showing some possibilities because of the huge amount of surface area. That wasn't in his report, since he didn't uncover it. But I would suspect that if it really _did_ work well, it would be quite hard to get the hydrogen released for use. But I don't really believe the report I saw, either. There was only one source of information, the man proposing the idea. So I'm remaining skeptical for now.

Jon

A 24" cube of liquid hydrogen holds as much energy as 15 gallons of gasoline. That's certainly not an outrageous volume if the car is designed around it, less than 7% of the passenger+luggage volume of a Toyota Camry. Even if the dewar increases that by 50% or 75%, it's still not remotely decisive. OTOH, a 747-400 would have no passenger or cargo space left over if you tried to fuel it with liquid hydrogen. It would end up looking like the hideously ugly 747-LCF.

True.

If the liquid hydrogen was 1/2 the price of gasoline for equivalent energy we'd probably find a way to use it relatively safely (ie. so it doesn't kill more people than gasoline does), but it isn't and won't likely ever be.

As in those things that refer to hydrogen as a "source of energy"? lol

Best regards, Spehro Pefhany

Buy hydrogen is so plentiful!

Johm

Rockets use LH2 to obtain the maximum possible practicable exhaust velocity for chemical propellants, and therefore a high specific impulse. In fact, the Shuttle and other O2/LH2 bi-propellant rockets actually waste quite a bit of their LH2 fuel; if the propellants were mixed at the correct stoichiometric ratio to cause complete combustion of the liquid hydrogen, the combustion temperature would be so high that no engine bell material could withstand it, even with active cooling of the bell by the cryogenic fuel.

Energy density of gasoline is 9600 watthours per liter. Energy density of liquid hydrogen in theory is 2600 watthours per liter.

Effective energy density of liquid hydrogen is much, much lower, owing to compression and system loses. As well as the obscene size increase of the containment vessel.

There is no way in hell that ordinary hydrogen can remotely compete with room temperature carbon bonded hydrogen for automotive vehicle apps.

Exhaust velocity, no. Isp, yes (which velocity is a part).

Interesting. Cite?

Not!

Yes, dumbfuck, and the venting that takes place where THEY store their vast reserves gets caught and put back, you clueless fucktard.

It does not require being compressed to a liquid state, idiot.

And normal pressure vessels would work just fine. Ever see Nitrous Oxide tanks on a car?

Grow the f*ck up, idiot.

A 24" cube of gasoline would hold as much energy as 60 gallons of gasoline. ;-)

Then why didn't they use gasoline for the manned moon missions or for space shuttle engines, or for ANY rocket engines, for that matter?

No shit, dumbass. Competing with that number is NOT the goal, idiots!

Finally, we have someone that actually has a brain.