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Old 07-17-2008, 05:15 PM   #21
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I'm looking forward to the episode as we speak.
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Old 07-17-2008, 06:24 PM   #22
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I wonder what happens to that 4500psi tank when you smack it with an F-250.

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Originally Posted by Marquette View Post
It becomes a 0 PSI tank. My guess is the fun is what happens in between those two points.
A clever engineer would route the escaping gases to the airbags. It would be a self-collision detecting, and self energizing system. An elegant solution.

No, I don't want to volunteer for testing it.


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Old 07-17-2008, 06:59 PM   #23
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[quote=samclem;684790]
The car's small onboard compressor can be plugged in at home, it will refill the air tank in about 4 hours at a cost of $2 in electricity.

At 10cents/KwH, this would draw 22.8 Amps on 220v circuit running continuously for 4 hours. Must be one heck of a big tank or compressor. But if the range is 90 miles for the $2 charge, then it is only costing 2.2 cents/mile. If it were top become commercially viable, when the oil companies get thru, the 3 minute fill up will be $40, and they still won't wipe your windshield.

I spent a few years in the pressure vessel industry early in my career, and have witnessed many high-pressure tests, some of them to failure. We always filled the vessel with water to within a half-inch of the top before airing them up to design (or failure) pressure. You can't compress a liquid, so it limited the amount of compressed air in the cylinder) Even so, some of the failures were spectacular- a veritable exposion of air and water until all the air was out of the tank and internal/external pressures equalized.

Having millions of 4500psig compressed gas CF or FRP tanks on the highway would scare the hell out of me. You wouldn't need to call 911 in the event of a collision, the expoding tank(s) would notify them for you. Kinda like Onstar, but you wouldn't have to pay for it.
The DOT has very strict rules about transporting high pressure cylinders. . And imagine a chain reaction in a crowded parking garage when the first one went off, and the shrapnel pierced a few others....Turning the masses loose with them is incomprehensible in our regulatory climate- and millions of mobile compressed air bombs would be every terrorist's wet dream.

Nope, think we should pass on this one.
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Old 07-17-2008, 07:28 PM   #24
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I wonder what happens to that 4500psi tank when you smack it with an F-250.
If it's manufactured in accordance with military quality-assurance procedures, the answer is that nothing will happen because no one will actually be able to afford one... the 4500 psi tank, I mean, not the F-250!
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Old 07-17-2008, 10:09 PM   #25
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I spent a few years in the pressure vessel industry early in my career, and have witnessed many high-pressure tests, some of them to failure.

... some of the failures were spectacular- a veritable exposion of air and water until all the air was out of the tank and internal/external pressures equalized.

Having millions of 4500psig compressed gas CF or FRP tanks on the highway would scare the hell out of me.

...

The DOT has very strict rules about transporting high pressure cylinders. .
...

Nope, think we should pass on this one.
Except, those vessels were very likely a completely different design from what would be used in an air car. Probably cylinders, right? That is not what they will use in air cars - apples-oranges.

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Old 07-17-2008, 10:42 PM   #26
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Originally Posted by bigwonderfulwyoming View Post
The car's small onboard compressor can be plugged in at home, it will refill the air tank in about 4 hours at a cost of $2 in electricity.

At 10cents/KwH, this would draw 22.8 Amps on 220v circuit running continuously for 4 hours. Must be one heck of a big tank or compressor. But if the range is 90 miles for the $2 charge, then it is only costing 2.2 cents/mile. If it were top become commercially viable, when the oil companies get thru, the 3 minute fill up will be $40, and they still won't wipe your windshield.

I spent a few years in the pressure vessel industry early in my career, and have witnessed many high-pressure tests, some of them to failure. We always filled the vessel with water to within a half-inch of the top before airing them up to design (or failure) pressure. You can't compress a liquid, so it limited the amount of compressed air in the cylinder) Even so, some of the failures were spectacular- a veritable exposion of air and water until all the air was out of the tank and internal/external pressures equalized.

Having millions of 4500psig compressed gas CF or FRP tanks on the highway would scare the hell out of me. You wouldn't need to call 911 in the event of a collision, the expoding tank(s) would notify them for you. Kinda like Onstar, but you wouldn't have to pay for it.
The DOT has very strict rules about transporting high pressure cylinders. . And imagine a chain reaction in a crowded parking garage when the first one went off, and the shrapnel pierced a few others....Turning the masses loose with them is incomprehensible in our regulatory climate- and millions of mobile compressed air bombs would be every terrorist's wet dream.

Nope, think we should pass on this one.
You'll be pleased to know there are about 150,000 compressed natural gas powered cars and trucks running around the country every day. They typically run about 3200 psi in their storage tanks.

And to boot there are about 1600 compressed natural gas "filling stations" around the country.
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Old 07-17-2008, 11:06 PM   #27
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At 10cents/KwH, this would draw 22.8 Amps on 220v circuit running continuously for 4 hours. Must be one heck of a big tank or compressor.
A 6 or 7 HP compressor would be this size. Sears sells ones with motors this big (they are designed to compress a greater volume of air to a lower pressure than what the car would use.) Same size motor, in thousands of homes today. I'd say that they'll need to do a good job of soundproofing the compressor--most industrial ones are not something I'd like to hear running in the garage for 4 hours.
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Old 07-18-2008, 12:15 AM   #28
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Except, those vessels were very likely a completely different design from what would be used in an air car. Probably cylinders, right? That is not what they will use in air cars - apples-oranges.

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I'd love to see how they are going to get a 4500psig rating +safety factor, ~ 1.25X design pressure- out of anything other than a cylinder or sphere...
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Old 07-18-2008, 12:18 AM   #29
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You'll be pleased to know there are about 150,000 compressed natural gas powered cars and trucks running around the country every day. They typically run about 3200 psi in their storage tanks.

And to boot there are about 1600 compressed natural gas "filling stations" around the country.
Yes, but not running 4500 psig tanks made out of lightweight fiberglass... installed in little lightweight fuel efficient plastic cars.
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Old 07-18-2008, 07:17 AM   #30
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Yes, but not running 4500 psig tanks made out of lightweight fiberglass... installed in little lightweight fuel efficient plastic cars.
No shrapnel risk... instead, they'll be designed so it'll be like letting go of a balloon you're inflating. They'll shoot off the road and all over the air in the event of a crash
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Old 07-18-2008, 07:58 AM   #31
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Yes, but not running 4500 psig tanks made out of lightweight fiberglass... installed in little lightweight fuel efficient plastic cars.

Check it out.

http://www.americanchemistry.com/s_p...=1080&DID=6582
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Old 07-18-2008, 08:54 AM   #32
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I'd love to see how they are going to get a 4500psig rating +safety factor, ~ 1.25X design pressure- out of anything other than a cylinder or sphere...
One way is to do it just like the internets - a series of tubes.

Small tube - small surface area. Less surface area is less pressure. Essentially, a bunch of small tanks, all with an engineered weak spot to allow controlled bursting.

That said, now that I have read up a bit on the compressed air tech, I think batteries will bypass it (except for maybe the big industrial apps, where they use a cave as the storage tank). Maybe some short term apps, until battery $ come down a bit more. The problem with compressed air, is that you always gain heat during compression. So, 'charge' your air tank all night, and it has lost most of that heat by day, or by the time you drive home after work. So, that energy is lost.

Unless this air tech has a big cost advantage over plug in lithium (or carbon foam core lead-acid) hybrids, I don't think it will be a big player. Efficiency will be the name of the game, once costs come down.

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Old 07-18-2008, 11:02 AM   #33
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Thanks for the link, UncleHoney.

From it:

Quote:
Quantum Technologies developed the 87 lb. (39.46 kg) 5,000 psi TriShield™ tank, which contains an impermeable, modified polymer liner surrounded by a carbon fiber inner shell and a hard external shell made of a proprietary fiber/resin woven system and impact-resistant polymer domes on each end. . . .
To ensure its safety onboard vehicles, Quantum Technologies extensively tested the TriShield™ tank. It passed crash car tests as well as tests “firing armor-piercing bullets at it, dropping the cylinder from
six feet onto a concrete surface, placing it in a diesel fire, cycling it thousands of times,* and subjecting the cylinder to extreme cold and to corrosive liquids encountered in automotive environments, such as
battery acids, saltwater, brake oils, and methanols,” according to Neel Sirosh, a mechanical engineer and director of fuel storage systems at Quantum."
Sounds safe to me. I'm not sure that a modern car gasoline tank would do as well.
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Old 07-18-2008, 11:07 AM   #34
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One way is to do it just like the internets - a series of tubes.

Small tube - small surface area. Less surface area is less pressure. Essentially, a bunch of small tanks, all with an engineered weak spot to allow controlled bursting.

That said, now that I have read up a bit on the compressed air tech, I think batteries will bypass it (except for maybe the big industrial apps, where they use a cave as the storage tank). Maybe some short term apps, until battery $ come down a bit more. The problem with compressed air, is that you always gain heat during compression. So, 'charge' your air tank all night, and it has lost most of that heat by day, or by the time you drive home after work. So, that energy is lost.

Unless this air tech has a big cost advantage over plug in lithium (or carbon foam core lead-acid) hybrids, I don't think it will be a big player. Efficiency will be the name of the game, once costs come down.

-ERD50
Ah, lots of smaller 4500 psig fiberglass tanks.. Cluster bombs instead of one bigger one. I am feeling better already.

Multiple smaller tanks are less efficient at storing anything. (Why build water towers instead of storing water in gallon jugs?)
The weight/capacity ratio and manufacturing costs would kill them.

I agree with your asssesment on air vs. batteries. We already have a nationwide electrical grid in place; recharging stations will be easier to implement with current technology and infrastructure.
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Old 07-18-2008, 11:35 AM   #35
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You'll be pleased to know there are about 150,000 compressed natural gas powered cars and trucks running around the country every day. They typically run about 3200 psi in their storage tanks.

And to boot there are about 1600 compressed natural gas "filling stations" around the country.
150,000 is .0006% of the 250,000,000+ million vehicles on the road. I am glad it is that small. 1600 is 1.1% of the 140,000 filling stations. The infrastructure is too thin for this to be a quick fix.

I am all for alternatives to oil- but putting tens of millions of high pressure cylinders on our roads isn't a viable alternative, IMHO.
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Old 07-18-2008, 11:42 AM   #36
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Ah, lots of smaller 4500 psig fiberglass tanks.. Cluster bombs instead of one bigger one. I am feeling better already.

Multiple smaller tanks are less efficient at storing anything. (Why build water towers instead of storing water in gallon jugs?)
The weight/capacity ratio and manufacturing costs would kill them.

I agree with your asssesment on air vs. batteries. We already have a nationwide electrical grid in place; recharging stations will be easier to implement with current technology and infrastructure.
I never claimed it would be more efficient. But it could be more safe - safety is what you threw out. Engineering is all about balancing the trade-offs: cost (initial and on-going), safety, weight, size, convenience, flexibility, etc, etc, etc.

If the costs kill them, they won't succeed in the market. Simple.

Air compressors can run on electricity, so that is a non-issue. The question goes back to efficiency and installed cost. Heck, solar is almost 'free' once you get past the installation costs, but it still is not cost effective in most situations, once you factor in the installed costs.

For example, I wouldn't care if an air car was less efficient than a lithium electric car. If it gave me better cost/mile than a present ICE, or hybrid, and was offered at the same price, and the safety requirements were met, I'd consider one. It doesn't need to be better than all-electric, it only needs to be better than ICE/hybrid, and cheaper than all-electric initial cost.

I get a kick out of the Tesla forum guys going on about 2.5 cents/mile electric costs - after they pay $100K for their car! Heck, buy the car if you wish - but the per mile costs delta on a $100K car is silly.

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Old 07-18-2008, 11:47 AM   #37
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but putting tens of millions of high pressure cylinders on our roads isn't a viable alternative, IMHO.
The trouble is - it your *opinion*. You have not provided any facts to say that the designs of the air tanks under consideration would be any more/less dangerous than a tank of gas.

You only stated that *other* pressure tanks can be dangerous. You can't say that all designs are not safe, just because some designs are unsafe. Well, you can say it, but it has little meaning...

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Old 07-18-2008, 11:55 AM   #38
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150,000 is .0006% of the 250,000,000+ million vehicles on the road.
?

I can't follow your math. Is that 250,000,000 million vehicles? = 250,000,000,000,000? That sounds like a lot, I guess the Chinese are buying lots of cars

I assume the 'millions is redundant'. But that makes it 0.06%. But we would still need to compare miles driven, and injuries per mile driven from exploding NG tanks, versus exploding gas/diesel tanks.

And then consider that NG is flammable, air is not.

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Old 07-18-2008, 12:08 PM   #39
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Sounds safe to me. I'm not sure that a modern car gasoline tank would do as well.
Hey I didnt see anything about an f-250 in there. Seems to me they're trying to avoid the REAL test.

Preferably being driven by a half drunk dude with 150 pieces of old lumber in the back, held down by two partially shredded pieces of rope. But he's got his hand up there holding it in case the rope breaks.
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Old 07-18-2008, 12:33 PM   #40
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?

I can't follow your math. Is that 250,000,000 million vehicles? = 250,000,000,000,000? That sounds like a lot, I guess the Chinese are buying lots of cars

I assume the 'millions is redundant'. But that makes it 0.06%. But we would still need to compare miles driven, and injuries per mile driven from exploding NG tanks, versus exploding gas/diesel tanks.

And then consider that NG is flammable, air is not.

-ERD50
150 thousand / 250 million is .0006

I agree, air is inflammable, but a large volume of highly compressed air in a cylinder presents an explosive risk in the event of a crash. My concern is that by increasing the number of pressurized cylinders on the road- especially if we are putting them into little tiny plastic cars- increases the risk exponentially over what we have with the very small percentage of NG vehicles using big heavy steel tanks in well-protected (mostly commercial) vehicles with large crumple zones.

Risks can always be mitigated to some degree. The carbon fiber reinforced tanks look like interesting, but they remind me of another $6000 Mil-Spec toilet seat. Maybe mass production will make them viable. Who knows? I suppose it has as much chance as the infamous car that runs on water that is being touted by the big oil conspiracy theorists.

One thing about the current energy situation- it isn't going to go away on it's own; Americans are an automobile sociey, and the US is going to develop alternatives to oil. The resulting shift in engineering, manufacturing, marketing, and distribution could provide the US with the economic impetus we need to revitalize our moribund automotive economy- Unless we pi$$ it away and outsource the technology.

Personally, I like biofuels and electric (solar, wind, nuclear, hydro, or coal, take your pick) If Brazil can run their vehicles on cane-based ethanol, we can surely come up with something that will grow across most of the US with a similar energy content. (frost-resistant cane? better living thru genetic engineering?) Corn isn't the answer, it isn't efficient enough, and we can't divert foodstuffs to fuel forever.
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