[Rumor]

http://www.cnn.com/2008/TECH/08/08/a...?eref=rss_tech

Interesting concept, but there are a lot of people saying it isn't possible.

[richwig83]

That's not possible!!!

[torsoboy]

I'd be nervous sitting on that much compressed air. But cool concept.

[olePigeon]

Tata bought Jaguar and Landrover from Ford?

[olePigeon]

Originally Posted by torsoboy 

I'd be nervous sitting on that much compressed air.

I'd be more worried driving a vehicle that looks like it's vacuum formed from PVC.

[smacintush]

As a laymen it seems pretty unlikely to work, but what do I know.

[Shaddim]

I saw something about it on Top Gear, looks interesting... it won't sell for ****, but who cares?

[Eriamjh]

Originally Posted by torsoboy 

I'd be nervous sitting on that much compressed air. But cool concept.

Are you more comfortable sitting on 10-20 gallons of gasoline? I just can't see how compressing enough air to get any distance can be done without a very heavy and thick steel tank, but I'd love to be proven otherwise.

[stevesnj]

Oil company execs and lobbyists will never allow this car into the US. Sorry everyone.

Heres a video of his prototypes and engine design http://www.youtube.com/watch?v=QmqpGZv0YT4

[Laminar]

The problem with compressed air is that you only get about 30% of the energy you put into it back out. So with an electric car you plug it in and put, say, 100 units of energy into it. You see losses when batteries discharge and the electric motor has a certain efficiency rating, so you get maybe 65-75 units of energy back out. If you put that same 100 units of energy into compressing air to put into this car, you'll only get 30 units back out.

It would be cool if you could get a car to run off 100psi tanks, so you could just pull up to any gas station with free air for your tires and fill up there. I've seen a moped equipped with two SCUBA tanks that could go 8 miles on a single free fill up.

[Eriamjh]

Originally Posted by Laminar 

The problem with compressed air is that you only get about 30% of the energy you put into it back out.

Link?

ICEs are only about 20% efficient. That's a 50% increase!

[Laminar]

Originally Posted by Eriamjh 

Link?

ICEs are only about 20% efficient. That's a 50% increase!

I took a class last year on alternative energy sources and the professor of that class also taught a compressed air class. I got the 30% number from what he mentioned when he was talking about powering a vehicle with compressed air.

In some cases the method of energy storage is makes up for its efficiency. Gasoline is a pretty good holder of energy. I'm not sure why your link brings up the Carnot cycle...the Carnot cycle is a heat engine (I'd probably refrain from quoting web pages created by Physics 212 students...), an ICE uses the Otto cycle, and its efficiency is mostly just a ratio of the maximum and minimum volumes in the cylinder - the compression ratio. In a car with a 10:1 compression ratio (not at all uncommon) the maximum efficiency is going to be 60%, but with heat losses, friction, engine accessories, etc. the best you'll see is 20-30%.

The difference, like I said, is energy storage. To store the energy to drive 400 miles on gasoline requires a tank that can hold 14 gallons of liquid. That's pretty easy to do. But to store the same amount of energy in compressed air would require MASSIVE pressures. The same goes with a hydrogen-gas powered car. Hydrogen is VERY light and so trying to hold any significant amount of it requires a TON of compression.

[The Godfather]

Scuba-tank powered gocart
http://www.youtube.com/watch?v=9C70s...p;feature=user
http://www.youtube.com/watch?v=JC1c7...eature=related

Air powered vehicle race
http://www.youtube.com/watch?v=Ga97s...eature=related

[Chongo]

You still need lubricants

[stevesnj]

Originally Posted by Laminar 

But to store the same amount of energy in compressed air would require MASSIVE pressures. The same goes with a hydrogen-gas powered car. Hydrogen is VERY light and so trying to hold any significant amount of it requires a TON of compression.

Working with a Hydrogen tank and fuel cell I found this out also. Our hydrogen tank is 1"minimum thickness and concrete lined. And that was a 6 inch tall 1 liter tank. Putting a heavy hydrogen tank in a car is a lot of weight and reduced range, unless newer non-porous metals are used for the tank material.

[Laminar]

Originally Posted by chongo 

you still need lubricants

TWSS all caps

[Laminar]

I did some quick calculations for fun. A car that gets 30mpg can do 400 miles on 13.3 gallons of gasoline, which has an energy content of 114,000 BTU/gallon. Hydrogen (H2) has an energy content of 113,700 BTU/kg, so it would take about 13.33 kg of H2 to go the same distance, assuming the energy contained could be transferred to the wheels at the same efficiency. Using the ideal gas equation, compressing 13.33 kg of H2 into a 10 gallon-sized tank requires it be at 62,800 psi. A normal shop air compressor holds air at 90-125psi. This is roughly 620 TIMES the pressure we're used to storing gas at. I wouldn't want to sit on top of a container holding a highly combustible gas at over 62,000 psi - just imagine it getting punctured in an accident!

This is why we're not likely to see cars powered by stored hydrogen. Imagine the infrastructure required to refuel these cars - imagine the storage containers required at refill stations! A more probable method is an in-vehicle method that extracts hydrogen from something else. This is basically what fuel cells do.

edit: Hydrogen costs about $3-4/kg to produce large-scale, so it's not far off of gasoline in that respect.

[stevesnj]

Originally Posted by Laminar 

- just imagine it getting punctured in an accident!

This is why we're not likely to see cars powered by stored hydrogen.

edit: Hydrogen costs about $3-4/kg to produce large-scale, so it's not far off of gasoline in that respect.

After a year research on tank punctures and flammability the Hydrogen tank in a vehicle is safer and less destructive than a gasoline tank. I know you may say this is not right but it is true. You need a counter explosion to ignite a tank to blow it up. a puncture of compressed hydrogen, thus likely but mostly hard to puncture, will dissipate and could ignite in open flame but the puncture and release WILL NOT, I REPEAT, WILL NOT explode. The hydrogen gas release will turn into a blowtorch if ignited. Gas will explode. Hydrogen is safer in a car.

Article and pictures explaining Gas vs. Hydrogen leaks and experiment with pictures http://www.evworld.com/article.cfm?storyid=482

[Laminar]

Originally Posted by stevesnj 

After a year research on tank punctures and flammability the Hydrogen tank in a vehicle is safer and less destructive than a gasoline tank. I know you may say this is not right but it is true. You need a counter explosion to ignite a tank to blow it up. a puncture of compressed hydrogen, thus likely but mostly hard to puncture, will dissipate and could ignite in open flame but the puncture and release WILL NOT, I REPEAT, WILL NOT explode. The hydrogen gas release will turn into a blowtorch if ignited. Gas will explode. Hydrogen is safer in a car.

That seems counterintuitive at first especially considering this:



But I guess it makes sense. What kind of materials would be required to hold hydrogen at that kind of pressure?

[subego]

It doesn't seem like anyone has mentioned this, but I saw a short piece on a car solely powered by compressed air. One of the important technological breakthroughs was carbon fiber air tanks. They can get an appropriate strength without nearly the weight of steel or aluminum, and when they rupture they split open rather than shred open like a metal tank.

This particular car overcame some of the inefficiencies of compressed air by using a very light engine (you could lift it with one hand) which makes sense since it wasn't subjected to the pressure or heat that an IC engine needs to handle.

[stevesnj]

Originally Posted by Laminar 

But I guess it makes sense. What kind of materials would be required to hold hydrogen at that kind of pressure?

Current tanks are usually concrete lined on the inside but a tank about the size of a 20 gallon air compressor can hold enough for a few hundred miles..but it can also weigh 200lbs