Compressed air hybrid

[rjacob]

106 mpg 'air car' creates buzz, questions - CNN.com

Interesting. Storing energy as compressed air instead of electricity. More or less efficient? I'd hate to be around an air tank at 4,500psi that explodes.

[sohl]

MDI has been trying to get these vehicles into regular production for years. I think it can work, although I'd also have a bit of concern to have such a large very high pressure tank on board. The range-extending use of liquid fuel is relatively new thing for MDI, if I'm not mistaken. If I understand it right, they don't burn the fuel in the air motor pistons, so it shouldn't be too picky about the type of fuel used. That would mean that all kinds of alternative fuels (bio diesel, ethanol, methanol, butanol) could become usable in the same car! And LPG could also be used without too much trouble.

MDI's lightweight construction methods would also be very helpful to make a practical high-efficiency vehicle that has a small-displacement conventional engine. Turbo 500cc sport coupe? Turbo 1-Liter Minivan? Maybe!

Another kind of compressed air hybrid has been prototyped in the heavy truck world. It consists of a conventional diesel powertrain that is supplemented with a hydraulic pump/motor and pressure "accumulator" (compressed gas tank... air or pure nitrogen). During braking, the vehicle energy of motion is converted by the hydraulic motor into stored pressure in the accumulator tank. When the vehicle is ready to go, pressure is released and the hydraulic motor converts it into propulsive force to boost the off-the-line acceleration, reducing the demand on the diesel motor. It's a lot like the Prius or GM-two mode hybrid systems, except that you have hydraulic pump/motor in place of the electric generator/motor and a pressure tank in place of an electric battery pack. Sometimes this is referred as a "hydraulic hybrid". And would be really good for frequent start-and-stop driving situations like city passenger busses and garbage trucks. In the systems prototyped so far, I think the pressure capacity is only good for a small number of starts or stops, so this is not a long-distance vehicle technology, but it would really help some of the lowest-efficiency working vehicles that there are!

[MazdaMatt]

My paintball gun's air tank is 4500 psi and I dive into the dirt/rocks/walls with it. They build these things strong, especially the larger tanks that I fill from. There would also be a weak-point like in the large tanks that i fill from. If something goes wrong, the weak point breaks and air dumps out... quite violantly, but it beats an explosion.

An advantage of compressed air over electrical is that you COULD set up refueling stations that you can pull into, get a fillup and leave. Unlike an electric car that requires an overnight charge. This means that your "range" is not absolute. You drive your 200 miles, then stop and refill and get going again.

[aerohead]

Seems to me that so many energy conversions are taking place,that the laws of thermodynamics would overwhelm the ability of the vehicle to deliver on it's claims.

[Daox]

I wouldn't be worried about the tanks either. They are made incredibly strong. I don't remember where, but I've heard that it takes more than a .45 hand gun to pierce them.

As far as air goes, I've heard its just not an efficient energy storage medium. I've never seen numbers on it though. Electricity is definitly more readily avaliable. Also, most packs can be setup to be able to have a ~15 minute quick charge to regain 80% or so capacity, so overall range really isn't a huge issue.

[BrianAbington]

that french company that is puting them on the market uses carbon fiber tanks so they will shred instead of exploding.

from what I have seen these cars sound like an air compressor...and with a fiberglass body...would take alot of sounddeadner to cut down on the noise.

[jamesqf]

Originally Posted by rjacob

I'd hate to be around an air tank at 4,500psi that explodes.

But it doesn't bother you to be the same distance from ten or twenty gallons of highly-flammable liquid fuel, which (as we all know from TV car crashes :-)) bursts into flame on any impact?

[BrianAbington]

I agree the ford pinto proved that fact.

[aerohead]

Originally Posted by Binger

that french company that is puting them on the market uses carbon fiber tanks so they will shred instead of exploding.

from what I have seen these cars sound like an air compressor...and with a fiberglass body...would take alot of sounddeadner to cut down on the noise.

I believe Ford abandoned their Tonka Truck air hybrid concept for this very reason.'Said it was like a impact wrench going down the road.Across the street from me,at University of North Texas,there's a professor who's been working on a liquid nitrogen-powered"air-car".It uses a turbine(thought to be more efficient than a reciprocating engine),and it is plagued by high noise and low range.Cost of cryogenics would seem to dim enthusiasm toward this costly "fuel".--------------------------------- I think air launch is a winner,but then you have all these components and mass which are only used at stoplights.-------------------------- If you can synchronize the traffic lights,then "launching" becomes relatively meaningless.