Air Car....

[Dr Mordrid]

http://edition.cnn.com/2005/TECH/03/30/spark.air.car/

http://www.theaircar.com/

http://www.energine.com/eng/engine/engine2.htm

Dr. Mordrid

[Jon P. Inghram]

And then you can use a sterling engine to recover power from the heated air in the tank!

[Wombat]

And then you can use a sterling engine to recover power from the heated air in the tank!

Maybe I missed something in those articles, but why would that air be heated? In fact, it should be cool(ing) due to the Joule-Thomson effect, I think.

[Brian Ellis]

Air cars must be the most inefficient devices, ever!

Anyone who has blown up a bicycle tyre knows that the pump gets hot. So it is with a compressor. Most of the mechanical energy going into an adiabatic compression cycle is converted to heat (otherwise a diesel engine would not work), which is dissipated in the heat exchanger between the compressor itself and the primary reservoir. I would estimate that, with an average three-stage piston compressor going up to 300 bars (remember most industrial compressed air systems barely reach 10 or 12 bars at the most), that 80 - 90% of the mechanical power is converted to heat. As these are generally driven by an electric motor, the electricity has to be generated. In the USA, the electric power sector consumes 38.2 quads of energy and distributes 11.9 quads as electricity, giving an efficiency of 31.15%. Assuming a compression efficiency of 15%, this means that the initial fuel to air efficiency is 4.67%. Let's assume a miracle of 80% of the potential energy in the cars' air reservoir reaching the wheels (and that is ridiculously high), that would give an overall fuel to wheels efficiency of 3.74%. If you take a fuel-efficient car, like the Toyota Prius, you get a fuel to wheels efficiency of over 35%, nearly 10 x better than the air car.

May God preserve us from technoidiots.

And yes, as the air expands from the reservoirs through the pressure regulators and into the engine, it will extract heat and get very cooler (exactly the opposite adiabatic expansion as in the original compression). At least you wouldn't need aircon!

[Dr Mordrid]

Thanks Brian. I was waiting for someone to make the efficiency arguement

Technoidiots indeed.....

Dr. Mordrid

[Wombat]

If you take a fuel-efficient car, like the Toyota Prius, you get a fuel to wheels efficiency of over 35%, nearly 10 x better than the air car.

Except that for the air car you've mentioned the electrical grid inefficiency, the compressor inefficiency, the decompression inefficiency, and the transmission inefficiency.

Yet for the Prius you didn't mention the distillation inefficiency, fuel infrastructure inefficiency, combustion inefficiency, etc.... And what about the environmental damage?

I'm not saying that the air car is a great idea, but at least compare it honestly. There's no way the Prius gets a 35% crude->wheelpower efficiency.

[Dilitante1]

The one factor forgotten is the driver, politicians have tons of gas/wind and could very efficiently propel themselves all over the place

[GT98]

If you take a fuel-efficient car, like the Toyota Prius, you get a fuel to wheels efficiency of over 35%, nearly 10 x better than the air car.

The Prius is an over priced piece of shit that can't even come close to its EPA ratings. I can go out and get an old Honda CRX and get over 40 MPH with a pure gasoline engine. Hybrids are just a crutch and aren't worth the extra 5K+ they want over smiliar sized gasoline powered cars. You can't even make the difference up in saved gas money with a Hybrid with the price preium you have to pay

[Wombat]

The Prius is an over priced piece of shit that can't even come close to its EPA ratings.

Glad to know that you don't know what you're talking about. My coworker has a Prius, and he gets 60mpg, over hilly terrain to work, at 5,000+ft.

[Jon P. Inghram]

Glad to know that you don't know what you're talking about. My coworker has a Prius, and he gets 60mpg, over hilly terrain to work, at 5,000+ft.

But what kind of milage do the people passing him when going up hills on bicycles get?

Seriously, my mom had a old Geo Metro XFi that easily got 55+ mpg on the highway.

[DGhost]

mmm, 5000+ feet.

i get 10+ miles per meal over hilly terrain and utilize a much more efficent refining process

[Wombat]

mmm, 5000+ feet.

i get 10+ miles per meal over hilly terrain and utilize a much more efficent refining process

Can you carry 4 people at 80/mph?

[Wombat]

But what kind of milage do the people passing him when going up hills on bicycles get?

Seriously, my mom had a old Geo Metro XFi that easily got 55+ mpg on the highway.

Metros are damn tiny. The Prius has a decent size to it. Plus, those electric motors have all their torque ready from the starting line (note the hybrid Accord is the fastest Accord offered), so it's not all that pokey.

[DGhost]

Can you carry 4 people at 80/mph?

sadly, not yet. I am working on super-duper secret high-speed methods of doing that though!

in all seriousness... why is it that the efficency cars are not being sold to the economy market? that is where they would make the most inroads into the market...

[Wombat]

Do you mean the hybrids? Because the batteries cost money, and there's nowhere to put the batteries in a hatchback (most designs seem to put the batteries between the rear seat and the trunk).