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Old 02-06-2009, 06:21 PM   #11 (permalink)
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Originally Posted by Vwbeamer View Post
My personal opinion is that the whole air car thing is a scam to get investors. Compressed air is ineffective way to store energy.

Ever use an air grinder? you have to have a 5 hp compressor to run the thing and it burns a lot of energy. A simple hand held electric grinder will do the same work cheaper.

Now i know the pressure is supposed to be a lot higher, around 300 bar. But air compressed is hot air, when air cools it will contract, so pressure is lost as the tank cools.

This would be cool if it's true, but I'm naturally skeptical of this idea.

I could see it being used as regenerative braking. where a cylinder is used to compress sir while braking, and then the air flow is reversed and used to drive the cylinder.
Yea, the loss of compressive heat hurts a lot. AFAIK, you lose something over 40% of the energy. IMO, small batteries or supercapacitors and motors are still the best bet for regenerative systems.

I'm thinking there must be some way for a compressing station to reclaim some of the energy in the hot gas they produce. They could then transfer cooled air to your vehicle with little loss, improving overall system efficiency. an alternative would be to heavily insulate the storage tanks on your car.

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Old 02-07-2009, 01:20 AM   #12 (permalink)
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If the compressor station can use the heat for district heating or process heat, and the car is covered with heat exchangers to re-warm the air between multiple expansion stages, you could wind up with the same sort of over-unity benefits as a heat pump.

I'm sure I've ranted here before, against the dangers of a "fuel" that can give up all its energy instantly, without mixing with air first. The french Air Car is a stock scam, IMHO. A magazine got to test one, and the range was 39km, not the advertised 200.
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Old 02-07-2009, 02:03 PM   #13 (permalink)
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from my understanding there are air cars being used in really hot climates but no one has figured out how to make them work in the rest of the world, just like an IC engine produces heat that you can use to heat the inside of the car and produces heat beyond what you need to heat the car, air cars produce cold above and beyond what you need.
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Old 02-07-2009, 03:40 PM   #14 (permalink)
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Compressed air doesn't store enough energy.

Now as a temporary storage medium in a hybrid car, I think they make sense
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Old 02-07-2009, 04:02 PM   #15 (permalink)
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For short-term storage, you could conserve the heat, and keep the size manageable for safety. However, since hybrids usually benefit from more range, they would already have electric motors, and overall, it would be more efficient to add a small amount of capacitor storage to the battery bank, to be used first when going from accelerator to brake and vice-versa. That would eliminate the inefficiency of battery charging/discharging for significant portions of a city run. For the high power rates involved in braking from high speed, air motors would be a nice auxiliary, but how often would they get to pay their way?
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Old 02-08-2009, 02:31 AM   #16 (permalink)
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I sell High Pressure Breathing air compressors

Compressed air cars would be good for my business but I do not think it will happen. Too many obstacles and the range is too short. I know there are some pretty sharp minds working on it but still I am not holding my breath on it. I have been contacted about supplying compressors for that purpose but when you look at actual air needs and pressure then most realize it will not work as well as they hoped. Also there is a bunch of difference between a 125 PSI shop air compressor and a 4500 or 6000 PSI compressor.
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Old 02-08-2009, 08:58 PM   #17 (permalink)
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Batteries in cold climates vs compressed air

In regard to the post about compressed air not being reliable in cold weather, for those out there who are familar with vintage aircraft will note that on the russian prop driven aircaft (Yak52 etc), the engine is cranked over by compressed air rather than a battery powered electric motor. the extreme cold would render useless any battery that is exposed to the elements.

Other vehicles which require large cranking loads also utilise compressed air driven starter motors (Diesel Drive haul trucks for example), as well as steering, braking (compressed air drives the hydraulinc braking circuit). Many of these vehicles also operate in the extremes of cold. so the technology is already out there and understood.

In all applications, dry air is imperitive to ensure prevent freezing air lines.
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Old 02-08-2009, 11:01 PM   #18 (permalink)
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Quote:
Originally Posted by aussie_modder View Post
In regard to the post about compressed air not being reliable in cold weather, for those out there who are familar with vintage aircraft will note that on the russian prop driven aircaft (Yak52 etc), the engine is cranked over by compressed air rather than a battery powered electric motor. the extreme cold would render useless any battery that is exposed to the elements.

Other vehicles which require large cranking loads also utilise compressed air driven starter motors (Diesel Drive haul trucks for example), as well as steering, braking (compressed air drives the hydraulinc braking circuit). Many of these vehicles also operate in the extremes of cold. so the technology is already out there and understood.

In all applications, dry air is imperitive to ensure prevent freezing air lines.
CA starting is also the preferred method where there is a likelyhood of explosive gasses being present such as in some marine applications or where electric starting is not feasible.

The quality of the installation is the key to reliability not necessarily the type of starting system selected.

Pete.
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Old 02-08-2009, 11:14 PM   #19 (permalink)
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Transmitting energy via compressed air has been around for at least 125 years. Do you not think that if it did not have show-stopper, it would have taken over in that time. Are 125 years of engineers morons? Do you think compressed air was squelched by some sort of oil company conspiracy?

No. There is a show-stopper.

Air compressors are ony about 25% efficient. The rest gets thrown away as low-grade (unusable) heat.

Compressed air power is OK where you do not want a build up of heat, like industrial tools or in an explosive environment.
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Old 02-09-2009, 12:07 AM   #20 (permalink)
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It would be nice to have a windmill on the roof to run an air compressor in the house. In the winter, it could help heat the house while compressing air for the car. In the summer it could heat the water in the water heater. Maybe it could also be used for cooking.

When the air expands in the car engine, it gets cold so it can be used for the air conditioner without using additional energy.

If the car has its own portable windmill, it could recharge itself just by parking in a windy area. It seems like a good way to keep driving when gasoline gets scarce.

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