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Discussion Starter #1
Ok, you were right not to like the alternators on the rear axle but what about instead of having a gas engine to run the generator have a air motor to run it, in France they have a company that's invented a air car (MDI) with a safe air tank for storage and in australia there's a small but powerful air motor (its a rotary type) if you don't believe me on Google videos under air powered cars you can find them. this would eliminate the use of gas completely, I think it could be worked out. I still want free ride, well anyway I want off oil
 

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How is the air tank refilled?

If you have to plug it in to run a compressor to refill an air tank, then you couldn't make any trips over 500 miles or so without stopping for a while.
 

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Discussion Starter #3 (Edited)
you have to fill the gas tank too. why cant you put air in the tank with an air hose, gas stations can put in high pressure air tanks even wall marts can do it, you could get air almost anywhere its not going to be that bad, keep an open mind about this it could be a way to make trips or go anywhere you wanted to. I just want to get away from using oil. The only problem I see is the air motor is very noisy
 

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The size of the car's air tank would be very huge & heavy, compared to the 7 gal gas tank, to give the car the comparable range. It's probably not do-able in the Volt.
The gas tank also doesn't "require" any Walmarts or gas stations to buy & install any items & equipment currently non existant there.
The whole idea of the Volt car is that it's user freindly, "plug & Play", for "Today's" market, & can be driven anywhere in the USA a gasoline vehicle can, without the worry of knowing where/if any "special" filling stations are ...
Eventually the ICE could & most likley will be designed to run on Ethanol (cellulosic & otherwise), &/or other bio fuels, instead of Oil, as they actually become more common/available in the US ....
 

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Discussion Starter #5 (Edited)
well the air tanks are made of a new fiber optic material very light and a high pressure air compressor is not all that non existent you could carry one around with you and find a plug in somewhere, with a little imagination this could be a way of independence, and even if not it only takes half an hour or less to fill from a gas station air hose for fifty cents and that could be improved on. Ok I would hope something like the Volt would work but if not put it in something else but lets get going on it, I want off oil really bad
 

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There are numerous ways to provide energy to recharge the Volt's battery - ICE, air motor, etc., etc. Just realize that all of these methods still are subject to the laws of thermodynamics. When considering a closed system, nothing is 100% efficient. If you think you have figured out a way to get "something for nothing", you obviously missed something somewhere along the line.
 

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Oh where is Jason when you need him??:D The problem with the air motor idea is that it is ultimately not as efficient as a battery. It is however theoretically cheaper than a battery and this is why it is of interest to Tata motors in India. I personally have little hope for an air car future.

With an air motor, you are taking electricity, using it to compress gas and there are thermal energy losses involved. Then the gas is allowed to expand and do it's work, but again there are additional energy losses. Also, the air motor requires a large infrastructure of expensive air compressors to be installed, but everyone has electricity already installed. Just taking the electricity and sticking it into a battery cuts out the middle man. Only problem being, the cost of the battery.
 

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It's a mystery to me as to how much interest there is on the air-powered car. Unless they have some magic, the physics of storing energy with compressed air usually don't work.

To run a car off of compressed air, you would have to compress the air to very high pressures. The compressed air then generates a lot of heat, which is eventually lost energy. At very high compression levels (like that used for scuba tanks), as much as 80% of the energy is lost in heat. That energy is not recovered when the compressed air is used.

The only viable solution to this is to have a source of heat to re-heat the air as it's being decompresed. Compressed air utility-grade electric storage systems do this by putting the compressed air storage next to a conventional power plan, and then using the waste heat from the plant to re-heat the air. Even with the addition of the 'free' waste heat, they only get out about 2/3rds of the energy that they put into compressing the air.

Like a lot of other ideas, this sounds like a wonderful and practical idea - if we could only find a loophole around those pesky laws of physics.
 

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At very high compression levels (like that used for scuba tanks), as much as 80% of the energy is lost in heat. That energy is not recovered when the compressed air is used.

The only viable solution to this is to have a source of heat to re-heat the air as it's being decompressed.
agreed, however you do get some of that energy back when you decompress the tank because it's temperature goes down and heat flows into the tank. Also, I think they can make carbon fiber tanks that can hold over 350 atm. At some point you get a large enough storage of energy that it becomes feasible in an automobile. It would be nice if one of us were to provide some sort analysis to demonstrate what is needed to provide say 53kW and what the end to end efficiency is.
 

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agreed, however you do get some of that energy back when you decompress the tank because it's temperature goes down and heat flows into the tank. Also, I think they can make carbon fiber tanks that can hold over 350 atm. At some point you get a large enough storage of energy that it becomes feasible in an automobile. It would be nice if one of us were to provide some sort analysis to demonstrate what is needed to provide say 53kW and what the end to end efficiency is.
Unless you somehow use or recover that heat at compression time, or you're using the temperature drop from decompression for something that would otherwise sap power such as air conditioning, you don't magically get that energy back. The energy that has gone to heat and then is dissipated either during storage or by a heat exchanger at compression time is lost unless you use or store it then. The eventual recovery of some heat from the atmosphere as you release the compressed air and the warmer surrounding air warms the tank back up to ambient temperature is negligible compared to the amount of heat you dissipate during the initial compression of the air.
 

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I agree in part

Unless you somehow use or recover that heat at compression time, or you're using the temperature drop from decompression for something that would otherwise sap power such as air conditioning, you don't magically get that energy back.
I agree that the initial compression could be modeled as isentropic, and then you'll have heat transfer across the tank boundary until the tank temperature reaches ambient.

The energy that has gone to heat and then is dissipated either during storage or by a heat exchanger at compression time is lost unless you use or store it then. The eventual recovery of some heat from the atmosphere as you release the compressed air and the warmer surrounding air warms the tank back up to ambient temperature is negligible compared to the amount of heat you dissipate during the initial compression of the air.
I just disagree that the amount of heat transfer across that same tank boundary is going to be negligible when you start to decompress the tank. It would of course need to be exposed to atmosphere.

Also, you could provide insulation around the tank to prevent the initial heat transfer.

When all is said and done the practical limitations may very well make this an unreasonable solution for an EREV, but I believe using compressed air for energy storage does have some technical merit, especially if you take into account the technical limitations of the thermodynamics.
 
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