Compressed Air Cars

reeac

masonn wrote: »

Seen this on a documentary some times ago. The French car had a range of 200 miles at speeds of up to 60 mph and I seem to remember that to refill the air tanks took minutes rather than the hours it take to recharge batteries on electric vehicles.

Also on the same program there was an Aussie compressed air forklift truck that used air powered rotary engines.

Compressed air will have nothing like the stored energy of a hydrocarbon fuel.

Quite likely the forklift truck was for use in an inflammable environment where you couldn't have a petrol, diesel or electric motor.

Mr_Toad

Been Googling, this is the Aussie company. http://www.engineair.com.au/

Weird_Nev

Ask yourself: Where does the energy to compress the air come from?
Is it not better to use thermodynamics to expand some gas?

I hate this country and it's lack of basic science education.

Mr_Toad

The OP was asking if the tech was viable I was merely pointing out that there are people who build compressed air powered vehicles.

As far as I'm aware we're not discussing either the science or the efficiency.

Is thermodynamics to expand gas better? More efficient, at the moment yes but better? It currently uses a resource that is running out, expensive, bad for the environment and controlled by other countries.

Compressed air, and other ideas might seem like a bit of a joke now but without this research engineering and science wouldn't move on.

The first internal combustion engines were inefficient and underpowered and it's taken years to improve them. Who knows what improvements might be made to compressed air technology in the future.

Look at battery technology and how far that has still to go before it will be a serious competitor to petrol and diesel.

worried_jim

TrickyWicky

kaya wrote: »

car engines are really just big air pumps anyway, we get our "air" from mixing fuel, air and a spark

Erm no, we get it from tree's that generate oxygen. From fuel, air and a spark we get carbon dioxide and all sorts of other sinful nasty chemicals. Do you work for an oil company or something? Are you fearing for the security of your job? - Fear not, I have an interesting solution..

For these compressed air vehicles, surely with so much CO2 around the planet we could just capture it, compress it and use it to fill these new air powered vehicles air tanks?

Sure, it'll mean the CO2 is pumped back out again but at least its being used, recaptured, re-used, recaptured etc. The capturing part of the process is two fold - it takes it out of the environment and gives the oil companies something positive to do while still making their money - win-win. Of course they'll become so greedy about it that they'll setup huge CO2 capturing farms to catch as much as possible thus cleaning our air and bringing the planet back to its senses. Once the oil companies have these farms setup they'd have the infrastructure in place to capture other nasties that we've released too.

DVardysShadow

Dave_C wrote: »

Some quick sums:
A SCUBA tank holds about 2000 litres of compressed air
A one litre (1000cc) engine at 2000 rpm shifts 2000 litres of air/fuel mixture per minute
So a compressed air engine uses a scuba tank full of air per minute.
For an hour's motoring you need 60 scuba tanks.
Which will weigh a lot, use up a lot of space and need filling every hour.
Then there's the cost of running the compressor.

Now at 40mph at 40 MPG one gallon of petrol/diesel will last an hour. It takes up a lot less room and the fuel tank can hold a few hour's worth of driving.

No contest

Dave

I appreciate your analysis. One small point - the first approximation to the the air shifted by a 1 litre engine is 0.5 litre per rev, assuming 4 stroke, not the full litre, because the cylinder is sealed for a consecutive up and down stroke once every 2 revolutions.

Gloomendoom

Dave_C wrote: »

Some quick sums:
A SCUBA tank holds about 2000 litres of compressed air
A one litre (1000cc) engine at 2000 rpm shifts 2000 litres of air/fuel mixture per minute
So a compressed air engine uses a scuba tank full of air per minute.
For an hour's motoring you need 60 scuba tanks.

You will need more than that because, for the engine to work, the pressure on one side of the cylinder must be higher than the other. That 2000 litres of air in the scuba tank is measured at atmospheric pressure.

DVardysShadow wrote: »

I appreciate your analysis. One small point - the first approximation to the the air shifted by a 1 litre engine is 0.5 litre per rev, assuming 4 stroke, not the full litre, because the cylinder is sealed for a consecutive up and down stroke once every 2 revolutions.

Reciprocating compressed air engines are like steam engines. The four stroke cycle doesn't apply and would be utterly pointless.

redux

I'd be amazed if any compressed air car could travel more than two or three miles on a tankful.

Even a paint spraygun uses a few litres of air a minute, so if you turn off the compressor and use just its reservoir you'll only get a few minutes of falling pressure before it stops delivering anything.

A car is something that needs a lot more energy to shift than a pot of paint.

TrickyWicky

redux wrote: »

I'd be amazed if any compressed air car could travel more than two or three miles on a tankful.

I seem to remember they had managed something like 35 miles per tank iirc and that was just a prototype but as always these things get improved over time.