The Compressed air engine: Is it a scam?

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Offline McQueen

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The Compressed air engine: Is it a scam?
« on: 08/09/2007 16:12:44 »
According to the manufacturers and the article at Wikipedia it uses compressed air to drive the pistons in a modified piston engine. The compressed air is supplied from an onboard tank filled with air at 3000 psi , this compressed air is injected into the piston cylinder and used to push the piston down giving the motivating power. The only emissions from such an engine are air. The downside to using such an engine is that since there is no heat to speak of it will be difficult to heat your car, the upside is that if you happen to live in a country with a hot climate, air-conditioning would be one side effect of the expanding air, that could be used to air-condition your vehicle. The compressed air car has already gone into collaboration with an automobile company in India : Tata’s who are going to produce the ‘city cat’, some time in the near future. What do you have to say about such an engine? Will it work or is it a scam? McQueen.
« Last Edit: 08/09/2007 16:14:20 by McQueen »
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Offline syhprum

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« Reply #1 on: 08/09/2007 17:16:59 »
Compressed engines are of quite possible we boys used to use them to power our model aircraft during WWII but the amount of power you can store in a compressed air bottle is pretty limited.
Much more can be stored in compressed Helium but the cost is prohibitive and it is only used by military and space agencies.
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The Compressed air engine: Is it a scam?
« Reply #2 on: 08/09/2007 17:50:22 »
But, like hydrogen powered cars, compressed air is merely a means of delivering power that has been generated elsewhere - it is not a primary means of generating power.

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Offline syhprum

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« Reply #3 on: 08/09/2007 18:32:41 »
Both liquid air and electric light cars were quite common at the turn of century and probably outnumbered steam and petrol propelled vehicles for town use.
The big problem with liquid air is that a source of heat is required but for a ladies dog cart or tete a tete limited by law to 12 mph not much power was required and a 'radiator' operating in the reverse manner to which they do today sufficed.
Where Helium wins out it can be compressed to a great degree without liquefying.
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Offline Bored chemist

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« Reply #4 on: 08/09/2007 19:50:03 »
Much more can be stored in compressed Helium
Why?
I can see that it's lighter than air but the weight of the tank will be  much bigger than the weight of the gas anyway.
Also, since nitrogen and oxygen are well above their criticl temperatures in normal air, they cannot be liquefied by compression.
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Offline syhprum

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« Reply #5 on: 08/09/2007 20:40:02 »
I have been trying to find the source my information without success, I have seen an article probably in the 'Scientific American' depicting spherical containers that are filled with highly compressed Helium which comprised an energy storage system that stored more energy per Kg than any batteries.
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Offline lightarrow

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« Reply #6 on: 08/09/2007 21:08:27 »
When I was 15, I had the same idea for an engine with compressed air. At that time no one among friends and school mates knew much about this (I didn't know it was exploited in the IIWW). They said I was crazy. So I stopped thinking about it. Now I see it again!

Ok, so, another idea I had at those times for an engine: a  couple of big disks, one over another, spinning in opposite directions. No pollution (from the veichle, not from the energy plant of course), virtually no noise, very high torque.

Of course, as George wrote, they are just a means of delivering power that has been generated elsewhere; the convenience is in the possibility to centralize the production of power, making this process more efficient; let's remember that in a car's combustion engine only ~ 20% of the petrol's energy is converted into the veichle's movement.
« Last Edit: 08/09/2007 21:10:05 by lightarrow »

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Offline syhprum

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« Reply #7 on: 08/09/2007 21:22:21 »
Flywheel power storage has certainly been used on vehicles, I remember TV coverage of a railway shunting engine that stopped at an electricity supply, spun up its counter rotating flywheels and then went to work.
these were common low tech wheels but since then high vacuum enclosed ones have been developed
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Offline McQueen

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The Compressed air engine: Is it a scam?
« Reply #8 on: 09/09/2007 04:54:37 »
Syhprum
 
Quote
Compressed engines are of quite possible we boys used to use them to power our model aircraft during WWII but the amount of power you can store in a compressed air bottle is pretty limited.

I think that what Syhprum has to say is more or less correct, although there are several other things in the literature about the air-engine that I find hard to believe. If I am not mistaken the model aircraft that Syhprum is talking about used compressed air in the same way as an inflated balloon, (i.e) the reactive forces of the gases escaping from the nozzle push the balloon (plane) in the opposite direction. Such toy planes are still available today.  The literature on the air-car says that 340 litres of compressed air are stored at  4500 psi. OK, so 340 litres corresponds to a tank 2.25’ x 2.25’ x 2.25’ or 19,683 cu ins of compressed air approx. Let us suppose that the cylinders in the engine are 3” x 3” so they have a volume of  21 cu ins approx. A normal car works at the following rpm. Starting speed 300 rpm, idling speed 1000 rpm, slow speed ( about 20mph) 2400 rpm, moderately high speed (30- 40 mph) 3600 rpm. Since most of us drive at or about 30 mph (45km/hr) we take this as the bench mark. 3600 rpm means that the engine fires 60 times every second, this gives 60 x 21 or a usage of 1,260 cu ins per sec. And 75,600 cu ins min. Since the amount of pressure needed to run the engine is 500 psi and the pressure in the tank is at 4500 psi, we divide 75,600/8 (approx) = 9,450 cu ins are used by the engine every minute. Since the tank has a capacity of 19,683 cu ins, the engine will run for 19,683/9,450 = 2 mins. The point is there is no way to replace this compressed air, compressed air is similar to generating electricity, if you try to compress to a higher pressure, you need more power and to compress to 4500 psi or even 450 psi would require a huge amount of power ! The second thing is how far can you go in 2 minutes, it takes two minutes just to get out of the garage, although theoretically, if you had a straight road you could go 60 kms in that time.  Apart from the huge amount of energy that would be needed to fill the tanks, there is the question of heat. A diesel engine compresses to about 16 : 1 or about 240 psi, during compression temperature rises to 500 degrees centigrade. The literature tells us that the air tank can be filled in 2 minutes! The temperature must rise to several thousands of degrees centigrade at the very least! Now the Dunlop Aviation Services,  Tyre factory in England when it first opened tried to use compressed air to test the bursting point of  airplane tyres, these are some of the toughest tyres in the world. The tyre exploded when the pressure reached 800 psi demolishing most of the test facility with it, nowadays they use water instead of air to inflate the tyres to bursting point ! The point I am trying to make is that that amount of pressure (4500 psi) at that temp (3000 degrees C?) is just not safe, every car would be like a 1000lb bomb waiting to go off. McQueen.





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Offline syhprum

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« Reply #9 on: 09/09/2007 06:01:19 »
Our model aircraft used twin cylinder horizontally opposed engines about 2 cc displacement with the air intake controlled by a rotary sleeve valve.
Details could probably be found in the modellers magazines of the period
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Offline McQueen

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The Compressed air engine: Is it a scam?
« Reply #10 on: 09/09/2007 07:45:54 »
Quote
Our model aircraft used twin cylinder horizontally opposed engines about 2 cc displacement with the air intake controlled by a rotary sleeve valve.Details could probably be found in the modellers magazines of the period
Wow! That's sommething I'm hearing for the first time. How long could they stay in the air ? Quite interesting I'll look it up, if I can. McQueen
Yes Syhprum , you were right, here is a link. Quite fascinating!
« Last Edit: 09/09/2007 08:07:08 by McQueen »
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Offline DoctorBeaver

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The Compressed air engine: Is it a scam?
« Reply #11 on: 09/09/2007 08:10:04 »
Our model aircraft used twin cylinder horizontally opposed engines about 2 cc displacement with the air intake controlled by a rotary sleeve valve.
Details could probably be found in the modellers magazines of the period

I've only come across electric or petrol engines for model planes. Or, of course, elastic bands!
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« Reply #12 on: 09/09/2007 13:23:20 »
A long time ago a friend of mine had a model aircraft engine that ran like a steam engine but on the little CO2 cylinders you could get for making soda water. I never saw it in use in a model so I don't know how well it worked.

Incidentally, it's true that a high pressure air tank in a car would make it a potential bomb. The next question is, what does the gasoline tank do that's different?
In order to propell the vehicle you need stored energy; however you do it that is a potential danger.
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Offline McQueen

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« Reply #13 on: 09/09/2007 14:31:19 »
Quote
incidentally, it's true that a high pressure air tank in a car would make it a potential bomb. The next question is, what does the gasoline tank do that's different?
In order to propell the vehicle you need stored energy; however you do it that is a potential danger.
True! In many respects, the air-car engine is something that we all appreciate. But   in many respects it places us in the position of the poverty stricken vicar who visited the Manor and was given a bad egg for breakfast, for the amusement of the Lord. When asked what his breakfast was like. He replied "Well......it's good in parts!"  So, yes the aircar is a good thing, but it can power the engine for only a minute or so and then you need to think about refuelling. The rest of the time it runs on a gasoline engine. So what's the difference, not much. The Rotary Pulse Jet Engine would probably be much a better  alternative and more practical! McQueen
« Last Edit: 09/09/2007 14:34:12 by McQueen »
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« Reply #14 on: 09/09/2007 14:36:14 »
Look at the positives if you happen to take a dip in your local lake and forget to remove your car all them air tanks in your boot will stop you sinking. [:)]
 Or if it did still sink your engine would still work so you could drive back out. [;D]

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Offline DoctorBeaver

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« Reply #15 on: 09/09/2007 16:22:43 »
Look at the positives if you happen to take a dip in your local lake and forget to remove your car all them air tanks in your boot will stop you sinking. [:)]
 Or if it did still sink your engine would still work so you could drive back out. [;D]

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Offline lightarrow

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« Reply #16 on: 09/09/2007 18:59:51 »
Flywheel power storage has certainly been used on vehicles, I remember TV coverage of a railway shunting engine that stopped at an electricity supply, spun up its counter rotating flywheels and then went to work.
these were common low tech wheels but since then high vacuum enclosed ones have been developed
Thank you for this information. It was not only science-fiction, then!  [;D]

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Offline lightarrow

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« Reply #17 on: 09/09/2007 19:16:34 »
Look at the positives if you happen to take a dip in your local lake and forget to remove your car all them air tanks in your boot will stop you sinking. [:)]
 Or if it did still sink your engine would still work so you could drive back out. [;D]
Or, if you have to stay deep under water for long time, you have enough air to breathe.  [;)]

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Offline Bored chemist

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« Reply #18 on: 09/09/2007 20:25:20 »
"Apart from the huge amount of energy that would be needed to fill the tanks, there is the question of heat. A diesel engine compresses to about 16 : 1 or about 240 psi, during compression temperature rises to 500 degrees centigrade. The literature tells us that the air tank can be filled in 2 minutes! The temperature must rise to several thousands of degrees centigrade at the very least!"

Why on earth would the temperature need to be high?
It's perfectly simple to fit intercoolers on multi stage compressors. I regularly work with gases at 4500psi, they are practically at room temperature; if they ever got anywhere near 3000 C the steel tubing would melt.
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Offline McQueen

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The Compressed air engine: Is it a scam?
« Reply #19 on: 09/09/2007 23:16:11 »
Quote
Why on earth would the temperature need to be high?
It's perfectly simple to fit intercoolers on multi stage compressors. I regularly work with gases at 4500psi, they are practically at room temperature; if they ever got anywhere near 3000 C the steel tubing would melt.
But could this be done in 2 - 3 minutes ? Surely filling a 340 litre tank with air at 4500 psi in that amount of time would have to resullt in some heat? McQueen
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« Reply #20 on: 10/09/2007 13:53:02 »
When you compress air, the tank gets hot - diving bottles get hot and they use water to coolem. This is lost energy because you are using isothermal compression, effectively. The beauty of the IC engine is that it's adiabatic - more efficient.
Pneumatic engines  are pretty useful, though - what would your dentist do without his drill or how would they dig up roads so effectively without the lightweight pneumatic high-power breaker?

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« Reply #21 on: 10/09/2007 23:23:12 »
Remember if you are using air that is already compressed to 4500psi and at room temperature in a much larger cylinder you can rapidly fill the car tank with it because the overall filling process will not cause a large rise in temperature because the initial gas expanding into the empty tank will cool down and then warm up again as it is compressed by more gas entering the tank the only excess heat will be caused by the absorbtion of heat during the initial period when the gas is cold.  this could be prevented by making sure the tank is reasonably well insulated.
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Offline McQueen

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« Reply #22 on: 11/09/2007 15:38:58 »
Soul surfer
Quote
Remember if you are using air that is already compressed to 4500psi and at room temperature in a much larger cylinder you can rapidly fill the car tank with it because the overall filling process will not cause a large rise in temperature because the initial gas expanding into the empty tank will cool down and then warm up again as it is compressed by more gas entering the tank the only excess heat will be caused by the absorbtion of heat during the initial period when the gas is cold.  this could be prevented by making sure the tank is reasonably well insulated.
I am not too sure about this, what about Boyle's Law. Again look at the time constraints the tank has to be filled in 2 - 3 minutes. I can understand controlling the temp. if the filling took a longer time but......McQueen.
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Offline syhprum

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« Reply #23 on: 11/09/2007 17:03:46 »
Can anyone well versed in physics and good at arithmetic tell me how many Joules of energy are stored in 320 liters of air compressed to 300 Bar.
I don't think it amounts to a lot

I make it about 1.38 KW hours, a small slow vehicle might mamage on about 5 KW and run for 15 minutes or so ! 
« Last Edit: 11/09/2007 17:24:55 by syhprum »
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Offline lightarrow

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« Reply #24 on: 11/09/2007 20:25:41 »
Can anyone well versed in physics and good at arithmetic tell me how many Joules of energy are stored in 320 liters of air compressed to 300 Bar.
I don't think it amounts to a lot

I make it about 1.38 KW hours, a small slow vehicle might mamage on about 5 KW and run for 15 minutes or so ! 
Work done by the gas (assumed as ideal) on isothermal expansion ~ 5.48*107 J.
For adiabatic expansion is more complicated.

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Offline syhprum

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« Reply #25 on: 12/09/2007 09:25:35 »
5.48*10^7 Joules

Please tell why my calculation is so wrong!

I assume the air is enclosed in a cylinder of 1 meter cross sectional area and 96 meters long!
The compressed air at 300 bar is in the top 32 cm giving a force of 3*10^7 Newtons on the piston.
It is now allowed to expand pushing the piston 96 meters with an average force over the stroke of 1.5*10^7 Newtons which I calculate (wrongly!) as 1.44*10^9 Newton meters (Joules).

Failed "O" level maths 1941.
« Last Edit: 12/09/2007 09:27:35 by syhprum »
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Offline McQueen

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« Reply #26 on: 12/09/2007 10:18:36 »
I think your original estimate of 1.38 KW Hr was nearer to the mark syhprum. McQueen
« Last Edit: 12/09/2007 10:20:25 by McQueen »
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Offline McQueen

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« Reply #27 on: 12/09/2007 15:03:20 »
The compressed air car is  a much desired development in the search for an alternative cleaner, non-polluting form of motivating power that can be used in transportation. For the past 150 years the IC Piston engine, working on the Otto cycle and first invented in 1866 by Nicholaus Otto, has been the mainstay of personal and commercial road transport.  Yet with all the billions of dollars spent on trying to improve the performance of the IC Piston engine, every working sequence of the engine being examined and tested with the latest computer technology and simulations, by millions of people around the world, it is amply clear that if a solution is to be found for a more efficient engine, it won’t be based on IC piston technology. Even with all the 21st. Century innovations and improvements, such as MPFI, double overhead cams, multiple exhaust and inlet valves etc., the IC piston engine efficiency remains at 20%!
Think of it, an amazing and unacceptable 80% of the energy in the fuel used is wasted, by comparison, rockets and jets have an efficiency of 70% and better, or to put it another way, are more than two and a half times as efficient as piston engine cars, they are also, relatively, pollution free. Unfortunately, both turbines and rockets require or have required until this date, continuous combustion to deliver this order of efficiency. When used in road transport they are therefore very fuel inefficient using about 8 – 10 times the fuel used by a piston engine of similar size.
The compressed air car comes as a welcome and audacious challenge to IC Piston technology, it is an almost viable technology. The Compressed air car engine does work, for those of you who have doubts, you can check out this link on model airplanes that use compressed CO2 to run a piston engine. http://blacksheepsquadron.com/index.html
Of course one has to take into account that CO2 is far denser than air and would therefore work better as a compression agent, however the point is that the compressed air engine technology is viable, or as I had previously stated, almost  viable. The reason I say this is that a tank of compressed air with a capacity of 340 litres, (taken from the MDI Car specifications web-site) the compressed air would last for a maximum of 2 minutes. You can perform the calculations for yourself. A tank holding 340 litres corresponds to a cube with 2.25 ft sides. This tank is filled with compressed air at 4500 psi or 300 bars approx. The optimum rpm of the engine is 4500rpm, compressed air engines tend to perform best at a given rpm. Now if the cylinder capacity is about 8 cu ins. then at 4500 rpm, the engine would use 4500/60 = 75 x 8 = 600 cu ins in one second and 36,000 cu ins in one minute. The capacity of the tank is 27 x 27 x 27 cu ins or 19,683 cu ins. But the piston needs only about 500 psi  to work, so to get an accurate figure we have to divide 36,000/9 = 4000.  So the energy in the tank will last for 19,683/4000 = 5 minutes approx.  The point is that it often takes five minutes just to get the car out of the garage also once you use all that compressed air there is no way to re-charge the compressed air, so after about 4 –5 minutes you have to go to a service station and recharge. To recharge air at 4500 psi takes about a compressor working at 500 KW! 500KW, is enough to supply electricity to a fairly large town.  The longer range of 200km – 300 km is only achievable when an IC piston engine is onboard. Again to recompress the air with an onboard motor would take at least 3 – 4 kours. So while it is a wonderful technology, it is far from viable at the moment. TheRotary Pulse Jet Engine, has none of these shortcomings and if allowed I will discuss it in my next post. McQueen
« Last Edit: 12/09/2007 15:17:54 by McQueen »
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Offline lightarrow

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« Reply #28 on: 12/09/2007 18:02:54 »
5.48*10^7 Joules

Please tell why my calculation is so wrong!

I assume the air is enclosed in a cylinder of 1 meter cross sectional area and 96 meters long!
The compressed air at 300 bar is in the top 32 cm giving a force of 3*10^7 Newtons on the piston.
It is now allowed to expand pushing the piston 96 meters with an average force over the stroke of 1.5*10^7 Newtons which I calculate (wrongly!) as 1.44*10^9 Newton meters (Joules).

Failed "O" level maths 1941.
You are missing Boyle's law: PV = k = constant at T constant, so P = k/V; pressure decreases with volume and the average pressure is not given by an arithmetic average (if that's the way you computed the average force).
You have to do an integral to compute the work done by the piston:
∫P(V)dV from V1 = 0.32 m3 to V2 = 96 m3
where P(V) = nRT/V, so: ∫nRT/V dV = nRT ln(V2/V1); you get n from P1V1 = nRT. I chose T = 300K (27°C) to simplify my computations.

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Offline syhprum

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« Reply #29 on: 12/09/2007 19:22:38 »
I realised that my simple assumption that the average pressure on the piston would be half the maximum would lead to an error but as my figure was 26.3 times yours I did not think this was the only cause.
My next guess was that the force would drop of at an exponential rate 1/2.718 but the error is still 18 times!.
your figure equates to 16.2 KWh which would not take the vehicle very far!.
The penny has now dropped I failed to take account how quickly the pressure would drop as the piston moved.
syhprum

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Offline McQueen

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« Reply #30 on: 15/09/2007 00:30:25 »
Quote
Can anyone well versed in physics and good at arithmetic tell me how many Joules of energy are stored in 320 liters of air compressed to 300 Bar.
I don't think it amounts to a lot

I make it about 1.38 KW hours, a small slow vehicle might mamage on about 5 KW and run for 15 minutes or so ! 
Your calculations are actually surprisingly close to the manufacturers own claims, they state that 320 litres of air at 300 bar is equivalent to about 1.5 litres of petrol (or ).3 US gallons) and has an energy equivalent to 1.5KW hours. So yes it should run for 15 minutes, so how come the claims are for a range of 200 - 300 Kms? I think that is only when an IC engine is present onboard to assist. McQueen
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Offline lightarrow

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« Reply #31 on: 15/09/2007 01:45:15 »
5.48*10^7 Joules

Please tell why my calculation is so wrong!

I assume the air is enclosed in a cylinder of 1 meter cross sectional area and 96 meters long!
The compressed air at 300 bar is in the top 32 cm giving a force of 3*10^7 Newtons on the piston.
It is now allowed to expand pushing the piston 96 meters with an average force over the stroke of 1.5*10^7 Newtons which I calculate (wrongly!) as 1.44*10^9 Newton meters (Joules).

Failed "O" level maths 1941.
I don't think you have failed, if you can still make these computations !
However 1.44*10^9 Joule = 400 kWh not 1.38 kWh.

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Offline syhprum

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« Reply #32 on: 15/09/2007 06:50:18 »
Not really understanding the subtleties of calculus I did a numerical integration moving the the piston sufficiently each time to actually half the pressure which gives very nearly the correct answer.
at school they drummed some calculus into us parrot fashion but never gave us any idea how to applie it to real life situations.
I don't know how I got 1.38 KWh my second attempt gave 400 KWh
syhprum

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« Reply #33 on: 15/09/2007 23:07:21 »
Isothermal processes are not good value in terms of efficiency.
Boyle's Law refers to isothermal changes.  A piston engine using compressed air would gradually cool down  because the  changes in pressure and volume would lead to cooling  cooling.
Compressing a gas produces a lot of heat which has to be taken away - or will leak away in time. The energy involved is a significant proportion of the input energy so efficiency is compromised.
However, there is no reason to discount compressed gas as a source of energy. (Or, more correctly, a way of storing energy.) A very simple engine can convert the energy into a useful form - how about a siren using CO2 canisters, for instance? Very loud and the power source lasts for years and years without running down. Unlike batteries.
Utility rather than efficiency is sometimes the prime concern.
« Last Edit: 15/09/2007 23:13:17 by sophiecentaur »

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Offline McQueen

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The Compressed air engine: Is it a scam?
« Reply #34 on: 16/09/2007 04:21:28 »
Quote
A very simple engine can convert the energy into a useful form - how about a siren using CO2 canisters, for instance? Very loud and the power source lasts for years and years without running down. Unlike batteries.
In fact the uses of compressed air in Industry, apart from those that you have quoted, that readily come to mind such as a dentists drill and the Jack hammer, are too numerous to ennumerate.  There is no doubt that the aircar does work, but as you point out it just does not work efficiently. McQueen
« Last Edit: 16/09/2007 04:23:04 by McQueen »
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Offline lightarrow

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« Reply #35 on: 16/09/2007 14:50:02 »
Isothermal processes are not good value in terms of efficiency.
Boyle's Law refers to isothermal changes.  A piston engine using compressed air would gradually cool down  because the  changes in pressure and volume would lead to cooling  cooling.
Compressing a gas produces a lot of heat which has to be taken away - or will leak away in time. The energy involved is a significant proportion of the input energy so efficiency is compromised.
However, there is no reason to discount compressed gas as a source of energy. (Or, more correctly, a way of storing energy.) A very simple engine can convert the energy into a useful form - how about a siren using CO2 canisters, for instance? Very loud and the power source lasts for years and years without running down. Unlike batteries.
Utility rather than efficiency is sometimes the prime concern.
Yes, and what is worse is that a compressed air engine couldn't even be totally isothermal, but something between isothermal and adiabatic, so the work produced is even less.

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Offline syhprum

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« Reply #36 on: 27/09/2007 20:09:39 »
There is an intersting article in the 'New Scientist' about the use of windmills in Iowa to compress air and store it in natural underground reservoirs so that the power generated by the windmills overnight is available during the day.
The compressed air is not used directly to drive turbines but to replace the the compressor stage in conventional gas fired turbines leading to a large increase in efficiency.
« Last Edit: 27/09/2007 20:12:44 by syhprum »
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Offline Bartvl

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« Reply #37 on: 12/11/2008 12:43:11 »
I don't exactly know if this massage is here at the good place. But we have to investigate a motorcycle (maximum speed 30 kmh) what is going forward with compressed air. Do you know what parts we need therefor? I think we need a air engine and a heater. But I don't know what other parts we need. Can you help us?

Thank you very much.

Bart

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lyner

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The Compressed air engine: Is it a scam?
« Reply #38 on: 12/11/2008 18:55:18 »
Something to store the compressed gas in?
Buy/ hire CO2 canisters from a brewery if this is a brief investigation. Diving cylinders (air) would be expensive to buy but you could go 'down the road' to get them charged and the regulators would not be too costly. HEALTH and SAFETY could be an issue for you - or, at least, it should be for your supervisors.
I would think that a turbine would be best bet for getting something working quickly.
This is not a trivial exercise unless you have access to some serious machine tools.
Scrap Heap Challenge comes to mind. Could be fun.

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Offline yor_on

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« Reply #39 on: 13/11/2008 15:22:52 »
So if you allow for the air to cool of you will have it under pressure at room temperature.
But then, when filling it to another tank, won't it want to expand inside that new area, and won't that motion transfer to energy/heat??

And as more air is pressed in from the already pressured tank.
Won't that air, also wanting to expand, collide with the molecules already there, producing even more heat/energy?

So the faster you fill it the less heat, would that be correct?
But then the friction in the connections between the two tanks will be a problem, or?
I need to stop reading this:)
"BOMB DISPOSAL EXPERT. If you see me running, try to keep up."

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lyner

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« Reply #40 on: 13/11/2008 16:51:11 »
Re the motorcycle and Yor-on: Wouldn't the obvious thing be to vent the gas to the outside after it's done its expanding / work? Or are you not talking of the motorcycle?

What two tanks?

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« Reply #41 on: 14/11/2008 00:09:29 »
sorry Sophie, got to eager there.
Was reading the first page and the discussion of heat.

Totally missed page two I'm afraid, as I started to wonder how the compressed air would behave if 'let out' to an empty tank.
Reading your answer to the Question posed I agree.
It sounds like an advanced challenge if they are going to modify a bike engine to air?
Perhaps its a theoretical exercise?

And yes, my thoughts do seem to fit in somehow?
Strange:)
"BOMB DISPOSAL EXPERT. If you see me running, try to keep up."