Car That Runs on Compressed Air Questioned by Critics (w/ Video)

November 3, 2009 by Lisa Zyga, weblog
Guy and Cyril N?gre of MDI stand with the AirPod. Image credit: MDI.

( -- As electric cars begin breaking into the short-distance vehicle market, one French company thinks that it has an alternative to the electric vehicle: a car that runs on compressed air. Motor Development International (MDI), located near Nice, France, unveiled its bubbly-looking AirPod last year, and has ambitious plans to begin manufacturing the car by early 2010. But some of its critics think that's a bold claim that will be extremely difficult to realize, especially considering that the company has yet to bring a car to market despite several past attempts.

The AirPod is the creation of father-son team Guy and Cyril Nčgre, the president and R&D coordinator of MDI, respectively. At 220 kilograms, the vehicle runs on 80 kilograms of air compressed to 350 bars (or 350 times the atmospheric pressure at sea level). It has a top speed of 28 mph (45 kph) and an estimated range of 137 miles (220 km). According to the company, it takes about three minutes to fill the tank, using just 1.5 euros of electricity. The driver steers the with a joystick, and two passengers can sit in the back seat, facing backward. The only direct exhaust from the car is very cold air.

The Nčgres have been working on pneumatic-propelled engines since the early '90s, when they formed MDI. The latest generation of this technology uses a simpler engine than its predecessors, and the company got a boost in 2007, when Tata Motors bought the Indian rights to MDI's technology. But MDI's efforts to bring a short-distance sedan to market turned in a different direction in January 2008, when the mayor of Paris announced plans to purchase thousands of city cars to be rented out by the hour. MDI created the small AirPod to compete with the electric and other vehicles in the contest to become the city car of Paris.

The Nčgres think that the AirPod has certain advantages over in the city car market, including its short fueling time and its long-lasting carbon fiber pressure tank, in contrast to expensive batteries that eventually wear out and need to be replaced. MDI estimates that the AirPod will cost about €6000 ($9,000).

However, not everyone agrees that the AirPod will live up to these expectations. MDI sent their performance specs to IEEE Spectrum, which had some concerns with the company's claims. In their analysis, IEEE Spectrum estimated that the AirPod's range could be less than a third of what MDI has claimed, due to energy being wasted in the process of expanding the air before it is sent to the engine.

Some automotive engineers think that compressed air is simply not a practical power source for vehicles due to the laws of thermodynamics. They point out that the AirPod's 200-liter tank doesn't carry much more energy than one liter of gasoline. In the IEEE Spectrum, two engineers, Denis Clodic of the Ecole des Mines de Paris and Pascal Higelin of the University of Orléans, said that pneumatic hybrids (vehicles that combine compressed air and fuel combustion) are promising. But they worry that, if MDI's AirPod fails, the entire concept of compressed air might suffer from the negative experience.

For the time being, MDI is looking forward to getting the AirPod to market. In early 2010, the company plans to begin producing one AirPod per hour at its first assembly line at Carros, France, and working toward setting up three more assembly plants. The company also hopes that the city of Nice may be interested in using AirPods in a rental car program similar to the one planned for Paris, and possibly in other crowded European and Asian cities.

More information:

via: IEEE Spectrum

© 2009

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3.3 / 5 (10) Nov 03, 2009
It's a interesting idea, but please if you want to get people excited about a car, design it so I wouldn't be ashamed if someone saw me in it.
Nov 03, 2009
This comment has been removed by a moderator.
1.2 / 5 (5) Nov 03, 2009
Unfortunately in order to use the car, you need to hire two additional people to push you when you need a start.
2.5 / 5 (6) Nov 03, 2009
It's a interesting idea, but please if you want to get people excited about a car, design it so I wouldn't be ashamed if someone saw me in it.

Why does it matter what it looks like?
3.8 / 5 (5) Nov 03, 2009
Be creative is more important then the ultimate goal. Give this people a chanche and embrace creativity! This technology hase potential.
3.7 / 5 (9) Nov 03, 2009
"Why does it matter what it looks like?"

Why do you have a hard time understanding the role of and importance of design and aesthetics? While it is fundamentally subjective, the consumer market is loaded with research and information on what consumers enjoy, why go argue with that only to make the transition in to major markets more difficult?

Just because *YOU don't care, doesn't mean a lot of us don't, we do and we like to care because having things we are mentally comfortable with creates a pleasurable experience.

And since we DO care and YOU DO NOT, all the more you shouldn't care if we had an impact on or opinion of its design, in fact it demonstrates why you shouldn't care if we have an opinion since the results are irrelevant to you.

... and yes, that is a shitty design, please give us something that isn't so awkward.
3 / 5 (4) Nov 03, 2009
Hmm, there are plenty of numbers to crunch given here.

80 kG air at 350 bars, OK. "Euros 1.5" in 3 minutes, somebody's hiding something!

Who fails to do arithmetic is doomed to nonsense.
3.6 / 5 (5) Nov 03, 2009
This looks very promising. I hope it pans out. TATAS are an excellent company and Guy Negre might just pull it off. If he does....History will bemade. Keep up the good work !!
4.8 / 5 (5) Nov 03, 2009
We test drove the prototypes in February and were impressed. And CMM, where do you come up with having two people push the car? It simply isn't true.

The only thing that needs to be resolved at this stage is to make efficient compressors. Up until now, compressors are notoriously inefficient. However, imagine having a solar array and wind turbines, you have a very clean fleet.

We feel this design makes sense for deliveries, postal services and of course, ice cream stores.

It will be interesting to see where it goes. Unfortunately, there was a lot of push back in France from sources that are related to car makers and the obvious petroleum industry. So those negative comments, even if some might be correct come from the wrong sources.

The team with the Electric Car
2 / 5 (3) Nov 03, 2009
"So those negative comments, even if some might be correct come from the wrong sources."

Since when is 'truth' dependent on its source?
2 / 5 (4) Nov 03, 2009

This is a scam. Their range is not 1/10 of what they say it is. They have never had an independent test, just around the lot, block.

Nor is compressing air eff or cheap. You lose much of the energy as heat which is why the air coming out is cold.

An EV would be less expensive, longer range, faster and you don't have to worry about being blown up if the tank fails from a defect or accident. That Tata invested in it makes me wonder about them.
5 / 5 (3) Nov 03, 2009
Without being too critical of the design, aside from it being unbelievably ugly, I have to take into questions the safety aspects.

Even as a town car, the probability of someone plowing through you at an intersection is quite high and I'm horrified to think of what would have if this little prickly thing meets an SUV.

Also, I'd like to see some independent tests too, 1.5 euros and 3 minutes sounds too good to be true.
4.3 / 5 (3) Nov 03, 2009
The petroleum company must be putting a lot of money in these people that are criticizing the air car...
4 / 5 (4) Nov 03, 2009

Have you seen what other European cars look like? This really isn't that off the wall for their style.
3 / 5 (2) Nov 03, 2009
From http://en.wikiped...gine#MDI
In the original Nègre air engine, one piston compresses air from the atmosphere to mix with the stored compressed air (which will cool drastically as it expands). This mixture drives the second piston, providing the actual engine power. MDI's engine works with constant torque, and the only way to change the torque to the wheels is to use a pulley transmission of constant variation, losing some efficiency. When vehicle is stopped, MDI's engine had to be on and working, losing energy. In 2001-2004 MDI switched to a design similar to that described in Regusci's patents (see below), which date back to 1990.[8] It has been reported in 2008 that Indian car manufacturer Tata was looking at a MDI compressed air engine as an option on its low priced Nano automobiles." looks better as it doesn't need a transmission.

5 / 5 (2) Nov 03, 2009
Why would this engine need to be idling when not moving? This makes little sense. Shouldn't it be as easy as opening an air valve when you want to move?
3.5 / 5 (2) Nov 04, 2009
That video showed a loud, silly, dangerous contraption that will never sell. What were they thinking??
1 / 5 (2) Nov 04, 2009
If they converted half the distance for speed they'de have a system that can go like 100km at a top speed of 90kph... not bad, wouldnt mind seeing how turbocharged miniaturized lightweight turbines would handle on this
1 / 5 (1) Nov 04, 2009
This engine makes little sense for a car , but it may be useable for a motorcycle.
3.5 / 5 (2) Nov 04, 2009
You need to know Paris a little better. They have banned large trucks, and buses must gain special licences. They rent bikes that are stored in the streets at drop off points all around the city. They hate polution and noise. If innovative commercially managed individual public car transport is going to work anywhere, Paris would be a very good proving ground. As for potential energy from compressed non-combustible gas, it looks like another large green engineering playground ... let's have some fun with it!
5 / 5 (2) Nov 04, 2009
Compressed air motors require moisture free air. If the air has not been dried then the motor will spew a mix of lubricant and water all over the place and that "gunk" has a foul smell and is a pollutant and will quickly plug up the motor. The motor must have dry air. The most common way to dry air is by refrigeration and of course it cost money to operate the air dryer. Has that been figured in? Wet air in an air motor will freeze up and plug up the exhaust port quickly even on hot days. In freezing weather the motor will really freeze if the air isn't dry.
2 / 5 (2) Nov 04, 2009
Since you are not using external air but air that came from a tank which came from a controlled source (a compressor which could easily include a dehumidifier) - where's the problem?

The aesthetics are questionable, but since it's aiming to be a rentable vehicle (much like the bikes already very successfully employed in Paris) I see no problem there. If it's cheap and you have a guaranteed parking space at the drop off point (a HUGE plus in Paris) it will be embraced quickly.

At the speeds you can go in Paris I'd also not be too concerned about crash safety. (and I'd also not be concerned at all about meeting an SUV - there aren't many there. You would never be able to find a parking space for one)

Even if the range is less than stated it would be enough for local/city traffic.
Nov 04, 2009
This comment has been removed by a moderator.
1 / 5 (1) Nov 04, 2009

At the speeds you can go in Paris I'd also not be too concerned about crash safety.

I'm sure Princess Diana's two boys would find your comment enlightening.
5 / 5 (1) Nov 05, 2009
Since you are not using external air but air that came from a tank which came from a controlled source (a compressor which could easily include a dehumidifier) - where's the problem?

Air can hold a large amount of water and it all comes from the atmosphere. Somewhere in the chain the water has to be removed and kept out. Anyone who has worked around air motors and compressors knows that water in the air supply is a constant and significant problem. An air dryer system to remove water is NOT easily incorporated into the compressor, if it was it would have already been done. Pneumatic systems are high maintenance.
2.5 / 5 (2) Nov 05, 2009
In the proposed system the cars would be parked (and refueled) at central stations which could easily have such infrastructure. Googling for "dehumidify compressed air" delivered plenty of working solutions for doing this minimal cost.

I'm sure Princess Diana's two boys would find your comment enlightening.

If she had ridden one of these things she'd still be alive. Your point?
5 / 5 (1) Nov 05, 2009
If it is all done at a central location you still have the issue of polluted waste water from the system and what to do with it. Dealing with that waste will increase the energy usage and cost of the system.
High velocity air running through the system can quickly degrade the plumbing as fast moving micro debris scours the inside of the plumbing and the motor. The motors also require lubricant which must be added to the air. Look in any compressed air system and you see oilers all over the place. That oil gets exhausted, not recovered. I have a lot of experience with compressed air systems and they are troublesome, nasty, and high maintenance. I think compressed air is a poor choice for motor vehicle power.
5 / 5 (2) Nov 07, 2009
Reciprocating engines all work on compressed air. Even the one in your car. The air is compressed by an explosion (sparking the air/fuel mixture), causing the pistons to move. Over 90% of the energy in the fuel is dissipated as heat, making the system very inefficient, since the heat is wasted and must be dissipated. Guy Nègre's idea is to use pre-compressed air to power the pistons, thereby doing away with the explosion, combustion, and waste of heat.
Since in a conventional engine, less than 10% of the (fossil) fuel's energy is used for power, and over 90% is wasted as heat, you really only need, in Guy Nègre's engine and compressed air tanks, the equivalent of the useful 10%.
As a city car, it does not need to go faster than the 50kph speed limit in urban areas in France. Its crash resistance need not be as great as that of a vehicle of greater mass traveling at much higher speeds.
If you want to take such a vehicle on the highway, that's another story.
not rated yet Nov 08, 2009
finally a car that will assure me of getting may "A" kicked at the local pub that doesn't have the word "smart" on it.
not rated yet Nov 08, 2009
Reciprocating engines all work on compressed air. Even the one in your car. The air is compressed by an explosion (sparking the air/fuel mixture), causing the pistons to move. ...........

Nice try but there is a huge difference between an internal combustion engine and a compressed air motor. I also neglected to mention the very poor low speed torque air motors have.
1 / 5 (1) Nov 08, 2009
"Nice try but there is a huge difference between an internal combustion engine and a compressed air motor. I also neglected to mention the very low speed torque air motors have."

Yes, and man will never fly.
And don't forget, space travel is impossible.
Guy Nègre (a retired aerospace engineer who has also worked in Formula 1) is attempting to combine a piston engine with a different source of compression than combustion. It's not just a compressed air motor. The miserable video attached to this article is a joke. It would have been better to link to one of the numerous videos that one can see on YouTube, such as http://www.youtub...=related or -- if you understand French,
5 / 5 (1) Nov 08, 2009
I never said man could not fly or make the air motor work in a car, rj74210. That's not what this is about. I have decades experience with pneumatic systems and I am stating my opinion about pneumatic drives. They are indeed an inferior form of locomotion when applied like this. Pneumatics is not something new. This has been tried before. Pneumatic drives are simply not up to the task for what these people want. As I have stated before they are nasty, dirty, troublesome, high maintenance and they are not new either. They have been around for over a century. They have their place in industry as a quirky alternative to internal combustion or electric drives but it is a very limited place. As a form of vehicle propulsion they are not up to the task. The videos do not sway me at all. If you're inclined do some research on the old Paris city wide pneumatic system from back in the 1800s. Like I said this air powered dream is not new.
1 / 5 (1) Nov 08, 2009
How about a small on-board solar/fuel/electric compressor that runs all the time compressing air for future use. My car sits 22 out of 24 hours generally. Also a problem with electric battery technology; the payload weight does not go down with use of electric power, as it does in a gasoline powered vehicle. Air has a very low payload weight compared to fuels and batteries, just the weight of the tank. Another aspect to consider. nes pa?
2.5 / 5 (2) Nov 08, 2009
As to the aesthetics, as a graphic and industrial designer for 40 plus years, I like the shapes and result. The 'shock of the new' is a problem that all designers deal with. Most cars today are an endless variation of a bland 'market based' theme like we were stuck in during the tailfins-und-chrome era. Chris Bangle BMWs are a typical example of bumps and bustles with no meaning or soul. Just things to make the rig look different. I am sure he would like to more but is restrained by the market folk. Just a guess...
3 / 5 (2) Nov 08, 2009

Do the math on how much sunlight falls on a car roof (hint: Look up 'Solar Constant'). You wouldn't be able to convert enough power over a 12 hour sunny day in order to make up for the extra weight of the compressor (much less gain enough power to get you anywhere). Solar powered cars only work under EXTREME conditions (like the Australian solar challenge. And you wouldn't want to sit in one of those contraptions on a regular basis)
2 / 5 (3) Nov 09, 2009
They were not able to get the car certified in France so they ended up getting it certified in the UK. There are many powers that have been scuttling the MDI teams potential for almost 20 years now. They should be congratulated for persevering through the toughest of times and making it so close to the finish line.

Three cheers for Guy and Cyril and the MDI team!!!
not rated yet Nov 09, 2009
can someone post a link to better details on their key innovation - their earlier offering i saw cleverly took in natural air and compressed it (like in an ICU) to lets say 100 bar, then they let in the compressed air at 350bar - this means the exhaust air is warm, not freeezing - and this extracts more energy from the 350bar reservoir. Its a bit like triple-expansion on old steam engines - and in fact could be developed into a triple or double expansion powerplant with 2 or 3 different sized cylinders.
5 / 5 (1) Nov 09, 2009
One of the big problems between the theoretical range and the actual range is pressure.

As the tank gets depleted the pressure drops and the power output drops. So imagine that as you gas gauge hits "half a tank" you can only go half as fast with half the acceleration. Now at 1/4 tank... well, you get the idea.

So there are ways to keep the pressure constant, but that requires MUCH more energy so the overall range becomes MUCH lower.

The air car is more of a gimmick that looks easy and clean because it has "air" in the title.
1 / 5 (1) Nov 09, 2009
Its too slow. A turtle on the road. If it can get up to normal speed it will survive in its city driving niche. Batteries will probably beat it in performance. Ultracapacitors might surpass it also. A small commuter car based on ultracapacitors might be viable.
5 / 5 (1) Nov 09, 2009
the pressure drop of air is a problem... this makes the constant energy available from liquid fuels look pretty good... how about a multi-modal technique that uses solar when avaiable and a small constant speed liquid fuel motor to fill in. The real kicker would be a micro-nuke like those being developed now. I noticed a news item a while ago that mentioned a remote Alaskan village that was considering a micro-nuke power plant. Take the concept even smaller and lets have micro-nuke batteries...

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