August 05, 2003
Compressed Air Hybrid Car Could Increase Fuel Efficiency

UCLA researchers have developed a method to add a compressed air energy storage system to cars for a low cost and low weight increase.

Air hybrid cars could bring big fuel savings for city drivers, according to a recent study released by UCLA engineers. Experiments based on modeling and simulations showed that the air hybrid engine improved fuel efficiency by 64 percent in city driving and 12 percent in highway driving. The study also suggested that by adopting the air hybrid approach, carmakers could avoid some of the manufacturing costs associated with the more common electric hybrid design.

Tsu-Chin Tsao, professor of mechanical and aerospace engineering at the UCLA Henry Samueli School of Engineering and Applied Science, and graduate student Chun Tai have been collaborating with engineers at Ford Motor Co. and consultant Michael M. Schechter for more than a year on an air hybrid vehicle design that uses a camless valvetrain. Tai presented the team's findings at the Society of Automotive Engineers World Congress in March.

Like its cousin the electric hybrid, air hybrid vehicles are being explored as a more fuel-efficient means of traveling the nation's roads, especially in urban areas, where stop-and-go traffic leads to a wasteful use of gas. During a typical day of city driving, fuel energy used to accelerate the vehicle is partially wasted during deceleration, when kinetic energy is converted into heat in the friction brakes.

Fuel economy could be greatly improved, say researchers, if that braking energy could be captured, stored and later used to help the vehicle speed up, for instance.

To make the air hybrid design work, Tsao introduced a few clever modifications to a traditional 2.5 liter V6 engine, including a valve design that allows the engine to not only burn fuel more efficiently, but to compress and expand air captured during braking as well. When it is compressed, air can store energy that is neither toxic nor explosive. Once the air is expanded, the burst of energy that is released can be used to help accelerate the car.

The concept is closely tied to that of electric hybrid vehicles, which are becoming an increasingly well-known alternative to traditional automobiles and have already proven capable of reusing braking energy. While still fueled by gasoline, the electric hybrid vehicle's engine and transmission combination is augmented by an energy conversion and storage system housed in a black box under the car's hood. This collection of sophisticated electronic components captures brake energy, stores it as electricity and then releases it when it is needed.

The additional hardware required to make it work includes a battery and a supplemental electric motor, which adds weight to the car and drives up costs. Manufacturers are forced to reduce weight in other ways.

"Automobile manufacturers are turning to more expensive lightweight materials like aluminum to compensate for the added weight involved with the electric hybrid approach," Tsao said. "With an air hybrid you don't have to worry about that."

Thanks to Tsao's innovative valve design, the air hybrid can achieve similar fuel efficiencies but needs only an air storage unit weighing no more than 30 kilograms.

"The air hybrid does not require a second propulsion system," Tsao said. "This approach allows for significant improvements in fuel economy without the added complexity of the electric hybrid model."

The UCLA researchers avoid the need for an additional motor by introducing greater functionality into the engine's valve system. During conventional combustion engine operation, the camshaft causes the intake and exhaust valves to open and close in a synchronized fashion to let in air and fuel and to let out exhaust. The camshaft is designed to perform in a predictable and fixed way. The same operation occurs over and over — nothing more.

Tsao's industrial collaborators designed an electrohydraulic camless valvetrain system that allows for more variable valve operation, with greater control over when a valve opens and for how long. Tsao developed methods to precisely control the valve operation over a wide temperature range. This, in turn, makes it possible for the traditional engine to do more than just burn fuel.

Tsao's proposed valve system allows the engine to operate in four different modes. When a vehicle decelerates, the engine is used as an air compressor to absorb the braking energy and store it into the air tank. Whenever the vehicle stops, at a red light for example, the engine is shut down. Once the light turns green and the driver touches the accelerator pedal, the engine is started by compressed air. As the car speeds up, the engine is used as an air motor to drive the vehicle until the compressed air is depleted, at which point the engine is switched to conventional combustion mode and begins burning fuel.

Road tests are needed to prove Tsao's concept, and other challenges need to be addressed before air hybrid vehicles become widely accepted. "We want to optimize the size of the air storage tank, and begin testing the air hybrid operation using a diesel engine," Tsao said.

Compressed air for vehicle propulsion is already being explored by others. Ford is even exploring compressed air hybrids. There is even a group exploring compressed fluids to store energy for vehicles. But this latest report looks like it might point the way for the development of a cost effective compressed air hybrid design.

The ability to add refinements to the basic internal combustion engine model of vehicle propulsion is a major reason why the prospects for hydrogen power cars are overrated. This latest report is another example of why this is the case.

By the way, there is another reason why the life of the internal combustion engine might eventually be greatly extended: the development of a technique to use either light or electricity to drive a reaction to fix carbon from carbon dioxide and hydrogen from water to make synthetic liquid fuels could remove one big environmental argument against hydrocarbon fuels and internal combustion engines. A major objection to the use of hydrocarbon fuels (whether gaseous or liquid) is that the fuels are almost always (one exception being subsidized corn-derived ethanol - which may cost more energy to produce than it provides) derived from fossil fuels and hence their burning adds to the total carbon dioxide content of the atmosphere. But if liquid fuels were made from atmospheric carbon then the effect would be to create an artificial carbon cycle that mirrors the natural carbon cycle of plants and animals. The use of liquid hydrocarbon fuels would no longer cause a net increase in atmospheric carbon dioxide.

How efficient could the process of converting electrical energy to hydrocarbons be made? How hard is the problem to solve for large scale production? Is the problem easier or harder to solve than it is to develop and build fuel cells and all the components of a hydrogen economy?

Share |      Randall Parker, 2003 August 05 05:35 PM  Energy Transportation

Patrick said at August 5, 2003 7:43 PM:

Compressed air CAN be explosive. Pretty much anything that can store enough energy to drive a car will produce some sort of explosion if the energy is released all at once. Even batteries.

John Moore (Useful Fools) said at August 6, 2003 10:30 AM:

Darn, this is a clever idea! Good find.

And I agree with the other poster... it can go boom, but so what?

Fred Boness said at August 6, 2003 2:58 PM:

I hope they aren't really using something as primitive as an air tank. An accumulator would be better. The difference is that with an air tank the pressure can be from 0 to max. An accumulator has a piston or bladder with pressure on one side. The working side then has pressure from that base charge (say 100 PSI) to max. All the energy stored is useable.

ian page said at August 7, 2003 1:59 AM:

BTW: The idea of artificially driving a carbon cycle is great...but it still has to answer questions about where the energy actually comes from in the first place. If it comes from fossil fuels we get nowhere!

However IF this provides a mechanism for storing and conveying electricity from solar, wave, tidal, wind sources it could be a really important step forward.

ahawk said at August 7, 2003 12:22 PM:

These air hybrid vehicles could offer another advantage if you could clean the air with them. If a cost effective filter could be developed it could clean the air as the car compresses it, but These filters would probably need to be changed regulary. Imagine if the more cars on the road around a city the cleaner that air would be of pollutants.

Luther Rangeley said at September 8, 2003 11:39 PM:

In 1931 German engineering journals reported a 1200 horsepower diesel-air hybrid locomotive. The air engine ran the train and the diesel engine ran the compressor. The waste heat from the diesel engine was used to expand the air supply. Net result was that the hybrid used 26% less diesel fuel for a given range of travel than a straight diesel locomotive.

Emmett Redd said at October 16, 2003 8:57 AM: describes a system to change waste into oil. A good portion of our waste comes from non-fossil fuel origins.

victory said at October 23, 2003 2:39 AM:

plase sent to me more to my e. mail

Mars said at October 28, 2003 9:46 PM:

I do think this technology is very interesting and I hope it will be popular sort of transportation vehicles. Please send me more information in detail and show me how to contact with the right person to introduce the technology into some countries. Thank!

Anne Kozelisky said at April 26, 2004 3:25 PM:

Very interesting technology. So is ahawk's brilliant idea for the air filters. There's also the air car in Europe that is being developed, see for more details. I'd like updates on the progress of this technology. Thank you.

LeRoy Pea said at July 24, 2004 6:04 PM:

Patent research for hydtogen, electric and air cars. Please visit PEA RESEARCH.

G.S.Gunasegarane said at March 10, 2005 12:13 AM:

Sir, this a novel idea to work with. I have also guided a batch of undergraduate B.Tech students in Mechanical Engineering to convert the existing two wheeler engine to run on compressed air exclusively without any sort of combustion. We are yet to make some more advanced studies on the same. So, I will be thankful if you could send me more technical details of the compressed air vehicles and also with regard to the throttling systems.
Thanking you

Deep Dark said at April 5, 2005 6:32 AM:

Only one problem, what is the energy cost of replacing enough of the world vehicle fleet to make a real difference in oil consumption?

Where does this energy to build the replacement fleet come from?
What other uses will have to be sacrificed to achieve it?
Who will make those decisions?
How will they be enforced.
How long will the transition take?

The world is full of technological fixes that would work, if they had been started 10 years ago.

It is now, officially, too late to start any of these schmes with any possibility that they will save the situation.

Although it is not a solution, massive, really massive reduction in oil use is going to be mandatory.

Andrew Knight said at April 21, 2005 9:35 PM:

This air hybrid idea could be really exciting if a simple system to convert conventional gas or deisel powered vehicles: During braking, cut off fuel supply while leaving carburetter butterfly valve 'open' and diverting the exhaust (which would then be mostly air) into an air tank. Feed it back into the intake during acceleration..a time-shifted supercharger.

Robert Klim said at April 24, 2005 5:25 PM:

Air-electric hybrid could have solar cells on top running compressor or battery charge. Long periods in city or parked would increase fuel efficently. Somehow the government could stadardize charging system in cars allowing charging on the move. Cities and highways could have charging strips where maser, lazer, or even alt magnetic systems could recharge a moving car. I like the diesel engines hybrids because of the greater amount of possible fuels.

air said at May 4, 2005 9:48 AM:

Rapid compression of air will create very high temperatures which will reduce the effectiveness of the (originaly described) system. Those same high temperatures will reduce the theoreticaly efficiency significantly.

'Interesting that the 1931-German-engineers (noted above) used some of (?) the heat to improve the efficiency of the diesel engine in their hybrid design. I hope Tsao used a deisel engine and tried that approach. But I expect there would still be too much heat generated too rapidly.

... How to solve that problem?

Is there an alternative to simple "compression"? For example, could the air be rapidly dissolved in a liquid? If the air/liquid interface were large enough, it might be possible. It might be quite an engineering feat. As an example of a similar feat, it is estimated that the air/liquid interface in human lungs is roughly the size of a tennis court.

Air is mostly nitrogen. The relevant question: Is there some way to modify the mechanical compresssion of nitrogen to have the same effect as simple mechanical compression but which avoids any heat-related problems.

P. Lind said at May 15, 2005 8:56 AM:

Look at what has already been done! News from Guy Negre!

Neat eh?

Andrew said at June 1, 2005 8:39 AM:

I enjoyed reading about this concept and I agree that something needs to be addressed as how we can produce energy and lower our consumption of fossil fuels. Many point to hydrogen as the next generation of automobiles. However, creating hydrogen form water is not an easy task and in the end is consuming energy at the local power plant. The air compression idea is unique. It would allow for much of the energy that is lost as heat to be gained as energy for the next accerating movement. I am interested in possibly putting this onto my own car if possible. Not only could it save gas when in operation, it could also be used to increase acceleration if installed to be used on a conventional vehicle that still burns fuel when accelerating from stop. Most fuel that is burned if I remember correctly is within the inital movement from 0 to 15 mph. Please send more info and when such a concept could be placed on older vehicles.

Charlie said at June 12, 2005 4:41 PM:

I am not a scientist but could we simply use highly compressed air in tanks like we use for welding and use pneumatic motors at the wheels to propel the car? When the tanks ran low than we could stop at one of many stations that have attendants that can clamp an air nozzle to the high pressure tanks and recharge them? Say 1500-3000 psi? Eliminating a heavy cast iron reciprocating piston engine will considerably lighten the car and reduce the load of the pneumatic engines.
No idling, only use energy when the wheels move. Energy would be used to compress air at the fueling stations but this has to be more efficent than our current system?
What do you think?

Padam Jain said at July 9, 2005 6:59 AM:

This air hybrid idea could be a drastic revolution to contol economy as well as
air pollution also for hi density population and upcomming contries.

Padam Jain

John Rogers said at July 22, 2005 9:25 PM:

Use a diesel engine to drive an air compressor which supplies an air storage tank.

Utilize the exhaust heat from the diesel (counter flow) to further heat the compressed air which will drive a compressed air engine which in turn provides power to one pair of wheels.

Use any waste heat to drive a "freon" engine which operates like a steam engine. The freon engine can provide power to the other set of wheels and a generator to recharge the standard automobile battery. The "freon" is to be kept in closed circuit.

The compressed air tanks can be recharged overnight at home using an electric motor connected directly to the compressor. For short trips, the compressed air can be directly reheated to add energy without the use of the diesel engine.

Braking can also be used to compress air or charge an accumulator.

Many variations can be used in the above scenario.

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miro said at August 13, 2005 7:14 AM:

the air hybrid is great idea but with no good implementation yet.
I notice many people don't realize why hybrid and why air... In city driving about 30% from the fuel goes into a kinetic energy that is wasted during braking. The hybrid can recover this waste but this is not the only advantage. The biggest advantage is the ability to improve the regime of the primary engine.
What most of the people do not understand is that the IC engines are efficient only in narrow range. You don't want to run a disel or gazoline engine in idle mode because they just waste fuel nor you want to overload them. For example Toyota Prius has a 55kw gas engine and without the electrical one you would run it the whole range from 0kw to 55kw and you would end up with serious fuel consumption and lazy car. By adding electrical motor you have another 30kw and the gas engine can be run only in the range 20-40kw which is much better than 0-50kw. And both engines will produce power from 0 to 80kw ;-)
Of course this can be done for a short time but this is what you need - a little bit more power during acceleration. In fact the elecrical accumulators are big not because they have to store too much energy, but because they have to be able to charge/recharge for too short time. The time is what makes the electrical parts big - not the total energy they deal with... For example if you hit the brakes your car may produce over a 100kw for few seconds and if you want to regenerate them all you'll need a really big generator.
Now why air should be better than electricity... It's because the efficiency. With the elecrical hybrids you have energy transformations from mechanical to electrical and backwords. If you have generator with 90% efficiency, batery with 80% and electrical motor with 90% you loose about 35% in the path. So running the gas engine to charge the batteries drops down the system efficiency and you can easily loose what you gain.
In the air hybrids no energy transformation is required. Simply every combustion engine has to make a compression first and then combustion and expansion. About 30% from the power produced during the working expansion is fed back for compression.
The idea of the air hybrids is to move the compression in the time. If you have a storage for compressed air and your engine does not need to compress you will get boost of 30% more output power. Latter, when less output power is required the engine can be "forced" to compress more air in order to refill the storage. In theory a very small storage is required to improve significantly the engine's regime. Moreover in stop and go traffic you don't have to shut down the engine instead during the stops and breaks it will be doing compression and during the accelerations it will expand only.
I don't understand however why they are trying to keep the current engine design and using complex valve trains. It would be much simpler to split the engine in separate compressor and expander. I would rather use a variable displacement units (radial or axial piston type). Imagine one unit working as compressor and another as expander connected with a common shaft. However if the displacement allows reversing you can get very interesting modes. For example during braking the expander can be reversed and both units can work as compressors. And the opposite during the acceleration both units can work like expanders. It's like to make a 4-stroke engine to run only on working and exost strokes. This will give about 3 times more power from the same engine volume.
The variable displacement will also allow to control the power aginst the speed. By increasing the displacement you get more flow and more power at the same speed and the opposit when you cruise and not much power is needed a small displacement will reduce the flow and the engine power.
Of course this design is more suitable for a Disel cycle where the combustion takes place at constant pressure and the combustion chamber can actually be external device, but this is even better because the combustion process will not be so time critical. Moreover it needs only one simple fuel port. And since there are no moving parts in the chamber I don't think it will be a problem to have good ceramic isolations etc.
I can think of one drawback of the design - the variable displacement compressors are not so efficient as the cilinder pistion type. So at perfect load such an engine may be less efficient than standard ones, but who drives at perfect load?
In any other respect this design should be better - you can have the same or even better thermodinamic parameters, you can have real idle mode - fuel can be supplied only when the engine is producing useful power regardless wheather the engine is rotating or not. For a fraction of a second the the whole engine can be reversed into a compressor, so the whole braking energy can go into the air tank which does not need to be that big, just good thermo insulation is enough.
And of course the biggest advantage is that the design does not require second engine and the cost should not be higher ;-)

Alfred Eugene, Pearl said at August 16, 2005 5:28 PM:

The compressed air hybrid car would be optimized if instead of a single engine, four small engines were incorporated into the design.


The operator of the car could select "economy" all the way up to "hill climb" and an on-board computer could determine how many of the four engines would need to run at any given time to keep the compressor tank at the pressure required to fulfill the operator's desired power range. Hell, for a simple task like this, all that's really needed are pressure switches on a sliding actuator.

Since the primary engine would be turning a compressor when not being called on to assist the stored air pressure in turning the driving wheels, why not run at peak efficiency all the time? Each engine of, say, 250cc's could run at its optimum RPM for power output (torque). In other words, it would run at wide open throttle and be full-time supercharged as well. This would result in weight savings (who needs a flywheel when running flat out!). It would also be both fuel efficient and clean-burning.

Not only that but a "lock-out" could exist that would allow only a single engine to run. This would be handy for handing the car keys to a valet. Or to a 16 year old to take the family car to school, or out on a date. 250cc's doesn't exactly tear up the pavement (or get on the freeway to Mexico).

Keeping things lightweight is another important point. While an electric hybrid requires a heavy subframe to support batteries, an air compressor hybrid needs literally nothing if the engineers are smart enough to make the compressor tank the backbone of the car, i.e. it supports the car rather than the other way around.

The engines would also be extremely lightweight (no flywheel, remember?). I would recommend a two-row six cylinder radial design to optimize weight reduction, reliability, consistent power output and minimal vibration. Golly gee, something this compact could be located under the seats (remember, there's four of 'em).

If the front wheels of the car were driven by high pressure from the compressed air tank, and the rear wheels driven by low pressure diverted directly from the engines, regenerative braking could be apportioned to 70% front 30% rear (how smart will the designing engineers be?) an optimum braking parity could be acheived by this design.

This would also result in four wheel drive upon hard accelleration, but only two wheel drive otherwise. (I call this "faux-wheel drive" he-he)

Now, anybody out there like quizes? Is it true that a two-row six cylinder radial engine only requires one single cam lobe to actuate all of its 12 intake and exhaust valves? yes or no.

The answer is yes! Get out a piece of paper and prove it to yourself, it's true! I designed this engine to be the most materials efficient engine possible and envisioned the air compressor hybrid car around it years ago, though it may take years for the car companies to finally get it right. They'll no doubt flounder for a decade before incorporating all the above. They'll probably do just what the author says and use some stupid normally aspirated V-6 displacing 3200cc's with a graduated air intake rather than take my advice about optimizing power output.

miro said at August 17, 2005 2:46 AM:


I don't understand your setup... You have radial engines driving a compressor only, or a compressor and the rear wheels?

BTW, not only a compressed air hybrid can be optimised with four engines but any car will be... Although they get this effect by different means - not by adding extra engines but either by switching off a bank of cilinders or like SAAB by changing the engine working volume....

karthee said at August 19, 2005 2:58 AM:

hay it's pretty amazing to hear about this innovative technology. i am in my final year of my engg .i wish to do my project in this area. i will be thankfull if u mail me more details regarding electromechanical valve actuators and other technical details regarding air hybrid vehicle.with regards karthee.............

Dino Snider said at August 26, 2005 6:10 AM:

To quote, "The ability to add refinements to the basic internal combustion engine model of vehicle propulsion is a major reason why the prospects for hydrogen power cars are overrated."
Hydrogen combustion engines exist. The advent of computer programmable fuel injectors even allows multifuel capability. The cost to modify a standard fuel engine is about $1000. 32.5% urea in aqueous solution scrubs out the NOX pollution.
All-electrics -and hybrids- may generate ground level ozone by high power electrical discharge.
And gasoline/diesel costs billions of dollars and thousands of lives here in Ontario every year...
Does gasoline *really* make 'more sense' - once the cost of negative externalities that society picks up the bill for are considered?

jan said at September 4, 2005 12:29 PM:

I will try to run diesel motor on compressed air. Simply, instead of bringing diesel do fuel pump I will bring there compressed air. The fuel pump drives compressed air directly to valve at the moment when the piston has the position "up". Instead of explosion there comes an expansion. Could somebody comment this solution, please?


Sione Vatu said at September 6, 2005 11:22 PM:

Hydrogen engines do not exist in the sense that they are a practical alternative to a petrol or diesel burning internal combustion engine. Forget hydrogen. It is very hard to burn in a piston engine due to its propensity to detonate uncontrollably (H2 will ignite in all proportions from 5% to 98% in air and all it takes is heat, unlike gasoline or diesel). It is expensive and very difficult to store. As for $1000.00 to convert a car; that's BS pure and simple. If it was so easy there would be many more hydrogen cars about (like there are zero around here). Fact is, H2 is difficult to get and twice as difficult to use! Look mate, making silly statements does not cause hydrogen engines to suddenly turn up. Dreaming and wishing and making up lies is for little wee children to do.

As for "externalities that society picks up." What nonsense! Consider that without the internal combustion engine most of us would be either dead or living in extreme poverty. When you consider "externalities" (which really are a fiction) it soon becomes clear that the car makers should be collecting enormous royalty pay-outs from govt. and all of us! The ease of personal transport they enable generates much welfare, wealth creation, empowerment and satisfaction etc.etc.etc. If you disagree, start walking.

Returning to the case at hand; air hybrids. These make a lot of sense. Air-hybrids are for the most part based on available technology; reliable and light weight. There are several sound alternative options to choose from. You do not have to use the sophisticated valve gear the UCLA researchers favour. I'm not saying there is anything wrong with their approach. There are just easier methods available. The UCLA approach has certain manufacturing cost and logistics advantages for high production runs. It also does exactly what is stated above; it time shifts the work of compression. But it is going to take some really solid research to enable. That's why separate compressors and expanders etc. may be ann easier option to pursue for some organisations.

Summing up. I do not expect to see fuel cells or suchlike for a long time to come. An air-hybrid is something that is possible and useful in a reasonably short time frame.

jacob J webber said at September 11, 2005 5:32 AM:

I quite disagree with 'sione Vatu' about hydrogen power being 'for little wee children to do'. I think it is wrong to dismis something that saves the invironment just because its hard to develop. Nobody's saying saving the invironments going to be easy and developing a hydrogen engine isn't. It will take time, money and effort but it will do good rather than hybrid cars which i believe to be a botch up job to save a few quid and will just delay damage to the atmosphere rather than stop it. As I say hydrogen cars will take time and money and those with hybrid cars who won't spend this are buying hybrid cars to save money not the environment.

jacob J webber said at September 11, 2005 5:42 AM:

sounds no better than battery hybrids. batery hybrids can store mare energy

Miro said at September 14, 2005 3:15 AM:

Jan wrote:
"I will try to run diesel motor on compressed air"

If you add compressed air with the intake you get "supercharging", but this is only usable if you keep the fuel injection and the rest of the operations. Note that you cannot mix compressed air and diesel fuel because they will burn and you can damage the fuel lines.
From other side if you don't use any fuel then there is no point of feeding your motor with uncompressed air. Normally the engine is producing power because you get more power from the expansion stroke than you waste for the other 3 strokes. This is true only if you add heat. Without a heat source it is a pure waste of energy to compress and expand air.
So you should feed your engine only with compressed air and you can use the intake valve instead of the fuel injector which is too small. Of course you would have to modify both the intake and exaust valves and their control too, and from 4-stroke to make a 2-stroke engine.
These modifications are enough to make the engine runnig, but not enough to make it reasonably efficient. The problem is that the pressure change always goes with a temperature change. Which means that in order to load your tank you will have to compress some air but doing so you will make it very hot too. Most likely you will let the heat to escape and your compressed air will get to the ambient temperature. If you don't get this heat back you loose most of your input energy.
You can get some part back by heat recovery - you need multiple decomression stages. For example if you use two pair of cylinders and compressed air at 200 bars in the first cylinder you can let it to expand 10 times (eventually by changing the valve timming), so it will get about 20 bars and temperature much lower than the ambient. Then from the first cylinder you can pass the air through a heat exchanger. This will heat the air back to the ambient temperature and it will increase its pressure (or volume) and then you can use it to feed the second cylinder.
My explanation probably is not perfect so you'd better check

dr mobius said at September 17, 2005 5:34 PM:

This all sounds very interesting. I recently heard about someone who has doubled the gas mileage by using liquid nitrogen to cool the car. Has anyone else heard about this and can point me to more information??? The idea I think is T(hot) - T(cold) delta is greater and so more efficient.


jason said at October 18, 2005 4:55 PM:

QUOTE: Compressed air CAN be explosive. Pretty much anything that can store enough energy to drive a car will produce some sort of explosion if the energy is released all at once. Even batteries.

Uh, but Gas or petrol isnt? People like you hold back the future. Steam engines are explosive. Duh, we are all gonna blow up. Lets not do this, even though it costs us 2 dollars to fill up the car, because its dangerous. I think its less explosive that a tank full of compressed LPG!!!!!!!

Edward Elliott said at November 4, 2005 10:44 PM:

Very interesting some of the comments, regarding the use of compressed air and fuel. As a backyard tinker, I build an engine that does such as this, the CAFEC ICompressed air, fuel, external combustion) Engine. See a short video of it running at

This kind of engine is the first step in ridding us of the Henry Ford, internal combustion engine, (Note: nothing wrong with the internal combustion, just that it way out of date and there better methods available) ake a lok at our engine, and leave some comment.



J.P. said at November 6, 2005 8:44 AM:

This is really neat stuff here. I am interested to find out more about how compressed air can be explosive. Are we talking about spontaneous combustion or just compressed air blowing out it's container?

I also really like the quicktimes from Edward E. Compressed air engines have always fascinated me for some reason. You wanted comment Edward, ok... very cool! We need more real life videos like that!

I would be interested to see that same engine run with a variable "throttle" and some type of load, maybe a big fan so load increases with RPM. Use a really big air tank with a measured charge, and try to do something like blow a ball up a tube with full throttle, incrementally increasing, or stepped/bursting methods. That could tell us what driving techniques (or computer models) would work best with a mechanically fixed engine configuration coupled to a variable energy input source.

I'll mail 5 bucks if you post another video!

Edward Elliott said at November 8, 2005 12:15 AM:

Just loaded another short video, this one shows the Mr Scrap (Our nickname for the engine)running on air only. Will be posting more as we learn more about this fantastic new power source. Each day new discovery are made, our next move is to set the engine up and just run it on air from a scuba diving tank. The tank holds 80 cfm at 3000 psi and weighs 30 lbs empty, full I don't know until I pick up the tank. It costs $4.80 US to fill it, less than a gallon of gas, so if this runs this small engine for 30 minutes, this power source could be a winner. We will be posting a video on the test.There are no valves in this engine, no starter is required, no fan belts are needed, so far all we got is two moving parts and we use water for lubrication. This engine by adding two valves can capture all the kinetic energy that is generated. I read on the Internet, 1000 lbs of batteries is equivalent to 1 gallon of gas, wonder how far 1000 lbs of compressed air would go. It going to be fun if we ever get enough funds together to have the emissions tested. I think we may do alright in this area because we can use un-leaded gas. The biggest advantage, with air, no wall street giant can strangle the public over shortages because of bad weather conditions. Should visit, and see the hatred for the Ford and their emissions.

Note, I find the videos run better if it in the skin mode.

Douglas W Hubbard said at December 28, 2005 9:22 PM:

Somebody has to look at the basic physics, here. They have a 300 liter tank at 300 atmospheres of pressure going through (nearly) isothermal expansion. Depending on what they consider the ambient temperature to be, you get total Megajoules of energy to be in the range of 30's to 40's. Under those conditions (300 liters at 300 bar, -100C) you have an air mass of about 173 kg. That is about .2 to .26 MJ/kg of "fuel" (ie. compressed air). That is about 150 times LESS than a kilogram of gasoline! In fact the entire compressed air tank has about the energy storage capacity of roughly 1 kg of gasoline (about one THIRD of a gallon of gasoline). The range and performance of this car seems to have little to do with any innovation with the use of compressed air. Its just a very TINY car with regenerative braking. I weigh about 200 and I'm 5'10". I don't think I would be very comfortable in this car.

Furthermore, the complexity of the compressed air-driven motor is absolutely irrelevant for the energy-storage limits of the system. In fact, I doubt an engine with this many moving parts could really be all that efficient compared to simpler existing systems. They couldn't patent the basic idea of a compressed-air driven car, so they could only patent a particular type of engine and system - for which I see no advantages over the public domain methods.

Doug Hubbard

Posted by: Doug Hubbard on December

tom carr said at January 10, 2006 5:44 AM:

What is to stop a car running two compressed air tanks so that whilst one is bieng re-presuriesed by the brakes the other could be heated by the engines coolant to increace the pressure which should produce more power?

If a cheep car like this could be developed to fill the 50km commute gap this would greatly reduce the smog problems within cities that suffer from stop start traffic and there would be the oppertunities for governments to give tax breaks.

if anyone has any ideas or relevent websites i am tom at

Alejandro Dal Monte said at February 17, 2006 10:15 PM:

Armando: No recuerdo tu nombre. Si recuerdo a un muchacho alto, fuerte, rubio, que hablaba con entusisamo de diversos sistemas de propulsion de vehiculos, mucho mas eficientes que los tradicionales. Era por los anos 60 o 70, en la facultad de ingenieria. Años despues lei algo sobre un Ingeniero Regusci que andaba por Montevideo con una moto que recargaba aire en los compresores de las estaciones de servicio. Asumi que era el mismo. No creo me recuerdes. Mi nombre es Alejandro Dal Monte, petizo, rubio, de ojos celestes que siempre estaba silbando. Cambie de rama y pase a la informatica. Actualmente estoy en Japon y he recorrido todo el mundo. Quiero comunicarme contigo, para hablar de tus proyectos, que se complementan con los mios. Seguire buscandote. Alejandro

Walter Haas said at March 7, 2006 9:21 AM:

Is the MDI air car in productin now.If not why not,if so what nations.What is the situation with the South Korea company Energine.Who develope this engine first.Is the design different regarding these two companies.

Thank You,

Walter Haas

eric said at March 14, 2006 8:47 PM:

Why not an electric air car hybrid, that can also use liquid nitrogen? You use what ever energy source is the cheapest or available. This way you are not locked into one technology.

Don Wharton said at March 25, 2006 10:51 AM:

The use of compressed air storage of energy is conceptually interesting. Battery storage has several problems. The batteries have only a certain number of charge/discharge cycles before they must be replaced. The large size in dictated by power which must be stored and returned later. Compressed air storage should have neither of these disadvantages. It need not degrade with use and it could store and release energy quite quickly.

I am extremely skeptical of the MDI compressed air car concept. They claim reasonable distances in test runs for a car based on compressed air. Any scientist or engineer which analyses their claims will say that they simply cannot store the energy required to do what they claim.

However, if the storage is up to the energy of one liter of gasoline that is excellent for the storage of energy from regenerative braking. One could store the energy of braking as one goes down an small mountain and then use it to go far up the next mountain. One simply must be realistic about the amount of energy to be stored.

I would love to know the results of Ford’s research into the concept.

Don Wharton

Sasa Trajkovic said at August 24, 2006 6:08 AM:

I am a Ph.D studnet from Sweden and my project is to design and test an air hybrid system. To my help I have fully variable pneumatic valves. So far I have tested the system in compression mode and air-motor mode. Soon I will also be able to use the compressed air to supercharge the combustion. If some one is interested in knowing more feel free to contact me.


salvatore Bologna said at August 27, 2006 9:26 PM:

My name is sal bologna i am an investor interested in financially backing an air car or air atv project.
If you are interested call me at 863-214-3807

vishal said at August 31, 2006 12:22 AM:

I want to know about compressed air in car's system. so you give me imformation about it.

cd said at September 4, 2006 8:07 PM:

All very interesting but the main advantages of a compressed air hybrid are: no additional battery weight, no dangerous high voltage (nobody has mentioned that one yet), regenerative braking (energy otherwise lost). Now if we can capture all the heat lost out the tailpipe and through the radiator and use it to heat the air that is another definite plus (consider the gas laws), raise the temperature, raise the pressure. Any improvement at this point is worth considering. We all know the ICE is grossly inefficient but we're not likely to eliminate it overnight but there is room for improvements, improvements that as long as gas was cheap no one cared to implement because the extra cost and complexity were not worth the effort. Better engine designs are needed along with more ways to capture and use wasted heat, these may make alternative fuels (which generally cost more) more attractive. It is my opinion that a compressed air hybrid would provide a much needed short term solution to our energy and pollution woes, perhaps the same as electric hybrids but more sensible and cost effective. This technology exist now and should be implemented, someday in the future we may have cars that run on cold fusion but that is future not present.

Ken Visser said at September 22, 2006 2:30 AM:

Just thought I would throw my two cents in on a project I had some undergrads do last year.
We converted a snow blower IC engine to run on compressed air, plumbing up a scuba tank to the spark plug hole, reworking the cam to make it a two stroke and connecting the whole thing to a golf cart. Total cost was about $500, mostly for parts to get the donated golf cart to be mobile. See for article and video

Brian said at November 13, 2006 2:37 PM:

We are working on a new air-hybrid engine that incorporates many of the ideas mentioned, and some very important parts that are not mentioned. If you would like to discuss air hybrid motors and your are a mechanical/aero engineer who is retired or living off investments, please e-mail me at This motor should enable a car that gets 25 mpg with a standard engine to get 100+ mpg. It could work well in an x-prize car.

You must be very able to think out of the box, be able to ask quality questions that lead to quality solutions, and be willing to stay the course for the long haul. We do this for the fun of it and receive no pay until we produce. If you don't love the engineering you won't want to go where we go. It is a journey and adventure, starting with a new power system, a new house combined-heat-and-power system, moving to aircraft and personal air vehicles, all funded by electricity generation and real estate development that enable us to do more engineering.


qwertyui said at May 31, 2007 6:38 PM:

This article fucken sucks! It has more comments than info i need info for my reaserch, dumb asses, geeks, and nerds you guys dont know shit! Yeah.

Jason said at June 3, 2007 2:55 PM:

Wouldn't a air compressed car hybrid with an electric engine provide the distance, torque, longevity, and lack of polution in terms of miles required for adequate comparison... Added to that you could install solar absorption plating on the body and air recompresor in the engine and and something to recycle the brake keneitic engergy that is lost. In truth we are just bullshiting this problem was solved years ago. But everytime there is a new technology out the oil and car industries buy the patent and lock it away then tell us what vehicles to like and we simply nod our heads. Both air and compressed air would destroy the parts and fuel industry thats why they force a new fuel on us like ethanol and hydrogen so they can have something to sell and parts for it lol. Believe it or not there is battery out there right now that allows for 300 miles on one charge. One of the oil companies holds majority of control of it after they bought the company from GM who initially stoped the CEO of the company from revealing his new battery technology. Money Money Money.... and let the world go to hell lol.

BigDaddy69_77 said at June 7, 2007 12:38 PM:

Jason, are you talking about Ovshinski? Is everybody here familiar with Lee Rogers' design? For those too lazy to click: he's using 4 tanks, so while one is discharging the others are filling. He initially charges the system with nitrogen, then it pretty much runs itself with a compressor and a large hood scoop. He's just converted a regular Dodge engine to run off it by using air in place of gasoline. His intention was to create a $1000 conversion kit for all cars, but apparently the automakers threatened him into submission since he initially refused their billion dollar offer. Now he refuses to discuss it. His only problem was trying to get it to run SLOW enough without losing its charge.
How about the Neal tank at Anybody want to comment on its feasibility?
I love the idea of photovoltaic film in the paint to collect sunlight all day and compress air while parked.
This guy also seems to have some interesting ideas to triple mileage by electrolysing hydrogen and oxygen from water mixed with old battery (sulfuric) acid and pumping it into the carburetor on the fly to enrich the combustion phase. He claims he was getting 67mpg out of a previously 15mpg engine and had ideas for further improvements.
This guy seems to be doing the same thing, although he's using an unnamed proprietary (common and inexpensive) metal alloy with salt water to optimize his electrolysis.
Okay, now here's a thought, how come nobody is bringing gravity into the equation for vehicle propulsion with compressed air? What if the shock absorbers could be converted into little air compressors and every bump and pothole and corner took the multi thousand pounds of vehicle weight to constantly compress air into storage tanks? In that vein, why couldn't similar "compression struts" be mounted under roads, bridges, railroad tracks, etc. to capture the vertical energy of passing traffic, trains, or wind on bridges? We must be talking about nearly infinite billions of pounds of energy being lost. Why couldn't we convert that energy of motion into the power of stored compressed air?
Also, let's get the word out on kinetic energy batteries also. Basically envision an alternator creating current but now remove friction by suspending the spinning parts in a magnetic field and then remove air resistance by placing the whole unit in an evacuated chamber. Perhaps super high pressure compressed air could be used to "energize" such kinetic energy powerplants which could power a vehicle.
By the way, current carbon fiber reinforced air tanks hold well in excess of 10,000 pounds of pressure and I think they are heading quickly for 20,000 pound or more capacities as increased demand encourages more exotic solutions. Such improvements in technology make them lighter, stronger and hopefully, eventually, cheaper, although they're not out of reach now.
And whatever happened to the superlight, superstrong, superhot, superefficient and clean ceramic engines that should have been built decades ago? I remember the inventor finally figured out that he could use the carbon/graphite from the exhaust as his dry "lubricant" then I think he died. That was his only unsolved problem I recall since the engine ran at such high heat that any liquid would burn off.

jimmy said at August 7, 2007 1:21 PM:

crap i thought of this exact idea last night but i guess they beat me to it, o well!

Anne Srinivas said at September 12, 2007 7:20 AM:

Pls send me pics of these cars and slides since i am going to give paper presentation at our college

chee said at October 9, 2007 10:41 AM:

while we can not do alot here in the states due to law suits, other areas are exploring out of the box. if you know of anyone who has a viable motor, air, etc. please email me:

Claes Bratt said at October 11, 2007 12:18 PM:

Hello !

I would like to add some other ideas. You have herad about saving CO2 in
mountainsrooms and so on from burning coal in in energy plants.

Now what to do with this CO2, you can leda it back to forests or plants
by building greenhouses and use the CO2 as fertilization. It is common
for ordinay vegetable plants and you will have an increase in growing
speed by 3 times because the efficient co2 ppm is 1000 ppm for the

Second if it is possible to add a compression device to the car engine we can
compress the CO2 to fluid and use the above mechanism. But I have not
done any computations on it, but my guess is that it can be done.

Thats all, thank you

Linda said at February 20, 2010 9:19 AM:

What about a car that uses an electric engine to start the car, then powers the air motor to compress air and also start the Air engine when the compressed air is at its maximum which then switches off the electic engine and also charges the battery, when the battery is full starts the electric engine and so on. To start this process you can either put in compressed air or even charge the car through the mains or even both.

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