22-01-2011, 02:43 PM
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Abstract
The Air car is a car currently being developed and, eventually, manufactured by Moteur Developpement International (MDI), founded by the French inventor Guy Nègre. It will be sold by this company too, as well as by ZevCat, a US company, based in California.
The air car is powered by an air engine, specifically tailored for the car. The used air engine is being manufactured by CQFD Air solution, a company closely linked to MDI.
The engine is powered by compressed air, stored in a glass or carbon-fiber tank at 4500 psi. The engine has injection similar to normal engines, but uses special crankshafts and pistons, which remain at top dead center for about 70% of the engine's cycle; this allows more power to be developed in the engine.
Though some consider the car to be pollution-free, it must be taken into account that the tanks are recharged using electric (or gasoline) compressors, resulting in some pollution, if the electricity used to operate the compressors comes from polluting power plants (such as gas-, or coal-power plants). Solar power could possibly be used to power the compressors at fuel station.
Introduction
An Air Car is a car that can run on compressed air alone without the use of conventional fuels used in present day automobiles. The car is powered by an air engine. The air engine is an emission-free piston engine using compressed air. The engines are similar to steam engines as they use the expansion of externally supplied pressurized gas to perform work against a piston.
For practical application to transportation, several technical problems must be first addressed:
• As the pressurized air expands, it is cooled, which limits the efficiency. This cooling reduces the amount of energy that can be recovered by expansion, so practical engines apply ambient heat to increase the expansion available.
• Conversely, the compression of the air by pumps (to pressurize the tanks) will heat the air. If this heat is not recovered it represents a further loss of energy and so reduces efficiency.
• Storage of air at high pressure requires strong containers, which if not made of exotic materials will be heavy, reducing vehicle efficiency, while exotic materials (such as carbon fibere composites) tend to be expensive.
• Energy recovery in a vehicle during braking by compressing air also generates heat, which must be conserved for efficiency.
It should be noted that the air engine is not truly emission-free, since the power to compress the air initially usually involves emissions at the point of generation.
Two technologies have been developed to meet different needs:
1. Single energy compressed air engines
2. Dual energy compressed air plus fuel engines
The single energy engines will be available in both Minicabs and City cats. These engines have been conceived for city use, where the maximum speed is 50 km/h and where MDI believes polluting will soon be prohibited.
The dual energy engine, on the other hand, has been conceived as much for the city as the open road and will be available in all MDI vehicles. The engines will work exclusively with compressed air while it is running under 50 km/h in urban areas. But when the car is used outside urban areas at speeds over 50 km/h, the engines will switch to fuel mode. The engine will be able to use gasoline, gas oil, bio diesel, gas, liquidized gas, ecological fuel, alcohol, etc.
Both engines will be available with 2, 4 and 6 cylinders, When the air tanks are empty the driver will be able to switch to fuel mode by using the car’s on board computer. The vehicles do not have normal speed gauges. Instead, they will have a small computer screen that shows the speed and engine revolutions. The system allows for infinite possibilities such as GSM telephone systems, GPS satellite tracking systems, programs for delivery people, emergency systems, internet connections, voice recognitions, map presentation, traffic information... in three words: the future is now.
Unlike the majority of traditional cars on the market, MDI´s vehicle's have fiber glass bodies which makes them light, silent urban car. The car's body is tubular, light weight, and is held together using aerospace technology.
Regarding security, the seatbelt system is different from what we know. One part of the belt is anchored to the floor of the car, like traditional cars. The other part of the belt, in stead of being attached to the side of the car, is also anchored to the floor of the vehicle. This helps to secure the bodies of the driver and passengers in the case of a collision.
MDI is also considering a system to replace traditional keys. This system would utilize an access card. With this card it would be possible to open the car from a short distance away without having to actually insert anything in the car.
In the single energy mode MDI cars consume less than one euro every 100Km. (around 0.75 Euros) that is to say, 10 time less than gasoline powered cars.
When there is no combustion, there is no pollution. The vehicle's driving range is close to twice that of the most advanced electric cars (from 200 to 300 km or 8 hours of circulation) This is exactly what the urban market needs where, as previously mentioned, 80% of the drivers move less than 60Km. a day.
The recharging of the car will be done at gas stations, once the market is developed. To fill the tanks it will take about to 2 to 3 minutes at a price of 1.5 euros. After refilling the car will be ready to drive 200 kilometers.
The car also has a small compressor that can be connected to an electrical network (220V or 380V) and will recharge the tanks completely in 3 or 4 minutes.
Because the engine does not burn any fuel the car's oil (a liter of vegetable) only needs to be changed every 50,000Km. The temperature of the clean air expulsed form the exhaust pipe is between 0 and 15 degrees below zero and can be subsequently channeled and used for air conditioning in the interior of the car.
History
It cannot be claimed that compressed air as an energy and locomotion vector is precisely recent technology. In fact at the end of the 19th century the first approximations to what could one day become a compressed air driven vehicle already existed, through the arrival of the first pneumatic locomotives. Yet even two centuries before that Dennis Papin apparently came up with the idea of using compressed air (Royal Society London, 1687). The first recorded compressed-air vehicle in France was built by the Frenchmen Andraud and Tessie of Motay in 1838. A car ran on a test track at Chaillot on the 9th July 1840, and worked well, but the idea was not pursued further.
1890 and 1902 ten compressed air trams circulated in Bern, Switzerland.
In 1892, Robert Hardie introduced a new method of heating that at the same time served to increase the range of the engineIn
1926 Lee Barton Williams of Pittsburg USA presented his invention: an automobile which, he claims, runs on air. The motor starts on gasoline, but after it has reached a speed of ten miles an hour the gasoline supply is shut off and the air starts to work. At the first test his invention attained a speed of 62 miles an hour.
In January 1932 what appears to be the first journalistic article ever written about a car driven by compressed air was published.
In 1934, 21-year-old Johannes Wardenier announced he developed the world’s first fuel-less automobile. For weeks Dutch newspapers reported of an incredible invention that would change the world for ever. Not long after that he was mysteriously imprisoned in a mental institution, his design for the engine was stolen and he was kept under constant guard and never allowed to see anyone.
In 1976 Ray Starbard from Vacaville, California developed a truck that is able to drive on compressed air. He felt that he had invented the power system of the future, a system that would greatly change the automotive face of the world. ´It’s the car of the future, there’s absolutely no doubt in my mind´ Starbard comments ´and all because of mother nature’s purest gift – Air¨.
In 1979, Terry Miller decided that compressed air was the perfect medium for storing energy. He developed Air Car One, which he built for $ 1,500. Terry’s engines showed that it was feasible to manufacture a car that could run on compressed air. He patented his method in 1983 (US4370857).
George Miller said the air car he invented in 1984 would run forever. Miller envisioned his invention to be a solution to fuel and pollution problems, and the end to the middle east wars. The 58 year old retired coal miner and bricklayer from Johnstown, USA used a medium size, four cylinder engine out of a twelve year old Opel. Air from one of the tanks is fed into it through the spark plug holes, and air pressure moves the piston. The air is circulated out of the engine and back into the tank.
Until 1987 the German company Arnold Jung Lokomotivenfabrik GmbH produced locomotives functioning on compressed air to be used in mines. In the 1980’s they were still selling and renovating locomotives.
Currently the tram association in Bern Switzerland (BTG) is developing a locomotive according to the original plans. It is expected to be ready in 2012.
At present (2010) various persons and companies are developing compressed air motors applicable to transportation, apart from the many companies that produce and commercialize compressed air motors for industrial purposes.
Working
Air powered cars run on compressed air instead of gasoline. Since the car is working on air there is no pollution. A two cylinder, compressed air engine, powers the car. The engine can run either on compressed air alone or act as an internal combustion engine. Compressed air is stored in fiber or glass fiber tanks at a pressure of 4351 pounds per square inch. The air is fed through an air injector to the engine and flows into a small chamber, which expands the air. The air pushing down on the piston moves the crankshaft, which gives the vehicle power.
This car is also working on a hybrid version of their engine that can run on traditional fuel in combination with air. The change of energy source is controlled electronically. When the car is moving at speeds below 60kph,it runs on air. At higher speeds, it runs on a fuel such as gasoline diesel or natural gas.
Air tanks fixed to the underside of the vehicle can hold about 79 gallons (300 litres) of air. This compressed air can fuel the car upto 200km at a top speed of 96.5kph.When the tank nears empty it can be refilled at the nearest air pump. The car motors require a small amount of oil about 0.8 litres worth that have to change just every 50,000km.
Technology description
1. The first piston takes in ambient air and compresses it to approximately 300 psi and 200*f in the compression chamber during the first cycle of the engine
2. When the piston pause, a small amount of compressed air from the tanks is released into the expansion chamber to create a low pressured, low temperature volume of about 140psi.
3. Shortly before the valve to the exhaust cylinder is opened, a high-speed shutter connects the compression and expansion chambers. The sudden pressure and temperature difference between the low chambers creates pressure waves in the expansion chamber, thereby producing work in the exhaust chamber that drives the piston to power the engine.
The air tanks for storing the compressed air are localized underneath the vehicle. They are constructed of reinforced carbon fiber with a thermoplastic liner. Each tank can hold 3,180 ft3 of air at a pressure of up to 4,300 psi. When connected to a special compressor station, the tanks can be recharged within 3-4 minutes. They can also be recharged using the on-board compressor 3-4 hours after connecting to a standard power outlet.
TECHNOLOGY OVERVIEW
These new vehicles incorporate various innovative and novel systems such as storing energy in the form of compressed air, using new materials such as fiberglass to build the car and vegetable oil for the motor lubrication.
Numerous innovations have been integrated in the engine design. As an example, there is a patented system of articulated conrods that allow the piston to pause at top dead center. The following graph indicates this movement of the piston in relation to the driving shaft rotation.
The car engine runs on compressed air and incorporates the three laws of thermodynamics.
1. The first law states that energy can neither be destroyed nor be wasted.
2. The second law describes the disorder within substances.
3. The third law defines that only in crystals at 0o k, there is absolute disorder.
The car incorporates these laws of thermodynamics in the following way. First, the pressure that is created within on-board tanks during compression is in direct proportion to the energy that has been stored in it. This process is equivalent to the energy stored in a wire spring when it is compressed. Furthermore, thermal energy is dissipating from the system, thereby lowering the temperature of a compressed gas volume that expands. This process is equivalent to harnessing energy that has been stored
Components of the Air car
• Compressed air tanks
The compressed air tank is a glass or carbon-fiber tank. These tanks hold 90 cubic meters of air compressed to 300 bars. This system is not dangerous in case of an accident as there is no risk of operation. Because these are the same tanks used to carry the liquid gas used by buses for public transport. The tanks enjoy the same technology developed to contain natural gas. They are designed and officially approved to carry an explosive product: methane gas.
In the case of a major accident, where the tanks are ruptured, they would not explode since they are not metal. Instead they would crack, as they are made of carbon fiber. An elongated crack would appear in the tank, without exploding, and the air would simply escape, producing a loud but harmless noise. Of course, since this technology is licensed to transport an inflammable and explosive gas (Natural gas), it is perfectly capable inoffensive and non-flammable air.
The tanks in CATs vehicles are composed of an interior thermoplastic container which ensures it is airtight. This is held in a coiled and crossed carbon fiber shell. This technique is the result of many studies into factors such as: mechanical specifications, density of material, choice of fibers etc. The conditions of use are maximum effective pressure (300 bar) and the temperature of use: from –40°C to 60°C.
The tanks are submitted to numerous tests to meet official approval, among which are:
Airtight testing
Pressure testing (1.5×300=405 b)
Rupture testing (2.35×300=705 b)
Cycles at ambient and extreme temperatures
Fire-resistance testing
Resistance to cuts
Shock and fall testing
During rupture testing, the tank cracks, but does not break up, producing no splinters or fragments. In the event of a cracked tank, it is most likely to occur within the cylinder itself.
The tanks used in the CAT´s vehicles should last for a period of fifteen years, to be tested every five years and are subject to wear and tear according to conditions of use. The tanks weigh 35 - 40 kg for 100 liters of air at 300 bars. In the MiniCat´s the tanks weigh 70 - 80 kg. For extra security, a protective plate is fixed underneath the vehicle’s chassis and in addition limits access to the circuit of high pressure air. There is also an extraction system to deal with water produced by condensation.
• Engine
The CAT’s 34 Engine is a 4-cylinder engine which will be used in cars in serial production.
This engine was developed between the end of 2001 and the beginning of 2002. It uses an innovative system to control the movement of the 2nd generation pistons and one single crankshaft. The pistons work in two stages: one motor stage and one intermediate stage of compression/expansion.
The engine has 4 two-stage pistons, i.e. 8 compression and/or expansion chambers. They have two functions: to compress ambient air and refill the storage tanks; and to make successive expansions (reheating air with ambient thermal energy) thereby approaching isothermal expansion.
Its steering-wheel is equipped with a 5kW electric motto-alternator. This motor is simultaneously:
The motor to compress air, the starting motor, the alternator for recharging the battery
An electric moderator/brake, a temporary power supply (e.g. for parking).
No clutch is necessary. The engine is idle when the car is stationary and the vehicle is started by the magnetic plate which re-engages the compressed air. Parking maneuvers are powered by the electric motor.
• Gear box
Gear changes are automatic, powered by an electronic system developed by MDI. A computer which controls the speed of the car is effectively continuously changing gears. The latest of many previous versions, this gearbox achieves the objective of seamless changes and minimal energy consumption.
• Moto-alternator
The moto-alternator connects the engine to the gearbox. It has many functions:
• It supports the CAT´s motor to allow the tanks to be refilled.
• As an alternator it produces brake power.
• It starts the vehicle and provides extra power when necessary.
• The Air Filter
The MDI engine works with both air taken from the atmosphere and air pre-compressed in tanks. Air is compressed by the on-board compressor or at service stations equipped with a high-pressure compressor.
Before compression, the air must be filtered to get rid of any impurities that could damage the engine. Carbon filters are used to eliminate dirt, dust, humidity and other particles which, unfortunately, are found in the air in our cities.
This represents a true revolution in automobiles - it is the first time that a car has produced minus pollution, i.e. it eliminates and reduces existing pollution rather than emitting dirt and harmful gases. The exhaust pipe on the MDI cars produces clean air, which is cold on exit (between -15º and 0º) and is harmless to human life. With this system the air that comes out of the car is cleaner than the air that went in.
• Brake power recovery
The MDI vehicles will be equipped with a range of modern systems. For example, one mechanism stops the engine when the car is stationary (at traffic lights, junctions etc). Another interesting feature is the pneumatic system which recovers about 13% of the power used.
• Articulated con-rod
The MDI con-rod system allows the piston to be held at Top Dead Centre for 70% of the cycle. This way, enough time is given to create the pressure in the cylinder. The torque is also better so the force exerted on the crankshaft is less substantial than in a classic system.
• Distribution and valves
To ensure smooth running and to optimize energy efficiency, the engines use a simple electromagnetic distribution system which controls the flow of air into the engine. This system runs on very little energy and alters neither the valve phase nor its rise.
8. The body
The MDI car body is built with fiber and injected foam, as are most of the cars on the market today. This technology has two main advantages: cost and weight. Nowadays the use of sheet steel for car bodies is only because of cost - it is cheaper to serially produce sheet steel bodies than fiber ones. However, fiber is safer (it doesn’t cut like steel), is
Easier to repair (it is glued), doesn’t rust etc. MDI is currently looking into using hemp fiber to replace fiber-glass, and natural varnishes, to produce 100% non-contaminating bodywork.
10. The Chassis
Based on its experience in aeronautics, MDI has put together highly-resistant, yet light, chassis, aluminum rods glued together. Using rods enables to build a more shock-resistant chassis than regular chassis. Additionally, the rods are glued in the same way as aircraft, allowing quick assembly and a more secure join than with welding. This system helps to reduce manufacture time.
11. Electrical system
Guy Nègre, inventor of the MDI Air Car, acquired the patent for an interesting invention for installing electrics in a vehicle. Using a radio transmission system, each electrical component receives signals with a microcontroller. Thus only one cable is needed for the whole car. So, instead of wiring each component (headlights, dashboard lights, lights inside the car, etc), one cable connects all electrical parts in the car. The most obvious advantages are the ease of installation and repair and the removal of the approximately 22 kg of wires no longer necessary. Whets more, the entire system becomes an anti-theft alarm as soon as the key is removed from the car.
Developers and manufacturers
Various companies are investing in the research, development and deployment of Compressed air cars. Overoptimistic reports of impending production date back to at least May 1999. For instance, the MDI Air Car made its public debut in South Africa in 2002, and was predicted to be in production "within six months" in January 2004. As of January 2009, the air car never went into production in South Africa. Most of the cars under development also rely on using similar technology to Low-energy vehicles in order to increase the range and performance of their cars.
1. MDI (Motor Development International)
MDI has proposed a range of vehicles made up of Air Pod, OneFlowAir, CityFlowAir, MiniFlowAir and MultiFlowAir. One of the main innovations of this company is its implementation of its "active chamber", which is a compartment which heats the air (through the use of a fuel) in order to double the energy output. This 'innovation' was first used in torpedoes in 1904.
2. Tata Motors
As of May 2007 Tata Motors of India had planned to launch a car with an MDI compressed air engine in 2008. Tata subsequently announced that the technology was still in development stage and the launch of a commercially viable vehicle in the near future was not possible.
In December 2009 Tata's vice president of engineering systems confirmed that the limited range and low engine temperatures were causing difficulties.
3. Air Car Factories
Air Car Factories SA is proposing to develop and build a compressed air engine. This Spanish based company was founded by Miguel Celades. Currently there is a bitter dispute between Motor Development International, another firm called Luis which developed compressed-air vehicles, and Mr. Celades, who was once associated with that firm.
4. Energine
The Energine Corporation was a South Korean company that claimed to deliver fully assembled cars running on a hybrid compressed air and electric engine. These cars are more precisely named pneumatic-hybrid electric vehicles.[27] Engineers from this company made, starting from a Daewoo Matiz, a prototype of a hybrid electric/compressed-air engine (Pne-PHEV, pneumatic plug-in hybrid electric vehicle). The compressed-air engine is used to activate an alternator, which extends the autonomous operating capacity of the car. The CEO is the first compressed air car promoter to be arrested for fraud.
A similar (but only for braking energy recovery) concept using a pneumatic accumulator in a largely hydraulic system has been developed by U.S. government research laboratories and industry, and is now being introduced for certain heavy vehicle applications such as refuse trucks.
5. K'Airmobiles
K'Airmobiles vehicles were intended to be commercialized from a project developed in France in 2006-2007 by a small group of researchers. However, the project has not been able to gather the necessary funds.
People should note that, meantime, the team has recognized the physical impossibility to use on-board stored compressed air due to its poor energy capacity and the thermal losses resulting from the expansion of the gas.
These days, using the patent pending 'K'Air Fluid Generator', converted to work as a compressed-gas motor, the project should be launched in 2010, thanks to a North American group of investors, but for the purpose of developing first a green energy power system.
6. Engineair
Engineair is an Australian company which manufactures small industrial vehicles using an air engine of its own design.
Models
A) Family
A spacious car with seats which can face different directions. The vehicle’s design is based on the needs of a typical family.
Characteristics: Airbag, air conditioning, 6 seats.
B) Van
Designed for daily use in industrial, urban or rural environments, whose primary drivers would be tradesmen, farmers and delivery drivers.
Specifications: Airbag, air conditioning, ABS, 2 seats, 1.5 m3.
c) Taxi
Inspired by the London Taxi, with numerous ergonomic and comfort advantages for the passenger as well as for the driver.
Specifications: Airbag, air conditioning, 6 seats.
D) Pick-Up
The "pleasure" car: designed for excursions, outdoor sports or water sports. Also suitable for tradesmen and small businesses.
Dimensions: 3.84m, 1.72m, 1.75m
Weight: 750 kg
Maximum speed: 110 km/h
Mileage: 200 - 300 km
Maximum load: 500 Kg
Recharging time: 4 hours (Mains connector)
Recharging time: 3 minutes (Air station)
Specifications: Airbag, air conditioning, 2 seats.
E) Mini Cat’s
The smallest and most innovative: three seats, minimal dimensions with the boot of a saloon: a great challenge for such a small car which runs on compressed air. The Minicat is the city car of the future.
Specifications: Airbag, air conditioning, ABS, 3 seats, 1.5 m3.
Commercialization
As soon as the MDI engines and vehicles are commercially viable (within 1-3
years, depending on the version) they will have a market, with very limited
competition, if any, for an estimated period of 10-15 years.
The commercial strategy is currently concentrated on the urban markets, with
products including taxis, delivery vans and pickup trucks.
Based on a new concept of local vehicle production and sales, MDI promote
regional manufacturing license rights in the form of franchised turnkey factory
systems. Such a turnkey factory will have a normal production capacity of
2000-4000 vehicles per year and will employ some 130 people. A model factory is
being constructed in Brignoles, France.
A taxi called "TOP" (Taxi Zero Pollution) and pickups truck, were built. In May
1998, the first road tests of these prototypes were done in Brignoles, France.
A great interest in the zero pollution concept has been expressed by the news
media. Since May 1998, the taxi "TOP" has been the subject of more than 40
television programs and several newspaper and magazine articles around the
world.
To manage the development process successfully, MDI has contracted its product research and development activities to CQFD Air Solution, a company based in
Brignoles, France. Here, under the direction of Guy Negre, some 30 engineers and
technicians have at their disposal the most modern equipment for engine
and vehicle development, testing and production, supported by the latest in
information technology.
The company says the cars will initially go on sale in France, where the first assembly line is due to start production in the middle of next year.
The MiniCATS three-seater compact, a commercial version of a prototype showcased at the 2002 Paris Motor Show, will be priced at $9,500(Rs.4,00,000). The City CATS six-seater sedan will retail for $16,500(Rs.7,00,000).
Advantages
Compressed-air vehicles are comparable in many ways to electric vehicles, but use compressed air to store the energy instead of batteries. Their potential advantages over other vehicles include:
1. Much like electrical vehicles, air powered vehicles would ultimately be powered through the electrical grid. Which makes it easier to focus on reducing pollution from one source, as opposed to the millions of vehicles on the road.
2. Transportation of the fuel would not be required due to drawing power off the electrical grid. This presents significant cost benefits. Pollution created during fuel transportation would be eliminated.
3. Compressed-air technology reduces the cost of vehicle production by about 20%, because there is no need to build a cooling system, fuel tank, Ignition Systems or silencers.
4. Air, on its own, is non-flammable.
5. The engine can be massively reduced in size.
6. The engine runs on cold or warm air, so can be made of lower strength light weight material such as aluminium, plastic, low friction teflon or a combination.
7. Low manufacture and maintenance costs as well as easy maintenance.
8. Compressed-air tanks can be disposed of or recycled with less pollution than batteries.
9. Compressed-air vehicles are unconstrained by the degradation problems associated with current battery systems.
10. The air tank may be refilled more often and in less time than batteries can be recharged, with re-filling rates comparable to liquid fuels.
11. Lighter vehicles cause less damage to roads, resulting in lower maintenance cost.
12. The price of filling air powered vehicles is significantly cheaper than petrol, diesel or biofuel. If electricity is cheap, then compressing air will also be relatively cheap.
Disadvantages
The principal disadvantage is the indirect use of energy. Energy is used to compress air, which - in turn - provides the energy to run the motor. Any conversion of energy between forms results in loss. For conventional combustion motor cars, the energy is lost when chemical energy in fossil fuels is converted to heat energy, most of which goes to waste. For compressed-air cars, energy is lost when chemical energy is converted to electrical energy, and then when electrical energy is converted to compressed air.
1. When air expands in the engine it cools dramatically (Charles law) and must be heated to ambient temperature using a heat exchanger. The heating is necessary in order to obtain a significant fraction of the theoretical energy output. The heat exchanger can be problematic: while it performs a similar task to an intercooler for an internal combustion engine, the temperature difference between the incoming air and the working gas is smaller. In heating the stored air, the device gets very cold and may ice up in cool, moist climates.
2. Conversely, when air is compressed to fill the tank it heats up: as the stored air cools, its pressure decreases and available energy decreases. It is difficult to cool the tank efficiently while charging and thus it would either take a long time to fill the tank, or less energy is stored.
3. Refueling the compressed air container using a home or low-end conventional air compressor may take as long as 4 hours, though specialized equipment at service stations may fill the tanks in only 3 minutes. To store 14.3 kWh @300 bar in 300 l (90 m3 @ 1 bar) reservoirs, you need at least 93 kWh on the compressor side (with an optimum single stage compressor working on the ideal adiabatic limit), or rather less with a multistage unit. That means, a compressor power of over 1 Megawatt (1000 kW) is needed to fill the reservoirs in 5 minutes from a single stage unit, or several hundred horsepower for a multistage one.
4. The overall efficiency of a vehicle using compressed air energy storage, using the above refueling figures, cannot exceed 14%, even with a 100% efficient engine—and practical engines are closer to 10-20%.For comparison, well to wheel efficiency using a modern internal-combustion drivetrain is about 20%,Therefore, if powered air compressed using a compressor driven by an engine using fossil fuels technology, a compressed air car would have a larger carbon footprint than a car powered directly by an engine using fossil fuels technology.
5. Early tests have demonstrated the limited storage capacity of the tanks; the only published test of a vehicle running on compressed air alone was limited to a range of 7.22 km.
6. A 2005 study demonstrated that cars running on lithium-ion batteries out-perform both compressed air and fuel cell vehicles more than three-fold at the same speeds. MDI has recently claimed that an air car will be able to travel 140 km in urban driving, and have a range of 80 km with a top speed of 110 km/h (68 mph) on highways, when operating on compressed air alone, but in as late as mid 2009, MDI has still not produced any proof to that effect.
7. A 2009 University of Berkeley Research Letter found that "Even under highly optimistic assumptions the compressed-air car is significantly less efficient than a battery electric vehicle and produces more greenhouse gas emissions than a conventional gas-powered car with a coal intensive power mix.
Conclusion
The air car which is the result of a long research and development is a clean, easy to drive, high performance car. MDI has achieved what the large car manufactures have promised in a hundred years time.
The end product is a light weight vehicle that can reach speeds up to 220 km/h (even though the legal limit is 120), a product that does not pollute like twentieth century vehicles and does not take a lifetime to pay off. Essentially, MDI has developed a modern, clean, and cheap car that meets most people’s needs.
