Compressed-air car

Tata/MDI OneCAT

A compressed air car is an alternative fuel car that uses a motor powered by compressed air. The car can be powered solely by air, or combined (as in a hybrid electric vehicle) with gasoline/diesel/ethanol or electric plant and regenerative braking.

Overview

The compressed air car has been mentioned in Popular Mechanics as being the true car of tomorrow, with a range comparable to an electric vehicle or fuel-cell car. The hybrid version with gasoline/diesel/ethanol would not offer zero emissions at the tailpipe, while the compressed air/electric version would.

History

Main articles: Compressed air vehicle and air engine

Technology

Engines

Main article: Compressed air engine

Compressed air cars are powered by engines fueled by compressed air, which is stored in a tank at high pressure such as 30 MPa (4500 psi or 300 bar). The storage tank is likely to be made of carbon-fiber in order to reduce its weight while achieving the necessary strength. Instead of mixing fuel with air and burning it to drive pistons with hot expanding gases; compressed air cars use the expansion of compressed air to drive their pistons.

The idea is not new. There have been prototype cars since the 1920s and compressed air has been used in torpedo propulsion as well.

Storage tanks

Main article: Compressed air tank

Compressed air is a heavy way of storing fuel, 300 litres (11 cu ft) air at 30 MPa (4,500 psi) contains about 16 kWh of energy (the equivalent of 1.7 liters [0.44 US gal, 0.37 imp gal] of gasoline, assuming a 100% efficiency of the engine). During rupture testing, the tank cracks, but does not break up, producing no splinters or fragments.

All four major manufacturers that are developing air cars have designed safety features into their containers. In contrast to hydrogen's issues of damage and danger involved in high-impact crashes, air, on its own, is non-flammable. It was reported on Discovery's Beyond Tomorrow that on its own, carbon-fiber is brittle and can split under sufficient stress, but creates no shrapnel when it does so. Carbon-fiber tanks safely hold air at a pressure somewhere around 4500psi, which is good when compared with steel tanks.

Emission output

Compressed air cars are emission-free at the 'tailpipe'. Since a compressed air car's source of energy is usually electricity, its total environmental impact depends on how clean the source of this electricity is.

Due to this reason, a compressed air car's emission output can vary both with location and time. Different regions can have very different sources of power, ranging from high-emission power sources such as coal to zero-emission power sources such as wind. A given region can also update its electrical power sources with time, thereby improving or worsening emissions output.

Advantages

The principal advantages of an air powered vehicle are:

• Refueling can be done at home using an air compressor or at service stations. The energy required for compressing air is produced at large centralized plants, making it less costly and more effective to manage carbon emissions than from individual vehicles.
• One manufacturer promises a range of 200 kilometres (120 mi) by the end of the year at a cost of € 1.50 per fill-up. That manufacturer failed in its promise as of January, 2009.
• Compressed air engines reduce the cost of vehicle production by about 20%, because there is no need to build a cooling system, spark plugs, starter motor, or mufflers.
• The rate of self-discharge is very low opposed to batteries that deplete their charge slowly over time. Therefore, the vehicle may be left unused for longer periods of time than electric cars..
• Expansion of the compressed air lowers its temperature; this may be exploited for use as air conditioning.
• Compressed-air vehicles emit few pollutants, mostly dust from brake and tire wear.
• Air turbines, closely related to steam turbines, are a technology over 50 years old. It is simple to achieve with low tech materials. This would mean that developing countries, and rapidly growing countries like China and India, could easily implement a less polluting means of personal transportation than an internal combustion engine automobile.
• Lighter vehicles would result in less wear on roads.
• The price of fueling air powered vehicles may be significantly cheaper than current fuels. Some estimates project $3.00 for the cost of electricity for filling a tank.
• Reduction or elimination of hazardous chemicals such as gasoline or battery acids/metals
• Some mechanical configurations may allow energy recovery during braking by compressing and storing air.

[]== Disadvantages == Like the modern car and most household appliances, 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 oil is converted to usable fuel - including drilling, refinement, labor, storage, eventually transportation to the end-user. For compressed-air cars, energy is lost when electrical energy is converted to compressed air.

• When air expands, as it would in the engine, it cools dramatically (Charles law) and must be heated to ambient temperature using a heat exchanger similar to the Intercooler used for internal combustion engines. The cooling 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 the Intercooler, 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.

• Refueling the compressed air container using a home or low-end conventional air compressor may take as long as 4 hours though the specialized equipment at service stations may fill the tanks in only 3 minutes.

• Tanks get very hot when filled rapidly. SCUBA tanks are sometimes immersed in water to cool them down when they are being filled. That would not be possible with tanks in a car and thus it would either take a long time to fill the tanks, or they would have to take less than a full charge, since heat drives up the pressure.

• 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.

• 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 same speeds. MDI has recently claimed that an air car will be able to travel 140km in urban driving , and have a range of 80 km with a top speed of 110km/h on highways, when operating on compressed air alone.

Crash Safety Unproven

North American crash testing has not yet been conducted, and skeptics question the ability of an ultralight vehicle assembled with adhesives to produce acceptable crash safety results. Shiva Vencat, vice president of MDI and CEO of Zero Pollution Motors, claims the vehicle would pass crash testing and meet U.S. safety standards. He insists that the millions of dollars invested in the AirCar would not be in vain. To date, there has never been a lightweight, 100-plus mpg car which passed North American crash testing. Technological advances may soon make this possible, but the AirCar has yet to prove itself, and collision safety questions remain.

The key to achieving an acceptable range with an air car is reducing the power required to drive the car, so far as is practical. This pushes the design towards minimizing weight. In a collision the occupants of a heavy vehicle will, on average, suffer fewer and less serious injuries than the occupants of a lighter vehicle. An accident in a 2000 lb (900 kg) vehicle will on average cause about 50% more injuries to its occupants than a 3000 lb (1350 kg) vehicle. Air cars may use low rolling resistance tires, which typically offer less grip than normal tires. In addition, the weight (and price) of safety systems such as airbags, ABS and ESC may encourage manufacturers not to include them.

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.

The AirCar

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.

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. 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.

K'Airmobiles

K'Airmobiles has presented two running prototypes of VPA (Vehicles with Pneumatic Assistance). Their leaders now seek to gain the means of developing several projects of urban or leisure VPP (Vehicles with Pneumatic Propulsion). K'Airmobiles propose a different technology with their VPP , which may allow a reasonable range, generally with compressed air tanks of about 50L-100L/3000 psi capacity only.

These ecological vehicles use the technology of the compressed-air engine K'Air, developed in France by a small group of researchers, which thus proposes a range of projects around an idea: that of the urban or leisure compressed-air vehicles.

K'Airmobiles is the name given to a set of projects relating to "VPA" (Vehicles with Pneumatic Assistance) and "VPP" (Vehicles with Pneumatic Propulsion), These models are conceived like ultra light vehicles (limited to 250 kg max.), and their consumption of compressed air was calculated to remain lower than 120 L/min., although developing a dynamic push able to reach 4kN.

Two VPA prototypes are operational today, the "K'AirBike" and the K'AirKart. Two new VPP prototypes, the one-seater "K'AirTrike" and the three-seater "K'AirMobile Max" were intended for public presentation in October and November 2007 respectively.

MDI and Tata Motors

Main articles: Motor Development International and Tata Motors

MDI has proposed a range of vehicles developed on an identical concept, made up of MiniCATs and CityCATs.

The MDI MiniCAT is claimed to have a range of 'up to' 1000 miles when fitted with an internal combustion engine, but that drops to 30 miles when used in ZEV mode at low speeds in cities. OneCAT is anticipated to be priced in a range ($5,100 to $7,800) within reach of consumers in a developing economy, such as India.

The ultralight bodies of the vehicles would be made of glued-together fiberglass and injected foam, and the aluminum chassis would also be glued, not welded, to simplify manufacturing.

The engine will be available in two versions. The Mono Energy air engine is a true air engine. The Dual Energy engines are Internal combustion engines, which use hydrocarbon fuels.

They have licensed 12 factories : 5 in Mexico, 3 in Australia and New Zealand, 1 in South Africa, and 3 in France. MDI Andina S.A would like to sell the car in Colombia, Peru, Ecuador and Panama. MDI has entered into an agreement with Tata Motors, to produce air cars in India. Zero Pollution Motors will be the first company to manufacture and sell a car in the U.S. called the "Air Car" using MDI technology. ZPM will begin taking reservations in early 2009 for US deliveries in early 2010. Lately, the words FRAUD and SCAM tend to pop up whenever MDI is mentioned. That is because MDI has yet to produce a single car to sell and none of their planned launches had ever come true. MDI simply make an outrageous claim or announce a planned launch of their cars and then try to sell licenses to investors. So far, the best an air car can do in any public demonstration was just over 7 km on a full tank.

Tata

As of May 2007 Tata Motors of India planned to launch an MDI air car in 2008.. As of January 2009 this has not happened.

Electro-Tech Enterprises

Electro-Tech Enterprises is a small company that specializes in electric air vehicles using a new technology discovered by themselves that is currently in the proto-type phase.

Engineair

Engineair is an Australian company which manufactures small industrial vehicles using an air engine of its own design. http://www.engineair.com.au

See also

• Air engine
• Charging station
• Compressed air energy storage
• Compressed air vehicles
• Engine swap
• Eolo Car
• Plug-in hybrid
• Pneumatics
• Virginia Polytechnic Institute