Compressed-air vehicle
Encyclopedia
Compressed air
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....
, which is stored in a tank. Instead of mixing fuel with air and burning it in the engine to drive pistons with hot expanding gases, compressed-air vehicles use the expansion
Free expansion
Free expansion is an irreversible process in which a gas expands into an insulated evacuated chamber.Real gases experience a temperature change during free expansion...
of compressed air to drive their piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
s. One manufacturer claims to have designed an engine that is 90 percent efficient.
Compressed-air propulsion may also be incorporated in hybrid systems, e.g., battery electric propulsion and fuel tanks to recharge the batteries. This kind of system is called a hybrid-pneumatic electric propulsion. Additionally, regenerative braking can also be used in conjunction with this system.
Engine
One can buy the vehicle with the engine or buy an engine to be installed in the vehicle. Typical air engines use one or more expander pistons or rotary expander like the QuasiturbineQuasiturbine
The Quasiturbine or Qurbine engine is a proposed pistonless rotary engine using a rhomboidal rotor whose sides are hinged at the vertices. The volume enclosed between the sides of the rotor and the rotor casing provide compression and expansion in a fashion similar to the more familiar Wankel...
. In some applications it is advantageous to heat the air, or the engine, to increase the range or power.
Tanks
The tanks must be designed to safety standards appropriate for a pressure vesselPressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...
, such as ISO 11439.
The storage tank may be made of:
- steelSteelSteel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, - aluminiumAluminiumAluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, - carbon fiberCarbon fiberCarbon fiber, alternatively graphite fiber, carbon graphite or CF, is a material consisting of fibers about 5–10 μm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in crystals that are more or less aligned parallel to the long axis of the fiber...
, - KevlarKevlarKevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
, - other materials, or combinations of the above.
The fiber materials are considerably lighter than metals but generally more expensive. Metal tanks can withstand a large number of pressure cycles, but must be checked for corrosion periodically.
One company stores air in tanks at 4,500 pounds per square inch
Pounds per square inch
The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...
(about 30 MPa) and hold nearly 3,200 cubic feet (around 90 cubic metres) of air.
The tanks may be refilled at a service station equipped with heat exchangers, or in a few hours at home or in parking lot
Parking lot
A parking lot , also known as car lot, is a cleared area that is intended for parking vehicles. Usually, the term refers to a dedicated area that has been provided with a durable or semi-durable surface....
s, plugging the car into the electrical grid via an on-board compressor
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...
. The cost of driving such a car is typically projected to be around €0.75 per 100 km, with a complete refill at the "tank-station" at about US$3.
Compressed air
Compressed airCompressed air
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe, 10 percent of all electricity used by industry is used to produce compressed air, amounting to 80 terawatt hours consumption per year....
has a low energy density
Energy density
Energy density is a term used for the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored...
. In 300 bar containers, about 0.1 MJ/L and 0.1 MJ/kg is achievable, comparable to the values of electrochemical lead-acid batteries. While batteries can somewhat maintain their voltage throughout their discharge and chemical fuel tanks provide the same power densities from the first to the last litre, the pressure of compressed air tanks falls as air is drawn off. A consumer-automobile of conventional size and shape typically consumes 0.3-0.5 kWh (1.1-1.8 MJ) at the drive shaft per mile of use, though unconventional sizes may perform with significantly less.
Emission output
Like other non-combustion energy storage technologies, an air vehicle displaces the emission source from the vehicle's tail pipe to the central electrical generating plant. Where emissions-free sources are available, net production of pollutants can be reduced. Emission control measures at a central generating plant may be more effective and less costly than treating the emissions of widely dispersed vehicles.Since the compressed air is filtered to protect the compressor machinery, the air discharged has less suspended dust in it, though there may be carry-over of lubricants used in the engine.
History
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
locomotives and trams in cities such as Paris (via a central, city-level, compressed air energy distribution system), and was previously the basis of naval torpedo
Torpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...
propulsion.
During the construction of the Gotthardbahn
Gotthardbahn
Gotthardbahn was the name of a private Swiss railway company which operated the railway line from Immensee to Chiasso . Nowadays this term usually does not refer to that company, but to the railway line itself...
from 1872 to 1882, pneumatic locomotives were used in the construction of the Gotthard Rail Tunnel
Gotthard Rail Tunnel
The Gotthard Rail Tunnel, is a 15-kilometre long railway tunnel and forms the summit of the Gotthard Railway in Switzerland. It connects Göschenen with Airolo and was the first tunnel through the Gotthard massif...
and other tunnels of the Gotthardbahn.
In 1903, the Liquid Air Company located in London England manufactured a number of compressed-air and liquified-air cars. The major problem with these cars and all compressed-air cars is the lack of torque produced by the "engines" and the cost of compressing the air.
Recently several companies have started to develop compressed air cars, although none have been released to the public, or have been tested by third parties.
Advantages
Compressed-air vehicles are comparable in many ways to electric vehicleElectric vehicle
An electric vehicle , also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion...
s, but use compressed air to store the energy instead of batteries. Their potential advantages over other vehicles include:
- 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.
- 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.
- Compressed-air technology reduces the cost of vehicle production by about 20%, because there is no need to build a coolingCoolingCooling is the transfer of thermal energy via thermal radiation, heat conduction or convection. It may also refer to:-Techniques:* Air conditioning* Air cooling* Computer cooling* Cryogenics* Conduction * Infrared solar cells* Laser cooling...
system, fuel tank, Ignition Systems or silencerMufflerA muffler is a device for reducing the amount of noise emitted by the exhaust of an internal combustion engine. A US Patent for an Exhaust muffler for engines was granted to Milton and Marshall Reeves in 1897....
s. - Air, on its own, is non-flammable.
- The engine can be massively reduced in size.
- The engine runs on cold or warm air, so can be made of lower strength light weight material such as aluminiumAluminiumAluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, plastic, low friction teflon or a combination. - Low manufacture and maintenance costs as well as easy maintenance.
- Compressed-air tanks can be disposed of or recycled with less pollution than batteries.
- Compressed-air vehicles are unconstrained by the degradation problems associated with current battery systems.
- 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.
- Lighter vehicles cause less damage to roads, resulting in lower maintenance cost.
- 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
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's lawCharles's lawCharles' law is an experimental gas law which describes how gases tend to expand when heated. It was first published by French natural philosopher Joseph Louis Gay-Lussac in 1802, although he credited the discovery to unpublished work from the 1780s by Jacques Charles...
) and must be heated to ambient temperature using a heat exchanger similar to the IntercoolerIntercoolerAn intercooler , or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric cooling, which removes...
used for internal combustion engines. 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 the IntercoolerIntercoolerAn intercooler , or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric cooling, which removes...
, 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 (4 mi).
- A 2005 study demonstrated that cars running on lithium-ion batteries out-perform both compressed-air and fuel cell vehicleFuel cell vehicleA Fuel cell vehicle or Fuel Cell Electric Vehicle is a type of hydrogen vehicle which uses a fuel cell to produce electricity, powering its on-board electric motor...
s more than threefold at same speeds. MDI has recently claimed that an air car will be able to travel 140 km (87 mi) in urban driving, and have a range of 80 km (50 mi) with a top speed of 110 kilometre per hour on highways, when operating on compressed air alone.
Possible improvements
- Compressed-air vehicles operate to a thermodynamic process as air cools down when expanding and heats up when being compressed. As it is not possible in practice to use a theoretically ideal process, losses occur and improvements may involve reducing these, e.g., by using large heat exchangers in order to use heat from the ambient air and at the same time provide air cooling in the passenger compartment. At the other end, the heat produced during compression can be stored in water systems, physical or chemical systems and reused later.
- It may be possible to store compressed air at lower pressure using an absorption material within the tank. Absorption materials such as Activated carbonActivated carbonActivated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...
, or a metal organic framework is used to store compressed natural gasCompressed natural gasCompressed natural gas is a fossil fuel substitute for gasoline , diesel, or propane/LPG. Although its combustion does produce greenhouse gases, it is a more environmentally clean alternative to those fuels, and it is much safer than other fuels in the event of a spill...
at 500 psi instead of 4500 psi, which amounts to a large energy saving.
Vehicles
Trikes
Three mechanical engineering students from San Jose State UniversitySan José State University
San Jose State University is a public university located in San Jose, California, United States...
; Daniel Mekis, Dennis Schaaf and Andrew Merovich, designed and built a bike that runs on compressed air. The total cost of the prototype was under $1000 and was sponsored by Sunshops (on the Boardwalk in Santa Cruz, California
Santa Cruz, California
Santa Cruz is the county seat and largest city of Santa Cruz County, California in the US. As of the 2010 U.S. Census, Santa Cruz had a total population of 59,946...
) and NO DIG NO RIDE (from Aptos, California
Aptos, California
Aptos is a census-designated place in Santa Cruz County, California, United States. The population was 6,220 at the 2010 census.Aptos is an unincorporated area of Santa Cruz county, consisting of several small communities...
.). The top speed of the maiden voyage in May 2009 was 23 mph.
http://www.youtube.com/watch?v=NBeky4EuyBc
Three wheeler
"Ku:Rin" named air-compressed three wheeler vehicle is created by TOYOTA in 2011. The speciality about this vehicle is it has registered a record breaking highest speed 129.2 km/h (80mph) even if it has engine which uses only compressed-air. This car was developed by the toyota companies "Dream car workshop". This car is nicknamed as "sleek rocket" , or "pencil shaped rocket".Motorcycles
A compressed-air powered motorcycle, called the Green Speed Air Powered Motorcycle was made by Edwin Yi Yuan, based on the Suzuki GP100 and using the Angelo Di Pietro compressed air engine.Mopeds
As part of the TV-show Planet MechanicsPlanet Mechanics
Planet Mechanics is a British TV program shown on the National Geographic Channel. The programme was broadcast on Sunday at 7:00 pm. The show has ended after the first series.-Background:...
, Jem Stansfield
Jem Stansfield
Jem Stansfield is an inventor and television presenter, currently working in the United Kingdom. He has appeared on Scrapheap Challenge , Science Shack , Home On Their Own , Zero to Hero , Men in White , Bang Goes the Theory , Wild Thing I Love You , and Planet Mechanics Jem Stansfield is an...
and Dick Strawbridge
Dick Strawbridge
Lieutenant-Colonel Richard Francis "Dick" Strawbridge, MBE, , is a British engineer, television presenter and environmentalist...
have converted a regular scooter to a compressed air moped. This has been done by equipping the scooter with a compressed-air engine and air tank.
Cars
Several companies are investigating and producing prototypePrototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
s, and one plans to offer cars late 2009, early 2010.
Buses
MDI makes MultiCATs vehicle that can be used as busBus
A bus is a road vehicle designed to carry passengers. Buses can have a capacity as high as 300 passengers. The most common type of bus is the single-decker bus, with larger loads carried by double-decker buses and articulated buses, and smaller loads carried by midibuses and minibuses; coaches are...
es or truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
s. RATP has also already expressed an interest in the compressed-air pollution-free bus.
Locomotives
Compressed-air locomotives are a kind of fireless locomotiveFireless locomotive
A fireless locomotive is a type of locomotive designed for use under conditions restricted by either the presence of flammable material or the need for cleanliness...
and have been used in mining and tunnel boring.
Watercraft and aircraft
Currently, no water or air vehicles exist that make use of the air engine. Historically certain torpedoTorpedo
The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...
es were propelled by compressed-air engines.
See also
- Alternative fuelAlternative fuelAlternative fuels, known as non-conventional or advanced fuels, are any materials or substances that can be used as fuels, other than conventional fuels...
- Alternative propulsion
- AirbusAirbusAirbus SAS is an aircraft manufacturing subsidiary of EADS, a European aerospace company. Based in Blagnac, France, surburb of Toulouse, and with significant activity across Europe, the company produces around half of the world's jet airliners....
, compressed-air tanks maker - Air cars
- Air engine
- Charging stationCharging stationAn electric vehicle charging station, also called EV charging station, electric recharging point, charging point and EVSE , is an element in an infrastructure that supplies electric energy for the recharging of electric vehicles, plug-in hybrid electric-gasoline vehicles) or semi-static and mobile...
- Compressed air energy storageCompressed air energy storageCompressed Air Energy Storage is a way to store energy generated at one time for use at another time. At utility scale, energy generated during periods of low energy demand can be released to meet higher demand periods....
- Compression ratioCompression ratioThe 'compression ratio' of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity...
- Eolocompressor
- Global warmingGlobal warmingGlobal warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
- Plug-in hybrid
- PneumaticsPneumaticsPneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...
External links
- Study: "Air Hybrids" Yield Fuel Savings (Society of Automotive Engineers)
- Hydraulic Hybrid Research (United States Environmental Protection AgencyUnited States Environmental Protection AgencyThe U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
) - OSEN page about Compressed Air Technology
- Compressed-air vehicles history
- Photograph of the 1903 Liquid Air Company car
- Regusci Air, Armando Regusci's official web