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54-404: Compressed-air cars use a thermodynamic process . Air cools when expanding and heats when compressed. Thermal energy losses in the compressor and tankage reduce the capacity factor of compressed air systems. In 2020, Dr. Reza Alizade Evrin of Ontario Tech University developed an isothermal compressed air vehicle. This prototype used low pressure air tanks and exhaust air recovery to power

108-558: A natural process is a transfer between systems that increases the sum of their entropies, and is irreversible. Natural processes may occur spontaneously upon the removal of a constraint, or upon some other thermodynamic operation , or may be triggered in a metastable or unstable system, as for example in the condensation of a supersaturated vapour. Planck emphasised the occurrence of friction as an important characteristic of natural thermodynamic processes that involve transfer of matter or energy between system and surroundings. To describe

162-470: A pressure vessel . Pistonless engines using compressed air are very quiet. There is no fire hazard after accidents, unlike systems that utilize combustion fuels or high power batteries. Compressed air engines reduce the cost of car production, because there is no need to build a cooling system, spark plugs, starter motor, or mufflers. The rate of self-discharge is very low compared to batteries. A fueled, compressed-air vehicle may be left unused for

216-734: A solar concentrator . Direct mechanical compression avoids the Carnot inefficiencies of heat engines. Insulated storage of compressed air avoids energy conversion and battery storage. Heat-based systems might use tankage of solar-heated molten salts driving a heat exchanger rather than an onboard heat recovery system. Electric energy, electric grids and their issues might be avoided. There have been several dubious claims with undisclosed information. The "di pietro" engine has been tested partially with CAD and finite element analysis programs. The results were published by Jarosław Zwierzchowski from Lodz University of Technology in 2017. This motor

270-418: A car using compressed air as an energy source. However, it utilizes a hybrid system. A gasoline engine propels the car more than 70 km/h or when the compressed air tank has been depleted. In January 2015, there was disappointing news from France: PSA Peugeot Citroën has delayed indefinitely the development of its promising-seeming Hybrid Air powertrain, apparently because the company has been unable to find

324-550: A chamber whose volume is decreased to compress the air. Once the pressure is greater than the pressure outside the discharge valve , a port or valve opens and air is discharged into the outlet system from the compression chamber. Common types of positive displacement compressors are The capacities for both single-stage and two-stage compressors are generally specified in Standard Cubic feet per Minute (SCFM) or litres per minute and pounds per square Inch (PSI) or bar. To

378-588: A development partner willing to share the huge costs of engineering the system. Development costs are estimated to 500 million Euros. Production volumes would have to be more than 500,000 cars a year to repay these costs. The head of the project left Peugeot in 2014. APUQ (Association de Promotion des Usages de la Quasiturbine) has made the APUQ Air Car, a car powered by a Quasiturbine . Thermodynamic process Classical thermodynamics considers three main kinds of thermodynamic processes : (1) changes in

432-419: A lesser extent, some compressors are rated in actual cubic feet per minute (ACFM). Still others are rated in cubic feet per minute (CFM). Using CFM alone to rate a compressor is ambiguous because it represents a flow rate without a pressure reference. i.e. 20 CFM at 60 PSI. Single stage compressors usually fall into the fractional through 5 horsepower range. Two-stage compressors normally fall into

486-424: A longer time than an electric car. They reduce or eliminate hazardous chemicals such as gasoline, battery acids and related metals such as lead. Compressed air cars are safer in more situations: Compressed air has a lower Energy density than liquid nitrogen or hydrogen . While batteries somewhat maintain their voltage throughout their discharge and chemical fuel tanks provide the same power densities from

540-417: A paraffin heat exchanger system. Its energy efficiency reached 74%. This is as much as 90% of the efficiency of lithium-ion electric cars . It had a driving range of 140 km (86 mi.). Efficiency and range might be increased by a number of practical improvements. For example, combining the storage tank into the car chassis, higher pressure tanks, new rotary engines, and a more efficient heat exchanger. Also,

594-486: A pipeline can be utilized.Compressed air is normally filtered to protect the compressor machinery. Therefore, discharge air has very little suspended dust. There may be some lubricants emitted by some systems, but further development might reduce this with oil free compressors and intercoolers Composite pressure vessels and pneumatic components could permit compressed air cars to be a circular industry . The materials would have to be biobased or recycled . Electric energy

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648-417: A process variable. It is often useful to group processes into pairs, in which each variable held constant is one member of a conjugate pair. The pressure–volume conjugate pair is concerned with the transfer of mechanical energy as the result of work. The temperature-entropy conjugate pair is concerned with the transfer of energy, especially for a closed system. The processes just above have assumed that

702-408: A renewable solar source is also possible using a phase change material such as a molten salt . Energy efficiency of the 2020 isothermal prototype vehicle was 59.4% of a lithium-ion vehicle. Compressed air technology adapts to renewable energy and possibly a circular economy , if biobased or recycled composites can be used. Thus it is more sustainable than electric cars . For example, there

756-450: A shape. Carbon fiber hydrogen fuel tanks are as light as plastic but six times the strength of steel and four times the stiffness. “When a bullet penetrates a hydrogen tank, it does not explode. Instead, hydrogen leaks out through the bullet hole. In a standard collision test, not even a tiny amount of hydrogen was detected because none had leaked out." Compressed air can also be produced by attaching an air compressor or hydraulic pump to

810-399: A size and purpose compressors can be stationary or portable. To ensure all compressor types run efficiently with no leaks, it is necessary to perform routine maintenance. The cost of maintenance only accounts for 8% of the life cycle cost of owning an air compressor. According to CAGI air compressor performance verification data sheets, the higher the isentropic efficiency is, the better

864-450: A system, (2) cycles in a system, and (3) flow processes. (1) A Thermodynamic process is a process in which the thermodynamic state of a system is changed. A change in a system is defined by a passage from an initial to a final state of thermodynamic equilibrium . In classical thermodynamics, the actual course of the process is not the primary concern, and often is ignored. A state of thermodynamic equilibrium endures unchangingly unless it

918-422: A system, a cyclic process is described by the quantities transferred in the several stages of the cycle. The descriptions of the staged states of the system may be of little or even no interest. A cycle is a sequence of a small number of thermodynamic processes that indefinitely often, repeatedly returns the system to its original state. For this, the staged states themselves are not necessarily described, because it

972-399: A theoretical slowness that avoids friction. It also contrasts with idealized frictionless processes in the surroundings, which may be thought of as including 'purely mechanical systems'; this difference comes close to defining a thermodynamic process. (2) A cyclic process carries the system through a cycle of stages, starting and being completed in some particular state. The descriptions of

1026-449: A variety of power sources. While direct drive gasoline or diesel-engines and electric motors are among the most popular, air compressors that utilize vehicle engines, power-take-off , or hydraulic ports are also commonly used in mobile applications. The power of a compressor is measured in HP ( horsepower ) and CFM ( cubic feet per minute of intake air). The volume of the pressure vessel and

1080-403: A vessel with definite wall properties. The internal state of the vessel contents is not the primary concern. The quantities of primary concern describe the states of the inflow and the outflow materials, and, on the side, the transfers of heat, work, and kinetic and potential energies for the vessel. Flow processes are of interest in engineering. Defined by a cycle of transfers into and out of

1134-403: A wind turbine or by using a river, tidal or wave hydropower turbine. These all convert directly from mechanical to pneumatic energy. Eliminating electricity from the cycle gives higher efficiency overall. It is also possible to use thermal solar energy with a parabolic or Fresnel lens solar concentrator to power a thermal Stirling engine . This can move the compressor or pump. Solar Stirling

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1188-401: Is a particularly useful visualization of a quasi-static process, because the area under the curve of a process is the amount of work done by the system during that process. Thus work is considered to be a process variable , as its exact value depends on the particular path taken between the start and end points of the process. Similarly, heat may be transferred during a process, and it too is

1242-560: Is a thermodynamic process that obeys the relation: where P is the pressure, V is volume, n is any real number (the "polytropic index"), and C is a constant. This equation can be used to accurately characterize processes of certain systems , notably the compression or expansion of a gas , but in some cases, liquids and solids . According to Planck, one may think of three main classes of thermodynamic process: natural, fictively reversible, and impossible or unnatural. Only natural processes occur in nature. For thermodynamics,

1296-718: Is an eccentric shaft vane motor that uses low air pressure. The tanks must be designed to safety standards for a pressure vessel . ISO 11439 is a similar standard, for compressed natural gas tanks. The air storage tanks usable in compressed air cars can be low pressure (9 atm) or high pressure (240+ atm). Thus, they can be made of composite materials like thermoplastics and fiber reinforced thermoplastics, This might permit low priced tankage. It might be made by rotational molding . Such tanks can be much lighter than lithium-iron batteries and 70% lighter than steel tanks. They resist rust from air, water and condensation. They last longer with less maintenance. To reduce car weight further

1350-451: Is called a " quasi-static " process. This is a theoretical exercise in differential geometry, as opposed to a description of an actually possible physical process; in this idealized case, the calculation may be exact. A really possible or actual thermodynamic process, considered closely, involves friction . This contrasts with theoretically idealized, imagined, or limiting, but not actually possible, quasi-static processes which may occur with

1404-545: Is customary to think of the "processes" described by the paths as fictively "reversible". Reversible processes are always quasistatic processes, but the converse is not always true. Unnatural processes are logically conceivable but do not occur in nature. They would decrease the sum of the entropies if they occurred. A quasistatic process is an idealized or fictive model of a thermodynamic "process" considered in theoretical studies. It does not occur in physical reality. It may be imagined as happening infinitely slowly so that

1458-463: Is described by a path through a continuous progression of equilibrium states. Defined by flows through a system, a flow process is a steady state of flow into and out of a vessel with definite wall properties. The internal state of the vessel contents is not the primary concern. The quantities of primary concern describe the states of the inflow and the outflow materials, and, on the side, the transfers of heat, work, and kinetic and potential energies for

1512-606: Is interrupted by a thermodynamic operation that initiates a thermodynamic process. The equilibrium states are each respectively fully specified by a suitable set of thermodynamic state variables, that depend only on the current state of the system, not on the path taken by the processes that produce the state. In general, during the actual course of a thermodynamic process, the system may pass through physical states which are not describable as thermodynamic states, because they are far from internal thermodynamic equilibrium. Non-equilibrium thermodynamics , however, considers processes in which

1566-447: Is more efficient than solar steam or photovoltaic. Compressed air cars are emission free. They also do not require a connection to the electric grid. A wind turbine or other renewable energy source can directly drive an air compressor or hydraulic pump . Compressed air cars do not rely on petrol stations or an electric grid . While centralized infrastructure might not be needed, it is an option. Tankage can be directly shipped, or

1620-411: Is much less use of metals, or toxic battery chemistries. A centralized manufacturing and electric grid might be less necessary. Efficiency is also helped by the low weight of composite pressure vessels relative to steel tanks or lithium-ion batteries . Weight might be further reduced if the tanks support the car chassis. Pneumatic engines also have lower weights than electric engines. Refueling

1674-817: Is no single type of compressor that could be used for any application. Air compressors have many uses, such as supplying clean high-pressure air to fill gas cylinders , supplying clean moderate-pressure air to a submerged surface supplied air diver , supplying moderate-pressure clean air for driving some office and school building pneumatic HVAC control system valves, supplying a large amount of moderate-pressure air to power pneumatic tools , such as jackhammers , filling high pressure air tanks (HPA, air tank), for filling tires , and to produce large volumes of moderate-pressure air for large-scale industrial processes (such as oxidation for petroleum coking or cement plant bag house purge systems). Air compressors are also widely used in oil and gas, mining and drilling applications as

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1728-459: Is not used, so there is no need for metals like copper, iron in magnets, etc. There can be a single conversion of mechanical energy to pneumatic or hydraulic energy. Therefore, compressed air can have high energy efficiency when using mechanical renewable energy such as wind turbines or hydropower. Thermal energy to mechanical energy conversion is possible, but less efficient due to Carnot conversion inefficiencies. Thermal storage of heat from

1782-650: Is possible in many places using only wind, solar power or hydropower to move an air compressor , hydraulic pump or Stirling engine . Pneumatic power has energy synergy, because it is well suited to automotive mechatronics . Many car systems can be powered by small air motors. For example, active pneumatic suspension , pneumatic steering, or pneumatic shock absorbers. Expansion of the compressed air creates cold temperatures, and can directly provide air conditioning or climate control. Energy recovery systems with regenerative suspension and regenerative braking produce low pressure compressed air. This can be stored in

1836-464: Is released. When tank pressure reaches its lower limit, the air compressor turns on again and re-pressurizes the tank. A compressor is different from a pump because it works on a gas, while pumps work on a liquid. Compressors may be classified according to the pressure delivered: There are numerous methods of air compression, divided into either positive-displacement or roto-dynamic types. Positive-displacement compressors work by forcing air through

1890-400: Is some form of air- or water-cooling, although some (particularly rotary type) compressors may be cooled by oil (that is then in turn air- or water-cooled). The atmospheric changes are also considered during cooling of compressors. The type of cooling is determined by considering the factors such as inlet temperature, ambient temperature, power of the compressor and area of application. There

1944-407: Is the transfers that are of interest. It is reasoned that if the cycle can be repeated indefinitely often, then it can be assumed that the states are recurrently unchanged. The condition of the system during the several staged processes may be of even less interest than is the precise nature of the recurrent states. If, however, the several staged processes are idealized and quasi-static, then the cycle

1998-402: Is to compress air into a storage tank, for immediate or later use. When the delivery pressure reaches its set upper limit, the compressor is shut off, or the excess air is released through an overpressure valve . The compressed air is stored in the tank until it is needed. The pressure energy provided by the compressed air can be used for a variety of applications such as pneumatic tools as it

2052-440: The pressure vessels can be used as structural parts of the chassis . Advanced 700-atmosphere pressure vessels have been developed for hydrogen cars . Crash tests showed good safety. Fiber reinforced thermoplastic tanks only rupture in collisions. They do not shatter or explode. Hydrogen tanks require ‘high strength’ to prevent rupture and ‘high stiffness’ for durability. Strength resists an external force. Stiffness maintains

2106-455: The 5 through 30 horsepower range. Roto-dynamic air compressors include centrifugal compressors where Rotating vanes impart kinetic energy to a gas and stationary passages convert velocity into a rise in pressure, and axial compressors , where rotor blades impart the kinetic energy and stator blades convert it to a rise in pressure. Due to adiabatic heating , air compressors require some method of disposing of waste heat . Generally this

2160-444: The boundaries are also impermeable to particles. Otherwise, we may assume boundaries that are rigid, but are permeable to one or more types of particle. Similar considerations then hold for the chemical potential – particle number conjugate pair, which is concerned with the transfer of energy via this transfer of particles. Any of the thermodynamic potentials may be held constant during a process. For example: A polytropic process

2214-479: The design past phase 1, the "proof of the technical concept", and were proceeding to full production for the Indian market. Tata moved to phase 2, "completing detailed development of the compressed air engine into specific vehicle and stationary applications". In February 2017, Dr. Tim Leverton, president and head at Advanced and Product Engineering at Tata revealed that the project was "starting industrialisation" with

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2268-453: The energy output. This 'innovation' was first used in torpedoes in 1904. As of January 2009, Tata Motors of India had planned to launch a car with an MDI compressed air engine in 2011. In December 2009 Tata's vice president of engineering systems confirmed that the limited range and low engine temperatures were causing problems. Tata Motors announced in May 2012 that they have assessed

2322-401: The first to the last litre, the pressure of compressed air tanks falls as air is drawn off. There are mechanical methods (e.g. continuously variable transmissions or auxiliary motors) to reduce this effect, but they add expense. Various companies are investing in the research, development and deployment of compressed air cars. The MDI Air Car made its public South African debut in 2002. It

2376-550: The first vehicles to be available by 2020. Other reports indicate Tata is also reviving plans for a compressed air version of the Tata Nano , This had previously been under consideration as part of their collaboration with MDI. Engineair is an Australian company. It produced prototypes of small vehicles using a rotary air engine designed by Angelo Di Pietro . The company is seeking commercial partners to utilise its engine. Peugeot and Citroën announced that they intended to build

2430-408: The flushing medium, aerating muds in underbalanced drilling and in air pigging of pipelines. Most air compressors either are reciprocating piston type, rotary vane or rotary screw . Centrifugal compressors are common in very large applications, while rotary screw, scroll, and reciprocating air compressors are favored for small and medium-sized applications. Air compressors are designed to utilize

2484-448: The geometry of graphical surfaces that illustrate equilibrium relations between thermodynamic functions of state, no one can fictively think of so-called "reversible processes". They are convenient theoretical objects that trace paths across graphical surfaces. They are called "processes" but do not describe naturally occurring processes, which are always irreversible. Because the points on the paths are points of thermodynamic equilibrium, it

2538-425: The staged states of the system are not the primary concern. The primary concern is the sums of matter and energy inputs and outputs to the cycle. Cyclic processes were important conceptual devices in the early days of thermodynamical investigation, while the concept of the thermodynamic state variable was being developed. (3) Defined by flows through a system, a flow process is a steady state of flows into and out of

2592-418: The states of the system are close to thermodynamic equilibrium, and aims to describe the continuous passage along the path, at definite rates of progress. As a useful theoretical but not actually physically realizable limiting case, a process may be imagined to take place practically infinitely slowly or smoothly enough to allow it to be described by a continuous path of equilibrium thermodynamic states, when it

2646-614: The stored pressure indicate the volume of compressed air (in reserve) available. Gasoline and diesel-powered compressors are widely used in remote areas with problematic access to electricity. They are noisy and require ventilation for exhaust gases, particularly if the compressed air is to be used for a breathing air supply. Electric-powered compressors are widely used in production, workshops and garages with permanent access to electricity. Common workshop/garage compressors are 110-120 Volt or 230-240 Volt. Compressor tank shapes are: "pancake", "twin tank", "horizontal", and "vertical". Depending on

2700-499: The system passes through a continuum of states that are infinitesimally close to equilibrium . Air compressor An air compressor is a machine that takes ambient air from the surroundings and discharges it at a higher pressure. It is an application of a gas compressor and a pneumatic device that converts mechanical power (from an electric motor , diesel or gasoline engine , etc.) into potential energy stored in compressed air , which has many uses. A common application

2754-497: The thermodynamic treatment may be approximate, not exact. A quasi-static thermodynamic process can be visualized by graphically plotting the path of idealized changes to the system's state variables . In the example, a cycle consisting of four quasi-static processes is shown. Each process has a well-defined start and end point in the pressure-volume state space . In this particular example, processes 1 and 3 are isothermal , whereas processes 2 and 4 are isochoric . The PV diagram

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2808-399: The vessel. The states of the inflow and outflow materials consist of their internal states, and of their kinetic and potential energies as whole bodies. Very often, the quantities that describe the internal states of the input and output materials are estimated on the assumption that they are bodies in their own states of internal thermodynamic equilibrium. Because rapid reactions are permitted,

2862-720: The weight and cost of tanks and pneumatic parts might be reduced by using recycled and bio-based thermoplastics . This technology might develop into an inexpensive, clean transportation technology. The energy, vehicles and compressors might be produced easily by decentralized methods, even circular industry . Using plastic might permit open source fabrication using numerical control , including additive manufacturing . The compressed air for such vehicles might be produced easily by common types of renewable energy . For example, multistage air compressors and intercoolers or hydraulic pumps might be attached directly to trompes , hydropower , VAWT wind turbines or stirling engines using

2916-461: Was predicted to be in production "within six months" in January 2004. As of 2022, it was not in production. MDI has proposed a range of vehicles made up of AIRPod , 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

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