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Compressed air engine powered car, motorcycle, truck, locomotive, boat and ship

Compressed air engine is cheapest way to travel, five seat car can travel 100 km using 0.5 dollar worth of compressed air (cost of compressed air). This is so super-cheap compared to both gasoline and electric vehicles. There are comparisons in the net how much gasoline car and electric car cost (fuel plus other costs), and both fossil fuel car and electric car has about same cost to user, in some comparisons gasoline car is more expensive than electric, and in some comparisons electric car using costs are higher than in gasoline car. Also electric battery car has about the same carbon footprint as gasoline car, or even more, because of battery manufacturing, so electric car is not more environmental friendly or “greener” than gasoline car, it can actually have even larger carbon footprint than gasoline car, and electric power is produced in coal burning powerplants and nuclear powerplants, and those have nuclear waste problems etc. And rare metals needed for batteries are scarce so there is not enough rare metals in the Earth to make vehicles of whole world electric. The new idea of making batteries from aluminum and sulfur is possible, but batteries then become heavier and larger.
Because compressed air powered vehicle has so cheap “fuel” costs, it should be used instead of electric or fossil fuel vehicle. Compressed air can be made directly using mechanical power that comes from ocean waves powerplant, or wind turbine, not aircraft propeller - looking wind turbine but also other types of wind turbines also. When mechanical power is not transformed to electricity, efficiency is better in powerplants.
Not only cars, but motorcycles, trucks, locomotives, boats and ships can be build to use compressed air engine power, not fossil fuel. New types of compressed air engines (quasiturbine) can be used that are small, compact and light. Air tanks can be made from “superwood”, wood material that has strength of steel, hemp, or other biological “plastic” (bioplastics). Strong air tanks can be made using graphene strengthened material, carbon fibre etc.
In compressed air vehicle prototypes air tank is surprisingly small, making it bigger increases range that seems to be insufficient in those prototypes that have small air tanks. And when tank is expired it can be changed in gas station to tank tank that is full, so no waste time for “fueling” tank with air. So air tanks must be standard sizes and shapes and every manufacture then uses those standardized air tanks. There are then different air tanks for cars (perhaps small cars and larger cars have different size cars), then is tank size for lorries and then largest for big trailer trucks.
In cars the room used in front of car where engine is can be mostly filled with two ranks, one is in front and it is wide, filling space where is no car wheels, and the narrower tank that fits between car wheels in engine compartment, and lastly small quasiturbine almost directly connected to transmission that fits in small space and is flat so that air tanks fit inside engine compartment. Also front bonnet of car can be made higher, so that driver barely sees through narrow windows that are high, when huge air tanks in bonnet of car is in front of him. Car can also be made to be higher, further making air tanks bigger.
Big truck can be modified cab over engine truck, when in normal COE truck there is no engine bonnet, in air powered truck is huge “engine bonnet” that is just air tank, there is no engine inside bonnet. This bonnet is in front of front wheels, tank is large but relatively light so front wheels can be under truck cabin like in COE truck. Air tank bonnet can be so large that driver barely sees front, so cameras in front and video screens inside truck are needed so that driver sees front when driving, and driver must then practice to drive using mostly camera views from screens. Also camera and screen in car can help small car too if “engine compartment” of car that is mostly filled with air tanks, not engine, is very high. Or kind of station wagon car where aft section of car is one big air tank.
Motorcycle can have air bottles in place of motorcycle trunk boxes, those bottles are exposed to sunlight so mirror-like reflective surface is needed in bottles so that sun heat is reflected away. When driver is alone and passenger seat is not used air bottles can be long enough that they use passenger s space and then range of motorcycle is longer. Or simply sidecar is connected to motorcycle, it is not for passenger but for very big air tank.
In trucks not only front bonnet, but also space behind cabin can be used for air tank, so truck then has two air tanks, And truck tractor can be “B-double trailer truck” type in truck-trailer combination when air tank behind cabin is light and does not need wheels to support its weight. Both front bonnet air tank and air tank behind cabin can be almost square shaped width (diameter), with rounded corners. But their length is longer than width.
Compressed air locomotive looks like old steam locomotive, but air tank that looks steam locomotive boiler is perhaps wider and taller than old steam boiler, maximum size that fits inside railway tunnel (in EU 3,15 m wide and 4,65 m tall). And this air tank can be almost square diameter width shape also, with rounded corners. But drivers cabin is not in back of locomotive, but front, because air tank is so tall and wide that drivers don t see front if cabin is in back of locomotive. Air tank is exposed to sunlight so extra sun shade is needed only one cm or so outside air tank, so that air cools air tank, and this sunshade is made of reflective mirror-like material to reflect sunrays off. Also air tank of locomotive can be extremely long, much longer than typical steam locomotive, so that lots of air fits in tank. But tank is perhaps light. It must be high pressure tank. Even passenger jet plane hulls are transported using railways, so compressed air locomotive, which is just long air tank on wheels with small drivers cabin in front, can tow train. Or each railcar can have own air tank and air engine, so that actual locomotive is just small drivers cabin, not more.
Boat can have compressed air engine also and air bottles.
Compressed air powered ship can have storage of hundreds of air tanks, for safety reasons, so when ship comes to harbour, empty air tanks are changed to filled ones, or they are filled using air tube from ship port without air tank changing.
Compressed air engine can be made more efficient using heat exchanger, that heat exchanger can be in cars, trucks, boats and ships also. Compressed air engine can also be made more efficient using fuel burning that heats the air. Burning 6 litres of gasoline gives air powered car 500 km range, about 0,8 litre / 100 km fuel consumption. When 100 km requires 0,5 dollar worth of air, and if ethanol or methanol is used for burning fuel (butanol, vegetable oils, other biofuel, perhaps solid biofuel, gasoline, fossil oil etc. can be used) but if ethanol or methanol are used, ethanol perhaps 0,3 dollar per litre price and methanol 0,2 dollar, in their lowest production price of “methanol economy” (Wikipedia) or methanol economy, or mixture of ethanol, methanol, and other biofuels, only 0,3 dollar per 100 km is needed burning fuel, plus 0,5 dollars worth of air. So 0,8 dollar per 100 km fuel economy in five seat car.
Also perhaps compressed air engine, heat exchanger, and fuel burning can be combined, making compressed air engine more efficient still.
Also mechanical air charger (compressor) and turbocharger can perhaps be used to recover energy, perhaps mechanical and turbocharger can be used together in compressed air engine, comprex / hyprex turbocharger etc.
Perhaps bypass turbojet (turbofan) principle can be used, using air outside air tank together with pressurized air from tank, if that makes compressed air vehicle more efficient, or turbocharger has port that uses air outside air tank, mechanical charger takes air from outside of the air tank etc. when fuel burning is used, or perhaps even without fuel burning?
All those methods can perhaps be used in cars, trucks, locomotives and ships using compressed air engine. Ships can also use wind turbines (not aircraft propeller type but other kinds of wind turbines) to make compressed air when ship is in the sea. Solar panels can be in car / truck roofs that charge batteries of car, batteries use electric systems of car. Solar panels can be in ships also. Perhaps sunlight / stirling engines or solar panels can be in ships too to make compressed air, or hot steam that goes to quasiturbine, salt must be filtered from seawater perhaps, using osmosis etc. or pipes cleaned from salt from time to time using “soap pulse”, cleaning liquid pulse water mix sometimes, or tubes and pipes and system uses salt-resistant coating so that salt does not stick to it.
Electric vehicles make sense if vehicles are light quadracycle type, light vehicles with solar panels can collect enough electricity from sunlight that they have almost zero “fuel” (electricity) cost. But heavier vehicles need heavy and very un-ecological batteries, so compressed air vehicles that have already smallest “fuel” and operating costs among of all types of powered vehicles are best and cheapest travelling method, perhaps, even in locomotives and ships.
If it makes any sense, perhaps seawater can be used in sort of water jet / water pump engine in ships, and this waterjet / pump engine uses compressed air as power source, heated with fuel etc. and then this compressed high pressure air pushes water to quasiturbine etc. that gives power to ship s propeller, or simply high pressure fast air pushes water in waterjet type propulsion system without propellers or quasiturbine in the way. If that gives some more efficiency than just bare air blowing to quasiturbine.
If system of pressurized air pushing hydraulic fluid in quasiturbine or other type of compressed air engine gives more power than just air alone, and efficiency (operating cost, in air engine it is combined 0,8 dollar / 100 km in a car) is better, perhaps hydraulic fluid, like vegetable oil, mineral oil etc. can be used as working mass in compressed air engine. This hydraulic liquid circulates in closed system in engine, pushed by air. If that makes any sense, I don t know. If “fuel consumption” (air consumption) is worse than engine that uses just air, it makes no sense to make this compressed air & hydraulic fluid engine.
Liquid or gaseous hydrogen can also be used as burning fuel in compressed air engine, “hydrogen economy”.

There was more than slight mistakes in previous post, if compressed air engine uses fuel to heat pneumatic air and uses 6 litres in 500 km distance it is 1,2 litres per 100 km, not 0,8 litres. I again wrote everything in hurry. Also I understood wrong air tank heat, air tank must be keep hot, not cool, so air tank if exposed to sunlight must be painted black, some special paint that absorbs heat of sunrays as much as possible, so that air tank stays hot. Also tank must be protected from cold wind when vehicle is driven, so perhaps two layer cover system is best, first is black heat absorbing material in cool air outside vehicle, below it is small air space that is heated by this black painted cover, and below it is then the actual air tank. Tank is also covered with heat insulating material, and if air tank has low pressure, thermos bottle type insulation where almost vacuum is between two air tank walls is perhaps possible, and this air tank is covered by heat insulating material inside and outside, and after that there is still small air space that is heated by sunlight, heat comes from top surface that has black heat absorbing paint. This if air tank is near sunlight. If air tank is in bottom of the car this is not possible. Also heat exchanger can be in top of engine compartment of car or in the roof of the car. Paraffin or other material used as heat exchanger?
If compressed air is heated, and this consumes 1,2 litres of gasoline per 100 km, if instead of gasoline ethanol or methanol is used, and ethanol can be cheaply produced to have price of 0,3 dollar / litre and methanol 0,2 dollar, because ethanol and methanol have less energy density than gasoline, cost of both ethanol and methanol per 100 km is about 0,5 dollars. Compressed air also costs 0,5 dollar per 100 km. So only 1 dollar / 100 km fuel costs in a car. If only heat exchanger is needed without fuel burning, price is only 0,5 dollar per 100 km. More air is then needed, and air tank becomes heavier.
Air weights 1,2 kg per cubic meter. In text “Four-stroke high torque CAE (compressed air engine) performance” 2022 Wang, is bus that weights 11,7 tons empty (curb weight) and 18 tons loaded and can carry 96 people, so full load weight is actually 22 tons not 18. This bus has 2,8 cubic meter air tank, 35 MPa air pressure (345 atm, 345 times athmospheric pressure), so 1160 kg air weight (if I calculated right). Bus has 60-80 km range and 69 km/h top speed even if tank is not full.
If bus weights 22 tons, it has 1160 kg of air in tank, then car that weights 1 ton (like Citroen AX, Maruti / Suzuki Alto, Renault Kwik, Tata Nano etc.) where about 0,65 ton is car weight and about 0,4 ton passenger weight, Car can have 116 kg of air in tank. Total weight around 1,1 ton. It is 20 times lighter than 22 ton bus. So about 120 km/h perhaps top speed (air drag of high speed and rolling friction slowdown the car) and 160 km range about. This without heat exchanger, but if heat exchanger is included efficiency should improve very much? If fuel is also used to heat air power of air engine increases and range increases too, but now fuel cost is 1 dollar versus 0,5 dollar per 100 km if ethanol, methanol etc. is used. Instead of fossil fuel hydrogen can be used but that is expensive perhaps.
But this comparison is for 20 ton bus versus 1 ton car, and bus has high torque compressed air engine, so this comparison s unfavourable to small 1 ton car, range will probably be much higher than 160 km if car has engine that has less torque and about 100 km/h top speed like Tata Nano and those other small cars. Heat exchanger increases range even more, and fuel air heating even more (if it is needed).
Air tank is then 280 litres in 35 MPa pressure in small car. If compressed air engine is type that is very small, like rotating piston engine, quasiturbine or such, in engine compartment can be fitted air tanks, and if engine compartment space is increased so that hood is much higher than in normal car, then perhaps 280 litre air tank can be fitted in engine compartment. The engine compartment can also be made longer than in normal car, extending further forward from front wheels. If hood level is risen driver has difficulties to see downward in front of car, so camera is needed in front and its picture in car instrument panel display system when needed. Also the downside of car where fuel tank and spare tyre and exhaust pipe normaly are can be used to space additional air tank. Spare tyre can be in top of the roof of the car, or over (connected to) trunk hatch, like in some cross country jeep cars.
If more air is needed higher pressure than 35 MPa tank or tanks can be used. But air weight is then increased.
Heat exhanger can be in top of engine hood or in top of the car, it too has been painted with black heat absorbing paint or material that catches sun heat.
This is lightweight small cheap car suitable for third world countries, but because cars can be much heavier, heaviest cars, both electric and gasoline/diesel, are close to 3 ton weight, so increasing air weight from 116 kg to 500 kg or even close to 700 - 800 kg is not a problem, car just becomes heavier. And then problems with short range of air powered cars are no more, air powered car can be much more economical than electric car (only 0,5 dollar / 100 km fuel cost, or 1 dollar if air is heated with fuel. If heat exchanger is used without fossil fuel, cost of air is actually much lower than 0,5 dollar / 100 km).
Because cost of usage of electric cars are as high as gasoline cars, cost of fuel / electricity included, and electric cars have same size carbon footprint that fossil fuel cars have or even worse than gasoline cars, so electric cars are not any “greener” or environmental friendly than fossil fuel cars, and making of batteries for them drains out rare metal reserves of earth, compressed air cars can be the real solution for greener travel. And they have super cheap “fuel” costs.
Trucks can be compressed air powered also, heaviest road trucks are tow trucks, about 75 - 80 ton weight, so weight of air is not a problem if tow truck is modified to road rain use. Also heaviest timber truck with trailer has 106 ton weight in Europe, so weight of air can be several tons easily, no problem, or for example 12 tons weight of air in truck. Heaviest locomotive weighted 661 tons, so air weight is no problem in locomotives either. Locomotive can have slightly square shaped diameter but rounded long cylinder, which is painted black so that it collects sun heat, so locomotive even looks like old steam locomotive, but drivers cabin is in front not back of locomotive because air tank is as large and low pressure as possible so that air heat in air tank is low. Low amount of heat in large low pressure air tank can be perhaps stored better and keep warm longer than high temperature air in high pressure small tank? Trains can have compressed air train tanker railway cars, how many of them are needed, is decided based on the length of the trip train travels, so optimal amount of compressed air can be chosen for each length of train trip. Then locomotive with its own air tank can be lighter. Heaviest old locomotives weighted 500 - 600 tons. But if most of compressed air is in train tanker railway cars locomotive can be lighter. Heating air with biofuel makes more efficiency so not so much compressed air weight must be carried, but biofuel like ethanol or methanol with its cheapest price 0,3 and 0,2 dollar per litre is still more expensive fuel than compressed air. Using heat exchangers like paraffin - filled exchanger can save compressed air weight too. Same goes for heavy and light trucks and cars.
Trucks and busses can use truck / trailer and bus roof as the place where air tank is, very large air tank can be in roof of truck container and in truck roof. Same goes for busses. In some countries are double decker busses, if the upper deck is just air tank, very low pressure tanks can be used, so air is in low temperature there an stays hot longer time? So air tank volume is not a problem if roof of truck or bus is used as place where air tank is. It can be also in bonnet of truck if COE truck is used, the bonnet that normally holds engine is now big air tank, etc. solutions where to put air tank. In top of this air tank is also heat exchanger that collects heat from the sun. Also solar panels can be used in vehicle that make electricity for car / truck electrical systems or even give additional power to vehicle if in battery is full, and regenerative braking can be used also (in cars and trucks) to give additional power to vehicle.
Nowdays style when big and heavy electric cars are made for gasoline/diesel car replacement and very small and light vehicles like MDI AirPod are proposed for short / light travel, is exactly opposite what should be: compressed air engine cars and trucks should be made, and small quadracycle class vehicles should be electrically powered, taking power from sunlight using solar panels.
Electric cars should however be quite easily converted to compressed air engine type, they have large and heavy batteries, they can be swapped to large and heavy air tanks. Because cost of use of electric car is as high as gasoline car, changing electric car to compressed air power will make dramatic change to “fuel” costs and other costs, and compressed air is much more ecological friendly than electric batteries, whose manufacturing is sort of ecological nightmare.
Also boats and other marine vessels can use compressed air engine. If air bottles are low pressure and large, they can hung over sides of deck in baskets so that they don t waste vessel deck space or cargo room space. Baskets should be closed so that cold wind does not cool air bottles and baskets painted black, with sun heat collecting paint. When fishing vessel, which is larger than small boat but smaller than big fishing ship, goes to harbour, before docking from one side air bottle baskets can be risen up so that vessel can dock in harbour.
Large ships can use compressed air power also, cargo ship can have hundreds of air bottles, in sides outside of the actual deck. So the space needed for air bottles is not taken from deck or cargo space. When ships travel thousands of kilometres fuel heating of air is needed, although heat exchanger system is also used. Ethanol or methanol fuel, other biofuel, even solid burning biofuel etc. can be used.
AGE-85 is airplane ethanol fuel, 85% ethanol. It has 100/130 octane rating for aircraft engines. Similar fuel can be used in cars and trucks etc. also, ethanol is not dangerous like high octane airplane gasoline. This high octane fuel would lead to high engine efficiency in biofuel internal combustion (piston) engine.
If compressed air engine uses pistons, this biofuel that is used to heat pneumatic air from air tank, can also be used in pneumatic air engine s cylinder like four stroke etc. engine, it not only heats air but also makes air to expand in cylinder and gives additional power to movement of piston, although most of piston movement comes from pressure of pneumatic air? However this is not exactly hybrid internal combustion engine & compressed air engine hybrid, only that amount of fuel is used that is needed to heat air properly, if fuel ignition also gives slight extra power to piston that is extra.
Also recovery energy system like turbocharger, comprex/hyprex charger, or mechanical air charger (taking power from compressed air engine or from electric power that comes from solar panels). If mechanical compressor takes power from engine itself, it is possible that mechanical air compressor gives no any advantage.
There are modern versions of old world war 2 woodgas generators, they can use not only wood, but other kinds of biomass also, biowaste etc. If those new modern biogas generators are modified for cars and trucks to use, and trains and ships too, perhaps biogas generator power that uses biowaste to produce energy, so fuel (biowaste) is free, no fuel costs, and compressed air engine power combined.
Result is then biogas generator (modern woodgas generator that uses not only wood but other biomass also) and compressed air hybrid engine. Because both biogas generator and its biomass (biowaste) “fuel tank” and compressed air needs large volume. So both methods of operation can be combined in same engine hybrid. I don t know if this makes any sense.
Kerosene rocket fuel can be produced even from non-recyclable plastic waste (Skyrora), and kerosene is diesel fuel too. This Skyrora rocket fuel is more energetic than previous rocket fuel RP1, and RP1 was very energetic petroleum product. If this same process that makes rocket kerosene can be used to make super energetic diesel fuel from non-recyclable plastic waste that would be good, using subsidiary to cover this fuel s cost would make it useful energetic fuel and at the same time unrecyclable waste plastic filling world s oceans and landfills could be turned to fuel. Firm Lanza Tech makes ethanol from industrial waste, so that is ecological fuel too.
So fossil fuel can be more ecology friendly than electric vehicles. When those new methods make possible to turn waste plastic and industrial waste to fuel the decision to end all fossil fuel car and vehicle production makes no sense.
New method of ethanol production can make 0,3 dollar / litre ethanol from biowaste, so it is cheap biofuel too. Hydrogen can be also used as fuel, it needs pressure tanks also, and can be perhaps used as hybrid with pneumatic air from air tank in compressed air / hydrogen engine, but what is cost of large scale hydrogen manufacturing, and how cost-efficient it is compared to compressed air?
Compressed air can be made from ocean wave power (wave powerplants) and wind turbines, direct mechanical energy to air compressor, which is very efficient. Not only airplane propeller looking wind turbines but other types of wind turbines also. Even small private wind turbines can be used so that compressed air is then free for car / truck user, and this wind turbine can be used to make electricity when compressed air is not needed. Otherwise perhaps in gas stations empty air tanks are changed to full ones, so tank sizes and shapes must be standardized. Gas stations can have wind turbines and Stirling engines that make compressed air. Cities and towns can have compressed air energy storage, then in big cities and smaller towns have one large “gas station” for compressed air vehicles, the place where compressed air energy storage is, somewhere in the outskirts of city/town. But other independent gas stations can have their own air compressors, using wind and solar power for direct mechanical energy driven compressors. And those wind and solar driven air compressors can also be owned by private people, so then is no cost for fuel. Those wind and solar power systems can make electricity too, and hot water or steam for house warming.
There is rotary piston engine concept, old Gnome-Rhone aircraft engine WW1 era modernized: “Concept: modern rotary engine with integral flywheel effect” 2006. RIDE (rotational inertial dampening engine). If compressed air piston engine and rotational flywheel engine can be combined, it would be pneumatic air / heated air fuel engine with flywheel effect that saves fuel when cruising. Also rotary piston engine problems like ignition problems etc. can be perhaps solved when instead of fossil fuel compressed air, heated or not, is used.
“Water spray heat transfer gas compression for compressed air energy system” 2021. “Pacific Basin shipping, Nihon shipyard and Mitsui to collaborate on zero-emissions vessels” 2022. “Turbosteamer”.
If ship uses compressed air as powersource, and engine is piston engine in ship, perhaps water can be used as working mass in the engine: air pushes water to engine cylinder, and then water is the working mass, hydraulic fluid that makes piston move. Air itself has little torque power, but if air pushes water in engine cylinder, then perhaps torque can move even big ship. So it is then pneumatic-hydraulic engine in ships. Seawater is used so corrosion-resistant coating must be in cylinders and tubes or stainless steel, and some salt protection, perhaps cylinders and tubes would be cleaned using “soap pulse” sometimes in cylinders and tubes, if salt in seawater is a problem, or other methods to prevent seawater salt to make harm in engine, if that kind of salt protection is needed. Or salt is separated from seawater using osmosis etc.

If compressed air vehicle is used, then for example if Europe s heaviest timber truck with trailer is 106 tons, and 20 ton bus needs 1,16 tons of air to move it 80 km according to recent study, then about 23 tons of air moves 100 ton truck combination to 320 km, this without efficient paraffin heat exchanger and heating of air with fuel burning which extends range over 500 km perhaps. Passenger car can has about 0,5 dollar cost of air / 100 km “fuel” costs and if air fuel heating is used about 0,5 dollar more, so 1 dollar / 100 km fuel costs. When compared to gasoline or diesel fuel cost this is significant saving. Same goes for 100 ton truck also, if fuel cost is compared to diesel cost, because 100 ton truck / trailer weights much more than passenger car fuel cost is much higher than 1 dollar / 100 km but still much cheaper than diesel, even with fuel heated air range extending. Less than 23 tons is the loss of payload capacity, because truck does not use large amount of diesel (which has weight too in truck s fuel tank) but only small portion of some burning biofuel, but that 23 tons minus something loss of payload capacity is compensated many times more by the fuel cost savings, which are dramatic. Passenger cars too can have large amount of air, perhaps up to 500 kg, or even 700-800 kg air in their compressed air tanks, however tanks are not so big, pressure in the tanks can be increased or more space in car given to air tanks, for example in station wagon car air tank can be in the roof of car, over cubic metre large, or even several cubic meters, and in trains and busses too air storage can be in the roof. And top of it heat exchanger.
Modern cars, if they are not microcar-class, are heavy, heaviest are 2 tons or even close to 3 tons, so if compressed air weights 500 - 700 kg it is still possible to build a car that has this amount of air weight inside its air tanks. Microcar class cheap car can do with 120 kg or less air weight.
In trains most of compressed air can be in train tanker railroad cars and some of air weight in the locomotive, and so changing amount of those tanker train railroad cars just enough air for length of travelling distance can train use. Loss of cargo capacity is compensated by much cheaper cost of air compared to electricity or fossil fuels. Fuel heater can be used also, although it doubles “fuel” costs, but those costs are so low that increased fuel cost has barely no meaning. But without fuel heating costs cargo travel is only half of already quite minimal costs, if only heat exchanger is used without heating fuel.
Ammonia is going to ships engine use, replacing diesel. Firm AmmPower corp in Canada has made ammonia making process that uses only water and air to make ammonia, plus electricity. So ammonia can be made environmental friendly (minus electricity needed). Trains and trucks and cars can use ammonia also, but is it cheaper than methanol or ethanol? Or compressed air? Probably not cheaper than compressed air. Ammonia has 9 times energy density of lithium-ion batteries and 3 times energy density of compressed hydrogen gas.
For electric grids to make use of all electric grid capacity (In USA 68% of electric power is wasted in transfer losses of electric network, and only 32% of electricity goes from powerplants to consumers) firm Stem inc. has made Athena software which makes electric grid to work better. If that software can make about 90-95% of electricity to reach consumers instead of just 32%, that will mean that cost of electricity is then about only one third of what it is now.
There is “Newton battery” made by “Energy vault holdings” firm, that is energy store that uses gravity instead of compressed air, or water reserve power store of hydroelectric power plant, which are used to store energy in city-scale energy storing systems. But is force of gravity energy store (Newton battery) more economical than hydroelectric water reserve power or compressed air storage?
In battery technology aluminium-sulfur battery, sodium sulfur battery, “Solid Power lithium-metal battery”, “silicone-anode lithium-ion battery”, “salt-water-iron battery” , “Ilika Goliath solid state battery” are new battery types.
If boats and ships could use water as working mass, where pneumatic air pushes water to hydraulic engine, either rotary engine type piston-cylinder, quasiturbine, or that kind of piston-cylinder type that normal cars have, or other type of hydraulic engine, disc engine, wave disk engine, Szorenyi rotary engine, axial engine, pistonless rotary engine, high efficiency hybrid cycle, RKM engine, Gerotor, IRIS engine, or other types of motors that can use hydraulic or pneumatic power.
If compressed air engine is not used that uses pneumatic air or water (pushed by pneumatic air), then internal combustion engine which uses biofuels is another option, as cheap biofuels as possible. Methanol, ethanol, butanol, ammonia, and all kinds of biodiesel fuels are possible. If Otto engine type uses biofuel, it can perhaps be mix of methanol, ethanol, butanol and ammonia, and this mix between four different fuels is changed according to production capacity and availability of those four biofuels during year, so that burning properties of fuel mix stays the same and no modification in engine must be done although fuel mix is slightly different. Now all four fuels can be used instead of just one.
Other than pressurized air, flywheel is another way to use “direct” energy in cars or trucks or busses, but it has even worse efficiency than compressed air. However prototype vehicles have been build that use flywheel power, including busses, although they will not travel very far using flywheel power only, so they must be hybrid type with additional engine not just bare flywheel.
But there is idea that flywheel power can be in the engine itself, if engine is rotating when it is used. This rotating flywheel mass of rotating engine can have enough momentum that when car is freewheeling sheer flywheel power can power the vehicle, and only when speed has decreased engine starts again (it is constantly rotating even if fuel is not used) and when suitable speed is achieved fuel use stops again and engine and car wheels are just freewheeling. If car speed is 100 km/h the perhaps car accelerates to 115 km/h and then fuel use stops, car slowly slows down to 80-85 km/h and fuel is then burned again so that speed rises to 115 km/h etc., between this 115 km/h and 80-85 km/h speed change car is just freewheeling, its rotating engine gives momentum to wheels that together with car s mass keeps car moving. Same principle can be in trucks and trains also. So weight of engine is not a problem anymore, instead more heavy engine can give more momentum to car.
There are many prototypes and theoretical studies and patents about rotating engines, not only rotating piston engines but version of engines that are such that whole engine rotates.
Some types, they may have or may have not whole engine rotating capacity: Radial bi rotary balanced piston combustion engine, Circle cycle internal combustion engine, Hybrid engines corporation hyperstroke rotary engine, A cat-and-mouse type rotary engine design and performance evaluation 2010 Masami Sakia, netpage a3ird com Research and development of an effective anodyne rotary piston engine, netpage homebuiltairplanes com Diesel rotary piston engine, Veselovsky rotary piston engine, Green steam engine Robert Green, Flexible rotary transmission, the DOT piston rotary engine (Threee chdot), Axial vector motor, Sulzer Z-type rotating piston, netpage rotaryforum A new engine design with with rotary piston 2010, Radial piston motors Bosch Rexroth AG, Revolving block engine, cam engine, US patent 3724428 Rotary piston engine G Mederer 1973 (up to 40:1 compression rate), US patent 3724427 Rotary internal combustion engine K. Sauder 1973 (successive cylinders), netpage Dauglas Self: “Unusual internal-combustion engines”, “Unusual working fluids”, there is engines that use liquid air, carbon acid, caustic soda, and potassium, and acetylene engines were also used 100 years ago. Formula one cars used KERS system, such can be in regular cars also. Aquarius engine. Rotary power international Rotary rex. Axial engine, free piston engine, “Michel engine”, “Analytics, design and modeling of rotary vane engine, US patent 5277158 Multiple vane rotating internal combustion engine E: Pangeman 1994, swing piston engine, Rosen motors, “Punch powertrain”, PTM mechatronics.
Other: “IBM VolCas turn plastic waste into new PET plastic”, “Fortum EV battery recycling process”. “Japanese flexible lithium polymer battery developed using printing technology”, “New lithium battery captures carbon dioxide”, " List of prototype solar powered cars”.
I don t know how much electric cars use free rolling principle, car first increases speed and then no electricity goes to electric motor, it is just spinning freely (connected to powertrain) and this momentum together with mass of moving car gives car power to move, until speed drops below some limit and electricity goes to electric motor again. This freewheeling principle will work in other type of cars also, if there is cruise control button in car, and speed is 100 km/h, driver just pushes cruise control button, then speed accelerates automatically to 115 km/h without driver doing anything, in 115km/h electricity going to electric motor stops and car begin slow decrease of speed until speed is 80-85 km/h and then electric motor uses electricity again and again speed accelerates to 115 km/h etc, this is done by automatic cruise control, driver does not have to increase speed to 115 km/h and then stop, car does this automatically. When driver pushes cruise control button again car speed is now in full control of driver and this up and down speed variation is not used anymore. This freewheeling cruise control can save substantial amount of electric battery power, so lighter batteries can be used, car becomes lighter, and cost of electricity per 100 km is less. Usually cruise control is used to stabilize speed, in this case cruise control is used to save energy when it accelerates speed first over speed that driver has when he/she pushes cruise control button, then speed slowly decreases until electric motor “starts” again and again speed rises etc. So cruise control does not keep speed constant, it varies speed according to some parameters so that car can save energy. Electric motor is freewheeling too when electricity is not used, its mass is used as rotary rolling inertia to move car together with car s mass. This engine as flywheel inertia mass principle can perhaps be used in fossil/biofuel powered cars too and compressed air powered cars. And in trucks and trains perhaps too.

In previous post was that electric cars or other cars that has rotating engine, and this rotating engine can be used as flywheel that gives movement to car, can accelerate from 100 km/h speed automatically to 115 km/h speed and then electricity or fuel or compressed air injection stops and car just rolls down the road with inertia mass of flywheel engine and car s own mass, speed decreasing slowly until it is around 80-85 km/h, and then speed accelerates automatically to 115 km/h again. This “pumping” ride can save energy. But speed ticket is a problem. In Finland car speed over 9 km/h over speed limit means that police give it speed penalty, over 100 euros payment. But because this slight 15 km/h overspeed is for saving energy, it should be allowed. Car does not drive constantly 115 km/h in 100 km/h speed limit zone, it only accelerates to 115 km/h and immediately when that speed is reached power to engine stops and car speed slowly drops down to 80-85 km/h. So car does not all time go 115 km/h speed which must have the speed penalty ticket.
So legislation should be changed so that cars that use that sort of automatic speed accelerating system and cutoff for energy saving are allowed to use for example 120 km/h speed in 100 km/h speed limit zone when those cars when 120 km/h is reached automatically began slowing down to 80-85 km/h speed when engine power is cut off. If car constantly has speed over 109 km/h driver must then pay speed ticket. But those cars identified by model that they have cruise control - type automatic accelerating - cutoff energy saving system should be spared from speed ticket, when is observed that their speed goes “pumping” 120 km/h to 80 km/h and back automatically. How much does this automatic speed accelerating then power cutoff and then car is freewheeling speed slowly decreasing to 80 km/h saves energy I don t know. But rotating engines that have flywheel effect are suitable for this kind of thing, both electric (electric motors are by nature rotating motors) and fossil/biofuel engines that have either rotating cylinder or in other way engine rotates which brings flywheel effects. Powerful electric supercars that have big electric motors and heavy weight should benefit mostly from this kind of inertia used as power saving system.
Also in downhill driving power to engine should stop immediately if car has position sensors and those observe that car is going downwards, and car begin just freewheeling then. But modern electric cars probably already have this kind of automatic systems which cut off power when car goes downhill, I don t know. Also Formula One KERS -type system regenerative braking can collect energy when car is braking or going downhill.
There is water-methanol injection systems and camshafts sold for cars that are not from original manufacturer, they are tuning parts made by someone else than car manufacturer itself. Water - methanol injection can increase not only power output, but it can be used to save fuel, not so much gasoline engine needs if part of it is replaced by water-methanol injection in air intake. Methanol is cheap and water even cheaper. So fuel cost would be less if there would be water-methanol kits for cars, not to increase maximum power, but designed to decrease fuel costs.
Even more radical thing would be changing the original camshaft of car so that four-stroke engine becomes six-stroke engine, usually with water injection included. There are already made prototype conversions when mass-produced ordinary four-stroke engine has been converted to six-stroke versions by changing camshaft, new software or microprocessor, and water injection added. That will turn ordinary four-stroke engine to both more powerful and less fuel consumpting.
If those conversions would be in general sale, not only prototypes of scientific studies of six-stroke engines, ordinary cars, dozens of millions, could be converted to less fuel hungry versions. When water-methanol kits are sold for mass-produced engines, why can t six-stroke conversion kits be sold also? Even just adding water-methanol injection kit that has been designed to bring gasoline consumption low will decrease fuel cost significantly. If six-stroke conversion with water injection is used fuel saving is even more. When car engine is converted also engine can be changed to use biofuel, for example high octane rating AGE-85 ethanol that is used in piston powered airplanes. In cars it can be used also because it is cheap. Also turbochargers can be added, with intercooler, if car does not already have them. Like Lotus triple intercooler.
Water injection can be added to diesel engines also, engines of trucks and locomotives, with turbochargers and intercooler, like Lotus triple intercooler. Hyprex/Comprex turbochargers etc. Existing truck and diesel engines can be used, they are just modified to be more economical. Modification, if that is needed, can be done to engine that it can use biodiesel, ammonia etc.
“A review of water-steam-assist technology in modern internal combustion engines” 2021, this text has several engine types and also measurements how much fuel consumption is saved and power of engine increased when using for example water injection and six stroke engine.
The small cars mentioned in previous posts, Maruti Suzuki Alto, Renault Kwid, Tata Nano, Citroen AX, are not microcars but city car, crossover city car, and subcompact car class vehicles. Those relatively lightweight about 600 - 700kg small and very cheap cars made in India etc. countries cheaply could be perhaps base models of compressed air cars, about 100 - 120 kg air weight compressed air storage in quite low compression air tanks, 35 MPa or less, 280 litres needed air space, but if compressed air engine is small and compact then air tanks can be in engine compartment, and level of engine compartment hood risen substantially so lots of space under engine compartment hood, where compressed air storage is, and below car another air storage in space where fuel tank, spare tyre and exhaust pipe is. Spare tyre can be connected to back hatch like in some cross country jeeps. Only problem is Tata Nano which has problem to find suitable space for air tanks, perhaps smaller tanks, 70 MPa can be used and front of a vehicle used as small trunk, although space is so small that not much luggage can be put there. Bigger and heavier cars can have 500 kg or more air weight, electric cars are heavy also, and heaviest cars weight over 2 tons and are nowdays nearing 3 ton, both gasoline and electric cars, so weight of air is not much of a problem.
Recently during few years time progress has been made in compressed air engines for cars, their efficiency has improved and their previous faults corrected, so the negative imago that compressed air cars had, that they cannot compete with electric cars, is wrong in nowdays situation.
But compressed air has one great advance compared to any other fuel: it is cheap, only 0,5 dollar cost of compressed air can car spend in 100 km trip.