Question: could cars run on air in the future?

Simone Sturniolo answered on 24 Jun 2013:

No. What cars need in order to run is a form of energy that is cheap and easy to move around. The cheapest and easiest form of energy available at the moment is burning fuel. A car’s engine burns gasoline producing a lot of hot gas; this hot gas has a very high pressure and pushes against the pistons inside the cylinders; this force allows the car to move. Without the heat produced by the fuel, this would not be possible! Air does not burn all on itself, even though air is needed in order to burn something else, so it can not be a fuel.
Of course, you could compress air and store it in tanks (sort of like the ones that the scuba divers have), then carry it around in the car and use it to propel it. This would cause the car not to pollute the city while it circulates, but it would not be a ‘source’ of energy, because eventually you would need energy to compress the air that then you are loading into the car (and you would still need fuel, solar or nuclear power to do that!). Besides that, a car running on compressed air would need to carry very heavy gas tanks and would possibly run only a few miles with a full tank. So it wouldn’t be neither easy to move around, nor cheap!
Our best chance for a replacement for gasoline in cars is electricity. Electric engines are silent and very efficient, though not as fast as gasoline ones (but unless you’re a speed maniac, really, you’d probably be ok with them anyway. They’re perfect for everyday use). To store electricity on the car you could use either a battery or a “fuel cell”. You surely know what a battery is: these ones would be bigger than the ordinary ones we use in toys or remote controls, but not very different. It wouldn’t carry much energy though, so scientists are studying “super-batteries” which could work better and longer. A fuel cell is similar to a battery, but it produces electricity by “burning” something – either hydrogen or alcohol, or even methane. The difference from burning them in the normal way is that instead of heat, a fuel cell draws out their energy as electric energy, which is a much “purer” form of energy and can be used better! In this way, one can make much more road with the same amount of fuel. Fuel cells are a bit expensive now, but the bigger problem is to store hydrogen somewhere. Pressure gas tanks are a bit too heavy for cars, so we’re looking for different solutions, like absorbing it into a “sponge” made of metal!