Regular readers of this blog will know we talk a lot about different types of air compressors and their advantages – but what exactly is a compressor?

It’s not a stupid question, and there are a couple of different ways to approach it, so if you want the simple answer, then it is basically a piece of machinery to compress air, which can then be used just as a jet of high-pressure air, to spray a fluid, or to power an air tool of some kind.

But what is a compressor in principle? The science behind the machinery is much more elegant than you might first think.

An air compressor takes an external power source – electricity or diesel, generally – and it uses that energy to compress air into a smaller space, increasing its potential energy.

In essence, the energy packed into this compressed air is a kind of battery, storing that potential until it is released and used to power a tool or spray air or liquid in a particular direction.

Because of this, the way you use your air compressor can have a big impact on its overall energy efficiency, and variable speed compressors are increasingly popular, as they only supply the amount of compressed air needed for the particular application at hand.

Not all compressors use the same method to compress the air in the first place, either – the two main types are piston-driven and rotary screw compressors.

Pistons pump air through non-return valves into the compression chamber, where the pressure gradually increases as more and more air enters and cannot escape.

Rotary screw compressors, meanwhile, displace the air using a helical screw (think Archimedes’ method of lifting water, and it’s the same principle).

Finally, some air compressors use an impeller or rotor to move the air into the compression chamber – ultimately though, it’s all about moving a quantity of air into a smaller space to increase its pressure, and discharging that pressure later to release the stored energy.