Isambard Kingdom Brunel vacuum structure halts road scheme

[Edwin_m]

Added to this, compressed air is very inefficient.

Although it was a long time ago, I still remember

being surprised when, at college, we did a test

using an air compressor and an air motor to measure

the efficiency of the system. If I remember right,

the system came out ad less than 10 per cent efficient.

A great deal of the energy put into the system

ends up as heat.

It's because compressing the air makes it hot, this heat is then wasted.  A related problem with some compressed air systems is icing where it returns to atmospheric pressure. 

 

I think a vacuum-based system would be equally inefficient.