Question

Why don't we get most of our electricity from batteries?

Answer 1

Batteries, though extremely simple are inefficient, hence apart from their use for back up powers they are not very useful for power systems as we know it.

Explanation:

Batteries operate by using the chemical energy stored inside them. As we know it is called direct current or a DC source. There are few advantages that DC sources have, regardless of how you generate it:

1) They cant be stepped up or down, which is almost trivial in a AC current source. What this means is basically you cannot get a 10KV DC source by using a 100V DC source! But wait we do have 10KV sources, don't we? Those are actually generated by actually stepping up the line voltage(which in my case is 220V ) to 10KV AC source which is then converted to DC. This is a very efficient way of going about things. That is why AC power supplies first came into being, because the ease with which you could step up and down.

Now, there are some reasons why batteries are not used, these are because of the nature of chemical processes in them.

1) The energy scales associated with chemical processes are inherently small. What I mean by that is you don't get chemical batteries producing 100V (just a number). These processes by their very nature(chemical) have very low voltages.

2) Batteries you make be it lead acid, or carbon batteries are of fixed voltage values, like 1.5 V AA carbon or cadmium batteries. And it is very hard to change these values unless you choose different materials to make them. You would want your output to be easily tune-able, not really possible with batteries.

3) Also environmentally they are very polluting considering the heavy metals like lead and cadmium used in them, hence cleaner alternatives are being actively pursued.

These are a few disadvantages of batteries and DC sources in general. These are ones off the top of my head, feel free to add more.