The biggest challenge of solar and wind energy is that it is very hard to predict their generation. So, you might be thinking what if we replace all energy generation with solar and wind energy then how will we get energy when the sun does not shine and the wind does not blow?
One of the very effective solutions is to store the energy when it is produced in excess of the demand and use it when the production is below the demand. This is called energy storage. One way to store this energy is to use it to pump the water up into a reservoir and use it to produce hydroelectricity when needed. It is called “pumped hydro storage”. Today, 95% of the storage capacity in the world is in this form.
Another way to store energy which using batteries, which represent a very small percentage and require a lot of development to ensure it is viable and can be used at a time of necessity.
The good news is that there is heavy research going on in the field of batteries and there is huge hope.