Sierra you would probably need much more than 10% stored to make...

Sierra you would probably need much more than 10% stored to make fossil,fuels redundant? If anything , we 've all learnt in here than nature is a variable beast .... So maybe you'd need massive storage to cover periods of non renewable being out of action that over time would tend towards 10% average downtime but at any one period in itself may be extensive.

Maybe this alone would be cost prohibitive to making a completely green reliable source.