>you need a fossil-fuel base-load.

Basically saying this is wrong.

Technically, base-load refers to the minimum amount of energy demand on a given day. All sources and studies I have are from Germany, but our parliament, their adjacent (technical) offices and the universities here have concluded that "base-load" as a concept is wrong with today's power generation and the way a power grid works. Today they usually talk about residual-load, turning the paradigm around. Regardless of how it works, there are also renewable energies which can fulfil this classical "base-load" idea: Namely organic gas or geothermal power plants.