Comment by Manuel_D

Nuclear power is indeed a silver bullet. France supplied > 85% of its electricity demand with nuclear (with the rest being filled by pre-existing hydroelectricity). As is hydroelectricity and geothermal power for those countries with the appropriate geography. E.g. Norward produces 100% of electricity through hydro. Non-intermittent sources of energy don't need to be supplemented by alternative sources of energy.