Iceland both produces and consumes 100% electricity from renewables for instance. You have the issue you talk about with all generation that isn’t load-followi

Iceland both produces and consumes 100% electricity from renewables for instance. You have the issue you talk about with all generation that isn’t load-following, including nuclear. France solves this by exporting subsidized electricity in time of low demand while importing in time of high demand, which is winter. In the surrounding countries like Italy and Germany you have gas-plants that jump in when needed.