Size doesn't really matter, because most renewable schemes scale with area. Population density does. France has 116/km^2, China has 145/km^2, so almost a 25% higher overall population density. That translates to a little bit less space for wind, solar, hydro and so on per capita, but not by enough to make it infeasible. Add in nuclear power, and the scaling is quite easy - building a nuclear power plant is hard, but doubling the generating capacity doesn't come close to doubling the land area, as long as you have a supply of uranium (China has uranium mines, France doesn't).