I think you're overestimating the amount of space we have realistically available for renewable energy. At some point I did the math for Germany.

The average German needs around 144sqm of solar panels (located in Germany) to meet their primary energy demand of around 48MWh per year (taking into account average production of solar panels in Germany). Germany has a population density of around 4300sqm / person. So in the ideal case with no storage losses you need to cover more than 3% of Germany with solar panels if you want to meet primary energy demand with solar power. (Wind energy is slightly more dense in Germany, but I haven't done the math there).

Realistically you might get something like 1% of the land area without huge resistance of the local population. Probably less, which is why offshore wind is popular. 100% renewable generation is only realistic because you can safely assume that large parts of the primary energy consumption are wasted. For example internal combustion engines are at best 40% efficient. Burning things for heating also only gets you 1J of heating per Joule expended, whereas heat pumps get you 2-3J. You just can't get away with losing another factor two to generate syngas, or even more if you want liquid fuels.

Of course you can justify some inefficiencies if you're willing to transport energy from far away (say solar power from the Sahara), but that is ridiculously expensive compared to more local generation.