Not sure where you’re getting 250kwh/m2/year

I took solar irradiance where I live (around 1000kwh per year) and assumed 25% panel efficiency

Assuming we maintain exponential growth of both wind and solar (doubtful) we’re still a least two decades away from eliminating fossil fuel electricity generation

For electricity alone this should be doable. 560000km2 number assumes total replacement of all fossil fuels in all usecases. Electricity production is considerably smaller than that