This assumes 1 KW peak irradiance. Off course things will change based on latitude, season etc and one has to adjust for these factors however Solar is a no brainer in tropical and temperate climates alike at this point in my opinion.
This has a ~ 40 MW/ sq.km output with a lot of it still being open space for different reasons.
https://en.wikipedia.org/wiki/Kamuthi_Solar_Power_Project
This one has ~ 64 MW/ sq km output
https://en.wikipedia.org/wiki/Copper_Mountain_Solar_Facility
This one in US seems to be about ~ 53 MW/ sq km
So definitely he is purposely understating the potential of solar. Because it does not include future growth of tandem solar cells (Si + perovskite) taking it to more than 25-30% efficiency, or the fall in costs if they continue (albeit at a slower pace). Co-located Wind & solar power plants at suitable sites can be even more efficient with their reliability and capacity factors increasing if batteries added to the mix.
