[newyankee]

https://en.wikipedia.org/wiki/Bhadla_Solar_Park

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.

[credit_guy]

You are talking about peak power or capacity. He is talking about average, or generation. He explains the difference later in the chapter.