I saw this a while back when I went into a big research hole on this topic: https://news.cornell.edu/stories/2014/02/indoor-urban-farms-called-wasteful-pie-sky

I saw this a while back when I went into a big research hole on this topic: https://news.cornell.edu/stories/2014/02/indoor-urban-farms-called-wasteful-pie-sky https://news.cornell.edu/stories/2014/02/indoor-urban-farms-... . LEDs have certainly gotten more efficient and cheaper since that lecture, but I think the general argument is still the same. The sun is pretty damn powerful.