Only people who spend most of their life in densely crowded cities could think that the planet has so little space that you'd need to grow crops underneath solar panels for efficiency's sake.
Here [0] is a map of the world's remaining wilderness. Notice how it's nearly all desert, with the exception of the Amazon rainforest. And hey, guess what's happening to that?
We are short of space. And time.
[0] https://images.theconversation.com/files/256144/original/fil...
An interesting application of this technology would be building solar arrays along the edge of advancing deserts, with shade-tolerant plants with the sort of root systems which have been shown to halt and reverse desertification.
It's easier to do good things (such as halting the inexorable spread of the Sahara) if the operation is revenue-positive. Even though this would be more labor and less energy than just putting up a panel farm and calling it a day, it's more of a return on investment than the big old zero you'd get from just planting to try and fix dunes.
"In the contiguous United States, 127.4 million acres of crops are grown for animal consumption, compared to the 77.3 million acres of crops grown for human consumption.[23]"
>up to +2.5% for basil and +35% for spinach
There's a reason for this: Spinach cannot tolerate mid-summer heat, and doesn't need full sunlight. Was told this by local organic farmers here in coastal SoCal -- and because my own backyard plantings turned yellow and died.
2. Many plants are already grown in greenhouses.
Most desert ecosystems have a wretched excess of sunlight, and lack moisture.
Solar panels treat both of these: they capture a lot (but by no means all) of the sunlight, and serve as a nice, concentrated condensing surface for dews.
You can see this at a panel farm in dry areas: there's often a nice row of green in front of each panel, precisely where the condensing dew drips off them onto the ground below.
Though "we" as a whole are not limited by land, individual economic actors are limited by how much land they own.
Additionally, interconnection to the grid and node congestion are becoming larger percentages of the cost of solar, since they are roughly constant as the cost of solar plummets. Farms are somewhat ideal for medium size solar installations because they often have significant existing grid connections that are underutilized.
Now that we have economical solar tech, the actual implementation of solar installs will be highly dependent on regulations, economic motivations of individual economic agents, the knowledge and intelligence of thistle agents, and combinations with existing infrastructure. (For example, we are seeing batteries being installed in old fossil fuel plants, so that we can reuse those super expensive grid connections.)
When we're talking about humans, I'd agree that living in a crowded city is a terrible thing (though some people might like it). But when we're talking about industrial objects, efficiency is important.
We have flat unused ground. Lets focus on getting solar there and put our whiz-bang technical chops to work solving the more difficult problem of robust distribution and storage of power.