When I say footprint, I'm alluding to installations like the Taihang Solar Farm in China: https://www.youtube.com/watch?v=n731JjYSySY And, by footprint I mean the amount of space these panels occupy on the landscape.

Putting solar farms in a desert is an attractive idea and way less impactful than covering hillsides in green and temperate areas. My understanding, though, is that the transmission of all that energy is the real issue. You can build a giant solar farm in the Mojave desert but distributing it to farther parts of the U.S. is a problem.

Even if we created all our power from solar, it's negligible in land use compared to things like roads or agricultural land.

I don't think this is a meaningful comparison because they are not interchangeable and they exist independently of each other. The large footprint of farmland and roads doesn't make solar appealing in comparison, it just means that other facets of civilization are worse in terms of land use. To me, at least, just because something is way worse does not mean the other thing is acceptable because of it.

I also believe the amount of land we would need to convert to solar would be mostly be newly developed land. We probably wouldn't be converting already productive and utilized land.

It is a meaningful comparison. Agricultural and road use is huge. The solar installation you linked looks huge, but really, I could just as easily link an image of a uranium mine. Some of them are positively enormous - but that doesn't mean that land use for nuclear is.

A pessimistic scenario for Germany requires about 2.5% of the area for 100% renewable energy with today's technology. In a very densely populated country not exactly blessed with loads of sunshine hours. Taking into account the possibility of dual use (PV on buildings, wind turbines on farmland etc) we'll probably use about two times as much land for renewables than we use for cemeteries. It's very manageable.

And you would cause untold destruction to amazon rainforests, among other things.

No, you can't just pave desert with panels and magically solve power generation without ugly environmental consequences, that doesn't work even in computer games.

> And you would cause untold destruction to amazon rainforests, among other things.

Why would putting all the panels in a desert do that to a rainforest on a different continent?

And how much of the Sahara do you think we’d need to cover in PV if for some strange reason we didn’t put any on rooftops, brownfield land, parking lots, car bodies, and (for most of the world) closer deserts?

http://www.wolframalpha.com/input/?i=area%20sahara%20%2F%20%...

Because, surprisingly, various ecosystems including Amazon rainforests are dependant on sand picked by wind from Sahara. Ecology can be weirder than you think, and having intercontinental dependencies is surprisingly common.

Sensitive enough that 0.5% land use change would do that?

I don't remember the exact numbers from studies, but EU-funded research in that area suggested vastly higher numbers as part of removing fossil fuel dependency

I suggest following the Wolfram Alpha link I gave above. My assumptions, to explain the magic numbers visible in that formula, are 20% efficient and 25% capacity factor.

(And the other person was actually saying electricity, which is what WA is inferring in that calculation)

Except it is not practical to colocate all of the worlds solar power in a single location, and wind farms are even less space efficient by orders of magnitude when compared to energy density of nuclear per area.