Until recently the limiting factor on utility scale solar was high costs. Now intermittency looks like the most important constraint. Land availability is not the bottleneck for the US or most other countries. There are some countries that have a dense enough population and/or low enough insolation that land availability is a significant constraint on solar deployment (Japan, Taiwan, UK, Belgium...) but that's not common.
The real annualized power of the Topaz Solar Farm comes to 6 megawatts per square kilometer, using its 2015 generation total of 1,301,337 MWh. At that areal productivity[1], if you could ignore intermittency, it would take ~95,000 square kilometers to supply the 2013 US electricity demand of 4,986,400,000 MWh.
The US Corn Growers Association estimated that 27% of US corn grown in 2011 was for ethanol, and corn covered 92 million acres:
Converting 27% of 92 million acres to square kilometers, the US is using about 100,500 km^2 to produce ethanol.
But you can't ignore intermittency, so (barring much improved storage, which may happen but can't be assumed) solar PV is not a drop-in replacement for nuclear power.
[1]Other areas of the US get less sun than central California, but newer farms with more efficient panels and single axis tracking increase areal productivity significantly over the fixed-tilt CdTe construction of Topaz, so I think that 6 MW/km^2 is a reasonable number to use.
The real annualized power of the Topaz Solar Farm comes to 6 megawatts per square kilometer, using its 2015 generation total of 1,301,337 MWh. At that areal productivity[1], if you could ignore intermittency, it would take ~95,000 square kilometers to supply the 2013 US electricity demand of 4,986,400,000 MWh.
The US Corn Growers Association estimated that 27% of US corn grown in 2011 was for ethanol, and corn covered 92 million acres:
http://www.ethanolproducer.com/articles/8611/world-of-corn-r...
Converting 27% of 92 million acres to square kilometers, the US is using about 100,500 km^2 to produce ethanol.
But you can't ignore intermittency, so (barring much improved storage, which may happen but can't be assumed) solar PV is not a drop-in replacement for nuclear power.
[1]Other areas of the US get less sun than central California, but newer farms with more efficient panels and single axis tracking increase areal productivity significantly over the fixed-tilt CdTe construction of Topaz, so I think that 6 MW/km^2 is a reasonable number to use.