< clearly the great promise of solar is in companies that are focusing on large scale solar projects.> (vozinthehead)
Sorry, the addition of more large scale generators requires reinforcement of the grid, which will be difficult, primarily due to NIMBY. Small distributed generators closer to the power system loads will add stability to the grid and avoid power distribution system losses - the smaller and the closer, the better.
NREL and this report disagree with your assumptions.
The report, “On the Rise: Solar Thermal Power and the Fight Against Global Warming,” concludes that a patch of solar arrays some 100 x 100 miles could power the country. That's slightly more than what’s already been excavated for strip mining for coal, the group notes.
The National Renewable Energy Laboratory has identified the potential for more than 7,000 gigawatts (GW) of concentrating solar power generation on lands in the Southwest -- more than six times current U.S. electricity consumption. When the sun isn't shining, the plants could release stored energy.
< NREL and this report disagree with your assumptions.> (vozinthehead)
I am familiar with the concept of powering the US from solar installations in the US desert southwest. It is proposed in a December 2007 Scientific American article, "A Solar Grand Plan", by Ken Zweibel et al.
My point is not that a large scale plant would not be efficient or economic. It is that the current power distribution system is fragile. Further centralization of power generation will require a further large investment in reinforcement of the power distribution systems and construction of long-haul transmission systems. NIMBY says it won't happen. Distributed solar (or whatever) says that such a large investment in the grid is not necessary.
The Scientific American article shows a solution to the US's long term energy generation needs using very conservative assumptions, e.g., no technical improvements beyond 2020. The article purposely uses conservative assumptions to show that a solution does exist for the generation needs at a finite upper limit in cost - $420 billion in subsidies from 2011 to 2050. The article alludes to transmission costs but not to NIMBY nor to grid stability.