“...if fully exploited to their maximum economic potential, so-called “renewables” will end up supplying somewhere in the range of 20-30% of projected energy demand.”
You don’t see where ‘maximum economic potential’ is the lynchpin of that statement ? Did the studies you refer to take into account a drop in costs of PV by a factor of 10 this early in the game ? The DOE computer model NEMS predicted almost $4K per kw installed costs for residential PV for the 2004 - 2009 time period, and $3K out to 2014, and $1,500 after 2020.
Instead, Nanosolar is talking about panel costs dropping to $300 per kw which would make the total installed cost only $1,500 per kw for residential systems. In 2008 rather than 2020. Which means the NEMS model needs serious revision and residential PV penetration will be much higher than ever forecast.
And no matter how much the cost comes down, you're still going to have the issue of capacity factor. As much as we might wish otherwise, the sun doesn't always shine and when it does it isn't always with the same insolation, especially where I live, which is known for nothing if not it's cloudy days. Right now it is very raw and chilly, with a snow-rain mix that started yesterday and is predicted to last at least another day or two. A PV solar array isn't going to be doing too well on days like these.