Please read about the rate of growth of PV (it's been quite high for decades), tied to the "learning curve" of PV costs from a doubling in cumulative production capacity. There is a positive feedback loop occurring here, and it suggests that PV (and other solar) will become very, very big globally within the next decade.
From our reading, we have seen the:
Links
[1] http://www.economist.com/news/21566414-alternative-energy-will-no-longer-be-alternative-sunny-uplands
[2] http://en.wikipedia.org/wiki/Doubling_time
[3] http://en.wikipedia.org/wiki/Ivanpah_Solar_Power_Facility
[4] http://task49.iea-shc.org/
[5] http://www.dlsc.ca/
[6] http://energy.gov/energysaver/articles/passive-solar-home-design