The total installed PV capacity in the world at the end of 2011 was 70GW as per REN21.
The latest report from IMS Research show that about 31 GW new capacity will be added this year.
So, by 2012 we will be at 100 GW world PV capacity.
If we do a quick back of enevelope calculation (although I used an excel sheet for the same):
1) The world power demand today is about 16 TW (16,000 GW) and lets say, if we do our Energy Efficiency bit, it may double (instead of tripling) to around 30 TW by 2050
2) To supply 50% of this requirement by PV means we should have 15TW supplied by PV and taking a capacity factor of 20%, we need 75 TWp (75,000 GWp) PV capacity installed by 2050 in the world.
3) Based on past few years (2009-2012), the average capacity growth rate has been about 64%, but one can argue that this was just too exceptional and may not be the same in the future.
4) To reach 75,000 GW of PV by 2050 (in 38 years) from current (2012 end) base of 100 GW, we need a compound annual growth rate (CAGR) of about 19%. Again, this is the wonderful power of compounding that we are taugh about and if it has worked before for others, why not for Solar? With technology advancements, this growth rate maybe even lower than what is stated here.
5) In other words, with a CAGR capacity of 19% growth for PV over the coming years, we can meet 50% of the world's power requirement by Solar PV only in 2050.
I know that this is a lot of land, lot of $$ and lot of political will, but again, its definitely not impossible. A world with 50% PV by 2050 will be much better for our next generation, isn't it?
The next Tom Cruise movie will have a subtitle:
50% Solar in 2050
Recreated from original blog post authored by Nilesh Y. Jadhav at Solarika.org