I recently noticed an interesting convergence. The long term growth of both solar and wind capacity is exponential. The growth rate for solar is higher than for wind power but wind power is currently ahead in capacity. If we take a capacity factor of 20% for solar and 30% for wind, how long does it take to cover the roughly 20 TW of world energy demand?
For solar, taking 200 MW of capacity in 1995 and 100,000 MW in 2012
http://en.wikipedia.org/wiki/G... we get to 100,000,000 MW in 39 years from 1995 since (log(100 TW)-log(200 MW))/(log(100,000 MW)-log(200 MW))/17 years)=39 years. So 2034 is when we may expect solar PV to cover all energy demand.
For wind, taking 7,600 MW of capacity in 1995 and 369,553 MW in 2014
http://www.gwec.net/wp-content... we get to 60,000,000 MW in 39 years from 1997 since (log(60 TW)-log(7,600 MW))/(log(369,533 MW)-log(7.500 MW))/17 years = 39 years. So, 2036 is where we may expect wind power to cover all energy demand.
So, within just a couple years of each other, either technology can be projected to grow to cover all current demand.
A driver for ongoing exponential growth for PV is the still falling cost of manufacture. It is expected that panels will cost $0.36/W to produce in 2017.
http://www.greentechmedia.com/...
This seems to be a faster rate than pledges coming in for Paris are anticipating so we might have some confidence that those pledges are going to be met.