Read an interesting article a few days ago. If we were all to switch to electric cars, the world's consumption (and production) of electricity would need to more than double. Currently, global production of electricity from ethical sources is less than 9%, nuclear less than 1% and the remainder split roughly 2:1 between natural gas and coal.
Per Kw of energy, production of electricity from gas and coal is claimed to be almost twice as damaging as emissions from petrol and diesel exhausts, and the warming effects much longer lasting. Large areas of the middle east in particular generate almost 100% of their electricity from fossil fuel and have no real incentive to change because it is cheap (to them) and readily available.
Singapore has recently announced an intention to switch to electric vehicles, yet produces it's electricity almost entirely from fossil fuels and waste incineration!
I don't know the answer, but the assumption that the world can double electricity generating capacity and provide a reliable supply wholly from solar, wind, tidal and similar natural methods within 15 to 20 years is surely living in cloud cuckoo land?