If the rest of the world will go to 1/3th of 1st world energy consumption we will need a lot of new power in near future. "Renewables" are not enough even if we focus everything on building them.
I quote Dr. Ripudaman Malhotra @ TEAC7: (https://www.youtube.com/watch?v=CpXG3zyg3gk)
If we want to replace one cubic mile of oil by 2050 we need:
200 Three Gorges dam. One built quarterly. We have perhaps three (3) rivers left for such installations. So, no new big hydro. Small perhaps but I personally enjoy more of free flowing rivers than dam lakes.
2500 900MW nuclear plants. One built every week. Completely possible, no shortage of fuel with fast neutron reactors where the remaining 97% of nuclear fuel gets used.
7700 900MW consentrated solar parks 25% availability (10x size of Andasol CSP). 3 a week for next 50 years. This is possible but getting difficult.
3 000 000 1.65MW windmills 35% availability. 1200 per week for next 50 years. This is where it starts getting hard. We need 50 million tonnes of steel/year (possible) and lots of rare earths (not possible) for generators, transmission lines and electronics and billions of tons concrete for offshore installations. All of them are big carbon emitters. Low power density creates need for large power networks, transmissions losses reduce the efficiency of such system. Still I say go for it where the wind is constant, like trade wind regions.
4 200 000 000 (4.2 billion) solar roofs 2.2kw 20% availability. 250 000 new installations _every_ day till 2050. I am sorry, this is not possible. We don't have enough roofs at places where people can actually afford solar roofs and their lifetime, even if increased to 35 years, is not enough.
So this is why we must build 4th gen Uranium-Thorium reactors with passive safety systems. Reactors which operate at 700-800C and produce process heat. Then we can decarbonize things like concrete production and recycle municipal waste/biomass to liquid fuels etc.
These new plants are modular where every part except of the concrete can be swapped when it gets old or fails some way. Concrete is long lasting stuff. It is possible to get Colosseum like lifetimes for these installations, 2000 years easily. 4th gen reactors close the nuclear fuel cycle so the unusable radioactive byproducts are minimal and they have a short half life.
What is worrying me is that the projected energy consumption is nine CMO (all energy forms converted to oil) by 2050. We are using 3.5CMO now. So basically we have to build everything non-fossil source we can. This is possible with nuclear because that is the one which actually makes money to finance the other not-so efficient energy sources.