What challenges will we face in integrating more renewable energy sources into our electricity transmission system?
a) the existing high voltage lines are not close to the areas where we could generate renewable energy
b) existing power plants produce a lot of energy in one location but renewable sources are much more distributed
c) renewable energy generation tends to be much more variable which requires much more connectivity between different places, and we need to be able to transmit energy longer distances
d) all of the above