A simple analog for the grid reticulation is to think of a network of water pipes
the voltage is pressure , the current is volume
the problem with renewable is that they are like a mesa river , dry beds and sudden massive flooding
to use them you need to size for the largest flow , which is costly and often unused
for the conducting material , if you want a trickle , pretty much any conducting material will do
the consideration are cost , durability and ease of use
the problem with Aluminium is that the joints must be done very carefully , it crack if stressed too much and Aluminium has a love affair with oxygen , corrosion is a constant issue
I've worked in the old Soviet Union , they had plenty of hydro-power and very little copper ore deposits
most of the wiring was aluminum ( they kept copper for making bullets )
They also had fridges without motors ,using thermo-electric conversion ,not so efficient but silent .
but since electricity was virtually free , it didn't matter .
Two questions. First those thermoelectric fridges. Do they work on the ammonia water cookant loop like the natural gas fridges that used to be fairly common in southern ohio? http://home.howstuffworks.com/refrigerator5.htm Seems like an electric heatng element would work as well as a small flame to operave the separator, and probable last longer without the flame gasses.
Secondly does anyone make coated steel wiring? I have seen copper and aluminum, but never coted steel, just bare steel for electric fencing.