I don't like using aluminum wire in situations where it may be shallowly buried from a hydro and through the forest. Any nick in the positive wire and it turns to white powder. Then a devil of a time trying to find the break.
Chris
My system has 2 - 4 gauge aluminum wires buried in 1 1/2" poly pipe. The run from my powerhouse to the main house, and my battery bank, is 120'. There is no measurable power loss from one end to the other. The price was right, free from a barn that was being torn down......
As for the wire turning to powder, hmmmm, that's disturbing news. Hopefully, it won't be a problem since it's underground. I was thinking ahead enough to run a separate fish line through the pipe for future use, hope I don't need it for new cables!
And the pipe. I think it's best to keep the angle of descent as constant as possible. I used to have my pipe hanging from rope tied to tree branches in places! It's all buried now. That was a backbreaker to trench through a rain forest where cedar roots are 18 inches thick and a little rock turns into a huge boulder! I wore out a shovel and a good bar and chain on that job!
Good luck with your project, I'm looking forward to seeing the lights go on!
Jon