First, the only reason solar isn't so common in Alaska is that hydro is even easier to get power from, so your outback communities will often use small scale hydro instead of solar (especially in southeast Alaska).

Communities in the north will use diesel generators in the winter (nothing else is viable). Again, I assume you are talking about off grid communities, which is basically all of them except a few cities (and most cities have their own grids disconnected from the rest, especially Southeast Alaska).