As far as i know, the only lasting, zero-maintenance and zero-risk solution would be solar panels. They can be thrown into arrays now, so you can have 8 panels into a single block, then 8 of those crafted into a single block, etc.
Just make sure you've got twice as much power being generated during the daylight as you use in both day and night... That's the only drawback really .
Other generators such as all types of generators, reactors, etc. require maintenance, and water/wind mills are horrible in terms of setup and reliability. You could go for more fancy stuff like the lava cell condensing idea, but personally i prefer a simple approach for power .