Solar Array
No fuel, ever again. But only while the sun is up, and it's exactly as good as the four panels it's built from.
The panels decide what the array is worth: it keeps their material forever and reads its Reactivity. Output falls off as the sun gets lower and when the Weather closes in, and stops at night.
Pair it with a Power Bank. Banking a long day to spend through a long night is the whole of what a panel is for.