Planet Lumia relies on a single source of power, and while Maetel and Tetsuro are visiting, the system short circuits and the entire world is covered in darkness.
Planet Liger derives their energy from their star, whose entire surface area is covered with water
The 999 lands on a planet which relies purely on energy from its neighboring planet. The problem is that this other planet is constantly in turmoil and the imports are problematic.
Maetel and Tetsuro reach a planet called Ena. Maetel is very quiet, so much so that Tetsuro notices it. A volcano begins to erupt and a scientist saves the two. The scientist takes them to the power plant he works for. He begins to teach Tetsuro about the hi-tech plant. He then mentions the key energy-yielding element Enenium.