I thought this episode of Tsubasa Chronicles was interesting because they used electric transfer trucks and automated electric buses that had to charge themselves every few hundred miles and they charged themselves without human assistance. The main characters were able to see the charging...
I hate to drag this back up, but I seen an anime episode I thought was interesting. At minute 18 it shows a world under water.
Their sun was that whale that glowed and it swam near it to bring them light. It seemed to be the world's guardian.