Firewalkers by Adrian Tchaikovsky
Firewalkers are brave. Firewalkers are resourceful. Firewalkers are expendable.
The Earth is burning. Nothing can survive at the Anchor; not without water and power. But the ultra-rich, waiting for their ride off the dying Earth? They can buy water. And as for power?
Well, someone has to repair the solar panels, down in the deserts below.
Kids like Mao, and Lupé, and Hotep; kids with brains and guts but no hope.