Firewalkers by Adrian Tchaikovsky

FIREWALKERS ARE BRAVE
FIREWALKERS ARE RESOURCEFUL
FIREWALKERS ARE EXPENDABLE,young and poor underclass of ‘Firewalkers’ risk their lives to service the global billionaire elite as they prepare to escape a dying Earth and leave the rest of us to burn.
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 thanks to their investment, the sun can provide power.
But someone has to repair the solar panels when they fail, down in the deserts below.
Kids like Mao, and Lupé, and Hotep; kids with brains and guts but no hope.
The Firewalkers.