Batteries, fusion, and hydropower: Meet the 24 clean-energy startups that Bill Gates is backing

· Microsoft cofounder and former CEO Bill Gates is the second richest person in the world, with a net worth over $100 billion. 
· He's invested a sizeable chunk of cash into clean-energy companies, largely through a billion-dollar fund he spearheads called Breakthrough Energy Ventures. 
· Most of the startups he funds...