In sun-drenched Nigeria, 14 new solar farms were supposed to jumpstart a meager solar industry and generate huge amounts of power, about one-fifth as much as the country’s entire electric grid offers on a good day. But that ambition collapsed when Nigeria’s government wouldn’t provide critical guarantees to developers. It’s not that demand is low for clean power — the smallest solar systems for homes have exploded in popularity and created jobs — but big developers haven’t been able to overcome Nigeria’s reputation as a risky place to do business. It’s a problem across sub-Saharan Africa, where 83% of the people in the world who lack electricity live.