For decades, scientists have searched for technologies that would allow us to supply the world’s energy from only renewable sources. But optimism surrounding renewables masks some harsh realities. About 80% of the world’s energy still comes from fossil fuels—the same as in the 1970s. Since then, we’ve added renewable capacity, but it hasn’t outpaced population growth and the world’s demand for energy. Quartz follows the shifts driven by regulations versus economics and the technologies, companies, and personalities driving major developments.