Promising new technologies, including more efficient photovoltaic cells that can harvest energy across the light spectrum, have the potential to dramatically increase solar power generation in the next two decades. But major hurdles remain.

Today, despite recent progress, solar power accounts for about one percent of the world’s energy mix. Yet the International Energy Agency (IEA) says that solar energy, most of it generated by decentralized “rooftop” photovoltaic systems, could well become the world’s single biggest source of electricity by mid-century.

So how do we get from here to there?