How Solar Power Could Become the World's Dominant Energy Source in 35 Years

By 2050, the Sun could be the dominant source of electricity for human civilization. Thanks to falling costs, solar power could feasibly overtake fossil fuels as the top energy source in under 35 years. So says the world's top energy agency, the Paris-based IEA, which details the encouraging and fairly radical prospect in an ambitious new report.

The International Energy Agency lays out a roadmap for how photovoltaic panels—the kind on your neighbor's roof—could provide 16 percent of the world's electricity by 2050. Meanwhile, concentrated solar power plants, larger projects designed to reflect large amounts of sunlight onto a single point to drive a heat engine, may generate up to 11 percent.

Combined, that's 27 percent of the planet's power coming from solar—which would be more than coal, wind, hydro, or nuclear. Here's how that world could come to pass, according to the IEA.

"The rapid cost decrease of photovoltaic modules and systems in the last few years has opened new perspectives for using solar energy as a major source of electricity in the coming years and decades," IEA Executive Director Maria van der Hoeven said in Paris at the report's release.

As a result of that rapid cost decrease—driven mostly by China's aggressive manufacturing and booming demand in markets like Germany—solar PV is currently hitting the ground at a very rapid rate. Up to 100 megawatts of capacity are brought online every day now, according to the IEA, and there are already 150 gigawatts worth installed worldwide. In the US, rooftop solar is being installed so quickly that the utilities who operate the coal and gas power plants of yore are fighting tooth and nail to kill them.

It's not hard, in other words, to imagine a planet that gets 16 percent of its electricity from solar PV. Unsurprisingly, China will lead the charge:

This boom in solar PV—both in 'distributed' modes like rooftop panels and central plants like solar farms—could continue to accelerate until 2030, the IEA reckons. Then, when PV accounts for between five and fifteen percent of the world's electricity generation, when the markets are saturated, and the panels are atop most viable roofs, solar thermal energy will take over. By then, the IEA envisions, we'll have the technology and economies of scale necessary to make concentrated solar a financially feasible option for the carbon-free power plant of the future.

Concentrated solar plants have a major advantage over standard photovoltaic systems—they can store energy for use at night. The IEA says that the two technologies are largely complementary, and will develop in tandem. CSP will be big in India, the Middle East, and the US.

It won't be smooth sailing in either case, though.

"However, both technologies are very capital intensive: almost all expenditures are made upfront," van der Hoeven warned. "Lowering the cost of capital is thus of primary importance for achieving the vision in these roadmaps."

And therein lies the problem. Both reports assume governments round the globe will enact the "appropriate regulatory frameworks—and well-designed electricity markets, in particular" that are "critical to achieve the vision in this roadmap." Which is definitely possible, but not necessarily plausible. Our electricity markets are rarely "well-designed," and fossil fuels still have a lot of skin in this game.

Those aforementioned utilities are already working to undermine solar, by removing incentives and trying to make it more expensive. Luckily, they're often fighting losing battles against bipartisan coalitions, who seem to like the idea of owning their (clean) energy supply.

Concentrated solar power faces its own array of obstacles; it's still very expensive, and environmental groups are concerned about their impacts on wildlife (most famously, desert tortoises and birds). Just today, a major CSP project was cancelled, dimming the outlook for other near-term projects in the US.

Still, a lot can happen between now and 2030, and it remains a promising technology. There's a reason the IEA has enough confidence to believe it could plausibly meet 1/10th of the planet's energy demand. (The agency stresses that these reports are not forecasts, but roadmaps.)

Something needs to do exactly that, a few times over—something besides the fleet of fossil fuel-burning power plants that are currently warming our planet. We're on track to head way past 2˚C of warming, studies show. And the rapidly expanding specter of climate change is precisely why these blueprints need to be taken seriously, even if they're hugely ambitious (though perhaps not as ambitious as Stanford Prof. Mark Jacobsen's pathway to 100 percent renewables or Saul Griffith's WWII-style clean energy mobilization).

Uprooting the coal-fired power plants and internal combustion engines of the world, after all, and replacing them with clean energy sources is the banner project of the century—it's the only way we'll avoid the more catastrophic registers of climate change.