"It doesn't take much," Elon Musk told the National Governors Association. "If you wanted to power the entire United States with solar panels ... you only need about a hundred miles by a hundred miles."
But there's a problem with renewables we still haven't solved: storing power from when the sun is shining and the wind is blowing so we can use that power later. We do this all the time with batteries at home, but AA batteries won't cut it on a national scale. Replacing fossil fuels will require ingenious ways to store power.
Some methods have been around for a while. The U.S. has stored power in reservoirs since the 1930s. We pump water uphill when power is abundant and release it downhill to spin turbines when power is scarce.
In the same way, we can pump empty caves full of compressed air so it can be released to spin turbines later. We can even store power by beaming concentrated sunlight onto towers of molten salt, which can stay hot enough to turn water into useful steam for as long as a week.
And Musk is still pinning his hopes on batteries, which are easy to charge and transport.
Putting these technologies to use nationally will be a huge undertaking, though. Right now, the U.S. stores less than 3 percent of its total power needs at any one time. And we only meet 10 percent of our energy demand with renewables. To hit 100 percent would require an enormous investment, not only in solar panels and turbines, but in storage, too.
Critics worry that proclaiming the renewable renaissance is right around the corner can actually make it harder to move toward that future. It discounts other energy tech, like nuclear power, and ignores all of the research and development we still have to do to give renewables a bigger slice of the market.
The good news? We are moving toward that future. The U.S. government is issuing more permits for hydropower reservoirs, for example, and public and private sectors are both building better batteries.