Nuclear energy evangelists, seeing in it a carbon-free source of electricity that works whether or not the sun shines or the wind blows, are turning to China as a place to try out experimental designs.

Among them is Bill Gates, the Microsoft co-founder, who is chairman of TerraPower, a Bellevue, Washington startup developing what it calls a “travelling wave reactor.”

In September 2015, TerraPower finalized a long-sought contract with China National Nuclear Corp. to build a prototype of the reactor, followed by a commercial version. For China, the tie-up plays into an industrial trend in which it seeks to be the world’s clean-energy manufacturing powerhouse. While much of the world is pulling back from nuclear energy in reaction to the 2011 Fukushima nuclear accident, China will add 23 reactors by 2020 in order to supply 15% of the country’s electricity supply, up from 2% now.

“China is the center of activity because the demand for zero-carbon power is so huge,” says Richard Martin, energy editor at MIT Technology Review and the author of Superfuel, a book on experimental nuclear energy. The Chinese push is propelled by research institutions and state-owned enterprises, he told Quartz.

There are other places to build nuclear reactors, such as Canada and the US. But Gates tells Quartz that, if you are a nuclear energy experimentalist, China is the place to be. Here is a clip of Gates’ recent conversation with Quartz.