Last December, researchers at California’s National Ignition Facility achieved what many in the fusion industry have called its “Wright brothers” moment. Using a laser, they zapped a golden vessel with a microseconds-long pulse of energy and received a dividend in return: About 50 percent more energy than they put in. That feat is called ignition, and it’s a triumph that’s been awaited since the 1970s. The perpetually 30-years-out technology of fusion power suddenly looks closer.
Well, not all that much closer. The ignition experiment still consumed energy overall, because the laser burned a lot more power than it delivered to its target. And there’s still plenty to figure out about how to harness fusion energy for electricity. But the result has prompted a revival of long-established predictions that fusion will solve all humanity’s energy needs. Startups working on fusion have reported a surge of interest from investors this year. The US government has announced a record $1.4 billion in funding for research, the beginning of a 10-year drive toward practical fusion. The potential payoff is big: Figure out the science, the wisdom goes, and fusion will unlock “unlimited clean energy.”
In many ways, that’s accurate. Just look up there, at that burning ball in the sky. It’s got 5 billion years left in the tank. Various national programs, a big international effort called ITER, and at least 40 private companies are trying to ignite simulacra of that process here on Earth. The goal is to smush atoms together—typically two hydrogen atoms, forming helium—and in the process lose a little bit of mass which, because e = mc2, means releasing energy, too. So you can argue that fusion energy is as limitless as there are hydrogen atoms in the universe.
When you put it that way, wind farms and solar panels can also look limitless, fed by an infinite stream of pressure waves and photons. In reality, of course, they are constrained by practical concerns. Permits. Financing. The construction and supply chains that produce turbine blades and photovoltaic films. The restrictions of a complicated grid that demands power at the wrong times, or doesn’t have wires in the right places.
Which is why, as the physics progresses, some are now beginning to explore the likely practical and economic limits on fusion. The early conclusion is that fusion energy ain’t going to be cheap—certainly not the cheapest source of electricity over the coming decades as more solar and wind come online. But fusion may still find its place, because the grid needs energy in different forms and at different times.
“I was wondering how the heck could fusion ever compete economically with the amazing gains in renewable energy,“ says Jacob Schwartz, a physicist at the Princeton Plasma Physics Laboratory. It was a question that inspired a pivot from working on the superheated details of fusion engineering to energy grid economics. In a paper published this month in the journal Joule, Schwartz and his colleagues tapped a sophisticated model of the US grid between 2036 and 2050 to study the conditions under which it would be economical to build 100 gigawatts worth of fusion plants, enough to power approximately 75 million homes. Basically, how cheap would fusion have to be to build it?