More Responses to the Fusion Net Gain

At the Washington Post Megan McArdle is elated:

This is a long way from the dream of nuclear power that is safe (no worries about what to do with spent fuel rods!) and so abundant that it will be “too cheap to meter.” Scientists have been chasing this dream since the 1950s, so long that it has become a mordant joke: “Fusion is the energy of the future … and always will be.” For now, that old saw remains true; the reaction would have to generate hundreds or thousands of times more energy than went into it to begin to be an economical source of power. The hurdles to get there are enormous, possibly the most complicated engineering project humanity has ever undertaken.

So it’s probably premature for anyone to dance around the house in their bathrobe, singing “Clean, green energy for everyone!,” but … nope, actually, going to do the happy dance anyway. Scientists have accomplished a net energy gain from a fusion reaction. This is potentially the biggest news of the decade.

The editors of the Wall Street Journal are more reserved:

The news Tuesday that U.S. scientists have performed the world’s first controlled nuclear fusion reaction that generates a net energy gain is a refutation of American declinism. But don’t believe the hype that a fossil-fuel free world is near if only the government spends more.

Scientists have spent decades studying how to replicate in labs the nuclear fusion reactions that power the sun and stars. The fission reactions that power today’s nuclear plants involve splitting atoms and result in radioactive waste. Fusion entails combining atoms and theoretically could provide abundant, clean energy with no hazardous waste.

Hydrogen, fusion’s input, is the most abundant element in the universe, and no country dominates its supply, unlike some minerals used in lithium-ion batteries and wind turbines. The reactions also don’t generate CO2. But a stumbling block has long been figuring out how to generate more energy from the fusion reactions than is used to ignite them.

In the experiment that resulted in Tuesday’s breakthrough, the Lawrence Livermore National Laboratory used 192 lasers to heat and compress hydrogen atoms at more than 180 million degrees Fahrenheit. The reaction released 3.15 megajoules of energy for every 2.05 megajoules of input—with some major caveats.

The lasers are less than 1% efficient and used about 300 megajoules. As Lawrence Livermore director Kim Budil put it: “300 megajoules at the wall [socket], two megajoules at the laser.” Generating electricity from fusion would require such reactions to be performed every second of the day, a vast increase in laser efficiency and reduction in their size.

There’s good reason to be excited about the breakthrough, but the Biden Administration is overselling its immediate impact. “This milestone moves us one significant step closer to the possibility of zero-carbon abundant fusion energy powering our society,” Energy Secretary Jennifer Granholm said.

What the experiment proved is that scientists can recreate the physical reactions in stars. But scaling the technology and making it commercially viable by most scientists’ accounts will likely take another few decades.

while at Big Think Ethan Siegel is even more negative:

For the first time in history, that milestone has now been achieved. The National Ignition Facility (NIF) has reached ignition, a tremendous step towards commercial nuclear fusion. But that doesn’t mean we’ve solved our energy needs; far from it. Here’s the truth of how it’s truly a remarkable achievement, but there’s still a long way to go.

[…]

There are a myriad of takeaway points from this new developments, but here’s what I think everyone should remember about nuclear fusion as we move forward into the future.

• We really have passed the breakeven point: where the energy incident on a target — the key energy that triggers a fusion reaction — is less than the energy we get out of the reaction itself.
• That threshold is just over 2.0 megajoules of incident laser energy, far less than many who asserted 3.5, 4, or even 5 megajoules would be required to achieve the breakeven point.
• A new facility, one with lenses and apparatuses designed to withstand these new energies, must be constructed.
• A prototype energy-generation plant will need to leverage still-developing technologies: safely chargeable capacitor banks, large systems of lenses so that successive fusion-generating shots can be fired with a new set of lenses while the recently used set can be “healed,” the ability to harness and convert the released energy into electrical energy, energy storage systems that can hold and distribute the energy over time, including during the time between successive shots, etc.
• And the dream of a home fusion plant that lives in your backyard will have to be relegated to the far future; residential homes cannot handle megajoules of energy being pulsed through them, and the needed capacitor banks would create a substantial fire/explosion hazard. It won’t be in your backyard or anyone’s backyard; these fusion generating endeavors belong in a dedicated, carefully monitored facility.

Even with this undoubted breakthrough I doubt we’ll see practical fusion in my lifetime. It’s still on the horizon. The horizon is a little closer now but it’s still on the horizon.