Opinion | A fusion power breakthrough probably won’t solve climate change


Researchers at the National Ignition Facility at the Lawrence Livermore National Laboratory last weekend achieved something that had never been done before: They got a fusion reaction to produce more energy than was in the laser beams that went into sparking it. “Ignition allows us to replicate for the first time certain conditions that are found only in the stars and the sun,” Energy Secretary Jennifer Granholm declared at the formal announcement Tuesday, hailing it as a milestone that “moves us one significant step closer to the possibility of zero-carbon abundant fusion energy powering our society.”

The potential benefits stemming from what Ms. Granholm called “one of the most impressive scientific feats of the 21st century” are indeed tantalizing. Fusion can power a large city with a tiny amount of fuel. Unlike fission, in which atoms are split in conventional nuclear reactors, fusion leaves almost no toxic byproducts and poses no meltdown risk. Unlike solar and wind power, it produces electricity at a regular and predictable rate. And fusion’s fuel — hydrogen — is the most common element in the universe.

But the National Ignition Facility’s achievement, while a scientific coup, does not mean that a fusion-powered utopia is around the corner. Rather, history suggests that fusion power is unlikely to play a major role in the energy grid for years or decades — time that the planet does not have in the climate change fight. Other, less exotic sources of clean energy that are immediately scalable remain the most plausible options. Humanity must continue to invest in them, and urgently.

Fusion reactors work — in theory, anyway — by superheating hydrogen. Under the right conditions, atoms fuse together to create helium and, in the process, lose a bit of mass. That mass gets translated into huge amounts of energy, according to Albert Einstein’s famous equation, e = mc^2. But getting hydrogen hot enough requires vast amounts of energy. Scientists have for decades tried to produce a fusion reaction that puts out more energy than is put in. Repeated bouts of optimism and investment, particularly during the 1970s and 1980s, produced disappointing results.

Until now. At the National Ignition Facility, researchers used the world’s largest laser to point 192 laser beams at a pea-size hydrogen pellet and — finally, according to the Energy Department — produced 3.15 megajoules of energy from 2.05 megajoules of laser energy. (A joule is a unit of energy; it takes 1 joule to lift a 3.5-ounce apple one yard. A megajoule is 1 million joules.) This is a big step for researchers seeking to learn more about the dynamics of fusion reactions.

Megan McArdle

counterpointHistoric advance in nuclear fusion is truly something to celebrate

However, that 2.05 megajoule input did not represent all the energy that went into the ignition process — just the amount that inefficient lasers managed to get to the hydrogen pellet. It took far more energy in total — on the scale of 300 megajoules — to produce that 3.15 megajoules result. Scientists can improve the picture by using better lasers, but there is always likely to be substantial energy loss that would require a much more robust fusion reaction to make up.

Harnessing electricity from the energy produced in a fusion reaction is another challenge, points out Princeton University’s Wilson Ricks. Nor in conventional power plants, much of the heat produced will dissipate uselessly rather than transfer to the water that turns into steam to drive a turbine. This means an economic fusion reactor would have to create a lot more energy to produce enough electricity to justify the energy cost of ignition.

There are other potential fusion power options that do not rely on enormous lasers. Using a different approach, a multinational group is building a giant, doughnut-shaped reactor in the South of France that might produce a sustainable fusion reaction by 2035. Others promise more progress sooner. Yet, as with the National Ignition Facility’s method, the theoretical science is simple and clear, but achieving real-world results could be much harder.

Once demonstration reactors work, fusion technology will face another barrier: economics. Fusion reactors will have to compete against traditional fission facilities and increasingly cheap renewables. In the long run, fusion’s many benefits will probably make the technology a big part of the global energy mix. But that point is not likely to come soon enough for fusion to play a leading role in replacing the fossil fuels driving climate change, a transition that scientists say should happen over the first half of this century.

The playbook for that transition — which is likely to rely on more familiar and increasingly inexpensive clean-energy sources — remains the same as it has been for decades. Governments should invest in research but remain technology-neutral as much as possible, providing incentives to deploy any zero-carbon energy source that can help at a competitive cost — immediately. That will likely result in accelerated investment in wind and solar farms along with facilities that store energy for times when nature does not cooperate. Power plants that can burn hydrogen — via traditional combustion, not nuclear fusion — or natural gas plants that sequester the emissions they emit might be necessary to back up these renewables. A renewables-heavy grid will require massive high-capacity power lines to zip electricity from where the sun is shining and the wind is blowing to where people need it. Advanced fission reactors and machines that pull carbon dioxide directly out of the air might also help in the decarbonization effort.

While fusion physics advances, it is crucial that government and private investors do not lose sight of the pressing challenge that humanity faces now. Although the costs of wind and solar have plummeted, it is not guaranteed that governments will enable the massive build-out of infrastructure the world will need, that the transition to zero-emission cars will go smoothly, or that hard-to-decarbonize sectors such as agriculture, aviation and shipping will be able to cut emissions in time. So, people should celebrate the long-awaited marvel of a breakthrough with fusion — and then get back to work.

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