Can a "star in a bottle" make electricity?
Boyce Rensberger
(4/2025) If all goes well—and that is a very big assumption—one of science’s long-cherished dreams may become a reality in less than ten years. The dream is to make electricity from carbon-free, safe, nuclear fusion and to do it in a way that makes more energy than it consumes.
Nuclear fusion, as you may know, is a process very different from nuclear fission, the phenomenon that drives some 419 nuclear power plants now operating around the world. Fission uses heat released when atoms of uranium or, less commonly, plutonium are made to split into smaller atoms. Fusion, by contrast, forces hydrogen atoms through a series of reactions to fuse into helium, a phenomenon that also gives off heat. In both cases, the heat can then be used as in any other kind of power plant to boil water into steam that drives electrical turbines.
So, what’s happening now?
A private company spawned by M.I.T. announced in December that it will "independently finance, build, own, and operate" a grid-scale, thermonuclear fusion power plant in Chesterfield County, Virginia, just south of Richmond. Commonwealth Fusion Systems signed an agreement with that region’s power company, Dominion Energy Virginia. The fusion plant would be built on Dominion’s land. The newly made electricity would feed into Dominion’s grid.
Though many groups around the world are working to commercialize fusion energy, this would appear to be the furthest any group has ever gone toward delivering on that long-held dream. The goal first promised in the 1950s is to make electricity from a fusion process that gives off more energy than it consumes and do it on a sustained basis. Much of the appeal of fusion power is that the "fuel" is an isotope, or version, of hydrogen (called deuterium) that can be extracted from sea water plus another hydrogen isotope (called tritium) that can be made from lithium. Fusing the two isotopes yields helium, a safe and valuable "waste product." No greenhouse gases are produced.
A little background is in order.
In 1925 an astronomer named Cecelia Payne, whom I wrote about in 2023, discovered that stars are made almost entirely of hydrogen and helium, the two simplest elements and the first to come out of the Big Bang. They were created as loose atoms which eventually clumped together, the aggregation becoming ever larger as the growing mass exerted stronger gravitational pull. Once such a mass becomes great enough, the gravitational pressure deep inside creates intense heat—many millions of degrees. This ignites fusion reactions, and the great mass becomes a shining star. Nuclear fusion is the reaction that powers our local star, the sun.
The usual, over-simplified way of putting it is that the nuclei of hydrogen atoms, which are single protons, are forced to move so fast that they overcome their normal repulsion (both have a positive charge) and slam into one another, binding and creating helium, with its nucleus of two protons. In reality it’s more complicated, too complicated to fit in this space. The bottom line is that hydrogen nuclei fuse (making helium) and release huge amounts of energy as heat.
The idea of practical fusion power first arose in the Soviet Union in 1950. The world had recently seen what fission can do after the United States dropped atomic bombs on Japan. But fission was easier to control, so it became the only practical form of atomic energy, despite producing lethally radioactive waste products. The wastes of more than 400 fission reactors that have been operating for decades are usually stored on site.
But the dream of fusion power did not die. When I started as a science writer in the 1960s, scientists promised that practical fusion power lay "only 30 years" ahead. A few decades later it was still "30 years" away. Come that elusive day, fusion would produce electricity "too cheap to meter." The phrase was borrowed from advocates of fission power much earlier.
Work on fusion power continued through the decades with many different machines designed to replicate the intense heat and pressure inside the sun, creating what some dubbed "a star in a bottle." In 1950 Soviet scientists proposed a machine they called a tokamak. It bottled deuterium and tritium in a large donut-shaped ring surrounded by powerful magnets that repelled the charged particles from all directions, keeping them inside. The magnetic field’s pressure heats a cloud of hydrogen atoms as if they were inside stars, tearing away their electrons and forcing their nuclei to fuse into helium and release heat.
Countless engineers and scientists have worked to design and build fusion reactors in the tokamak form. Some worked, but none has achieved a system that would be practical. They all consumed more electricity than they could produce. Or, at best, some achieved "break-even."
The private company aiming to build in Virginia has developed a tokamak at its campus outside Boston that they say will finally reach the goal, possibly next year or in 2027. Led by M.I.T. professors and grad students and funded with some $2 billion in venture capital, it will use newly developed high temperature superconducting magnets to confine and heat the hydrogen nuclei. The tokamak proposed for just south of us would be an upgraded version.
As the company says in a news release: "Commonwealth Fusion Systems is the world’s leading and largest private fusion company. The company’s marquee fusion project, SPARC, will generate net energy, paving the way for limitless carbon-free energy."
They aren’t promising energy too cheap to meter, but neither are they saying the goal is 30 years away. They say their commercial fusion reactor will feed power to the grid in Virginia in the "early 2030s."
I might live to see it.
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