(Bloomberg) -- Commonwealth Fusion Systems LLC is looking to replace the boilers in fossil fuel power plants with the heat of the sun.
The US company is so confident in its fusion technology that it’s evaluating old coal and natural gas plants as locations to build its first commercial system even before its demonstration device is finished. Doing so would mark a step change for the energy transition and the shift from polluting fossil fuels to carbon-free fusion power, though fusion remains an unproven nuclear technology.
Commonwealth’s growing conviction that fusion is within reach after decades of research comes as the company completes the magnet that will be critical for containing the superheated plasma needed to generate power.
Building a plant from scratch would slow getting that power on the grid, which has the company targeting shuttered fossil fuel facilities. Commonwealth has narrowed the list to “a few” sites in the US and the UK. Not only do these facilities provide ample space for a commercial fusion system, they also have valuable connections to the local power grid.
Fusion offers the potential of abundant, cheap clean energy, but it requires harnessing clouds of plasma made from smashing hydrogen isotopes that can reach hundreds of millions of degrees Celsius, a task that’s proven fiendishly difficult. Commonwealth has raised more than $2 billion from the likes of Bill Gates and venture capitalist John Doerr, far more than any of its rivals, and expects to reach a major energy-generating milestone in early 2027.
While Commonwealth is considered one of the leaders in the fusion effort, it's still an industry that's been bedeviled with engineering complications and delays, and skeptics say that commercial fusion remains years away.
The key to success is the company’s magnets it uses to contain the superheated plasma in what’s known as a tokamak. They’re viewed as the best in the industry. Commonwealth says they’re strong enough to lift an aircraft carrier.
“Their magnets are state of the art,” said Chris Gadomski, head nuclear analyst at BloombergNEF.
The company successfully demonstrated in 2021 its so-called toroidal field magnets, which provide a strong, constant field to control the plasma cloud. The superheated plasma is ever-changing and finicky to contain. These magnets provide a stable, baseline field, but as the plasma shifts, the system needs another type of magnet that can be adjusted extremely rapidly to maintain control. That’s the achievement Commonwealth is announcing Monday, known as a central solenoid. Together, these two types of magnets can keep the plasma under control and keep the fusion reaction going.
“That was the last big, new technology that we needed to work,” said Bob Mumgaard, Commonwealth’s chief executive officer.
The tokamak concept dates to the 1950s, and researchers have already built versions that can trigger a fusion reaction, but electromagnets require significant amounts of power. That makes the systems more of a science experiment than a commercial power plant. To be practical, they need to achieve “net energy gain,” meaning they generate more energy than it takes to operate the device.
That’s Commonwealth’s goal, with its advanced magnets being the “key enabler,” said Alex Creely, director of tokamak operations. “It lets us go from almost good enough to more than good enough.”
Creely is leading the company's effort to build the Sparc demonstration system at its Devens, Massachusetts, headquarters. The building where it’s under construction is abuzz with construction workers and a maze of cables and wires. But the room where they plan to install the actual tokamak is almost empty.
In early November, workers were building a frame to hold the machine. The only sign of the tokamak to come is a life-size diagram that adorns one of the walls, standing 30 feet (9 meters) tall.
Next door, workers are assembling the powerful toroidal field magnets. The tokamak will need 18 of these, each comprising 16 layers carefully assembled by hand. At first, it took about 20 days to make each layer, but now the site can turn one out in a day.
Commonwealth will begin putting the pieces of the tokamak together next year, and Creely said it expects to start generating plasma by mid-2026. If all goes well, Sparc is expected to achieve net energy gain by early 2027.
Fusion researchers first reached net energy in December 2022, at Lawrence Livermore National Laboratory in California. Those scientists used a different approach, blasting a tiny fuel pellet with a powerful laser to trigger a fusion reaction. That proved it was possible to use fusion to generate energy, but it lasted a fraction of a second and it took months before they could replicate the results.
Commonwealth hopes to become the first commercial effort to do so and will try its hand with Sparc. The company wants to create a viable fusion system that will be reliable and economical, though it won’t incorporate the equipment needed to tap the energy to produce electricity. That won’t come until the next version: Commonwealth has plans to build what it calls Arc, a system that’s about twice as big and ready to generate electricity.
If the Sparc project goes well, Arc could be in service in the “early 2030s,” according to Mumgaard.
“We want to go as fast as possible,” Mumgaard said. ”We know we can do this now.”
There are dozens of companies developing fusion systems, using both lasers and magnets. They’ve collectively raised more than $7 billion to date, according to the Fusion Industry Association. With nations falling behind on their commitments to phase out fossil fuels, everyone from governments to tech companies are increasingly interested in fusion’s potential to deliver clean energy around the clock.
”If this works, it’s a total game-changer,” said Creely. “I’m at CFS because this project and this technology has the best chance of working.”
Finishing the solenoid magnet has given Mumgaard the confidence to look for a site to build Arc, even though the design won’t be finalized until Sparc is up and running. Doing so at a power plant that burned coal — one of the dirtiest fuels — would be fitting for the nuclear fusion industry that’s promised a carbon-free future for decades.
Commonwealth isn’t the first nuclear company to turn to fossil fuel plants as sites for nuclear power. Gates-backed TerraPower LLC began construction this year on an advanced nuclear fission plant at a coal plant in Wyoming that’s set to retire next year, and Type One Energy Group Inc. announced in February plans to build a fusion facility at an old coal site in Tennessee. For Commonwealth, one key to its strategy is avoiding tasks that have already been solved so it can focus on developing its own technology. Repurposing a retired power plant is a perfect example, according to Brandon Sorbom, chief science office.
“We can take things that produced a lot of heat using a boiler, and replace it with fusion,” said Sorbom. “The whole goal here is speed.”
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