Fueling Fusion

From Forbes:

“Legendary tech investor Steve Jurvetson, a Commonwealth Fusion backer who wrote his first check toward fusion research 25 years ago, is nearly giddy that this dream long deferred could soon become reality. ‘There’s plenty of naysayers until it’s done. Then they say it’s obvious.’

Boston-based Commonwealth Fusion Systems (CFS), an MIT spinoff, raised $1.8 billion from investors including Bill Gates and George Soros. CEO Bob Mumgaard says they’ll have a working reactor in 3 years [corrected]. His optimism is buoyed by Commonwealth’s successful summer test of new electromagnets engineered with superconductors made from rare earth barium copper oxide.

Mumgaard says these super powered magnets will enable Commonwealth to perfect their somewhat more traditional fusion approach of building a donut-shaped “tokamak” reactor, which Mumgaard calls a “big magnetic bottle” where powerful magnetic fields control balls of 100 million degree plasma — ‘star stuff.’

There are roughly 150 tokamaks around the world; the biggest one is under construction in France for $30 billion by an international consortium called ITER. The 20,000-ton machine, the size of a basketball arena, is slated to be complete by 2035.

But Mumgaard intends for Commonwealth Fusion to make ITER obsolete before it’s even completed. Its edge is in the application of high temperature superconductors made with rare earth barium copper oxide (aka ReBCO).

Superconductors move electrical current with virtually zero loss (far more efficiently than copper, for example). And they are key to making powerful electromagnets. Commonwealth has found that by making its magnets using a special barium copper oxide tape (like the tape found in a VHS cassette) it can achieve magnetic fields more powerful than the ones anticipated at ITER, but at 1/20th the scale.

Whereas ITER’s primary magnets (called solenoids) will weigh some 400 tons and achieve fields stronger than 12 tesla, Commonwealth is eyeing 15-ton magnets, each using 300 km of ReBCO thin-film tape, that will generate 20 tesla (for comparison, a magnetic resonance imaging machine does 1.5 tesla).

‘This unlocks the fusion machine,’ says Mumgaard. CFS tested the magnets last summer and declared it proof that the science of fusion was now virtually complete and all that’s left is to build the reactor. ‘We understand the material well and think we can do this in three years,’ says Mumgaard. ‘By 2030 we will see fusion on the grid.’

CFS is set to construct its fusion machine on a 47-acre site in Massachusetts, and is already working to source thousands of kilometers of ReBCO tape. Could availability of the rare earth become a limiting factor in fusion’s rollout? No says Mumgaard. ‘A fusion plant will have less rare earths than a wind turbine. Fusion is not about a resource you need to mine or pump. It’s about a technology.’”