The number of devices competing to produce sustainable fusion energy has grown again with the introduction of the “stellarator” by Germany’s Max Planck Institute for Plasma Physics.

For decades, scientists have labored to create chambers in which heat as high as 100 million°F combines with crushing pressures to melt hydrogen atoms together, releasing vast quantities of clean energy that could be captured and harnessed to power the world.

Donut-shaped test chambers called tokamaks are the current state of the art. They use almost unimaginably powerful magnets to hold hydrogen plasma in the center of their chambers, far enough from the walls that the massive heat unleashed by the reactions dissipates before it can melt any equipment.

So far, “success” has been defined by creating the target temperatures and pressures and maintaining them for a few minutes. Sometimes a fusion reaction occurs.

But now fusion’s stalled development has inspired other approaches.

Australian R&D start-up HB11 has re-imagined fusion from scratch and come up with a method that is not only simpler but also more promising, as we reported in “New Fusion Energy Method Revives Advocates’ Hopes” (2 Mar 2021).

Instead of relying on giant magnets and unearthly heat, HB11’s reactor is a largely empty metal sphere with a pellet of boron held in the center. The sphere has openings in its sides for two lasers: one establishes a magnetic field to channel the reaction and the other propels hydrogen atoms into the boron fuel pellet with enough force to fuse.

While tokamaks typically are at least as big as a small apartment building, and often larger, the stellarator is only about 16 meters wide—about 50 feet—and three or four meters tall.

Better yet, it has shown that it does a better job than tokamaks of keeping its hot hydrogen plasma stable and keeping heat and atomic particles inside the magnetic field where fusion takes place. 

Also, in theory, the stellarator could run indefinitely, while tokamaks need to shut down periodically for maintenance on their magnetic coils.

The new device achieves these benchmarks by incorporating 50 tortuously twisted superconducting electromagnetic coils, each weighing six tons.

The shape and placement of the coils around the ring-shaped stellarator was determined by modeling with a supercomputer.

Germany’s machine already has reached “tokamak-like performance” in early tests lasting as long as 100 seconds. Continuous runs of 30 minutes will mark a breakthrough on the way to commercial viability, stellarator boosters say.

Dreaming of that day, the start-up Princeton Stellarators, new this year, has raised $3 million to build a demonstration device that makes several design improvements on Germany’s version.

Renaissance Fusion in Grenoble, France, has secured €16 million in working capital and plans to show a working prototype by 2027.

The U.S. Department of Energy has funded Type One Energy in Madison, Wisconsin, to apply advanced manufacturing techniques to build a stellarator of its own.

TRENDPOST: It’s not only fusion’s technology that needs to progress but also its cost.

Germany’s stellarator cost more than €1 billion to create. Although commercial versions will cost far less to produce once a design is tested and validated, the cost will still be astronomical compared to other forms of clean energy. 

At the current rate of progress, fusion energy will not begin to make a meaningful contribution to the world’s energy economy before at least 2040. By then, more decentralized energy generation methods may be more firmly established and profit-minded investors could be scarce.

Germany’s Wendelstein 7-X stellarator. 

Graphic: Max Planck Institute for Plasma Physics

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