With a new $100M raise, Princeton’s Thea Energy is now a top-funded hybrid startup.

Thea Energy has raised an oversubscribed $100 million Series B round led by the US Innovative Technology Fund, the fusion startup told TechCrunch. The sum places the company among the best-funded fusion startups, giving it an improved chance of achieving a commercial reactor.

The new funding will help Thea scale up production of its uniquely designed micromagnets and start building Eos, its “power plant-friendly” demonstration device, from next year. Thea previously closed a $20 million Series A in early 2024. The new round brings the total private investment to $130 million, the startup told TechCrunch.

Magnets are at the heart of many fusion power plant designs – they are what keep a very hot substance called plasma compressed and hot enough to fuse atoms together, which then release heat and energy. But Thea’s magnets are different: each rectangular magnet can be configured to shape the entire reactor’s magnetic field. Thea likens this to the pixels on a computer monitor, which collectively follow software instructions to create the text and images displayed on the monitor.

For Thea, that flexibility will be important. The type of reactor you design is known as a stellarator. Stellarators are able to maintain plasma in a stable configuration, but to do so, they must twist and bend to accommodate the plasma. That’s in contrast to the tokamak, another advanced magnetic design, which uses brute force to keep the plasma closed.

But the unusual structure of the stellarator increases the complexity and cost of magnet manufacturing. Thea is betting that by coating its reactor core in ordinary magnets, it can use software to manipulate tiny rotating magnets and create a star-shaped magnetic field inside a very simple structure.

The software should also help with reactor assembly. Thea intentionally placed the test magnets out of alignment, but the software was able to compensate.

Thea hopes to complete its Eos demonstration reactor by 2030 with a commercial version, known as Helios, coming online in 2034. The timing puts it in line with rivals such as Commonwealth Fusion Systems, which has said it hopes to bring its Arc reactor online in Virginia in the early 2030s.

If Thea’s pixel-inspired magnets work, the company could enjoy a profit in production. His starting point is a series of full-scale replicas of his magnets in his lab in Jersey City. Meanwhile, other fusion startups pursuing magnetic confinement have had to build large assembly halls to make reactor-scale magnets.

However there are already signs that the planar coil design, as it is called for its pixel-inspired magnets, has reached its limit. When Thea was first completed at the Princeton Plasma Physics Laboratory, its reactor design called for planar coils only. As the company continues to work on this concept, it has added 12 large magnets of different shapes without planar coils to handle most of the plasma confinement. 300-plus tiny magnets now work to fine-tune the plasma. Reliance on large magnets destroys the company’s productivity to some extent.

Still, any simplification of fusion reactors — already some of the most complex devices ever made by humans — will help pave the way to fusion power. Another $100 million doesn’t hurt either.

Other investors participating in the round include General Innovation Capital Partners, Linse Capital, Calm Ventures, Climate Capital, Divergent Capital, Emerald Technology Ventures, Gaingels, Idemitsu Kosan, Overlay Capital, Timescale Ventures, and Whatif Ventures.