Realta Fusion and Zap Energy: DOE’s "innovative concept" fusion pilot picks

June 9, 2023, 7:00AMNuclear News

Realta Fusion of Madison, Wis., and Zap Energy of Everett, Wash., are just two of the eight fusion developers selected by the Department of Energy for funding last week under the public-private Milestone-Based Fusion Development Program. They are the two companies with power plant concepts that don’t fit neatly into established fusion confinement categories. As energy secretary Jennifer Granholm said when she announced the awardees, “Some are working on more technically mature approaches like tokamaks and stellarators and laser inertial fusion, and others are working on innovative concepts with lower technical maturity like mirror and Z-pinch, which could lead to more compact and lower cost systems.”

Together the Milestone awards for Realta Fusion ($3 million) and Zap Energy ($5 million) account for $8 million of the $46 million in funds announced May 31. Nuclear Newswire is taking a look at what these two innovators have in common, how their separate technologies distinguish them from other fusion developers, and where they began.

From campus to start-up, via ARPA-E: Of the eight selected Milestone companies, five are now receiving or previously have received funding from the DOE’s ARPA-E, including Realta Fusion and Zap Energy. In fact, both received ARPA-E funds in October 2020 through the BETHE (Breakthroughs Enabling THermonuclear-fusion Energy) program under the same category: “Development of Lower-Cost Concepts.”

The University of Wisconsin–Madison received about $10 million for the Wisconsin High-field Axisymmetric Mirror (WHAM) Project, which has since been spun out from the university as Realta Fusion.

Zap Energy was also incubated at a university—the University of Washington. ARPA-E’s first award for Z-pinch fusion R&D at UW was awarded under ARPA-E’s ALPHA program in 2015 for a project called Flow Z-Pinch for Fusion. Zap Energy was spun out from the university in 2018, and subsequent ARPA-E awards—in 2019 through OPEN 2018 and in 2020 through BETHE—went directly to the company.

While both companies use linear plasma concepts that the DOE thinks have the potential to provide low-cost fusion energy, at least in part because of their compact linear dimensions, their confinement methods are distinctly different.

A rendering of the WHAM project developed at the University of Wisconsin–Madison. (Image: Wisconsin Plasma Physics Laboratory)

Realta Fusion’s magnetic mirrors: Realta Fusion announced its launch on May 31—the day of the award announcement—with $12 million in financing—the $3 million from the DOE and a seed investment of $9 million from Khosla Ventures, a Menlo Park, Calif.–based venture capital firm. Cary Forest, a professor of physics at UW-Madison, led the ARPA-E–funded WHAM research, and he is now also cofounder and chief scientific officer of Realta Fusion.

Realta uses a compact magnetic mirror technology that the company believes can produce net energy at smaller scales than toroidal magnetic confinement systems and “has the potential to be a lower cost and less complex generator of zero-carbon heat and power.” The company is specifically targeting industrial heat and power as an early application for its fusion technology, which it says can operate at “a wide range of scales.”

According to ARPA-E’s description of the WHAM project, “Two mirror coils will be constructed using high temperature superconducting material. Hot and high-density target plasmas will be created using high-frequency electron-cyclotron heating from modern gyrotrons. Fast, sloshing ions will be created and energized by a novel radio-frequency heating scenario in which neutral beam injection is used to fuel ions, which are then accelerated in situ to high energy by high harmonic fast waves.” The Massachusetts Institute of Technology and Commonwealth Fusion Systems joined UW-Madison in ARPA-E funded WHAM research.

According to chief executive officer Kieran Furlong, the new Milestone funding “will enable us to build out our team and complete the physics design for our break-even class device, BEAM, which will be our last experimental step before designing industrial fusion energy systems.”

Zap Energy’s design creates a filament of plasma less than two feet long. The inset image is a high-speed camera photo of a plasma created in a Zap Energy device. (Image: Zap Energy)

Zap Energy’s Z-pinch: The thin line of plasma in a Z-pinch fusion concept carries an electrical current to generate its own magnetic field and “pinch” the plasma, compressing and heating it to the point that fusion can occur. Zap Energy’s fusion power concept would inject deuterium-tritium gas to form a plasma that accelerates down a coaxial accelerator before assembling into a single Z-pinch plasma column on the axis. Inside a Zap Energy plant, that narrow stream of plasma would be half a meter long and just one millimeter wide. Nuclear Newswire explored the technology in an article published in July 2022.

Zap Energy is building on a long history of Z-pinch fusion experiments around the world and approaching useful energy production by using sheared-flow stabilization to produce an axial plasma flow that varies by radius, with faster velocities farther from the center of the plasma column. That sheared flow would suppress instabilities and sustain the plasma. Fusion neutrons produced in the Z-pinch would be captured in a liquid lithium-lead blanket which serves as a heat-transfer fluid and tritium breeding medium.

Zap Energy claims its “breakthrough” technology “that confines and compresses plasma without costly and complex magnetic coils” could yield a “seriously cheap” power source. Zap Energy sees potential for factory-built modular power plants that could support multiple fusion cores, each rated at about 50 MWe.

“Zap’s selection reflects our tangible progress toward an achievable, grid-ready power source,” said Benj Conway, chief executive officer and cofounder of Zap Energy in a May 31 news release. “This program aligns with our aggressive milestones and bolsters our ability to succeed as quickly as possible.”

Zap Energy’s website has an extensive library of published research, blog posts, and news releases.

Look for more: Look for Newswire coverage of DOE’s six other picks for the milestone fusion program featuring inertial confinement (Focused Energy and Xcimer Energy), stellarators (Princeton Stellarators and Type One Energy), and tokamaks (Commonwealth Fusion Systems and Tokamak Energy).

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