Thea Energy has appointed Pat Schweiger as chief engineer. The company announced the move on November 3, 2026: Schweiger joins from Oklo, where he served as chief technology officer, and brings more than 40 years of experience in designing, building and operating power plants.
In his new role he will serve as the design authority for the company’s systems, with responsibility for integration. Thea Energy, headquartered in Kearny, New Jersey, is moving from its already demonstrated magnet hardware to its large-scale stellarator, called Eos, and to its first power plant, Helios. The stellarator is the magnetic confinement fusion configuration on which the company has built its architecture, which is based on planar coils.
Schweiger’s background spans both fission and fusion. He began his career at the US Department of Energy’s Fast Flux Test Facility, where he tested advanced materials relevant to fusion, as well as fuels, components, protocols and safety designs. He later served as chief engineer at Commonwealth Fusion Systems, where he grew the engineering organization to more than 400 people and led the design and construction of a high-field tokamak. In May 2025 he moved to Oklo, an advanced reactor company listed on the NYSE.
Brian Berzin, co-founder and chief executive of Thea Energy, explained the decision this way: “The companies that deliver will earn trust through engineering discipline.” Berzin added that Schweiger chose Thea because its architecture is designed to be practical and because the company is executing on its plan. His contribution will help bring the same pace to the construction phase.
Schweiger described his return to fusion by noting that his career began at a facility testing materials for fusion. In his view, the industry has reached a point where it must deliver on the promises it has made. He also said he has worked on almost every approach to fusion.
The appointment is the latest in a series of senior hires through which Thea Energy is building the team needed to take its plants from design to construction site. The move of a figure with experience in both fields of advanced nuclear, from a fission company to a fusion one, is a sign of how readily skills are moving between the two sectors.
The real test will be Eos. If systems integration holds up at the next scale beyond the magnets already proven, Helios can move from a design to the first plant capable of producing commercial electricity.
