How fusion power works and the startups pursuing it

Fusion Power: The Race to Harness the Stars Heats Up as Startups Push Toward Grid-Ready Energy

For over half a century, scientists have chased the dream of harnessing the power of the stars to light up our world. Fusion energy—the process that fuels the sun—has long been heralded as the ultimate clean energy solution, promising virtually limitless power with zero carbon emissions. Yet, for decades, the breakthrough always seemed just out of reach, perpetually a decade away. Now, a new wave of fusion startups is closing in on that elusive goal, racing to build reactors capable of delivering fusion power to the grid.

With over $10 billion poured into fusion startups and more than a dozen companies raising over $100 million each, the sector is experiencing a surge of momentum. Investors are drawn by the twin forces of skyrocketing energy demand from data centers and the tantalizing proximity of fusion’s “finish line.” But what exactly are these companies trying to achieve, and how close are they really?

The Science of Fusion: Taming the Power of the Stars

At its core, fusion power aims to replicate the process that powers the sun: fusing light atomic nuclei to release enormous amounts of energy. Humans have known how to fuse atoms since the development of the hydrogen bomb, but that’s uncontrolled fusion. The real challenge lies in achieving controlled fusion that produces more energy than it consumes—a milestone known as “net energy gain.”

So far, only a handful of experimental devices have managed to generate more energy than was used to trigger the reaction. None, however, have produced enough surplus energy to make a commercial power plant viable. That’s the hurdle fusion startups are now racing to clear.

Magnetic Confinement: The Leading Contender

The most widely pursued approach to fusion is magnetic confinement, which uses powerful magnetic fields to contain and control superheated plasma—the “soup” of charged particles at the heart of a fusion reaction.

To achieve this, magnets must be extraordinarily powerful. For example, Commonwealth Fusion Systems (CFS) is developing magnets capable of generating 20 tesla magnetic fields—about 13 times stronger than those in a typical MRI machine. These magnets are made from high-temperature superconductors and must be cooled to –253°C (–423°F) using liquid helium.

CFS is building a demonstration device called SPARC in Massachusetts, with plans to turn it on in late 2026. If successful, the company will move forward with ARC, a commercial-scale power plant in Virginia, as early as 2027 or 2028.

Within magnetic confinement, there are two main designs: tokamaks and stellarators.

• Tokamaks, first theorized by Soviet scientists in the 1950s, are shaped like a doughnut with a D-shaped profile or a sphere with a central hole. The Joint European Torus (JET) in the UK operated from 1983 to 2023, while the massive ITER project in France is expected to begin operations in the late 2030s. UK-based Tokamak Energy is developing a spherical tokamak design, with its ST40 experimental machine currently undergoing upgrades.

• Stellarators, on the other hand, use a twisted, irregular shape to optimize plasma stability. The Wendelstein 7-X stellarator in Germany has been operating since 2015. Several startups, including Proxima Fusion, Renaissance Fusion, Thea Energy, and Type One Energy, are also developing their own stellarator designs.

Inertial Confinement: Compressing the Future

The other major approach to fusion is inertial confinement, which compresses tiny fuel pellets until the atoms inside fuse.

Most inertial confinement designs use powerful laser pulses to compress the fuel pellet from all angles simultaneously. So far, this is the only approach that has achieved scientific breakeven—the point at which the reaction releases more energy than it consumes. These breakthroughs have occurred at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California. However, these experiments don’t account for the total energy used to power the facility, so the path to commercial viability remains challenging.

Despite this, nearly a dozen startups are betting on inertial confinement. Focused Energy, Inertia Enterprises, Marvel Fusion, and Xcimer are among those using lasers. Two companies are taking different approaches: First Light Fusion proposes using pistons, while Pacific Fusion plans to use electromagnetic pulses instead of lasers.

The Road Ahead: More Than Just Two Paths

While magnetic and inertial confinement dominate the fusion landscape, they aren’t the only approaches. Soon, we’ll see more details on alternative designs, including magnetized target fusion, magnetic-electrostatic confinement, and muon-catalyzed fusion.

The fusion race is heating up, and with billions in investment and a growing sense of urgency around clean energy, the dream of harnessing the stars may finally be within reach. Whether through magnetic or inertial confinement—or an entirely new approach—the next decade could mark the dawn of a new era in energy.

Tags: Fusion Energy, Nuclear Fusion, Clean Energy, Magnetic Confinement, Inertial Confinement, Tokamak, Stellarator, Commonwealth Fusion Systems, SPARC, ARC, ITER, National Ignition Facility, Net Energy Gain, High-Temperature Superconductors, Plasma, Laser Fusion, Scientific Breakeven, Energy Startups, Grid-Ready Power, Renewable Energy, Data Centers, Investment, Breakthrough Technology.

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