The mechanism of nuclear fusion power generation and startups pursuing it

For decades, humans have sought to harness the power of the stars to generate electricity on Earth. And for just as long, achieving that goal seemed just a decade away.

Now, a slew of startups are closer than ever, rushing to build fusion reactors that can power the grid.

Fusion startups have attracted more than $10 billion in investment to date, with more than a dozen companies raising more than $100 million. As energy demand from data centers grows and fusion startups move closer to the finish line, investors are drawn to the industry, with a number of large funding rounds closing last year.

The core of fusion power generation is to generate electricity by harnessing the energy released by the fusion of atoms. Humans have known how to fuse atoms for decades, from the hydrogen bomb, an example of uncontrolled nuclear fusion, to the countless fusion devices created in laboratories around the world. Experimental fusion devices were able to control nuclear fusion and produce more energy than was needed to cause a reaction.

But none of them have been able to generate enough surplus to enable power plants.

To solve this problem, fusion startups are trying different approaches. Experts have differing opinions on which ones have the best chance of success, but the industry is still in its infancy, so nothing is guaranteed.

Here we provide an overview of the main approaches to fusion power generation.

magnetic confinement

Magnetic confinement is one of the most widely used techniques, using powerful magnetic fields to confine plasma, the soup of superheated particles that is the heart of fusion devices.

The magnet should be very strong. For example, Commonwealth Fusion Systems (CFS) has assembled a magnet that can generate a 20 Tesla magnetic field, about 13 times more powerful than a typical MRI machine. To handle the amount of power required, the magnets are made of high-temperature superconductors but must be cooled to -253°C (-423°F) using liquid helium.

CFS is currently building a demonstration device called Sparc in Massachusetts on an even more accelerated timeline. The company plans to start producing electricity in late 2026, and if all goes well, construction on the Ark, a commercial-scale power plant in Virginia, is expected to begin in 2027 or 2028.

There are two main types of fusion devices that use magnetic confinement: tokamaks and stellarators.

Tokamaks were first theorized by Soviet scientists in the 1950s and have been widely studied ever since. Tokamaks come in two basic shapes. It’s a donut with a D-shaped outline and a sphere with a small hole in the center. Joint European Torus (JET) and ITER are two notable experimental tokamaks. JET operated in the UK from 1983 to 2023, and ITER is scheduled to begin operations in France in the late 2030s.

UK-based Tokamak Energy is working on a spherical tokamak design. The company’s ST40 experimental machine is currently undergoing an upgrade.

Stellarators are another major type of magnetic confinement device. It is similar to a tokamak in that it holds blood plasma within a donut-like shape. But unlike the geometric aspects of tokamaks, stellarators twist and rotate. The irregular shape is determined by modeling the behavior of the plasma and adjusting the magnetic field to match the plasma’s quirks rather than forcing a regular shape.

Wendelstein 7-X is a large stellarator with modular superconducting coils operated by the Max Planck Institute for Plasma Physics. Several startups are also developing their own stellarators, including Proxima Fusion, Renaissance Fusion, Thea Energy, and Type One Energy.

inertial confinement

The other main approach to nuclear fusion is known as inertial confinement, which compresses fuel pellets until the atoms inside fuse.

Most inertial confinement designs use pulses of laser light to compress fuel pellets. Several laser beams are fired at once, and their light pulses simultaneously focus on the fuel pellet from all angles.

So far, inertial confinement is the only approach that has broken through the milestone known as the scientific break-even point, when a reaction releases more energy than it consumes. These experiments were conducted at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California. In particular, the measurements used to determine scientific break-even points do not include things like the electricity needed to power laboratory facilities.

Still, nearly a dozen startups see enough potential in inertial confinement to design reactors around it. Focused Energy, Inertia Enterprises, Marvel Fusion, and Xcimer are some notable examples using lasers.

However, there are two companies that do not use lasers. First Light Fusion proposes using pistons, and Pacific Fusion plans to use electromagnetic pulses instead of lasers.

Further in the future

These are the two main approaches to fusion power generation, but they are not the only ones. We will soon add details on alternative designs such as magnetized target fusion, magneto-electrostatic confinement, and muon-catalyzed fusion.