How fusion power works and the startups that seek it

For decades, humans have sought to harness the power of stars to generate electricity here on Earth. For almost as long, achieving this goal always seemed only a decade away.

Now, a slew of startups are closer than ever, rushing to build fusion reactors capable of powering the grid.

Fusion startups have attracted more than $10 billion in investment More than a dozen have raised more than $100 million. Several large funding rounds have been closed in the past year, with investors drawn to the industry as demand for power from data centers grows and as fusion startups near the finish line.

At its core, fusion energy seeks to use the energy released from the fusion of atoms to generate electricity. Humans have known how to fuse atoms for decades, from the hydrogen bomb — an example of uncontrolled nuclear fusion — to any of the countless fusion devices being built in laboratories around the world. Experimental fusion devices were able to control nuclear fusion, and one was able to generate more energy than was needed to spark the reaction.

But none of them has been able to produce enough of a surplus to create a power plant.

To solve this problem, fusion startups are trying a number of different approaches. Expert opinions vary on which ones have the best chance of success, though the industry is still in its infancy, so nothing is guaranteed.

Below is a brief overview of the main methods of fusion power.

Magnetic confinement

One of the most widely used technologies is magnetic confinement, which uses strong magnetic fields to confine plasma, a soup of extremely hot particles at the heart of a fusion device.

The magnets must be very strong. Commonwealth merger regulations (CFS), for example, assembles magnets that can generate 20 Tesla magnetic fields, which is about 13 times stronger than a typical MRI machine. To handle the amount of electricity required, the magnets are made of high-temperature superconductors, which still need to be cooled to -253°C (-423°F) using liquid helium.

CFS is currently building a demonstration device called Sparc on a much faster schedule in Massachusetts. The company expects to be up and running sometime in late 2026, and if all goes well, it will begin construction on the Ark, Virginia, commercial power plant in 2027 or 2028.

There are two main types of fusion devices that use magnetic confinement: the tokamak and the stellar.

The tokamak theory was first developed by Soviet scientists in the 1950s, and has since been widely studied. Tokamak comes in two basic shapes – a D-shaped cake and a ball with a small hole in the middle. The Joint European Torus (JET) and ITER are two notable experimental tokamaks; JET operated in the UK between 1983 and 2023, while ITER is expected to begin operations in France in the late 2030s.

Based in the United Kingdom Tokamak energy He is working on a spherical tokamak design. Its ST40 experimental machine is currently undergoing upgrades.

Stellarators are the other main type of magnetic confinement devices. They are similar to tokamak in that they keep the plasma inside a donut-like shape. But unlike the geometric aspects of the tokamak, the stars twist and turn. The irregular shape is determined by modeling the behavior of the plasma and designing the magnetic field to work with its quirks rather than forcing it into a regular shape.

Wendelstein 7-X, a large star with superconducting gauge coils is operated by the Max Planck Institute for Plasma Physics. It has been operating in Germany since 2015. Several startups are also developing their own products, including Proxima Fusion, Renaissance Fusion, Thea Energyand Energy of the first type.

Inertial confinement

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

Most inertial confinement designs use pulses of laser light to compress fuel pellets. Several lasers fire simultaneously, and their light pulses converge on the fuel pellet from all angles simultaneously.

So far, inertial confinement is the only approach that has worked Break a milestone Known as scientific neutralization, this is 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. It is worth noting that the measurements to determine scientific equivalence do not include things such as the electricity needed to operate the experimental facility.

However, nearly a dozen startups see enough promise in inertial confinement that they are designing reactors around it. Concentrated energy, Inertia companies, Marvel Fusionand Excimer Some notable examples using lasers.

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

More to come

These are the two main paths to fusion power, although they are not the only ones. Soon, we will add more details on alternative designs including magnetic target fusion, electrostatic magnetic confinement, and muon-catalyzed fusion.