Over the past few years, nuclear fusion power has gone from being a joke, always thought to be a decade away, to an increasingly realistic and attractive technology that is luring investors off the sidelines.
While the technology may be difficult to master and expensive to build right now, fusion promises to produce nearly limitless energy on Earth by harnessing the sun's power source, nuclear reactions. If startups can perfect a commercially viable fusion power plant, it has the potential to upend a multi-trillion-dollar market.
The bullish wave driving the fusion industry has been driven by three advances: more powerful computer chips, more sophisticated AI, and stronger high-temperature superconducting magnets. Together, these are helping to enable more sophisticated reactor designs, better simulations, and more complex control schemes.
It probably doesn't hurt that in late 2022, a U.S. Department of Energy laboratory announced it had achieved a controlled nuclear fusion reaction that produced more power than a laser could impart to fuel pellets. While the experiment passed the scientific breakeven point but is still far from the commercial breakeven point, where the reaction produces more power than the entire facility consumes, it was a long-awaited step in proving that the underlying science was sound.
Founders have used that momentum to rapidly advance the private fusion industry in recent years: Fusion startups have raised $7.1 billion to date, according to the Fusion Industries Association, with most of that money going to a few companies.
Commonwealth Fusion Systems
Commonwealth Fusion Systems has come in at the top of the list in 2021 after raising a $1.8 billion Series B. Since then, the company has been quiet on the fundraising front (not surprisingly), but has been hard at work building Sparc, its first power plant in Massachusetts that aims to produce what the company calls “commercially meaningful” levels of electricity.
Sparc's reactor uses a tokamak design, resembling a doughnut. Its D-shaped cross section is wrapped in high-temperature superconducting tape that, when energized, creates a powerful magnetic field that traps and compresses superheated plasma. Heat from the reaction is converted to steam, which drives a turbine. CFS designed the magnets in collaboration with MIT, where co-founder and CEO Bob Mumgaard worked as a researcher in fusion reactor design and high-temperature superconductors.
Cambridge, Massachusetts-based CFS, backed by Breakthrough Energy Ventures, The Engine, and Bill Gates among others, plans to have Sparc up and running in the early 2030s.
General Fusion
General Fusion is in its 30th year and has raised $440.53 million to date, according to PitchBook. The Richmond, British Columbia-based company was founded in 2002 by physicist Michel Laberge, who wanted to demonstrate a new approach to nuclear fusion called magnetized target fusion (MTF).
In General Fusion's reactor, liquid metal walls surround a chamber where the plasma is pumped in. Pistons surround the walls and push them inward, compressing the plasma inside and creating a fusion reaction. The resulting neutrons heat the liquid metal, which is then circulated through a heat exchanger to produce steam that spins a turbine.
The company is currently building its first demonstration plant, LM26, and hopes to reach scientific breakeven by 2026. Investors include Jeff Bezos, Temasek, BDC Capital, and Chrysalix Venture Capital.
Helion
Of the fusion startups, Helion has the most aggressive timeline: It plans to have its reactor producing electricity in 2028, and its first customer is Microsoft.
Helion uses a type of reactor called a field-reversed configuration, in which magnets surround an hourglass-like reaction chamber with a bulge where the two sides meet. At either end of the hourglass, magnets spin the plasma into a doughnut shape, slamming it into each other at speeds of more than a million miles per hour. When the magnets collide in the middle, an additional magnet triggers nuclear fusion. When fusion occurs, the plasma's own magnetic field strengthens, inducing an electric current in the reactor's magnetic coils. That electricity is then extracted directly from the machine.
Everett, Washington-based Helion has raised $607.64 million, according to PitchBook, with investors including Sam Altman, Reid Hoffman, KKR, BlackRock, Peter Thiel's Mithril Capital Management and Capricorn Investment Group.
T.A.
Founded in 1998, TAE (formerly known as Tri Alpha Energy) was spun out of the University of California, Irvine by Norman Rostker. The company uses a magnetic-field-reversed configuration, but with a twist: After two plasma shots collide in the center of the reactor, the company bombards the plasma with particle beams to keep it spinning in a cigar shape. This makes the plasma more stable, giving it more time for fusion to occur and allowing more heat to be extracted to spin the turbines.
TAE has raised $1.32 billion, according to PitchBook, with investors including Alphabet, Chevron Technology Ventures and Venrock.
Zap Energy
Zap Energy doesn't use high-temperature superconducting magnets or super-powerful lasers to keep the plasma contained. Instead, it bombards the plasma with an electric current (get it?) and generates its own magnetic field. The magnetic field compresses the plasma by about a millimeter, at which point ignition occurs. Neutrons released by the fusion reaction collide with a liquid metal blanket that surrounds the reactor, heating it up. The liquid metal then circulates through a heat exchanger, producing steam to drive a turbine.
Like Helion, Zap Energy is based in Everett, Washington, and has raised $327 million, according to PitchBook, with backers including Bill Gates' Breakthrough Energy Ventures, DCVC, Lowercarbon, Energy Impact Partners, Chevron Technology Ventures and angel investor Bill Gates himself.