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Nuclear fusion

Nuclear fusion

Could commercial fusion power plants get us to net zero?

22 Mar 2022 James McKenzie
Taken from the March 2022 issue of Physics World, where it appeared under the headline "Fusion: it's hotting up". Members of the Institute of Physics can enjoy the full issue via the Physics World app.

James McKenzie applauds recent record investments in commercial fusion power plants, which could help us to create a net-zero economy

ST40 compact spherical tokamak

Fusion is simple. Two light nuclei merge to form a bigger nucleus, releasing energy. It’s what powers the stars, but building a fusion reactor that can deliver power in a controllable way isn’t easy. Fusion needs high temperatures, high pressures and a decent confinement time. Those demands have, however, triggered some amazing approaches to make fusion power a reality.

Trouble is, no-one really knows which will work best. What’s more, once you achieve fusion, you need to generate more energy than you put in, so that the ratio Q > 1. But a “break even” result has so far never been achieved by a fusion reactor here on Earth. In fact, what you really want is a Q between 5 and 10 so that your reactor produces a useful amount of power.

Fusion has an increasing commercial angle too with 35 fusion firms around the world.

The approach being taken at the ITER fusion reactor, which is currently being built by a huge international consortium in southern France, is to confine a hot plasma with large superconducting magnets in a doughnut-shaped tokamak. Set to come online in 2025, ITER will point the way to a commercial fusion reactor called DEMO, which will be built by 2060. I visited in 2019 and ITER is truly incredible to behold.

But it’s not the only game in town. Last year, China’s Experimental Advanced Superconducting Tokamak achieved a temperature of 120 million kelvin for 101 seconds. That beat the previous record of 100 million kelvin held for 20 seconds by South Korea’s KSTAR reactor in 2020. There’s also the Joint European Torus (JET) in Oxfordshire, UK – the forerunner to ITER – which still holds the record for the highest Q ever (it got to Q = 0.67 in 1997). JET has just run tests that produced more than 59 MJ of energy over five seconds, more than doubling the output achieved in 1997.

Industrial effort

Fusion has an increasing commercial angle too. According to The Global Fusion Industry in 2021 report, there are now 35 fusion firms around the world, which together have received more than $1.8bn of funding since the 1990s. The four biggest players – Commonwealth Fusion Systems (CFS), General Fusion, TAE Technologies and Tokamak Energy – account for 85% of that cash.

The report found that most private fusion companies expect fusion power to be supplying electricity to the grid in the 2030s. If their efforts succeed, that would put them well ahead of ITER, which largely froze its design in about 2001 and hasn’t been able to exploit recent huge advances in high-temperature superconducting (HTS) magnets. Indeed, since the report was released, investment in private fusion firms has skyrocketed.

CFS – which was spun out from the Massachusetts Institute of Technology in 2018 – last year successfully demonstrated a 20 T HTS magnet. Simulations suggest that this magnet could be powerful enough to let the firm’s SPARC Tokamak reactor achieve net energy from fusion. Since then, CFS has raised $1.8bn to build the reactor, which will pave the way for ARC – the first commercially viable fusion power plant. Development could begin in 2025.

As for Tokamak Energy, this British firm’s ST40 spherical tokamak reactor with HTS magnets reached a stunning 15 million kelvin in 2018. The firm, which received its last funding of £67m in January 2020, is now targeting a 100 million kelvin plasma from its upgraded ST40 reactor. I wonder if 2022 could also be a big breakthrough year for the company?

Meanwhile, last year the UK government announced a short list for sites for a prototype fusion plant known as Spherical Tokamak for Energy Production, or STEP. Based on technology pioneered by the UK Atomic Energy Authority’s Culham Centre for Fusion Energy (CCFE), STEP could be up and running by 2040. The final location is due to be decided this year.

CCFE, where JET is located, has also been chosen by General Fusion as the site for its fusion demonstrator plant. It uses a spinning liquid jacket to hold a plasma, which is compressed rapidly into a sphere using powerful pistons. The fuel fuses and the resulting heat is absorbed by the liquid metal and used to turn a generator. Having last November announced a further $130m investment, the firm hopes to start work this year on the reactor, which could be ready by 2025.

Another player in the market is First Light Fusion, which raised $25m in 2020 and last May installed a “hyper-velocity gas gun” on its “Machine 3”. It fires a projectile at a fuel target, with the resulting shock waves squeezing the fuel so much that it gets hot enough to fuse. The average net cost of generating electricity over the plant’s lifetime could be as little as $25/MWh – roughly half that of an onshore wind plant.

Several approaches are looking more and more credible with each technical milestone achieved.

Then there’s Helion, a US firm that last year announced the largest single fundraise in private-fusion history. It secured a $2.2bn funding package to build their seventh-generation fusion reactor called Polaris using deuterium and helium-3 fuel to directly produce electricity. Helion’s reactors are expected to be about the size of a shipping container and could deliver about 50 MWe, with the plants in operation by 2024.

The race is on

Making sense of all these achievements – and knowing who will win the race – is not easy as each reactor is different and faces its own technical difficulties. One common challenge, however, is the “cycle-time” between each scale-up step as this will ultimately determine the speed at which the power plant hits the market. It’s clear to me, though, that several approaches are looking more and more credible with each technical milestone achieved.

No-one is quite sure how big the fusion market will be as the timing, cost and power output of potential reactors are all so different. But fusion has many advantages over fission, including a great safety record, no long-lived waste, and the potential for cheap fuel. If fusion reactors can gain regulatory approval and show that they have a competitive price tag, we could see a commercial plant in as little as five to 10 years.

For fusion, it’s not a case of if – but when.

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