For Fusion, Smaller May Be Better, And Faster

Fusion Research Starts Big

Historically, efforts to produce fusion energy have been increasing the size of their experiments, with the goal of more pressure, temperature, and containment time (also known as the “Lawson Criteria”). The goal is to enable (usually) two hydrogen nuclei to overcome their room-temperature repulsion and join together to form a helium nucleus plus a high-energy neutron, whose energy is then transformed (eventually) into electricity. 

Nothing is a better example of this than the International Thermonuclear Experimental Reactor (ITER), a mammoth tokamak fusion machine built in France by an international consortium. Engineering design started on ITER in 1992, with construction of the reactor itself in 2013 (it is not expected to be completed until 2033). When finished, ITER will weigh 5,116 metric tons and have a diameter of nearly 20 meters.

As can be deduced from the timeline above, the scope of the ITER program is not particularly amenable to “rapid iteration” – it encompasses 21 years of design and 20 years of construction. In all fairness, ITER is not a “power plant” – it is a physics experiment to characterize plasma physics behavior at high temperatures and pressures over a reasonably long time. 

Commercial Fusion Will Start Smaller

This is one reason several companies looking to build real power plants are examining ways to shrink the size of fusion machines. Their primary goal is to rapidly iterate their designs so that functional (and economically viable) fusion power plants can be created and commercialized.

The reasons why minimizing fusion machine size is important are numerous:

• Big fusion machines take a long time to build. Besides building the machine itself, you have to both design it and prepare a sight, a 40-year process for ITER. While the “first ITER” is a one-off and subsequent ITER would be faster, even cutting it by 75% would still take a decade.
• Big fusion machines require a lot of costly materials. ITER is expected to use roughly ten metric tons of superconducting magnets. While high-temperature superconductor (HTS) magnets could significantly reduce the amount of material required (ITER uses conventional superconductors), a lot of material still needs to be produced.
• Creating and maintaining a high vacuum in a large cavity is complex and requires very exotic high-capacity vacuum pumps, often custom-built.

This doesn’t even count some exotic systems a powerplant would need, such as a thermal blanket to turn high-energy neutrons into heat energy for electricity generation.

Fusion Energy Will Get to Market Faster by Going Smaller

At NYC Climate this week, there were two panel discussions examining the commercialization of fusion energy, one by Jefferies Investment and the Fusion Industry Association and the other by the Columbia University School of Engineering. In both panels, focusing more on commercial fusion machine design was a critical part of the discussion, and reducing the size of fusion machines was one of the driving factors identified as necessary. Smaller components lessen the time and cost of manufacturing these parts; smaller components also increase the likelihood that the element can be acquired as “commercial off-the-shelf” – if not today, then in the near future. Several examples of the push for more commercialized, smaller reactors were cited in the panel discussion:

• Commonwealth Fusion Systems: Commonwealth’s next-gen reactor, SPARC, is a tokamak capable of producing 100MW of heat energy in pulses lasting roughly 10 seconds. It will use Commonwealth’s custom-designed HTS magnets to build a tokamak roughly 1/65th the size of ITER (Commonwealth is also selling magnets to other fusion companies).
• ZAP Energy: Zap uses a “Z-pinch ” technology that utilizes current inside the plasma to produce a magnetic field, eliminating the need for magnets. Moreover, Zap uses the “sheared-flow stabilization” technique to avoid the instability issues that long characterized Z-pinch. This is expected to allow Zap to build a fusion machine half the size of the typical tokamak at a much lower cost in a few years instead of decades.
• Avalanche Energy was also a champion of the smaller and better approach as it looked to solve power challenges for shipping, spacecraft, and off-grid (data centers, industrial, military) deployments. The world needs clean power for thousands of applications that traditional power grids cannot serve.
• Energy Singularity (China): While Energy Singularity was not at the Columbia conference, its accomplishments were being discussed, both from the standpoint of how it is speeding development and how China is pulling ahead of the West. Energy Singularity is building a tokamak based on HTS technology that is expected to reduce the e by 98%, enabling the construction period to shrink to 3-4 years. Energy Singularity expects a functioning machine with a Q greater than ten by 2027. 

The Commercial Future of Fusion Will Start with Smaller Machines

All of these programs demonstrate the potential value of focusing on commercial fusion power, particularly on smaller reactors, to achieve significantly lower cycle times between fusion machine iterations, allowing rapid progress toward the commercialization of fusion.