The hydrogen economy—brought to you by nuclear fusion?

In order to achieve the deep decarbonization necessary for the global energy transition, hard-to-abate sectors must replace their use of fossil fuels with clean physical energy carriers. Of these, hydrogen is the most efficient, leading to predictions of the advent of the "hydrogen economy." However, despite the fact that hydrogen is the most abundant element in the universe, it rarely exists on earth in pure form. It therefore has to be produced.

The vast majority of hydrogen produced today is "gray" hydrogen, or hydrogen produced using fossil fuels, typically with an end use as a chemical feedstock. Carbon-based hydrogen production, however, defeats the purpose of deep decarbonization. A variety of low-carbon hydrogen production methods exist, such as "green", "blue", and "pink" hydrogen, but all are in their industrial infancy. These methods will be necessary to meet ambitious hydrogen production goals such as Europe's REPowerEU initiative, which calls for 10 million tonnes of domestic hydrogen production and 10 million tonnes of imported hydrogen by 2030. However, in the long term, could fusion-produced hydrogen ultimately be the most effective energy source for hydrogen production? And conversely, could hydrogen production make nuclear fusion more economically attractive?

Hydrogen production and nuclear fusion are inherently linked, as the majority of fusion processes use hydrogen isotopes, deuterium and tritium, as their input fuel. For decades, scientists have considered that hydrogen could be an output of the fusion process, ever since a seminal study was published in 1980 by Manhattan Project veteran Meyer Steinberg. Today, as the fusion community works towards the achievement of a burning plasma, and hydrogen production ramps up to meet decarbonization goals, the possibility of fusion-produced hydrogen is more relevant than ever before. Why? Similarly to fusion electricity production, the process of making hydrogen with nuclear fusion would emit no CO2, would produce significantly lower-level and shorter-lived waste than pink hydrogen production, and would pose no risk of nuclear meltdown. Secondly, fusion's potential efficiency and resource abundancy make it a possible low-cost electricity option. If such cost-reducing factors could induce a mature fusion market to reach a levelized cost of electricity below USD50/MwHe, a 2021 study in the Journal of Fusion Energy indicated that fusion-produced hydrogen could become economically attractive. Finally, fusion-produced hydrogen would offer the possibility of energy sovereignty. Each country needs physical energy carriers for industry and transport, yet some countries are endowed with these natural resources, while others must rely on global markets to buy these necessary fuels. Fusion, on the other hand, could produce hydrogen with resources that are much more abundant and equitably distributed: deuterium and the lithium used to generate tritium. A fusion-backed hydrogen economy would not be defined by resource "haves and have-nots."  

Complementarily, hydrogen production could offer an additional revenue stream for fusion installations. A nuclear fusion reactor would function as a baseload power source, providing a constant and dependable source of electricity for the grid. However, when electricity demand is lower (e.g., at night), a fusion plant with hydrogen production capabilities would be able to use electricity produced at these off-peak times for hydrogen production. Some recent fusion plant designs, such as the one recently published by Japan's National Industry for Fusion Science, include such electricity and hydrogen cogeneration abilities. These dual revenue streams could both de-risk and promise higher returns on investment in fusion plants, incentivizing commercial development of fusion power.

Initial research has begun on the most effective method of producing hydrogen at a fusion plant. Three main possibilities exist: low-temperature electrolysis (using the electricity produced from the fusion process), high-temperature electrolysis (using the waste heat from the fusion reaction to make electrolysis more efficient), and thermochemical production (using the waste heat to induce a chemical conversion cycle to produce hydrogen). These same techniques are beginning to be implemented at hydrogen-producing fission plants. Given the similarity of thermal conditions, ongoing research in that field will have direct relevance for potential design choices of hydrogen-producing fusion plants.

Of course, fusion-produced hydrogen is impossible until fusion itself reaches an industrial stage. Technical questions, such as whether tritium contamination can be kept at sufficiently low levels in fusion-produced hydrogen, and economic factors, such as whether fusion will offer a more cost-effective option than other renewable sources for hydrogen production, will have to be answered. Beyond fusion, the transport and storage of hydrogen must become more cost-effective for a hydrogen economy to become feasible.

Despite the uncertainties, the potential benefits of a symbiotic relationship between fusion and hydrogen are sufficiently great to merit further study. Fusion could increase hydrogen production to levels that would help sustain a hydrogen economy, and using a hydrogen revenue stream could assist the widespread commercialization of fusion power, the "holy grail" of clean energy. If harnessing the synergies between these two forms of energy are able to mutually accelerate their industrial development, it would be a massive boon for humanity's efforts towards a zero-carbon future.

Jack Moore, from the United States, spent six months as an intern in the ITER Communication Division. He is currently completing a Master's Degree in International Development at the Sciences Po Paris School of International Affairs, with a particular focus on clean energy development in low- and middle-income countries.