The science of nuclear fusion is very complex. But at its core, the problem boils down to three basic and easy to understand ideas.
Nuclear fusion is all over the news these days, with the announcement of the Lawrence Livermore breakthrough using the laser ignition method. Fusing two nuclei to produce net energy is the way stars operate, and the desire to duplicate this on earth has fascinated scientists since the dawn of the nuclear age 80 years ago. Stars, however, use enormous gravitational forces to create the conditions of temperature and pressure necessary to fuse atomic nuclei. Humans must use other techniques, and there are several under development, from laser ignition to magnetic confinement and even a mechanical technique using shockwaves generated by hydraulic rams. No one knows which will allow the creation of a usable power reactor, but regardless of the technology, three basic concepts define whether any technology will become a practical source of power.
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Episode Transcript:
On December 5th, 2023, a team at Lawrence Livermore National Laboratories’ National Ignition Facility achieved a historic breakthrough in nuclear fusion research: they used 192 high-powered lasers to compress a tiny fuel pellet to induce nuclear fusion, a reaction that resulted in 3.15 megajoules of energy output.
The energy applied to the pellet was 2.15 megajoules, meaning the experiment achieved a key milestone in fusion energy development: net energy output. This is a big deal for the physics community, and the mass media have been reporting this breakthrough as a significant step towards commercial power production using fusion.
That’s a mistake, and here’s why: for nuclear fusion to become a common power generation technology, three critical criteria must be met.
The first is scientific breakeven. That’s what the Lawrence Livermore team has achieved, yielding more energy from the reaction then the laser energy applied to the target. From an engineering perspective, however, the total amount of energy consumed by the entire reactor system is considerably higher. Typical efficiencies of solid-state lasers are in the range of 60 to 70 percent; experimental results have been published at 80 percent efficiency. Added to this energy input for the lasers is energy that must be consumed in things like vacuum pumping, gas handling and cooling for the high-power equipment.
If, or more probably when, one of the fusion technologies produces more power than the total power applied to the entire reactor system, it will have achieved engineering breakeven, which is the second major criterion. Engineering breakeven means true system output power, although even this won’t be enough to create commercial power reactors.
The third and critical stage is commercial breakeven, the point at which the cost per watt emerging from the generation system is cost competitive with the cost per watt delivered by other generation technologies. Most fusion systems generate heat, which is converted into electricity the same way as every other thermal generating source, so conversion efficiencies from heat to electricity will be the same. This means that the fusion reactor has to be cost competitive with other heat sources like combustion, fission and geothermal.
Direct energy generation using technologies like solar panels or wind turbines, are already very cost-effective in many locations, especially with grid scale battery storage to take care of the intermittency problem. Photovoltaics in particular are coming on strong. As cell prices drop and efficiency increases in lockstep with improvements in battery technology, even a workable fusion reactor may struggle for a foothold in the commercial power generation space.
Even then, I think it has a bright future in the unexplored uses for a clean source of heat. Hydrogen production with non-electrolytic dissociation of water may be a possibility, and process heat for industry, a major user energy, makes sense for this technology. It could also be useful for space heat, and in the far future, as a form of high-efficiency spacecraft propulsion that could make interplanetary travel practical with much higher speeds.
This is all great, but the achievement at the National Ignition Facility achieves only the first step, scientific breakeven. It’s going to take engineering breakeven and then commercial breakeven before any fusion technology produces one watt of power out of your wall outlet. But it’s a start.
