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There is a long-running joke in fusion research: fusion energy is just 30 years away…and always will be. This statement appeared true but despite reactor designs being proposed and researched extensively for over 70 years, we still don’t have fusion energy. But in 2022, a fusion reactor was able to produce more energy than it used – the first sign that fusion power may become a reality — but has it really made fusion power more viable? And what is keeping us from using this fusion power?
Powering the Stars
First of all, what is nuclear fusion? The process itself is simple: two light nuclei fuse to form a heavier nucleus. Typically, nuclear fusion occurs between two hydrogen nuclei, which fuse to form a table helium-2 nucleus. According to E = mc2, the mass difference between the two hydrogen nuclei and the produced helium nucleus releases energy.
Scientists first discovered nuclear fusion during the 1920s when searching for the energy source of the sun. By the 1950s, research into fusion reactors was booming: Soviet scientists proposed the design for a tokamak, a fusion reactor that makes use of magnetic confinement; alongside other designs - namely the stellarator and reactors that make use of inertial confinement.
Why Fusion?
Nuclear fusion has attracted billions of dollars and research for decades for multiple reasons: it’s an energy source more efficient than any other form of energy so far, releasing almost four million times more energy than fossil fuels. It is sustainable, carbon-free, and accessible and it is far safer than its counterpart, nuclear fission. This means that fusion reactors have the potential to deliver completely clean, low-cost energy to households and industries, serving as the base of future, zero-emission energy systems. If this sounds too good to be true – it is, at least for now.
The Obstacles
Before research even began, scientists recognised the issue with building a fusion reactor: igniting the reaction. Fusion is dependent on the fusion of two positively charged nuclei - but under normal conditions, the two nuclei can never interact because like charges repel. In the sun, and in all stars where fusion occurs naturally, the immense pressure and extreme temperatures of the core overcome the repulsion and allow the two nuclei to fuse. On earth, however, this became researchers’ biggest nightmare - one that still hasn’t been completely resolved.
The sun’s core has a temperature of around 15 million Kelvins, and a pressure of 250 billion atmospheres. But in fusion reactors, the plasma (an ionised state of matter - in other words, a gas made of charged particles) is confined at lower pressures, boosting the temperature requirement to over 100 million Kelvins before the nuclei can fuse.
Reactions in a fusion reactor must fulfil three criteria before they can even begin to produce energy:
Extremely high temperatures
This allows the nuclei to overcome the electrostatic repulsion and allows high-energy collisions to occur
Sufficient plasma particle density - this is the concentration/number of ionised gas particles in a given volume of the plasma
When the particle concentration increases, the the probability of, thus the number of, collisions required for fusion also increases
Sufficient confinement time - this is the period of time during which particles are confined to a specific volume under the conditions that allow them to react
The plasma must be confined for a sufficient period of time for the nuclei to begin to fuse
The issue with nuclear fusion is that there has been only one instance in which the energy output from a reactor exceeded the energy required to fulfil the above criteria: the fusion breakthrough of 2022. This means that the energy gain factor - the energy output divided by the energy input (denoted by Q) - has yet to consistently exceed 1, or the 'break even’ point. Until a reactor is able to consistently produce more energy - and electricity - than it uses, all operating fusion reactors remain commercially unviable.
The Breakthrough?
On December 13th, 2022, the National Ignition Facility (NIF) in California recorded an energy gain factor of 1.5 (a 3.15MJ output compared to a 2.05MJ input), the highest ever energy gain factor - and the only one in history to exceed 1. The event was hailed as the only “genuine fusion breakthrough” and a “game changer” for fusion research ahead. But this breakthrough may not be as monumental as it seems.
In fusion research, there are two major energy gain factors. The first is the energy gain factor of the plasma - I’ll refer to this as Q (but it is also commonly referred to as Q-plasma and Q-fusion). This is the energy outputted from the reaction, compared to the energy inputted into the reaction itself, or the plasma (the energy required to ignite and maintain the fusion reaction). The second is the overall energy gain factor - this is the energy that can be converted into electricity and used in households and industries. I’ll refer to this as Q-electricity (but it is also frequently referred to as Q-total). This accounts for the total electricity outputted from the reaction, compared to the electricity consumed by the entire reactor - including electricity that is never fed into the reaction, but required for the operation of the reactor.
The issue with the breakthrough is that NIF’s reported energy gain factor was solely Q, not Q-electricity. In short, most of the energy used by fusion reactors never enters the plasma itself - so the NIF’s gain is not actually a sign of commercial viability. The overall electricity output (Q-electricity) of the reactor, still has not exceeded 1 - so if you replicate the NIF’s results in a commercial power plant, you would not generate electricity.
I say this not to discourage the investment into fusion power, but to place fusion research into the correct context. The truth is, as optimistic as I am about fusion - this breakthrough has not sped up the fusion timeline by much. The advancements required to lower operating energies and costs to raise the Q-electricity may still be decades away. Regardless, this breakthrough is a good sign for fusion reactors and garners the investment required to push fusion research to the next level.
What Happens Now?
Even if the NIF’s breakthrough is not a major game changer for fusion power - it is still a good sign for fusion reactor technologies. The fact that the NIF’s technology is almost 10 years old (quite a substantial age in this new age of technology), and still was able to achieve such a high energy gain factor is an optimistic indication for fusion research ahead - especially with the construction and improvement of various newer, possibly more efficient technologies.
One reactor with a very high potential for electricity generation is set to begin operation in 2025 - though full fusion is not expected to commence until 2035 due to construction delays. The ITER tokamak experimental reactor is projected to have a Q of 10 - which should pave the way for a Q-electricity of 1. The ITER reactor, however, will not convert the heat released from the fusion reaction into electricity as it is an experimental tokamak and not a commercial reactor - but it may spotlight the technology required for reactors that can.
Another emerging technology is the Helion seventh-generation reactor, the Trenta. Helion is the first private company to reach plasma conditions required for fusion (100 million Kelvins), and the technology is completely different from that used in most reactors - technology that originates from the 1950s. Perhaps the fresh approach of Helion’s generator may mark the beginning of viable fusion power.
There are dozens of other governmental and private organisations attempting to harness the power of fusion - and many investors who are eager to contribute to a source as beneficial as fusion. The future is bright for fusion technology - and so is the future for our zero-carbon, renewable energy system.
Learn more about fusion!
General information
Understanding fusion power
Fusion obstacles
ITER
Helion
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