Aug 19 2021

Nearing A Fusion Milestone

I have been covering research into fusion power for years, so I like to give updates when a significant advance is made. A recent announcement from the National Ignition Facility warrants such coverage.

Fusion is the process of combing light elements into heavier elements. It’s the process that fuels all suns, beginning by fusing hydrogen into helium. Protons of hydrogen are positively charged, so they repel each other. In order to overcome this electromagnetic force to get hydrogen protons to smack into each other with enough power to get them to fuse (by getting them close enough that the strong nuclear force takes over and binds them together) they need to be squeezed together at high temperature and pressure. Stars do this by being huge and having lots of gravity. Fusion research has been attempting to replicate the conditions at the core of stars on Earth.

There are two basic methods used, magnetic confinement and inertial confinement. Magnetic confinement uses powerful magnets to squeeze a plasma of hydrogen isotopes to high temperatures and pressures. This method has promise, but the trick is making magnets powerful enough and keeping the plasma from leaking. Further, you have to accomplish this without spending more energy than you get back from the fusion.

The National Ignition Facility uses the other method, inertial confinement, which essentially uses many powerful lasers (192 for the NIF) bombarding a confinement vessel causing it to explode with energy inward resulting in the high pressure and temperature, actually hotter than the core of the sun. Multiple fusion experiments have achieved the first goal – actual fusion. But that’s only the first step, and not sufficient to have a fusion reactor providing energy to the grid. The researchers report:

An experiment carried out on 8 August yielded 1.35 megajoules (MJ) of energy – around 70% of the laser energy delivered to the fuel capsule.

This is eight times the energy production of their previous record achieved a few months ago. It is 25 times the energy production from 2018. The rapid pace of this progress is what has many in the fusion community excited. But we are not there yet. As they indicate, this is only 70% of the energy that was put into the process through the lasers. Reaching the 100% threshold is called “ignition” and essentially means that the heat from the fusion itself is causing more fusion. That’s what we want – self-sustained controlled fusion.

While they did not achieve ignition, they did briefly achieve what they call “burning plasma” where heat from fusion does provide energy for further fusion, just not enough by itself. Burning plasma is essentially a proof of concept, meaning that they are on the way toward ignition. This is exciting, but I think some of the reporting and quotes from scientists are getting a little ahead of the game.

It’s important to recognize that technical problems often get more and more difficult to solve as the technology progresses. Initial rapid linear progress may fool people into thinking the ultimate goal is right around the corner. This keep happening over and over again. Some people thought we were close to fusion reactors 70 years ago. We saw the same thing with room temperature superconductors in the 1980s, and hydrogen fuel cars in the 2000s. Some technological progress is rapid, even geometric, like computing power and genetic sequencing. But in order to maintain that progress increasing resources are typically invested. Initial success brings in the money to fuel the increasing research necessary to maintain progress. But what if there is no money coming in until we cross some threshold? How long will we sustain research without any payoff?

That is where we are with fusion. This is a money hole until we achieve not only ignition, but a workable fusion power plant that can generate electricity. This requires other innovations we don’t have yet either, like how exactly will we bleed off heat from the reactor so that we can use that heat to generate electricity while still maintaining self-sustaining fusion?

Feeding the premature hype can therefore be counterproductive. Decades of such hype has lead to the common joke that fusion power is 30 years away and always will be. That has been true for the last 70 years or so, but might finally be changing. We are definitely getting a lot closer to the goal, so it’s easy to see why some might be getting excited. But I still think we need to temper expectations. That last 30% energy return to get to ignition may be 10 times or even 100 times harder to achieve than the first 70%. Or perhaps the new technology will take us over the finish line. We will have to wait and see.

If we do achieve ignition and are able to build a workable fusion power plant, what will that mean for our energy infrastructure? It’s hard to say. Fusion is touted as clean energy, because it is, but fusion power plants have to be huge to achieve ignition and any working plants will be extremely expensive. Economics will therefore likely be the primary determinant of whether or not fusion energy is in our near future. But they might be cost-effective if they can produce a massive amount of clean energy and operate for many decades.

If we achieve fusion power plants in time, they could displace fossil fuel powered plants. They could even make fission power obsolete. The window might be closing, however. By late in this century it’s likely that renewables and grid storage will simply be too cheap for fusion to compete. If we could get a plant operating by mid century, they would still likely have a niche. In order to survive long term, the technology will have to get more efficient and less expensive. This basically means cheaper and more powerful lasers, magnets, and superconducting material.

Even if fusion never finds a significant role on Earth because of other cheaper options, fusion power is a great option for space travel. Fusion engines would have a great specific impulse (power per weight of fuel), because hydrogen fuel is light and fusion creates lots of energy. Fusion might also be great for a Mars settlement, where solar is less efficient and dust storms are problematic. Beyond Mars solar energy gets rapidly too dim to be effective. It’s therefore still useful to develop this technology. Hopefully it can be bootstrapped by providing energy on Earth, at least in this century.

But again, we are not there yet. I hope to see ignition soon, but while I’m hopeful I’m not holding my breath just yet.

No responses yet