Unlimited Energy: Let’s Build a Mini Sun…
Intro to fusion energy
The sun powers all life on our planet. Just like all-stars, it produces unlimited energy through a process called fusion. By fusing light atoms like hydrogen together under HOT temperatures (we’re talking 15 million° hot 🥵) and high pressures like those found at the center of the sun. We get a million times more energy than we would from a regular combustion reaction.
But wait it gets better…
Replicating energy like the sun is getting people excited because Fusion is:
- Fast, occurs in a matter of seconds
- Clean, creates little nuclear waste and radiation compared to fission
- Requires few resources, its fuel is available in saltwater.
- Energy-dense, one liter of fusion fuel = 55,000 barrels of oil.
In theory, only 2 km³ of water could generate the same amount of energy as ALL of Earth’s oil reserves…🛢️😮
Nuclear power has two roads; fission and fusion. Fission is the opposite of fusion. Fusion is smashing 2 elements together to get a heavier element where fission is breaking an element down to get 2 smaller elements. Fission is what was used in bombs like Hiroshima and for our current nuclear power plants.
During fusion energy is released because the weight of the fused element is slightly less than the combined weights of the lighter elements. The difference in mass is energy being released.
So how do harness this magical energy on Earth?
When we heat up gas we get electrically-charged gas⚡, this is the 4th state of matter called Plasma. Plasma can be found in lighting and the northern lights. Despite its tiny abundance on earth, plasma makes up 99% of the universe.
Earth doesn’t have the high pressures that the Sun takes advantage of. So to compensate our plasma has to be HOT, up to 150 millionºC hot, like 10x the sun hot.
To generate this extreme heat we zap high energy particles with high-frequency waves in a reactor.
The resulting pressure eventually causes hydrogen isotope’s nuclei to collide, producing a helium nucleus. In the process, energy is released.
The best hydrogen isotopes to uses are Tritium and Deuterium.
We can find Deuterium in ordinary saltwater while Tritium is rare. Tritium’s scarcity in nature is a result of its radioactivity, with a half-life of 12.3-year. Our main source of Tritium is from fission reactions with lithium.
Tritium decays into Helium-3. But our atmosphere causes us to lose most of our Helium-3.
Hmmm…where don’t we have a strong atmosphere? 🌚
Unlike Earth, the Moon has been collecting Helium-3 for billions of years, there’s about a million tons of it stored on its surface.
To extract the Helium-3, we’d collect moon dust and heat it up to 600 °. Countries like China and companies like Moon Express are organizing moon missions to capture helium-3.
Deuterium-Tritium reactions are 20 times stronger and only need a third of the heat than Deuterium-Deuterium reactions, making it highly sought after.
In theory, we can regenerate an additional 15% more tritium during fusion through nuclear reactions by partly surrounding the plasma with lithium. Tritium will be produced from the lithium getting irradiated by neutrons from the reaction.
What wizardry do we use to host fusion?
All this magic can happen in magnetic confinements, where electric and magnetic fields hold plasma particles in a cage-like vacuum chamber, while laser beams are used to heat it.
Wait but what if this plasma that 10xs hotter than the sun escapes the confinement?! No need to worry, plasma is millions of times less dense than gas, it’s only a few particles flying around in the chamber and as soon as they escape they immediately cool down. You could put your hand into plasma and not feel any heat… don't try this at home.
The same fragility of plasma is why it’s important to shelter it from the environment. The confinement systems cost millions to billions of dollars and are complex.
The popular doughnut-shaped confinement is called a Tokamak. The plasma is held up by magnetic fields, the generated heat is used to create steam that turns motors, thus producing electricity.
The tokamak is intended to create conditions that make the fusion process self-sustaining.
A massive tokamak is underway by the ITER- an international effort of over 35 countries. It’s set to produce 500MW for every input. The project is over 60% complete and is expected to arrive by 2025 in France.
Another type of confinement is the stellarator, the actual confinement is much easier to maintain once it’s built than a tokamak. The plasma inside the stellarator is twisted, preventing it from escaping
The largest stellarator underway is called the Wendelstein 7-X (W7-X). It’s a 16-meter-wide ring, inside there’s twisted magnetic coils. The twists and complex machinery makes the stellarator more expensive than tokamaks to build, the Wendelstein 7-X (W7-X) took $1 billion and 1.1 million hours to build.
Aside from magnetic confinement, there’s also inertial confinement.
By aiming dozens of amplified lasers into a compartment heating it up into an x-ray oven. The heat creates pressure on a tiny capsule full of fusion fuel until for a billionth of a second a mini star is generated.
All these confinements deal with some of the hottest temperatures in our solar system, but some scientists think fusion is possible at room temperature…
Cold fusion is a theoretical way to conduct fusion at room temperature. By dissolving hydrogen into solid palladium-like metal. The electrical attraction of the solid would overcome the electrical repulsion of the hydrogen nuclei and eventually fuse.
Some scientists believe if you replace the electrons on hydrogen particles with 200x heavier electron like particles called muons. because the particles are heavier they’re held much closer together in orbit. This means that the atom it’s self will also be much smaller and the nuclei will also be 200x closer. When nuclei are closer together they’re much more likely to fuse.
But again, cold fusion is theoretical because these muon particles don’t last very long. In roughly 2 microseconds muons decay into an electron and neutrinos. We have to generate muons in particle accelerators, right now it takes up 5 GeV to create a single muon but that muon will only generate 2.7 GeV of energy. So we aren’t breaking even with cold fusion just yet.
Why isn’t our world powered by fusion yet?
Commercial applications are decades away… why?
Current fusion reactors are “parasitic power drains”— they eat up lots of the energy they produce.
Supporting equipment like liquid-helium refrigerators, water and vacuum pumps take up about 75-to-100 MWe. In the event that the fusion stops, the energy to power the reactor and supporting equipment would have to be bought by the local grid which can be costly.
Artificial fusion’s also restricted due to low particle densities and the difficultly of confining the energy.
We have to use heavier isotypes than hydrogen, like tritium and deuterium which are 1 followed by 24 zeros times more reactive.
Unlike fusion on the sun, where only clean energy is produced, fusion on Earth releases radioactive byproducts. They release radioactive neutron streams. The streams could be used for nuclear weapons such as weapons-grade plutonium 239.
When the energy is released from a fusion reaction and hits the walls of the confinement, the confinement material may become radioactive. Replacing damaged walls drives up costs.
Not only that our storage isn’t efficient. Only 10% of fuel gets used in the reactions while the rest quickly escapes the reaction region, in order to fully use up fuel this lost tritium must be scraped 10–20times from other regions of the reactor and be reinjected. For some reactors, this has caused 10% of their injected tritium to be lost forever.
This fuel problem means we’re going to continually be dependant on fission reactors for our tritium.
But there’s hope our reactors have been getting more advanced. there’s progress being made in reactor performance, a chart called Lawson's criterion mapping the hotness, density, and insulation of systems over time.
Since 1953 the U.S. government allocated +$30 billion for fusion research. It sure is expensive, but whoever builds an efficient fusion reactor will reap massive benefits, and revolutionize energy. Shifting or even abandoning fossil fuels.
It’s been less than 100 years since we understood fusion. With the advances of technology, fusion is getting closer in reach. One day we’ll be able to harness the energy process of the universe… for clean and almost unlimited energy.