Generating 20 T on the Way to the World’s First Net Fusion Energy Tokamak: Using an HTS
Let’s explain high-temperature superconductors and their importance in fusion energy with a breakthrough!
Let’s say everyone switched to using fusion energy today. Before long:
- We could reduce the reliance on fossil fuels and fight climate change,
- Increase global energy security and lower nuclear proliferation risk,
- Explore space on a bigger scale by improving transportation,
- See huge advancements in materials science,
- Build more powerful and practical etc.
However, in a month, an average citizen’s electricity bill would make them go bankrupt. Yet, were you aware that the fusion company can also face bankruptcy?🤔
That is because fusion couldn’t offset the energy that is used to carry out the reactions until recently. Hence, scientists are working on reaching net energy to reduce the cost of fusion and making it commercially available.
So, in this article, you’ll see where a breakthrough in high-temperature superconductors comes into play.
How We Produce Electricity from Fusion
In nature, fusion energy powers our sun and other stars. The fusion we make on Earth is by fusing the isotopes of hydrogen, called deuterium and tritium. To get electricity out of this reaction, we need an ionized plasma.
Ionization is when the atoms of gas heat to over 100 million°C, and plasma for fusion occurs, causing the electrons to separate from their atoms. Now, the plasma contains free electrons and positively charged ions.
However, plasmas are very unstable; therefore, they must be confined by
- Magnetic fields (magnetic confinement) or
- High-powered lasers (inertial confinement) to sustain nuclear fusion reactions.
By confining the plasma, ions fuse and a large amount of heat energy is released to later be converted into electricity.
Magnetic Confinement by Using Tokamak Reactors
In magnetic confinement, a series of powerful electromagnets create a magnetic field that traps the plasma.
The magnetic field prevents the plasma from escaping and allows it to heat to the high temperatures required for fusion.
The most available design for this is called Tokamak:
While in confinement with toroidal field coils, the fuel plasma is compressed and heated with the help of superconductors, bringing its pressure up to 250 atm.
Toroidal Field Coils
The coils are the primary mechanism of confinement of plasma with superconductors.
There are more than one set of coils in a Tokamak, but to put it simply:
- The first one creates a toroidal field that is parallel to the torus.
- That causes the central solenoid (a vertical magnet that carries current) to generate another magnetic field in the poloidal direction.
- Then, the last set of coils shape and place the plasma to make an outer poloidal field.
Combining these, a donut-shaped magnetic field that carries plasma occurs.
Superconductors
Superconductors are materials with no electrical resistance when cooled down to absolute zero.
That is because, in a superconducting material, the moving electrons get passed along from atom to atom in such harmony that they keep in sync with the vibrating nuclei.
That produces:
- No collisions,
- No resistance,
- And no heat
So, the stronger the current (the higher the T [for Tesla] on the coil, and the larger the magnetic field) is, it saves us from high energy consumption with better efficiency.
But these materials generally superconduct below the temperature of liquid nitrogen — which is what they are commonly cooled.
This means they require a lot of money, time, and energy consumption to bring them to the low temperatures and high pressures they work in and to keep them in these conditions.
That is why scientists are working on achieving superconduction at room temperature.
Cuprates
With that, Cuprates (a class of compounds that contain copper) are currently the highest temperature superconductors known (under atmospheric pressure) that reach up to 133 K (-140 °C; -220 °F).
That is related to copper being the second most conductive metal, plus
- its malleability,
- corrosion resistance,
- thermal resistance,
- and being less expensive. Making it the best choice for general electrical wiring.
But of course, since we are not dealing with something ordinary, even the “best” material does not have enough conductivity.
That is where a breakthrough that occurred after 100 years of the discovery of superconductors might help us get to a net energy future.
High-temperature Superconductors (HTS)
The boundary for the superconductor to be considered a high-temperature one is 77 K (−196 °C; −321 °F: the boiling point of liquid nitrogen).
Few records were set (93K with yttrium barium copper oxide) until room temperature superconductivity at 287.7 K (13.3 °C; 58 °F), and another record-breaking 20 T has been achieved for the first time in 2020.
That was a big deal since we thought the maximum amount we could reach was 13 T, and scientists working on SPARC did it under roughly two and a half million times greater pressure than the atmospheric one.
Why Focus On High-Temperature Superconductors?
In fusion reactors “Q” is the energy gain factor. Which means:
Q = the ratio of generated power to externally provided heating power.
Thus, the higher the Q or the magnetic field on the coil (T), the more successful the reaction’s outcome is.
Our goal is to reach net energy (to have more kinetic energy than the heat energy you put in). That is needed to make fusion viable for commercial use. And here is SPARC’s solution to that:
In search of the greatest factors to raise Q and to keep the plasma in such conditions, scientists found the best result when they looked into their Tokamaks superconductor.
Here is what researchers and engineers who work on the SPARC reactor said about this breakthrough:
“…The graph above shows the relationship between achievable fusion gain (Q) in SPARC and the maximum magnetic field at the toroidal field coil (T). — which corresponds to just above 20 T
In this relationship, the rest of the machine design (major radius, minor radius, elongation, etc.) and plasma physics assumptions (safety factor, confinement regime, stability limits, etc.) are kept constant.
This plot shows just how strongly fusion gain depends on the magnetic field and thus why this magnet is so game-changing.” — Alex Creely.
Takeaway
The development of high-temperature superconductors (HTS) is a major advancement in the field of fusion energy that already started to affect countless industries. HTS could enable the construction of smaller, more efficient fusion reactors that produce more energy than they consume. That would make fusion a viable source of clean, renewable energy accessible to everyone.
If companies such as SPARC are successful in the short term as they suggest, we will see a future where we can reverse crises such as global warming, other industries from medicine to space tech advance immensely; lastly, no citizen will have to go bankrupt to partake in a green, cheaper, net energy future.
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