Fremskridt inden for superledning baner vejen for en ny teknologisk revolution

Begrænsninger for superledning

Electricity has been one of the most transformative technologies in history, allowing for the transmission of a very useful form of energy over long distances. But every electric system faces electric resistance, which results in the generation of heat when an electric current is applied.

Der findes et alternativ, det såkaldte superledende materiale. Superledende materialer har nul elektrisk modstand, hvilket gør det muligt at anvende ekstremt kraftige strømme uden at generere varme eller kraftige magnetfelter.

Uden superledning ville mange moderne teknologier ikke være mulige, herunder partikelacceleratorer, MR-scannere og magnetisk levitationstog.

Problemet er, at alle disse anvendelser er baseret på lavtemperatur-superledning, hvor materialerne kun er superledende, når de køles ned til lave temperaturer som 20 K/-253 °C/-423 °F, ofte med flydende helium.

For nogle anvendelser som magneter i eksperimentelle fusionsreaktorer kan den nødvendige temperatur være så lav som 4 K (kun 4 grader over det absolutte nulpunkt), selvom dette forbedres (se nedenfor).

Such extremely low temperatures are hard to maintain and consume a lot of energy. So, while other technologies & applications could benefit from superconductivity, it is rarely economically viable to do so.

Højtemperatur-superledning

This is why the prospect of materials being able to stay superconductive at higher temperatures is an exciting prospect. In that context, “high” temperature can be as cold as -185°C to -135°C but this is a lot more easy to reach than the traditional superconductive temperature, using liquid nitrogen instead of liquid helium.

But of course, the ideal material would be superconductive at temperatures just below freezing or even room temperature.

Superledning ved stuetemperatur

In the summer of 2023, a piece of news went viral after the publication of a scientific article titled “The First Room-Temperature Ambient-Pressure Superconductor”. A material called LK-99 was described as working as a superconductor up to 127°C/260°F. That it used common materials like copper and lead (copper-substituted lead apatite – CSLA) only added to the potential of the discovery.

Copper crystals – Source: DOE

It even triggered a micro-bubble in equities related to superconductivity, for example, a +60% on American Superconductor (AMSC ) stock prices.

The claim was immediately contested and found to be hard to replicate.

LK-99 Superledning Historie

But this story is not over yet. In januar 2024, two other research teams have also observed LK-99’s potential for superconductivity.

Interestingly, each team recreated its own version of LK-99 through different manufacturing methods, indicating that the results observed are probably tied to the material more than some possible impurity or error.

So there is some hope this is not a false alarm. What seems to be the case is that the manufacturing process is, for now, extremely inefficient, making it easy for a test to come back negative.

So, it is perhaps no surprise that replicating the initial discovery of LK-99 has been anything but straightforward.

“…even samples synthesized following the current best-known process (the one they employed) tend to have a high percentage of non-superconducting matter mixed in with the purportedly superconducting bits. In that scenario, it’s easy to wrongfully declare samples as dead even after testing them.

one of the superconductive samples they based their paper on was fabricated back in November of 2023, determined to be a dud, and was about to be trashed at multiple points of its life.”

Source: Tom’s Hardware

Potentiale for superledning

Even if room-temperature superconductors remain elusive, researchers may find a way to keep material superconductive at temperatures as “high” as -80°C to -70°C.

This would completely change the possible application, as superconductivity can then rely on cooling technology used in freezers storing mRNA vaccines instead of more expensive liquid helium or nitrogen.

Among the possible applications already discussed in the 1990s are:

• Better MRI, with higher resolution and cheaper to build and operate, allows it to become a much more routine medical exam.
• Electromagnetic thrust drive systems (also called magnetohydrodynamic (MHD) drives) to propel ships through electrifying seawater.
• More powerful and efficient electric engines.
• Higher density and safer batteries with Superconducting Magnetic Energy Storage (SMES).
• Superconductive limiters, switches, and fuses to improve the electric grid infrastructure.
• Long-distance power transmission without losses, which could boost renewable energy efficiency, for example with solar panels still in the sun powering a city thousands of kilometers away.
• Cheaper and easier to maintain maglev trains or later on Hyperloop systems.
• Sensors/magnetometers (Superconducting Quantum Interference Devices – SQUIDS) for application in industrial settings.
• Superconducting quantum computing
  • (you can read more on quantum computing progress in our article “The Current State of Quantum Computing ”).
• Defense & Aerospace applications, including radiation shields, electromagnetic launches, magnetic bearings, sensors, railguns, coilguns, lasers, and other energy weapons.

Source: DOE

Superledning og kernesfusion

Nuclear fusion is another application that would greatly benefit from superconductors working at higher temperatures.

All various methods of achieving commercial nuclear fusion rely on extremely powerful magnets to contain and compress the plasma heated at tens or hundreds of millions of degrees.

After an initial success in 2021, a research team at MIT’s Plasma Science and Fusion Center (PSFC) worked on making a superconductive magnet powerful enough to be usable in nuclear fusion reactors.

The new fusion magnet design is superconductive at 16°K instead of the previous 4°K. One key innovation is the removal of all isolation around the magnet’s conductive wire. This, in turn, freed space for further improvements, like a simpler fabrication process or more structural strength.

Source: Phys.org

“Before the Sept. 5 demonstration, the best-available superconducting magnets were powerful enough to potentially achieve fusion energy—but only at sizes and costs that could never be practical or economically viable. Then, when the tests showed the practicality of such a strong magnet at a greatly reduced size, “overnight, it basically changed the cost per watt of a fusion reactor by a factor of almost 40 in one day”

Dennis Whyte – Hitachi America Professor of Engineering

They published their discoveries in a compilation of 6 scientific papers published in IEEE Transactions on Applied Superconductivity. They explained in detail how to build such 16°K fusion magnets, which generate a magnetic field as intense as 20 Teslas.

Testing The Limit

Eager to prove the new fusion magnet design can perform safely, they also actively put it in difficult situations. The last test resulted in the magnet partially melting in one corner. And even most of the magnet elements survived (95%+), demonstrating the robustness of the design.

What was equally impressive is that the researchers’ model perfectly predicted the way the magnet failed.

The experience also tested the supply chain for such material, using 300 kilometers (186 miles) of high-temperature superconductor in collaboration with CFS (Commonwealth Fusion Systems, an MIT-spinout company)

Fremtiden for fusions-superledende magneter

For a while longer, fusion reactors will rely on well-understood and tested superconductors using liquid helium to stay below 20°K.

However, it appears that higher-temperature superconductivity is not only possible but likely to be doable at much more manageable temperatures.

In the long term, such superconductive magnets could help improve fusion reactors’ performance, as well as bring down their price, allowing for commercial viability.

This would unlock an almost unlimited energy source for humankind, making our current issues regarding food production, desalination, climate change, space travel, etc., trivial.