Jordan Taylor Profile picture
Aug 3, 2023 17 tweets 9 min read Read on X
With all the buzz about #LK99 and the possibility of a room temperature superconductor, let's have a topical thread.

Can a superconducting induction coil make the perfect battery?

And is it world changing? Read on...
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The introduction of Variable Renewable Energy (VRE) into our power grids has had a number of effects, but prime among them is a massive increase in capacity variability, which electric grids must then adjust to.

Hence the recent spike in interest in grid-level energy storage. Image
Electrical energy can be stored in many ways: Electro-chemically with batteries, through kinetic energy with flywheels, gravitational potential with pumped hydro, through compressed air etc. All have pros & cons.

You can also store energy in a magnetic field...


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Spooky but true. Feed DC current into a superconducting inductor and you store energy, practically lossless, through the induced magnetic field, and recoup that energy by discharging the coil.

This works with superconductors: Anything else will lose energy in milliseconds. Image
Why? Pass a current through an incandescent light bulb and touch it. Once you've sucked your fingers, note where all that electrical energy went: Into heat through resistance in an imperfect conductor. Try to store energy in a copper magnet coil and you'll get the same thing. Image
Superconductors are different. The practically zero electrical resistance allows long term storage, so long as the magnetic field is contained and not inducing motion or current elsewhere. Round trip efficiencies are ~95%, and most of the 5% loss is the AC-DC inverter/rectifier. Image
Superconducting Magnet Energy Storage (SMES)  isn't just hyper efficient: It also has very high specific power (10-100,000 kW/kg) and an almost instantaneous ramp. They can also fully discharge near infinitely without degradation.

There are some drawbacks, but later... Image
... Firstly, toroidal or solenoid design? You can coil a SMES two ways: The solenoid is easier to manufacture but the toroid produces lower mechanical strain from the magnetic fields. In practice, this means solenoids work well for small installations, toroids for big ones.
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These magnetic fields are serious: A commercial non-research hospital MRI scanner can sustain magnetic fields of up to 3 tesla. There are videos showing what that can do.

Superconducting magnets can top out at well over 20T. This creates a structural design limitation... Image
Lorentz forces on moving charges ensure that magnetic storage systems will be exposed to significant stress loading, and this limits their ultimate potential: If we assume a reasonable 100MPa structural maxima, then specific energies in our magnet are limited to 12kJ/kg.
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The CMS magnet in the LHC supercollider reached 11kJ/kg, so 12kJ is a decent hypothetical maximum, and it's not much. It's higher than pumped hydro, but not by enough, and, unlike pumped hydro, SMES kgs are expensive.

High specific power, low specific energy. Fast but feeble. Image
So for this reason plus the need for cryogenics, and huge expense, SMES has been a small niche and only a scattering of systems exist, managing voltage sags, oscillation smoothing and in fusion & particle physics research. Long period power smoothing has not been tried with SMES. Image
But what if it was?
The world's largest battery storage array is Vistra Moss Landing Facility in California. It can store 1.6GWh and a max power of 400MW. Average costs are ~$1B/GWh.

What of SMES? Image
Current experimental installations are more expensive by several orders of magnitude, though there is potential for truly large scale implementation to bring costs down to parity through mass production. Lower still if new superconducting materials favour mass production.


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That's a big if. An additional issue is land use: A hypothetical 1GWh SMES would have a torus diameter in the 100m-500m range, which is not subtle, but manageable. Cost is the primary issue: Superconductor material first, cryogenics second. Image
Room temperature ambient pressure superconductors, if discovered and mass produced, could make it a plausible utility scale storage system, and with this we return to LK-99, but let's not be too optimistic. We need to multiply scale by orders of magnitude & reduce cost the same. Image
So as with so many things, if it happens and the hype around LK-99 becomes reality, SMES will be an evolution, not a revolution. The perfect battery remains imperfect for the time being.

Sources attached, all free downloads. I hope you enjoyed this!


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More from @Jordan_W_Taylor

Jul 4
In April on a mountain in Chile the Vera Rubin observatory gathered first light, and this telescope will be world-changing! -Not because it can see the furthest… but because it can see the fastest!

The Vera Rubin telescope thread! The value of speed, and unique technology… Image
Who was Vera Rubin?

She first hypothesized the existence of dark matter, by observing that the rotation speed of the edge of the galaxy did not drop off with radius from the centre as much as it should. The search for dark matter, and other things, will drive this telescope… Image
Does it see a long way?

Yes, but it’s not optimized for that: The battle of the big mirrors is won by the Extremely Large Telescope which, yes, is meant to see a long way. Vera Rubin is not that big, but that doesn’t matter because it has a different and maybe better mission. Image
Read 22 tweets
Jun 20
Rotating detonation engines: Riding the shockwave!

A technology that could revolutionise aviation, powering engines with endlessly rotating supersonic shockwaves. It could bring us hypersonic flight, super high efficiency and more.

The detonation engine thread… Image
Almost all jet engines use deflagration based combustion, not detonation, but while fuel efficiency has been improving for decades, we're well into the phase of decreasing returns and need some game-changing technologies.

One is the rotating detonation engine (RDE). Image
To understand the appeal of RDEs, you need to know that there are two forms of combustion cycle: Constant pressure, where volume expands with temperature, and constant volume, where pressure goes up instead.

Most jet engines use constant pressure. RDEs use constant volume. Image
Read 21 tweets
Jun 6
As a new graduate I once had to sit down and draft an engine test program for a subsystem of a new model of Rolls-Royce aero engine. It was illuminating.

So here's a thread on some of the weirder things that this can involve: The jet engine testing thread! Image
Fan Blade Off!

Easily the most impressive test: A jet engine needs to be able to contain a loose fan blade. In the FBO test, either a full engine or a fan & casing rig in low vacuum is run to full speed, then a blade is pyrotechnically released.
Frozen.

The Manitoba GLACIER site in Northern Canada is home to Rolls-Royce's extreme temperature engine test beds. Not only must these machines be able to start in temperatures where oil turns to syrup, but in-flight ice management is crucial to safe flying. Image
Read 15 tweets
Apr 26
How can humans realistically travel to another star, and why will it be an all-female crew that does it?

In this thread: Sailing on light, nuclear pulses, using the sun as a telescope and how to travel to another solar system. The interstellar thread! Image
Slow starts…

The furthest man-made object from Earth, Voyager 1, is one of the fastest. Launched in 1977, it performed gravitational slingshots off Jupiter and Saturn and is heading to interstellar space at 17 kilometres per second.

How long until it reaches another star…? Image
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Um… a long time.

Voyager 1 is moving at 523 million km, or 3.5 AU, per year. Our nearest star from the sun, Alpha Centauri, is 278 THOUSAND AU away. If Voyager 1 was heading that way (which it isn't) it would take almost 80,000 years to get there.

Damn. Can we go any faster? Image
Read 30 tweets
Apr 11
How do we make nuclear new builds cheaper?

It's the defining question of the energy market. Nuclear power is clean, consistent, controllable and low-carbon, but in the West it's become bloody expensive.

Are there construction techniques available to Make Atomics Great Again? Image
The problem.

Hinkley Point C, the world's most expensive nuclear plant, could hit a cost of £46 billion for 3.2 gigawatts of capacity, which is monstrous. Clearly nuclear needs to be cheaper, and in many places it already is. What are our options? Image
Steel bricks/ steel-concrete composites.

Construction can be chaos, and it's expensive chaos: Many bodies,many tasks, serious equipment. The more complexity, the greater the chance of delay, and delays during construction are the most expensive sort.

Steel bricks could help… Image
Read 17 tweets
Mar 14
You can't depend on the wind, and you can't sunbathe in the shade, but the sea never stops moving… can we power our civilization with the ocean wave?

The wave power thread! Image
If not wind, why not waves?

It's a fair question. Wave power is much more predictable than the wind, it's available 90% of the time and has a higher power concentration per square metre of any renewable energy source.

But it's almost unheard of. Why is it so difficult? Image
Several things are important in wave power: How we collect the energy, how we use that energy to generate power, and how we store, control and deliver it.

We'll start with collection, which is divided into attenuators, point absorbers and terminators… Image
Read 26 tweets

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