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Comment by ngcc_hk | Hacker News Reader

“They require substantial quantities of rare earth metals, however, which are expensive and are mostly mined in just one country – China – which has led to worries over security of supply.“

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To be clear this quote refers to the traditionally used magnets.

There are other potential sources in the world, but they will not be explored until there is a clear financial benefit to exploring them. That will most likely not happen until something goes wrong with the supply in China.

China only has 1/3rd of the worlds extractable deposits. Rare earth minerals is the typical "China Bad" scare story. They reduced the amount they sold because they wanted it themselves to value-add making electronics/renewables and being the vast majority of world supply it got them a better price.

Much like many other countries on earth do. OPEC even has multiple annual meetings where they all decide to collude on restricting oil supply.

If the rest of the world was truly worried they'd subsidise the industry, as it stands most countries throw away all their rare earths in tailing dams as mining byproduct because it's not worthwhile to extract it.

In contrast to the common expectation and statements in this article - most turbines are already not using the rare earth magnet design.

Study: Substitution strategies for reducing the use of rare earths in wind turbines [1]

>According to our estimations about 23% of the global installed capacity in 2015 is based on wind turbines using [permanent magnet] technology. The remaining 77% are using conventional electromagnets generators based on magnetic steel and copper windings, both of them posing no issues about the security of material supply.

[1] https://www.sciencedirect.com/science/article/pii/S030142071...

PM rotor generators have several disadvantages: they're heavy; magnetic flux fades in time, moreso under heat; inability to control the rotor's magnetic flux; probably expensive as well.

Mostly true, just not the price. A simple stator generator is about half the price of a PMM, and at least half the value.

In table 3* the study summarizes 4 categories of generator.

  Low speed Permanent Magnet     PMSG
  Low speed Excited Synchronous  EESG
  Mid to High speed Geared PM    PMSG
  High speed Geared Induction    DFIG

All these types are currently competitive in large wind turbine installations, with high PM content designs getting selected in quite a minority of cases, despite modest efficiency and maintenance bonuses, even at the current top end of generator scale ~8MW.

To get beyond 10MW generators advantages of PM are desired but are also lumbered by relative heaviness besides the price of rare earths. Superconducting Magnets do seem like the way upward then, if reliable 'super-cooling' can be achieved.

[*] https://www.sciencedirect.com/science/article/pii/S030142071...

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