Recent concerns about continuing availability of “rare earth” elements and the impact on the solar PV industry
Yttrium, Cerium, Promethium, Neodymium; hanging out in an intimidating gang at the bottom of the Periodic Table, excluded from school chemistry lessons, the exotic-sounding names and even the collective name for the fourteen “Rare earth elements” conjure up the idea of materials made precious by extreme scarcity.
|Not so scary now?|
A rash of headlines in recent times (examples: 1, 2, 3) have highlighted the importance of these materials for producing the gadgets essential for modern life. Items such as displays and batteries for mobile phones and laptops rely upon small amounts in their manufacture but also technologies in the rapidly emerging clean energy sector. According to these reports permanent magnets used in wind turbines and electric motors, chemical formulations for low energy light bulbs, and (most importantly, of course) solar cells apparently depend on these rare earths.
The reason for the headlines? China controls 90% of the production of rare earths and it was becoming clear that it wasn’t averse to using them for political leverage. A sensitive dispute with Japan over which country owns the Senkaku/Diaoyu islands, a few specks of land in the East China Sea, resulted in China restricting the export of rare earths to the fury of the Japanese whose high technology industries use loads of the stuff.
So, is it right to worry that the solar industry is built on shaky foundations? Are rare earth elements essential for solar cells? Would we have been better off in an industry that relied on hummingbird tears and mermaid’s toenail clippings to make its products?
Well, it turns out that rare earths aren’t all that rare, and that solar cells don’t actually use them anyway.
How Rare are Rare Earths?
Rare earths are actually relatively abundant in the Earth’s crust; about as plentiful as copper. The reason for the name is that they are well dispersed, and not often found in concentrations that can be economically extracted.
However, rare earth minerals have been mined in India, Brazil, South Africa and the USA as well as China. China only has 30% of the world’s rare earth deposits. However, in a move that will resonate with some in the solar PV industry, Chinese producers came to control production by supplying at much lower price, causing mines in other parts of the world to shut down.
As China seeks now to benefit from its control of the market by restricting supply and increasing prices, other producers are already starting to come back on line. For example Molycorp began work in 2011 to bring its Mountain Pass mine in California back into rare earth production.
Do Solar Cells Even Need Rare Earth Minerals?
I’ve had a good look around, and the only reference I can find to rare earth elements in solar, is that Cerium Oxide is sometimes added to glass used in solar modules to increase UV absorbtion.
It appears that the reason so many people have written that rare earth are ‘essential’ for solar cells can be traced to a report written by the US Department of Energy in 2010 “Critical Materials Strategy”.
Two forms of thin film PV materials were identified in the report as using critical (but not rare earth) elements. CIGS thin films use indium and gallium, and CdTe films use tellurium. (See the table below, summarizing the materials considered). The report then goes on to conclude that indium, gallium and tellurium all come from diverse sources.
In 2010, thin film PV dropped to only 13.5% of the market in the face of price competition from crystalline silicon cells, and CIGS and CdTe PV are only two thin film technologies among many.
So, a fine example of how journalism works. Two forms of the less widely-used types of solar PV get mentioned in a report that assessed strategic materials such as rare earths; rare earths hit the headlines in a trade war; and we end up with articles that suggest we’re going to run out of the raw materials for solar PV.