3 ms·

It's the Gallium Arsenide, from my understanding. There are processes to recover the Gallium, but it produces a waste that's very high in Arsenic.

Schroedingersat 4y ago
The only GaAs involved in solar is an optional amount in the power circuitry. CdTe was briefly a thing for abiut 30% of the market, but peoplewill want the Telerium soon enough. Modern panels are sand and about 50g/kW net of silver. Recycling is mandatory.
- landemva 4y ago
  I don't think solar cell recycling is mandatory, at least west of Mississippi. Going to need a reclamation fee added on to purchase price to get these disposed of in a different manner than the old tire dumps.
  - Schroedingersat 4y ago
    The Te, Ag, and Cu is plenty valuable (especially old high end panels with 50-100g of silver), and developed nations which already have recycling fees that build recycling supply chains and so reduce costs of processing will pay for them. There have already been trials for industrial scale reprocessing of the Si into new panels -- which should give old monocrystalline panels similar value after reprocessing to new due to material reductions offsetting the labour. It looks like there is some motion towards responsibility though https://www.solarrecycle.org/copy-of-vendors https://www.solarrecycle.org/copy-of-vendors And even paid decomissioning if they have some limited life left https://fabtech.net/ https://fabtech.net/ Plus even if you don't tear it apart it's still a piece of hail resistant glass that could have various uses. Frost the top and you have a table. Find use for 20 such items in your lifetime and none will make it to landfill.
pjc50 4y ago
Hmm.. there are a number of different chemistries, and they're not all clearly labelled like batteries. It appears the switch from phosphoros/boron dopants to gallium was quite recent: https://theconversation.com/the-sunlight-that-powers-solar-panels-also-damages-them-gallium-doping-is-providing-a-solution-164935 https://theconversation.com/the-sunlight-that-powers-solar-p... But that's gallium dopant rather than GaAs. There's also CIGS and CdTe "thin film" solar cells, which are extremely toxic in even small amounts. But those chemistries were never very popular. As far as I can tell most cells currently installed are poly or monocrystalline silicon cells, which contain phosphoros/boron dopants and aluminium metallization for the contacts. Those are the cheapest and also least toxic formulation. (Fun fact: you know what popular component uses GaAs? Red LEDs!)
- Schroedingersat 4y ago
  Most commercially viable cells use silver front side metallization (or both sides for bifacial). This represents about 50g/kW net of silver depending on location, but there are methods in the production pipeline to reduce it to 25g/kW. Tandem cells will reduce it to less silver than a control rod uses, but the commercialisationnpathway isn't set in stone yet. Worst case scenario, we hit silver limits, they get switched to Al front side and efficiencies drop back to 17%
  - pfdietz 4y ago
    Or switch to copper for the contact wires, with a Ni or Mo barrier layer (about 1 micron thick) to prevent the copper from reacting with the silicon.
    - Schroedingersat 4y ago
      I believe there is already a few 10s of nm thick layer of indium in production processes for that purpose (or to stabilize bonding?). Copper metallization works (usually with a nickel layer and a silver electroplate on top which uses substantially less Ag than a nuclear reactor of the same net power), but is presently considered cost prohibitive process-wise as it adds a few steps. The current process being rolled out is silver plated copper paste (each copper bead has a 10-30% silver coating) as well as some techs for laying it down more consistently (aligned screen printing where the line never crosses two layers of mesh, and once it matures, depositing it with laser). Silver consumption may briefly increase if the above facilitate a switch to heterojunction or topcon cells, but as soon as one of the 3 tandem chemistries being tried per day shows itself as a winner the voltage will increase and the fingers will get significantly smaller (to the point where Al may not cause a shading problem). At that point the shills will start whining about a 100nm thick layer of lead containing molecules while ignoring that it's less lead than your average tuna.
scythe 4y ago
There are no commercial panels made of gallium arsenide. They are used in space, where efficiency rules over everything else, and for certain military applications. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8200097/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8200097/ There was a company, Alta Devices, that planned to commercialize GaAs thin-film (so light on materials usage) solar panels with nearly 30% efficiency, but they were bought up by Hanergy which ran into financial troubles and shut it down. It's not clear what happened to their patent portfolio, but their equipment was liquidated in 2020, and the founder now works for UC Berkeley.

Schroedingersat 4y ago

The only GaAs involved in solar is an optional amount in the power circuitry. CdTe was briefly a thing for abiut 30% of the market, but peoplewill want the Telerium soon enough. Modern panels are sand and about 50g/kW net of silver. Recycling is mandatory.

landemva 4y ago
I don't think solar cell recycling is mandatory, at least west of Mississippi. Going to need a reclamation fee added on to purchase price to get these disposed of in a different manner than the old tire dumps.
- Schroedingersat 4y ago
  The Te, Ag, and Cu is plenty valuable (especially old high end panels with 50-100g of silver), and developed nations which already have recycling fees that build recycling supply chains and so reduce costs of processing will pay for them. There have already been trials for industrial scale reprocessing of the Si into new panels -- which should give old monocrystalline panels similar value after reprocessing to new due to material reductions offsetting the labour. It looks like there is some motion towards responsibility though https://www.solarrecycle.org/copy-of-vendors https://www.solarrecycle.org/copy-of-vendors And even paid decomissioning if they have some limited life left https://fabtech.net/ https://fabtech.net/ Plus even if you don't tear it apart it's still a piece of hail resistant glass that could have various uses. Frost the top and you have a table. Find use for 20 such items in your lifetime and none will make it to landfill.

pjc50 4y ago

Hmm.. there are a number of different chemistries, and they're not all clearly labelled like batteries. It appears the switch from phosphoros/boron dopants to gallium was quite recent: https://theconversation.com/the-sunlight-that-powers-solar-panels-also-damages-them-gallium-doping-is-providing-a-solution-164935 https://theconversation.com/the-sunlight-that-powers-solar-p... But that's gallium dopant rather than GaAs. There's also CIGS and CdTe "thin film" solar cells, which are extremely toxic in even small amounts. But those chemistries were never very popular. As far as I can tell most cells currently installed are poly or monocrystalline silicon cells, which contain phosphoros/boron dopants and aluminium metallization for the contacts. Those are the cheapest and also least toxic formulation. (Fun fact: you know what popular component uses GaAs? Red LEDs!)

Schroedingersat 4y ago
Most commercially viable cells use silver front side metallization (or both sides for bifacial). This represents about 50g/kW net of silver depending on location, but there are methods in the production pipeline to reduce it to 25g/kW. Tandem cells will reduce it to less silver than a control rod uses, but the commercialisationnpathway isn't set in stone yet. Worst case scenario, we hit silver limits, they get switched to Al front side and efficiencies drop back to 17%
- pfdietz 4y ago
  Or switch to copper for the contact wires, with a Ni or Mo barrier layer (about 1 micron thick) to prevent the copper from reacting with the silicon.
  - Schroedingersat 4y ago
    I believe there is already a few 10s of nm thick layer of indium in production processes for that purpose (or to stabilize bonding?). Copper metallization works (usually with a nickel layer and a silver electroplate on top which uses substantially less Ag than a nuclear reactor of the same net power), but is presently considered cost prohibitive process-wise as it adds a few steps. The current process being rolled out is silver plated copper paste (each copper bead has a 10-30% silver coating) as well as some techs for laying it down more consistently (aligned screen printing where the line never crosses two layers of mesh, and once it matures, depositing it with laser). Silver consumption may briefly increase if the above facilitate a switch to heterojunction or topcon cells, but as soon as one of the 3 tandem chemistries being tried per day shows itself as a winner the voltage will increase and the fingers will get significantly smaller (to the point where Al may not cause a shading problem). At that point the shills will start whining about a 100nm thick layer of lead containing molecules while ignoring that it's less lead than your average tuna.

scythe 4y ago

There are no commercial panels made of gallium arsenide. They are used in space, where efficiency rules over everything else, and for certain military applications. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8200097/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8200097/ There was a company, Alta Devices, that planned to commercialize GaAs thin-film (so light on materials usage) solar panels with nearly 30% efficiency, but they were bought up by Hanergy which ran into financial troubles and shut it down. It's not clear what happened to their patent portfolio, but their equipment was liquidated in 2020, and the founder now works for UC Berkeley.