[HN Gopher] Recycled silicon used in 19.7% efficient PERC solar ...
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Recycled silicon used in 19.7% efficient PERC solar cells
Author : taubek
Score : 33 points
Date : 2022-02-12 19:56 UTC (3 hours ago)
(HTM) web link (pv-magazine-usa.com)
(TXT) w3m dump (pv-magazine-usa.com)
| jiggawatts wrote:
| Why bother? It's not like silicon is some rare element that needs
| to be mined in distant, war-torn countries.
|
| It's literally sand!
|
| The hard part is purifying it. Starting from already manufactured
| electronics seems like an uphill battle because the silicon is
| already contaminated with precisely those elements that need to
| be removed from it to control its electronic behaviour!
| andrewxdiamond wrote:
| We as a society cannot keep disposing of things forever. We
| need to be making as many production streams cyclical as
| possible, or we will eventually run out of the easy-to-aquire
| resources
| kiba wrote:
| Would be more concerned with pollution and side effect before
| resources scarcity.
| slavik81 wrote:
| The earth's crust is 60% silicon dioxide. I don't understand
| how we could possibly run out.
|
| I mean, I get the value in recycling the panels. It's
| presumably easier to start with almost pure material than 60%
| pure. Still, if it were cheaper to start with a chunk of
| feldspar than an old panel, I don't think we'd have to worry
| about the lack of virgin materials.
| teruakohatu wrote:
| The world is producing vast quantities of solar panels, which
| will eventually end up in landfills. What they are doing is
| essentially just what say: removing sand from panels and
| separating the contaminants which can then be dealt with
| separately.
| hedora wrote:
| Sand mining causes significant environmental damage, and
| there's a shortage of sand from the less-delicate sources.
|
| Also, I imagine it takes a lot of energy to go from "we found
| this on the beach" to "this is ultrapure silicon for use in
| solar cells". We have essentially unlimited aluminum too.
|
| The purpose of recycled cans is saving energy and reducing
| pollution from extraction. I do wonder whether it's easier to
| start with glass from beverage bottles than from solar panels
| though.
| pfdietz wrote:
| Silicon is purified by conversion to trichlorosilane,
| followed by distillation. One doesn't need extremely pure
| silica as the input. An intermediate step for this is
| reduction of silica to metallurgical silicon which is not
| anywhere close to semiconductor grade (it's about 98% pure).
|
| Where one DOES want pure silica is in making the crucibles
| where silicon is melted. There's a particular mine in North
| Carolina (Spruce Pine) where this very pure silica is mined.
| We could make artificial pure silica, but this stuff is
| cheaper.
| orev wrote:
| All sand is not equal, and it is slowly becoming more scarce.
| There are already sand mafias popping up due to certain types
| of sand (used in construction) becoming hard to find. There are
| black markets, and shady practices already happening. Maybe the
| sand needed for semiconductors doesn't fall into this category
| yet (I don't know, maybe it does), but it doesn't hurt to start
| thinking about it.
| scotty79 wrote:
| We are already running out of one type if sand mostly due to
| the amount of concrete we make.
| _Microft wrote:
| The Fraunhofer Society is a research organization (tending
| towards the applied/engineering end of the spectrum), so the
| answer might be simply "because they can?".
|
| Beside that: if they can work out the economics of the process,
| why not? Waste disposal costs money which might shift the
| economics in their favour (as people would have to pay someone
| for disposal anyways, so they could as well pay the people who
| make new panels from old ones).
| [deleted]
| baybal2 wrote:
| How long would they last?
|
| A lot of record breaking cells are lab only due to them degrading
| so fast that it precludes any practical use.
|
| General rule, the purer the silicon, the less doping, the longer
| its life, albeit at low efficiency.
|
| Silicon cells above 20% were in labs decades ago, but practical
| designs with long life only appeared last decade.
| rererr wrote:
| To my knowledge, having a couple years working photovoltaic
| research, degradation is only a significant issue in the
| perovskite solar cells (basically organic molecules that react
| with or at least see property changes with adsorption of
| water). Others get maybe a bit of degradation (a couple percent
| maybe) in the near term, but what they are is what they are.
| Solid state devices are pretty stable, which is also why CPUs
| can work for long periods of time (same basic building block,
| the PN junction, and yet much more complicated).
|
| The problem with solar cell efficiency as being the top-line
| metric is that is that it outright ignores a very complex
| system. Never mind you got to string them together for panels.
| Nevermind you just spent $10k making that one cell and your
| yield is pretty garbage. Never mind that an incrementally more
| efficient cell doesn't move the needle much when a large
| fraction of the cost is delivery and installation. Nevermind
| intermittency is a huge problem for the technology in general.
|
| Another important thing to look into for the photovoltaic
| problem is the Shockley-Queisser limit [1], which shows that we
| don't even have a lot of room to run in terms of basic
| efficiency improvements (~50% for Si). That's a fundamental
| physical limit for single junction cells.
|
| In terms of scientific advancements, I would get much more
| excited to see improvements in energy storage technology.
| Photovoltaic deployment is probably also going to see more
| advancement based on improvements in manufacturing, logistics,
| and building construction. At this point achieving cell
| efficiency records is more just for the sci-peen.
|
| [1]
| https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi...
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