4 ms·

Efficiency of 0.25%. Like a dancing bear, the amazing thing is that it dances at all, not that it dances well.

kragen 2y ago
That's still 2.5 watts per square meter in direct sun, 0.5 watts per square meter as a round-the-clock average. More than enough to keep your cellphone charged with a square meter. A section of a farm is 2.6 million square meters. The bigger question is not what its efficiency is, which is to say, how much sunlight it needs per watt, but what its material consumption is—how much bismuth it needs per watt. Sunlight is abundant; bismuth isn't. But presumably it can be improved.
- pfdietz 2y ago
  Or just cover 1% of that area with PV.
  - kilpikaarna 2y ago
    Can you make PV at home? Thermoelectric devices are interesting because they can be manufactured using comparatively simple metallurgy. Not because their efficiency is competitive with semiconductor photovoltaics.
    - pfdietz 2y ago
      > Can you make PV at home? https://hackaday.com/2018/01/26/home-brew-solar-cells-for-the-chemically-curious/ https://hackaday.com/2018/01/26/home-brew-solar-cells-for-th... Not anywhere near as efficient as commercial PV cells, of course.
      - kilpikaarna 2y ago
        This is by the same person as the OP btw (and linked in the original article).
        pfdietz 2y ago
        So why did you ask the question, if it was answered in the original article?
        kilpikaarna 2y ago
        Rethorical question, sorry.
    - gene-h 2y ago
      Perovskite solar cells could be and dye sensitized solar cells can be[0]. The better question is why should one make solar cells at home? [0]https://www.instructables.com/How-to-Build-Use-A-Dye-Sensitized-Solar-Cell-DS/ https://www.instructables.com/How-to-Build-Use-A-Dye-Sensiti...
      - AtlasBarfed 2y ago
        Solar panels enabling offgrid power is tagcloud-related to surviving human civilization collapse. We're entering an era of decreased globalism, where megacorporation scale actually becomes a danger to society due to reduced warehousing/stockpiling and long extended supply lines, and of course offshored manufacturing that goes with that.
        margalabargala 2y ago
        Before solar panels become impossible to purchase, they will be difficult to purchase. Before solar panels become difficult to purchase, they will become more expensive to purchase. Mass produced solar panels have been getting both cheaper and easier to get. What you describe could happen, but it's far enough off that we have not seen even the first warning signs yet.
        lukan 2y ago
        "What you describe could happen, but it's far enough off that we have not seen even the first warning signs yet." Well, some disagree on there being no warning signs. https://thebulletin.org/doomsday-clock/2025-statement/ https://thebulletin.org/doomsday-clock/2025-statement/
        kragen 2y ago
        Yeah, if some shithead nukes China, solar panels would get expensive in a hurry.
        margalabargala 2y ago
        Okay, sure, but that's no different than the same identical "warning signs" that people have been flipping out about since the 1960s. Maybe some individual country will have some collapse, but all of human civilization will not. I.maintain that if you're worried about any of that, you are still better off stockpiling panels now, than developing ways to make your own much worse ones in your backyard. DIY photovoltaics can be a fun hobby but for someone worried about an actual collapse they can acquire a lifetime supply of solar panels and batteries for less money and time than setting up a custom fab that's able to operate in a collapse situation.
  - kragen 2y ago
    You can't reach 25% efficiency with monocrystalline silicon PV even with the entire industrial economy backing you up; those efficiencies require multijunction solar cells. Conveniently homebrewable PV panels, like the ZnO:Mg/Cu2O cells you link below, are closer to 1% efficient. The author reports 525mV and 0.9mA/cm², which works out to 4.7W/m², which would be 0.5% efficient if the illumination is one sun. They probably are a better approach than the thermoelectric approach, because not only are they more efficient, they use more abundant materials and thinner films of them. But either approach could plausibly defeat the other.
    - pfdietz 2y ago
      Oh good grief. The point I was making didn't require that it be exactly 1%.
      - kragen 2y ago
        With Simplifier's homebrew PV cells, it's closer to 50%.
        pfdietz 2y ago
        Obviously I wasn't referring to those, which are also a "dancing bear" technology.
    - philipkglass 2y ago
      Longi has demonstrated a champion monocrystalline silicon cell at 27.3% efficiency and it has silicon cells over 26% efficiency in mass production. It has demonstrated a champion silicon module at 25.4% efficiency. https://www.longi.com/eu/news/25-4-module-efficiency-world-record-hpbc/ https://www.longi.com/eu/news/25-4-module-efficiency-world-r...
      - kragen 2y ago
        Wow, I appreciate the correction! I'm apparently several months out of date.
- selimthegrim 2y ago
  You can make Schottky solar cells too with bismuth but as others have pointed out optimum operating temperature is different for thermoelectrics.
PaulHoule 2y ago
The best use of themovoltaics I've seen is https://www.rockfordchimneysupply.com/products/thermo-self-powered-stove-fan https://www.rockfordchimneysupply.com/products/thermo-self-p... since you've got a concentrated heat source that you want to spread around. Themoelectric devices have been active research field for a long time and there is still some hope of improvement because it is a largely a matter of discovering materials with a high electrical conductivity and poor thermal conductivity. https://en.wikipedia.org/wiki/Thermoelectric_effect https://en.wikipedia.org/wiki/Thermoelectric_effect

That's still 2.5 watts per square meter in direct sun, 0.5 watts per square meter as a round-the-clock average. More than enough to keep your cellphone charged with a square meter. A section of a farm is 2.6 million square meters. The bigger question is not what its efficiency is, which is to say, how much sunlight it needs per watt, but what its material consumption is—how much bismuth it needs per watt. Sunlight is abundant; bismuth isn't. But presumably it can be improved.

pfdietz 2y ago
Or just cover 1% of that area with PV.
- kilpikaarna 2y ago
  Can you make PV at home? Thermoelectric devices are interesting because they can be manufactured using comparatively simple metallurgy. Not because their efficiency is competitive with semiconductor photovoltaics.
  - pfdietz 2y ago
    > Can you make PV at home? https://hackaday.com/2018/01/26/home-brew-solar-cells-for-the-chemically-curious/ https://hackaday.com/2018/01/26/home-brew-solar-cells-for-th... Not anywhere near as efficient as commercial PV cells, of course.
    - kilpikaarna 2y ago
      This is by the same person as the OP btw (and linked in the original article).
      - pfdietz 2y ago
        So why did you ask the question, if it was answered in the original article?
        kilpikaarna 2y ago
        Rethorical question, sorry.
  - gene-h 2y ago
    Perovskite solar cells could be and dye sensitized solar cells can be[0]. The better question is why should one make solar cells at home? [0]https://www.instructables.com/How-to-Build-Use-A-Dye-Sensitized-Solar-Cell-DS/ https://www.instructables.com/How-to-Build-Use-A-Dye-Sensiti...
    - AtlasBarfed 2y ago
      Solar panels enabling offgrid power is tagcloud-related to surviving human civilization collapse. We're entering an era of decreased globalism, where megacorporation scale actually becomes a danger to society due to reduced warehousing/stockpiling and long extended supply lines, and of course offshored manufacturing that goes with that.
      - margalabargala 2y ago
        Before solar panels become impossible to purchase, they will be difficult to purchase. Before solar panels become difficult to purchase, they will become more expensive to purchase. Mass produced solar panels have been getting both cheaper and easier to get. What you describe could happen, but it's far enough off that we have not seen even the first warning signs yet.
        lukan 2y ago
        "What you describe could happen, but it's far enough off that we have not seen even the first warning signs yet." Well, some disagree on there being no warning signs. https://thebulletin.org/doomsday-clock/2025-statement/ https://thebulletin.org/doomsday-clock/2025-statement/
        kragen 2y ago
        Yeah, if some shithead nukes China, solar panels would get expensive in a hurry.
        margalabargala 2y ago
        Okay, sure, but that's no different than the same identical "warning signs" that people have been flipping out about since the 1960s. Maybe some individual country will have some collapse, but all of human civilization will not. I.maintain that if you're worried about any of that, you are still better off stockpiling panels now, than developing ways to make your own much worse ones in your backyard. DIY photovoltaics can be a fun hobby but for someone worried about an actual collapse they can acquire a lifetime supply of solar panels and batteries for less money and time than setting up a custom fab that's able to operate in a collapse situation.
- kragen 2y ago
  You can't reach 25% efficiency with monocrystalline silicon PV even with the entire industrial economy backing you up; those efficiencies require multijunction solar cells. Conveniently homebrewable PV panels, like the ZnO:Mg/Cu2O cells you link below, are closer to 1% efficient. The author reports 525mV and 0.9mA/cm², which works out to 4.7W/m², which would be 0.5% efficient if the illumination is one sun. They probably are a better approach than the thermoelectric approach, because not only are they more efficient, they use more abundant materials and thinner films of them. But either approach could plausibly defeat the other.
  - pfdietz 2y ago
    Oh good grief. The point I was making didn't require that it be exactly 1%.
    - kragen 2y ago
      With Simplifier's homebrew PV cells, it's closer to 50%.
      - pfdietz 2y ago
        Obviously I wasn't referring to those, which are also a "dancing bear" technology.
  - philipkglass 2y ago
    Longi has demonstrated a champion monocrystalline silicon cell at 27.3% efficiency and it has silicon cells over 26% efficiency in mass production. It has demonstrated a champion silicon module at 25.4% efficiency. https://www.longi.com/eu/news/25-4-module-efficiency-world-record-hpbc/ https://www.longi.com/eu/news/25-4-module-efficiency-world-r...
    - kragen 2y ago
      Wow, I appreciate the correction! I'm apparently several months out of date.
selimthegrim 2y ago
You can make Schottky solar cells too with bismuth but as others have pointed out optimum operating temperature is different for thermoelectrics.

PaulHoule 2y ago

The best use of themovoltaics I've seen is https://www.rockfordchimneysupply.com/products/thermo-self-powered-stove-fan https://www.rockfordchimneysupply.com/products/thermo-self-p... since you've got a concentrated heat source that you want to spread around. Themoelectric devices have been active research field for a long time and there is still some hope of improvement because it is a largely a matter of discovering materials with a high electrical conductivity and poor thermal conductivity. https://en.wikipedia.org/wiki/Thermoelectric_effect https://en.wikipedia.org/wiki/Thermoelectric_effect