6 ms·

Thermoelectric Solar Panel

50 points by adrianN 2y ago

pfdietz 2y ago
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
VladVladikoff 2y ago
Conventional solar cells also suffer from decreased efficiency (-0.45%/°C) as temperature increases, a the inclusion of TEGs could help dissipate this waste heat while simultaneously increasing solar panel efficiency.
- sunshinesnacks 2y ago
  Minor correction/note: most modern modules/cells have a temperature coefficient in the range of approx. -0.27 to -0.35%/°C. A little better than -0.45%. See fig 14 in [1] for data through 2021/22, and then the more recent transition to n-type cells is helping more [2]. This database [3] doesn't list module release date, but filtering for modules with STC rating over 500 W (decent proxy for "modern") gives an average of -0.34%°C, with a lot at or better than -0.30. [1] https://www.ise.fraunhofer.de/content/dam/ise/de/documents/publications/conference-paper/wcpec-8/Kraeling_3BO141.pdf https://www.ise.fraunhofer.de/content/dam/ise/de/documents/p... [2] https://www.nrel.gov/docs/fy22osti/82871.pdf https://www.nrel.gov/docs/fy22osti/82871.pdf [3] https://github.com/NREL/SAM/blob/patch/deploy/libraries/CEC%20Modules.csv https://github.com/NREL/SAM/blob/patch/deploy/libraries/CEC%...
- itishappy 2y ago
  I've done some research on exactly this, and the efficiencies of TEGs makes this a tough prospect. It started to work out in our favor when using concentrated solar to reduce the amount of paneling needed, but that's no longer an economic driver, and you get a much better return on investment by skipping the TEGs and just plopping a few extra panels down in a lake. You can also flip the configuration and use TEGs to generate power from the solar heating, but the terrible efficiency bites us again and you're better off buying more panels instead.
- danans 2y ago
  In the domestic/commerical, the simplest solution to this is to add more solar to compensate for the drop in efficiency. The next cheapest approach would be to cool the panels by heating water for domestic/industrial use, although the economics aren't as straightforward (depends on the cost of hearting fuel being displaced).
naasking 2y ago
You'll get better efficiency running a Stirling engine from a lightweight solar collector. I actually wonder how it would compare if you equalize the weight.
- kragen 2y ago
  That's an excellent idea, especially if you have aluminized mylar or stainless steel.
- PaulHoule 2y ago
  That's one of those areas that's been talked about in the literature ceaselessly since the 1970s with almost 0% commercialization. That's the normal scenario for energy technologies, cases like PVs and lithium batteries are the rare counterexample.
  - naasking 2y ago
    This is different. This person wants a solution that can be built with common materials with fairly standard tools and at small scale, not a scalable commercial power plant. You can build Stirling engines at home with common materials. We're not comparing 10MW power plants here. So the question is, for a comparable weight and size as this solution, how difficult would it be to build a solar powered Stirling engine and what would the power output be? I expect the Stirling engine to easily come out on top.
    - enva2712 2y ago
      rankine cycle lets you cross vapor dome to access latent heat. enables scaleup
      - hurplederp 2y ago
        [flagged]
        PaulHoule 2y ago
abdullahkhalids 2y ago
Compare this to a Phonovoltaic cell, which is similar to a photovoltaic cell, but instead of converting the energy of a photon into electricity, it converts the energy of phonons - packets of heat vibrations in solids [1]. Unfortunately, no one has as yet found a material with the right combination of thermodynamic properties to realize such devices. Otherwise, you could stick these to any source of high temperature heat and get electricity out. [1] https://en.wikipedia.org/wiki/Phonovoltaic https://en.wikipedia.org/wiki/Phonovoltaic
api 2y ago
Thermoelectric cells or Stirling engines could also be a good option for an off grid location that gets cold in the winter. Heat it with a wood stove, and charge your batteries off it too.
- biomcgary 2y ago
  My house has a super-insulated, passive solar design. I heat it with wood pellet stove, which requires electric power to run the fans and pellet feed system. I've often wanted to add a Stirling engine and a small battery to make it truly grid independent. However, the house design means I only burned about $20 worth of pellets this winter, so the ROI isn't remotely justifiable.
  - abdullahkhalids 2y ago
    What is the total mass of $20 worth of pellets?
- bradfa 2y ago
  There's already some wood pellet boilers on the market which can integrate a sterling engine, to supplement off-grid battery-backed photovoltaic solar panels for local electricity generation. The power output of the sterling engine isn't stellar, but that's to be expected, it's just to help when it's less sunny and you need space heating anyways. For example: https://www.oekofen.com/en-gb/pellematic-condens/ https://www.oekofen.com/en-gb/pellematic-condens/
sitkack 2y ago
Combine a Trombe Wall with a TEC. https://en.wikipedia.org/wiki/Trombe_wall https://en.wikipedia.org/wiki/Trombe_wall https://en.wikipedia.org/wiki/Thermoelectric_cooling https://en.wikipedia.org/wiki/Thermoelectric_cooling I don't think it would make much electricity. But a Trombe wall can trap a huge amount of heat.

50 points by adrianN 2y ago

pfdietz 2y ago

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

VladVladikoff 2y ago

Conventional solar cells also suffer from decreased efficiency (-0.45%/°C) as temperature increases, a the inclusion of TEGs could help dissipate this waste heat while simultaneously increasing solar panel efficiency.

sunshinesnacks 2y ago
Minor correction/note: most modern modules/cells have a temperature coefficient in the range of approx. -0.27 to -0.35%/°C. A little better than -0.45%. See fig 14 in [1] for data through 2021/22, and then the more recent transition to n-type cells is helping more [2]. This database [3] doesn't list module release date, but filtering for modules with STC rating over 500 W (decent proxy for "modern") gives an average of -0.34%°C, with a lot at or better than -0.30. [1] https://www.ise.fraunhofer.de/content/dam/ise/de/documents/publications/conference-paper/wcpec-8/Kraeling_3BO141.pdf https://www.ise.fraunhofer.de/content/dam/ise/de/documents/p... [2] https://www.nrel.gov/docs/fy22osti/82871.pdf https://www.nrel.gov/docs/fy22osti/82871.pdf [3] https://github.com/NREL/SAM/blob/patch/deploy/libraries/CEC%20Modules.csv https://github.com/NREL/SAM/blob/patch/deploy/libraries/CEC%...
itishappy 2y ago
I've done some research on exactly this, and the efficiencies of TEGs makes this a tough prospect. It started to work out in our favor when using concentrated solar to reduce the amount of paneling needed, but that's no longer an economic driver, and you get a much better return on investment by skipping the TEGs and just plopping a few extra panels down in a lake. You can also flip the configuration and use TEGs to generate power from the solar heating, but the terrible efficiency bites us again and you're better off buying more panels instead.
danans 2y ago
In the domestic/commerical, the simplest solution to this is to add more solar to compensate for the drop in efficiency. The next cheapest approach would be to cool the panels by heating water for domestic/industrial use, although the economics aren't as straightforward (depends on the cost of hearting fuel being displaced).

naasking 2y ago

You'll get better efficiency running a Stirling engine from a lightweight solar collector. I actually wonder how it would compare if you equalize the weight.

kragen 2y ago
That's an excellent idea, especially if you have aluminized mylar or stainless steel.
PaulHoule 2y ago
That's one of those areas that's been talked about in the literature ceaselessly since the 1970s with almost 0% commercialization. That's the normal scenario for energy technologies, cases like PVs and lithium batteries are the rare counterexample.
- naasking 2y ago
  This is different. This person wants a solution that can be built with common materials with fairly standard tools and at small scale, not a scalable commercial power plant. You can build Stirling engines at home with common materials. We're not comparing 10MW power plants here. So the question is, for a comparable weight and size as this solution, how difficult would it be to build a solar powered Stirling engine and what would the power output be? I expect the Stirling engine to easily come out on top.
  - enva2712 2y ago
    rankine cycle lets you cross vapor dome to access latent heat. enables scaleup
    - hurplederp 2y ago
      [flagged]
      - PaulHoule 2y ago

abdullahkhalids 2y ago

Compare this to a Phonovoltaic cell, which is similar to a photovoltaic cell, but instead of converting the energy of a photon into electricity, it converts the energy of phonons - packets of heat vibrations in solids [1]. Unfortunately, no one has as yet found a material with the right combination of thermodynamic properties to realize such devices. Otherwise, you could stick these to any source of high temperature heat and get electricity out. [1] https://en.wikipedia.org/wiki/Phonovoltaic https://en.wikipedia.org/wiki/Phonovoltaic

api 2y ago

Thermoelectric cells or Stirling engines could also be a good option for an off grid location that gets cold in the winter. Heat it with a wood stove, and charge your batteries off it too.

biomcgary 2y ago
My house has a super-insulated, passive solar design. I heat it with wood pellet stove, which requires electric power to run the fans and pellet feed system. I've often wanted to add a Stirling engine and a small battery to make it truly grid independent. However, the house design means I only burned about $20 worth of pellets this winter, so the ROI isn't remotely justifiable.
- abdullahkhalids 2y ago
  What is the total mass of $20 worth of pellets?
bradfa 2y ago
There's already some wood pellet boilers on the market which can integrate a sterling engine, to supplement off-grid battery-backed photovoltaic solar panels for local electricity generation. The power output of the sterling engine isn't stellar, but that's to be expected, it's just to help when it's less sunny and you need space heating anyways. For example: https://www.oekofen.com/en-gb/pellematic-condens/ https://www.oekofen.com/en-gb/pellematic-condens/

sitkack 2y ago

Combine a Trombe Wall with a TEC. https://en.wikipedia.org/wiki/Trombe_wall https://en.wikipedia.org/wiki/Trombe_wall https://en.wikipedia.org/wiki/Thermoelectric_cooling https://en.wikipedia.org/wiki/Thermoelectric_cooling I don't think it would make much electricity. But a Trombe wall can trap a huge amount of heat.