3 ms·

The company that makes them: https://www.dyaqua.it/invisiblesolar/_en/ https://www.dyaqua.it/invisiblesolar/_en/

xg15 4y ago
> Inside the module there are incorporated standard monocrystalline silicon cells. The surface, that is opaque at the sight but translucent to sun rays, allows the light to enter and feed the cells. When they talk about "sun rays", do they mean the UV portion of sunlight? Because if the material were transparent to visible light, it would be, well, transparent, wouldn't it?
- serf 4y ago
  >When they talk about "sun rays", do they mean the UV portion of sunlight? I don't think so, because they say they use a standard monocrystalline siicon PV cell -- which are (generally) crappy for UV scavenging. I would guess the material atop the solar cell is either slightly porous or made of a material that is mostly transparent to the right spectra of light, resulting in acceptable losses.
- isoprophlex 4y ago
  Monocrystalline Si has a 1.2 eV band gap iirc, meaning it absorbs everything smaller (more energetic) than ~ 1100 nm. Our eyes see, what, 200-600 nm? Removing the 200-600 nm bit leaves you with approx 50% of the energy left between 600 and 1100 nm, glancing at [1] This is all VERY back of the envelope... but I think these lose around half of the energy you'd get out of conventional panels. [1] https://www.researchgate.net/publication/303914764/figure/download/fig11/AS:668456865263619@1536383944156/Spectral-properties-of-solar-radiation-outside-the-earths-atmosphere-with-normalized.jpg https://www.researchgate.net/publication/303914764/figure/do...
  - scythe 4y ago
    Human visual range is generally 400-700 nm, although some small responsiveness remains up to 800 nm and down to 360. Below 400 nm is usually considered ionizing radiation. But even a ~20% reflection coefficient can make something appear "opaque" if viewed in sunlight and complete darkness behind it.
    - isoprophlex 4y ago
      Good point! You don't need to block the light completely -- I hadn't thought of that!
  - nomel 4y ago
    Here's a plot [1] of PV power, over the whole spectrum. Your envelope appears to be of high quality. It's unfortunate they don't just have actual numbers on their website, which is a pretty terrible indicator, especially with the orientation of the panels being around 45 degrees. [1] http://environmath.org/wp-content/uploads/2020/12/spectral_losses_p1.png http://environmath.org/wp-content/uploads/2020/12/spectral_l... from http://environmath.org/2020/12/17/why-solar-panels-cant-get-much-more-efficient/ http://environmath.org/2020/12/17/why-solar-panels-cant-get-...
  - whydoineedthis 4y ago
    The specs show it as .11 efficiency, and normal panels are about .22, so like litterally 1/2. That's pretty darn good for being visually appealing.
    - simplyaccont 4y ago
      on the other side, normal panels will usually cover part of the roof. those tiles will cover entire roof. hence even if efficiency lower, total output will be higher
      - bruce511 4y ago
        I agree, effeciency is only a concern as a function of space available. If you have a flat roof then all the space is available, and depending on your latitude flat can be a good orientation, especially in summer. Pompei roofs do not appear to be flat, but they do seem to be very low pitch, and the panels are curved, so the whole roof is likely in play. Back to your main point, effeciency in itself doesn't matter. If you have enough space, you just install more. That drives up the installation cost though, and things like cleaning them etc. Of course ultimately everything is space constrained, but generating 11% is better than 0%.
        simplyaccont 4y ago
        It's possible to install more panels, but in many cases it's harder to get coverage of more than 50-70 % of the roof due to it's geometry/multi-slopeness/vents/etc.
  - pjc50 4y ago
    Nice maths. For the benefit of the audience: if you imagine picking a point on that curve and drawing a square under and to the left of it, a solar panel captures only that energy from the orange region. Photons with longer wavelengths aren't captured: not enough energy to push an electron up the bandgap. Photons with shorter wavelengths have more and more energy to push an electron up, but can only capture 1.9226e-19 joules per photon of that energy at 1.2eV.
- Schroedingersat 4y ago
  You could get away with scattering 30% of the red light and have it look opaque. Letting most of the rest through.

xg15 4y ago

> Inside the module there are incorporated standard monocrystalline silicon cells. The surface, that is opaque at the sight but translucent to sun rays, allows the light to enter and feed the cells. When they talk about "sun rays", do they mean the UV portion of sunlight? Because if the material were transparent to visible light, it would be, well, transparent, wouldn't it?

serf 4y ago
>When they talk about "sun rays", do they mean the UV portion of sunlight? I don't think so, because they say they use a standard monocrystalline siicon PV cell -- which are (generally) crappy for UV scavenging. I would guess the material atop the solar cell is either slightly porous or made of a material that is mostly transparent to the right spectra of light, resulting in acceptable losses.
isoprophlex 4y ago
Monocrystalline Si has a 1.2 eV band gap iirc, meaning it absorbs everything smaller (more energetic) than ~ 1100 nm. Our eyes see, what, 200-600 nm? Removing the 200-600 nm bit leaves you with approx 50% of the energy left between 600 and 1100 nm, glancing at [1] This is all VERY back of the envelope... but I think these lose around half of the energy you'd get out of conventional panels. [1] https://www.researchgate.net/publication/303914764/figure/download/fig11/AS:668456865263619@1536383944156/Spectral-properties-of-solar-radiation-outside-the-earths-atmosphere-with-normalized.jpg https://www.researchgate.net/publication/303914764/figure/do...
- scythe 4y ago
  Human visual range is generally 400-700 nm, although some small responsiveness remains up to 800 nm and down to 360. Below 400 nm is usually considered ionizing radiation. But even a ~20% reflection coefficient can make something appear "opaque" if viewed in sunlight and complete darkness behind it.
  - isoprophlex 4y ago
    Good point! You don't need to block the light completely -- I hadn't thought of that!
- nomel 4y ago
  Here's a plot [1] of PV power, over the whole spectrum. Your envelope appears to be of high quality. It's unfortunate they don't just have actual numbers on their website, which is a pretty terrible indicator, especially with the orientation of the panels being around 45 degrees. [1] http://environmath.org/wp-content/uploads/2020/12/spectral_losses_p1.png http://environmath.org/wp-content/uploads/2020/12/spectral_l... from http://environmath.org/2020/12/17/why-solar-panels-cant-get-much-more-efficient/ http://environmath.org/2020/12/17/why-solar-panels-cant-get-...
- whydoineedthis 4y ago
  The specs show it as .11 efficiency, and normal panels are about .22, so like litterally 1/2. That's pretty darn good for being visually appealing.
  - simplyaccont 4y ago
    on the other side, normal panels will usually cover part of the roof. those tiles will cover entire roof. hence even if efficiency lower, total output will be higher
    - bruce511 4y ago
      I agree, effeciency is only a concern as a function of space available. If you have a flat roof then all the space is available, and depending on your latitude flat can be a good orientation, especially in summer. Pompei roofs do not appear to be flat, but they do seem to be very low pitch, and the panels are curved, so the whole roof is likely in play. Back to your main point, effeciency in itself doesn't matter. If you have enough space, you just install more. That drives up the installation cost though, and things like cleaning them etc. Of course ultimately everything is space constrained, but generating 11% is better than 0%.
      - simplyaccont 4y ago
        It's possible to install more panels, but in many cases it's harder to get coverage of more than 50-70 % of the roof due to it's geometry/multi-slopeness/vents/etc.
- pjc50 4y ago
  Nice maths. For the benefit of the audience: if you imagine picking a point on that curve and drawing a square under and to the left of it, a solar panel captures only that energy from the orange region. Photons with longer wavelengths aren't captured: not enough energy to push an electron up the bandgap. Photons with shorter wavelengths have more and more energy to push an electron up, but can only capture 1.9226e-19 joules per photon of that energy at 1.2eV.
Schroedingersat 4y ago
You could get away with scattering 30% of the red light and have it look opaque. Letting most of the rest through.