5 ms·

As usual with press releases, this pretends there is no prior art. Of course, stacking solar cells to increase efficiency has been a thing for five decades: htt

As usual with press releases, this pretends there is no prior art. Of course, stacking solar cells to increase efficiency has been a thing for five decades: https://en.wikipedia.org/wiki/Multi-junction_solar_cell https://en.wikipedia.org/wiki/Multi-junction_solar_cell

ndonnellan 9y ago
Yep, see 40% cells used 4 years ago in http://www.businesswire.com/news/home/20130426005162/en/Amonix-Achieves-World-Record-PV-Module-Efficiency http://www.businesswire.com/news/home/20130426005162/en/Amon... (36% eff in practical application due to system losses)
- k__ 9y ago
  Nice. What's the maximum? What's the current standard?
  - hwillis 9y ago
    Max so far is 46%[1], max theoretical is 86.8%[2] Most solar panels are 15% or better. The best residential cells are 22.2%[3], the commercial cells are 25.3%. The theoretical maximum efficiency of single-layer silicon PV cells is ~32%. [1]: https://www.nrel.gov/pv/assets/images/efficiency-chart.png https://www.nrel.gov/pv/assets/images/efficiency-chart.png [2]: https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi... [3]: https://us.sunpower.com/sites/sunpower/files/media-library/data-sheets/ds-x22-series-360-residential-solar-panels.pdf https://us.sunpower.com/sites/sunpower/files/media-library/d...
    - schoen 9y ago
      That's awesome. I remember always hearing 10% when I was a kid, which looks about right on that first chart, assuming it takes a few years before things are commercialized. It's terrific to see the march of improvements in efficiency.
    - deepsun 9y ago
      Curious, what is on spacecrafts. Maybe not really efficient at all, because weight and reliability is way more important out there, and also abundance of raw sunlight.
      - extrapickles 9y ago
        Usually much better (5-10%) as cost is no object, and they don't have the losses involved with the protective glass that terrestrial applications need. Edit: and they are usually triple junction.
      - mlindner 9y ago
        We used triple-junction solar cells on our satellite. If I remember right the cells ran somewhere around $100-$200 per square inch. I don't remember the efficiency, but they were left-over dumped cells that were donated to us by some group at NASA because they "expired" (they're kept under a nitrogen purge because they oxidize slowly and these had a leak, if memory serves, still worked great though) and a few were broken as they are more fragile than glass and are about as thin as a sheet of paper. They glow bright red when you forward bias them which you can use to visually detect dead portions of the cell/damage.
    - lucb1e 9y ago
      > max theoretical is 86.8% I recall hearing the theoretical max was somewhere around 36%, though it could well be my memory is faulty. I think this was from a video from around 2005. Is this "theoretical max" going up over time or do I misremember?
      - rsfern 9y ago
        I think 31% is the thermodynamic limit for a single p-n junction, and 86.6 is for an infinite stack of them [0]. I'm not sure whether these limits apply to non-planar geometries. [0]: https://en.m.wikipedia.org/wiki/Thermodynamic_efficiency_limit https://en.m.wikipedia.org/wiki/Thermodynamic_efficiency_lim...
      - hwillis 9y ago
        86.8% is for an infinite number of layers with concentrated solar. 33.7% is the max for a single layer p-n junction, which is what most readily available cells are. The most expensive, high efficiency cells, like those on spacecraft, are 3 layer. They are too expensive to be practical on Earth.
  - philipkglass 9y ago
    The current state of the art for commercialized multi-junction cells, used almost exclusively in space applications, is 30-32% cell efficiency: http://www.spectrolab.com/solarcells.htm http://www.spectrolab.com/solarcells.htm http://www.azurspace.com/index.php/en/products/products-space/space-solar-cells http://www.azurspace.com/index.php/en/products/products-spac... https://solaerotech.com/products/space-solar-cells-coverglass-interconnected-cells-cic/ https://solaerotech.com/products/space-solar-cells-coverglas... Multi-junction cells similar to these have so far reached efficiencies up into the mid-40% range with optically concentrated sunlight under experimental conditions, though such high efficiencies have not been reached in mass production. Multi-junction cells represent less than 0.01% of annual PV cell production. About 95% of annual PV cell production is based on different variants of single-junction crystalline silicon, with current commercial cell efficiencies in the 16-25% range. The 30% cells for space use also sell for more than 1000x the price-per-watt of a simple 16% silicon cell. A theoretical "infinite-junction" solar cell could achieve up to 68.7% efficiency under full-power illumination from the sun on a clear day, or up to 86.8% efficiency on a clear day under optically concentrated sunlight: https://en.wikipedia.org/wiki/Solar_cell_efficiency#Thermodynamic_efficiency_limit_and_infinite-stack_limit https://en.wikipedia.org/wiki/Solar_cell_efficiency#Thermody... The theoretical limit for single-junction silicon cells is 29.4%: http://ieeexplore.ieee.org/document/6557081/ http://ieeexplore.ieee.org/document/6557081/ SunPower has reached just over 25% efficiency industrially for its best cells, which are single junction silicon using advanced cell structures. The highest conversion ever achieved experimentally for single-junction silicon is 26.6%, announced just a couple of weeks ago: http://www.sciencedirect.com/science/article/pii/S092702481730332X http://www.sciencedirect.com/science/article/pii/S0927024817... The experimenters combined two leading industrial techniques for high efficiency silicon cells (interdigitated back contact structure, like SunPower uses, and heterojunction cells using amorphous silicon, like Panasonic/Tesla use) to reach the 26.6% record.
    - k__ 9y ago
      Cool, thanks :D What does an increase of 10% mean? That I could get 10% more Watts from the same area of panels? How much do we need? Would a houshold in Canada need much more panels than one in Mexico? Is 15% or 20% already enough to power a whole 1-family-house? Are batteries or PV panels the bigger problem here?
  - deleted 9y ago
    [deleted]
tssva 9y ago
I think you need to reread the article. "Conventional multi-junction solar cells" are mentioned in a quote from the lead author of the study.
- sbierwagen 9y ago
  I don't understand your objection. The title of the press release is "Scientists Design Solar Cell That Captures Nearly All Energy of Solar Spectrum". That title is not "Scientists develop new multijunction cell", but instead implies they've designed something novel. First paragraph: "Scientists have designed and constructed a prototype for a new solar cell that integrates multiple cells stacked into a single device capable of capturing nearly all of the energy in the solar spectrum. The new design converts direct sunlight to electricity with 44.5 percent efficiency, giving it the potential to become the most efficient solar cell in the world." That describes a multijunction cell, without mentioning that the idea is decades old. They describe an efficiency of 44.5%, without mentioning that other multijunction cells beat that efficiency years ago. I think you need to reread the article. Mentioning multijunction cells in the fourth paragraph is not a sufficient description of prior art.

ndonnellan 9y ago

Yep, see 40% cells used 4 years ago in http://www.businesswire.com/news/home/20130426005162/en/Amonix-Achieves-World-Record-PV-Module-Efficiency http://www.businesswire.com/news/home/20130426005162/en/Amon... (36% eff in practical application due to system losses)

k__ 9y ago
Nice. What's the maximum? What's the current standard?
- hwillis 9y ago
  Max so far is 46%[1], max theoretical is 86.8%[2] Most solar panels are 15% or better. The best residential cells are 22.2%[3], the commercial cells are 25.3%. The theoretical maximum efficiency of single-layer silicon PV cells is ~32%. [1]: https://www.nrel.gov/pv/assets/images/efficiency-chart.png https://www.nrel.gov/pv/assets/images/efficiency-chart.png [2]: https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi... [3]: https://us.sunpower.com/sites/sunpower/files/media-library/data-sheets/ds-x22-series-360-residential-solar-panels.pdf https://us.sunpower.com/sites/sunpower/files/media-library/d...
  - schoen 9y ago
    That's awesome. I remember always hearing 10% when I was a kid, which looks about right on that first chart, assuming it takes a few years before things are commercialized. It's terrific to see the march of improvements in efficiency.
  - deepsun 9y ago
    Curious, what is on spacecrafts. Maybe not really efficient at all, because weight and reliability is way more important out there, and also abundance of raw sunlight.
    - extrapickles 9y ago
      Usually much better (5-10%) as cost is no object, and they don't have the losses involved with the protective glass that terrestrial applications need. Edit: and they are usually triple junction.
    - mlindner 9y ago
      We used triple-junction solar cells on our satellite. If I remember right the cells ran somewhere around $100-$200 per square inch. I don't remember the efficiency, but they were left-over dumped cells that were donated to us by some group at NASA because they "expired" (they're kept under a nitrogen purge because they oxidize slowly and these had a leak, if memory serves, still worked great though) and a few were broken as they are more fragile than glass and are about as thin as a sheet of paper. They glow bright red when you forward bias them which you can use to visually detect dead portions of the cell/damage.
  - lucb1e 9y ago
    > max theoretical is 86.8% I recall hearing the theoretical max was somewhere around 36%, though it could well be my memory is faulty. I think this was from a video from around 2005. Is this "theoretical max" going up over time or do I misremember?
    - rsfern 9y ago
      I think 31% is the thermodynamic limit for a single p-n junction, and 86.6 is for an infinite stack of them [0]. I'm not sure whether these limits apply to non-planar geometries. [0]: https://en.m.wikipedia.org/wiki/Thermodynamic_efficiency_limit https://en.m.wikipedia.org/wiki/Thermodynamic_efficiency_lim...
    - hwillis 9y ago
      86.8% is for an infinite number of layers with concentrated solar. 33.7% is the max for a single layer p-n junction, which is what most readily available cells are. The most expensive, high efficiency cells, like those on spacecraft, are 3 layer. They are too expensive to be practical on Earth.
- philipkglass 9y ago
  The current state of the art for commercialized multi-junction cells, used almost exclusively in space applications, is 30-32% cell efficiency: http://www.spectrolab.com/solarcells.htm http://www.spectrolab.com/solarcells.htm http://www.azurspace.com/index.php/en/products/products-space/space-solar-cells http://www.azurspace.com/index.php/en/products/products-spac... https://solaerotech.com/products/space-solar-cells-coverglass-interconnected-cells-cic/ https://solaerotech.com/products/space-solar-cells-coverglas... Multi-junction cells similar to these have so far reached efficiencies up into the mid-40% range with optically concentrated sunlight under experimental conditions, though such high efficiencies have not been reached in mass production. Multi-junction cells represent less than 0.01% of annual PV cell production. About 95% of annual PV cell production is based on different variants of single-junction crystalline silicon, with current commercial cell efficiencies in the 16-25% range. The 30% cells for space use also sell for more than 1000x the price-per-watt of a simple 16% silicon cell. A theoretical "infinite-junction" solar cell could achieve up to 68.7% efficiency under full-power illumination from the sun on a clear day, or up to 86.8% efficiency on a clear day under optically concentrated sunlight: https://en.wikipedia.org/wiki/Solar_cell_efficiency#Thermodynamic_efficiency_limit_and_infinite-stack_limit https://en.wikipedia.org/wiki/Solar_cell_efficiency#Thermody... The theoretical limit for single-junction silicon cells is 29.4%: http://ieeexplore.ieee.org/document/6557081/ http://ieeexplore.ieee.org/document/6557081/ SunPower has reached just over 25% efficiency industrially for its best cells, which are single junction silicon using advanced cell structures. The highest conversion ever achieved experimentally for single-junction silicon is 26.6%, announced just a couple of weeks ago: http://www.sciencedirect.com/science/article/pii/S092702481730332X http://www.sciencedirect.com/science/article/pii/S0927024817... The experimenters combined two leading industrial techniques for high efficiency silicon cells (interdigitated back contact structure, like SunPower uses, and heterojunction cells using amorphous silicon, like Panasonic/Tesla use) to reach the 26.6% record.
  - k__ 9y ago
    Cool, thanks :D What does an increase of 10% mean? That I could get 10% more Watts from the same area of panels? How much do we need? Would a houshold in Canada need much more panels than one in Mexico? Is 15% or 20% already enough to power a whole 1-family-house? Are batteries or PV panels the bigger problem here?
- deleted 9y ago
  [deleted]

tssva 9y ago

I think you need to reread the article. "Conventional multi-junction solar cells" are mentioned in a quote from the lead author of the study.

sbierwagen 9y ago
I don't understand your objection. The title of the press release is "Scientists Design Solar Cell That Captures Nearly All Energy of Solar Spectrum". That title is not "Scientists develop new multijunction cell", but instead implies they've designed something novel. First paragraph: "Scientists have designed and constructed a prototype for a new solar cell that integrates multiple cells stacked into a single device capable of capturing nearly all of the energy in the solar spectrum. The new design converts direct sunlight to electricity with 44.5 percent efficiency, giving it the potential to become the most efficient solar cell in the world." That describes a multijunction cell, without mentioning that the idea is decades old. They describe an efficiency of 44.5%, without mentioning that other multijunction cells beat that efficiency years ago. I think you need to reread the article. Mentioning multijunction cells in the fourth paragraph is not a sufficient description of prior art.