3 ms·

Has anyone done any studies on the co2 emission of manufacturing one panel like this? Curious how long it will take to offset.

ponco 1y ago
A simple Google tells me (as I was curious) it's between 6 months to 20 years, with the average being 2 years. https://www.google.com/search?q=carbon+payback+time+solar+panels+study https://www.google.com/search?q=carbon+payback+time+solar+pa... Hard to imagine a large scale rollout like this would have been on the low quality side (plus hey its Germany after all).
elashri 1y ago
Yes there are many studies that did life cycle assessment of them. This is a good source [1] that analyze about 400 of these life cycle assessments. [1] https://docs.nrel.gov/docs/fy13osti/56487.pdf https://docs.nrel.gov/docs/fy13osti/56487.pdf
- slow_typist 1y ago
  That is more than ten years old, efficiency of PV is much better today, which probably brings emissions down a bit.
  - kragen 1y ago
    Efficiency has improved somewhat, but also, the cost to manufacture PV is enormously lower than it was then, which means that it's using much less materials and energy to produce. Therefore the energy payback time should be much shorter.
    - slow_typist 1y ago
      How much shorter depends on the fraction of the energy cost in the first place then. Price is not even an upper bound for energy which is cheap in China, and also production is probably subsidised.
      - kragen 1y ago
        It wouldn't be an upper bound if energy were free, but it isn't. https://worldpopulationreview.com/country-rankings/cost-of-electricity-by-country https://worldpopulationreview.com/country-rankings/cost-of-e... lists China as US$0.08/kWh, but that's the residential price; industry pays a bit more. But it's a countrywide average. Intensive investigations of Chinese "subsidies" from the US Department of Commerce have come up with embarrassingly little. The current €0.100/Wp price level (12¢/Wp) combined with the US$0.08/kWh given above does give us an upper bound of 1500 hours of full sun for the energy payback time. At a Californian 29% capacity factor, that's 7 months of operation. But in fact not 100% of the cost of the solar module is the cost of energy; there are some labor and raw materials costs as well, as well as capital costs and, astoundingly, some profit. So 3 months is probably a better estimate.
        slow_typist 1y ago
        Process energy will still be a lot cheaper than .08 US$/kWh in China. I doubt they process glass with electric ovens. OTOH that is primary energy then, which kind of supports your argument. Still other emissions in the silicon supply chain that cause global warming are also relevant. If I find the time, I‘ll look for recent LCA.
        slow_typist 1y ago
        Found these slides from Fraunhofer: https://www.ise.fraunhofer.de/content/dam/ise/de/documents/publications/studies/Photovoltaics-Report.pdf https://www.ise.fraunhofer.de/content/dam/ise/de/documents/p... Energy payback time around one year (p. 8)
        kragen 1y ago
        I'm delighted to see Fraunhofer's report! I'll read it carefully. You are probably right about the glass. Processing glass in electric furnaces has been a well-established technology for many generations, but it is more expensive than fossil-fuel-fired furnaces, and is used for making more expensive kinds of glass. But the glass in solar panels is an especially cheap kind of glass. Coal is probably the cheapest form of energy. https://www.coal-price.com/ https://www.coal-price.com/ says that currently in China coal is on the order of US$100 per tonne. Coal has up to 33MJ/kg, so that works out to 0.3¢ per megajoule, or 1.1¢ per kilowatt hour, or more if the US$100/tonne coal isn't the best anthracite. You probably can't literally run a glassmaking furnace with a coal firebox, because of the contaminants from the coal, but you almost certainly can't run it on cheaper energy than that. If 100% of the cost of the solar panels were coal energy instead of electric, that would extend my upper bound out from 7 months to a bit over 4 years. This seems to be in rough agreement with Fraunhofer's more informed estimate that you cite.
slow_typist 1y ago
585 kWh/m^2 median energy consumption for production according to a 2013 study cited on the Wikipedia article on energy return on investment. 440 W panel has about 2 m^2. It is probably a tad better now, because lower mass of silicon per meter squared. That translates to roughly 2.5 years of energy payback time in Germany under good conditions (azimuth SE to SW and elevation about 30 to 60 degrees, no shadow). Give a few extra months for the inverter and system losses. If you want to know exactly there are commercial databases used for LCA calculations. The carbon emissions depend on the energy mix of the supply chain (which is mostly in China, since Germany totally butchered domestic production). And the total climate effect is amplified by other emissions (leaking of technical gases in silicon production? But now I am way out of my field of expertise.) OTOH hand to calculate the offset of emissions you need to know what is going on in the grid. If windmills are shut down around noon to make room for PV, the offset is zero.
- cmenge 1y ago
  > If windmills are shut down around noon to make room for PV, the offset is zero. Very important point that is often ignored.
- nebula8804 1y ago
  Wow that is pretty good, lines up pretty nicely with the approx monetary break even as well. Impressive! Wonder if there is anything that can be done to lengthen the life of the panel as much as possible. I've read elsewhere that solar panels have a theoretical lifespan of 25 years with the panels slowly degrading and not failing all at once. I dont know if these specific panels are different but I wonder if the panels are kept clean or something if that would maximize the lifespan?
  - slow_typist 1y ago
    Degradation is more or less solved. Producers guarantee a maximum of .4 % power degradation per year for 25 or even 30 years. That may be offset buy rising energy costs alone. May be not if someone manages to producer cheaper batteries. Right now owners of older rooftop photovoltaics in Germany swap functioning modules for newer ones with better efficiency. Even if some small percentage of older modules fails it is probably not the fault of the cells but of connections in the module due to moisture. It is a system. In theory you can take the cells and build new modules. But that is too expensive compared to buying new modules.
cmenge 1y ago
Does importing a solar count against your countries co2 balance?

ponco 1y ago

A simple Google tells me (as I was curious) it's between 6 months to 20 years, with the average being 2 years. https://www.google.com/search?q=carbon+payback+time+solar+panels+study https://www.google.com/search?q=carbon+payback+time+solar+pa... Hard to imagine a large scale rollout like this would have been on the low quality side (plus hey its Germany after all).

elashri 1y ago

Yes there are many studies that did life cycle assessment of them. This is a good source [1] that analyze about 400 of these life cycle assessments. [1] https://docs.nrel.gov/docs/fy13osti/56487.pdf https://docs.nrel.gov/docs/fy13osti/56487.pdf

slow_typist 1y ago
That is more than ten years old, efficiency of PV is much better today, which probably brings emissions down a bit.
- kragen 1y ago
  Efficiency has improved somewhat, but also, the cost to manufacture PV is enormously lower than it was then, which means that it's using much less materials and energy to produce. Therefore the energy payback time should be much shorter.
  - slow_typist 1y ago
    How much shorter depends on the fraction of the energy cost in the first place then. Price is not even an upper bound for energy which is cheap in China, and also production is probably subsidised.
    - kragen 1y ago
      It wouldn't be an upper bound if energy were free, but it isn't. https://worldpopulationreview.com/country-rankings/cost-of-electricity-by-country https://worldpopulationreview.com/country-rankings/cost-of-e... lists China as US$0.08/kWh, but that's the residential price; industry pays a bit more. But it's a countrywide average. Intensive investigations of Chinese "subsidies" from the US Department of Commerce have come up with embarrassingly little. The current €0.100/Wp price level (12¢/Wp) combined with the US$0.08/kWh given above does give us an upper bound of 1500 hours of full sun for the energy payback time. At a Californian 29% capacity factor, that's 7 months of operation. But in fact not 100% of the cost of the solar module is the cost of energy; there are some labor and raw materials costs as well, as well as capital costs and, astoundingly, some profit. So 3 months is probably a better estimate.
      - slow_typist 1y ago
        Process energy will still be a lot cheaper than .08 US$/kWh in China. I doubt they process glass with electric ovens. OTOH that is primary energy then, which kind of supports your argument. Still other emissions in the silicon supply chain that cause global warming are also relevant. If I find the time, I‘ll look for recent LCA.
        slow_typist 1y ago
        Found these slides from Fraunhofer: https://www.ise.fraunhofer.de/content/dam/ise/de/documents/publications/studies/Photovoltaics-Report.pdf https://www.ise.fraunhofer.de/content/dam/ise/de/documents/p... Energy payback time around one year (p. 8)
        kragen 1y ago
        I'm delighted to see Fraunhofer's report! I'll read it carefully. You are probably right about the glass. Processing glass in electric furnaces has been a well-established technology for many generations, but it is more expensive than fossil-fuel-fired furnaces, and is used for making more expensive kinds of glass. But the glass in solar panels is an especially cheap kind of glass. Coal is probably the cheapest form of energy. https://www.coal-price.com/ https://www.coal-price.com/ says that currently in China coal is on the order of US$100 per tonne. Coal has up to 33MJ/kg, so that works out to 0.3¢ per megajoule, or 1.1¢ per kilowatt hour, or more if the US$100/tonne coal isn't the best anthracite. You probably can't literally run a glassmaking furnace with a coal firebox, because of the contaminants from the coal, but you almost certainly can't run it on cheaper energy than that. If 100% of the cost of the solar panels were coal energy instead of electric, that would extend my upper bound out from 7 months to a bit over 4 years. This seems to be in rough agreement with Fraunhofer's more informed estimate that you cite.

slow_typist 1y ago

585 kWh/m^2 median energy consumption for production according to a 2013 study cited on the Wikipedia article on energy return on investment. 440 W panel has about 2 m^2. It is probably a tad better now, because lower mass of silicon per meter squared. That translates to roughly 2.5 years of energy payback time in Germany under good conditions (azimuth SE to SW and elevation about 30 to 60 degrees, no shadow). Give a few extra months for the inverter and system losses. If you want to know exactly there are commercial databases used for LCA calculations. The carbon emissions depend on the energy mix of the supply chain (which is mostly in China, since Germany totally butchered domestic production). And the total climate effect is amplified by other emissions (leaking of technical gases in silicon production? But now I am way out of my field of expertise.) OTOH hand to calculate the offset of emissions you need to know what is going on in the grid. If windmills are shut down around noon to make room for PV, the offset is zero.

cmenge 1y ago
> If windmills are shut down around noon to make room for PV, the offset is zero. Very important point that is often ignored.
nebula8804 1y ago
Wow that is pretty good, lines up pretty nicely with the approx monetary break even as well. Impressive! Wonder if there is anything that can be done to lengthen the life of the panel as much as possible. I've read elsewhere that solar panels have a theoretical lifespan of 25 years with the panels slowly degrading and not failing all at once. I dont know if these specific panels are different but I wonder if the panels are kept clean or something if that would maximize the lifespan?
- slow_typist 1y ago
  Degradation is more or less solved. Producers guarantee a maximum of .4 % power degradation per year for 25 or even 30 years. That may be offset buy rising energy costs alone. May be not if someone manages to producer cheaper batteries. Right now owners of older rooftop photovoltaics in Germany swap functioning modules for newer ones with better efficiency. Even if some small percentage of older modules fails it is probably not the fault of the cells but of connections in the module due to moisture. It is a system. In theory you can take the cells and build new modules. But that is too expensive compared to buying new modules.

cmenge 1y ago

Does importing a solar count against your countries co2 balance?