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The article posted by wolfram74 is part one of two, covering solar PV history up through the early 1980s. Here's part two of the series with more recent histor

The article posted by wolfram74 is part one of two, covering solar PV history up through the early 1980s. Here's part two of the series with more recent history: https://www.construction-physics.com/p/how-did-solar-power-get-cheap-part-28a https://www.construction-physics.com/p/how-did-solar-power-g... Even this fairly long two-part discussion misses some of the more important technical developments of the past 20 years. Converting trichlorosilane to pure silicon via CVD growth in Siemens-type reactors is now much more energy efficient due to changes in rod geometry and heat trapping via reactor design. A significant minority of purified silicon is now manufactured via even more efficient fluidized bed reactors. The solar industry is dominated by Czochralski process monocrystalline silicon, but it's now continuous Czochralski: multiple crystals grown from a single crucible, recharging the molten silicon over time; the traditional process used a crucible once and then discarded it. The dominant silicon material has switched from boron doped p-type silicon to gallium doped p-type silicon (mentioned by pfdietz) to phosphorus doped n-type silicon (used by the currently dominant TOPCon cell technology as well as heterojunction (HJT) cells and most back contact cells). Changes in wafering that you mentioned (like the reduced kerf diamond wire saw) have reduced silicon consumption per wafer and therefore per watt, even holding cell technology constant. The dominant cell technology has moved from Al-BSF to PERC to mono-PERC to TOPCon. Heterojunction and back-contact cells are not yet dominant, but they are manufactured on a multi-gigawatt scale and will probably overtake TOPCon eventually. Each one of these changes has eked out more light conversion efficiency from the same area of silicon. Cells mostly still use screen-printed contacts made from conductive silver pastes, much like 20 years ago, but there has been continuous evolution of the geometry and composition of applied pastes so that silver consumption per watt is now much lower than it used to be. This is important because silver has the highest cost per kilogram of any material in a typical solar panel, and it's the bottleneck material for plans to expand manufacturing past the terawatt scale. Wafer, cell, and module manufacturing have become much more automated. That reduced labor costs, increased throughput, and increased uniformity.

justanotherjoe 2y ago
In terms of resource extraction needed for the batteries and the panels, how sustainable is it? The way I understand it is that you can't really repair broken panels and batteries... Can we still make these after, let's say, 500 years? I have no conception at all in this topic...
- pjc50 2y ago
  No, but I don't see a good reason why you can't recycle the cells especially given they contain a thin layer of silver. Google already finds local recycling firms, since it's required by WEEE. (The 500 years question has issues for all the other sources of energy as well!)
  - deleted 2y ago
    [deleted]
- ZeroGravitas 2y ago
  Yes, batteries are getting better at such a rate that you can recycle old batteries at end of life, lose 10% of the material in that process and build a new battery with new tech and less material that is better than the original. The resource extraction issue is more than these are so useful we're going to build an ever growing amount of them. Luckily they're made from widely available materials, with even more widely available substitutions possible e.g sodium batteries.
- adgjlsfhk1 2y ago
  You can't repair, but you can recycle (although doing so likely isn't very profitable until the exponential price decrease stops)
- ben_w 2y ago
  The resources all start off chemically bound in rocks that aren't famous for spontaneously generating or storing electricity. I don't see it being meaningfully more expensive to process smashed up old PV or batteries than starting from the natural state, and my expectation is that it would be easier. The exception would be if some of the chemical pathways turn into low-concentration atmospheric gasses that then diffuse all over the world, which is how we got the problem with CO2 (and unrelated problems with CFCs).
- pfdietz 2y ago
  Aside from silver for contact wires, PV panels are made (or could be made) with mundane materials available in essentially unlimited amounts. The total mass flowing through new PV panels each year if the US were fully solar powered would be much less than the volume of mundane material flowing through the system already. For example, the EPA estimated that in 2018 the US generated 600 million tons of construction and demolition waste (of which 143 million tons went to landfills.) https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/construction-and-demolition-debris-material https://www.epa.gov/facts-and-figures-about-materials-waste-...
angleofrepose 2y ago
Thank you and other commenters for the great rundowns here. I'm interested in a related question and I wonder if you or others could point me in the right direction: why was the mainstream consensus around solar power (and/or batteries) apparently so wrong for so long? More specifically -- and maybe a better question -- why didn't progress in solar and batteries happen sooner? I'm less interested in blame than in a systems analysis of how in the last half century powerful players seem to have missed the opportunity to start earlier investment in solar and battery technology. Solar and batteries are unique in energy infrastructure, as even any casual observer knows by now, and is certain to change many aspects of politics, industry and culture. It seems an inevitability that energy infrastructure will evolve from large complex components towards small and simple components, and I'm interested in engaging with the history of why "now" is the moment, rather than decades ago.
- mjamesaustin 2y ago
  It's a false assumption that technological progress happens automatically or even that it's based upon the passage of time. Progress happens as a result of many choices made by individuals to invest time and energy solving problems. Why is solar rapidly improving now? Because way more people are invested in making it better. Nascent technologies almost always face an uphill battle because they compete against extremely optimized legacy technologies while themselves having no optimization at first. We only get to the current rapid period of growth because enough people pushed us through the early part of the S curve.
  - angleofrepose 2y ago
    Sure, that makes sense. This is where I'm coming from with my interest in history: I heard an interesting argument somewhere that solar cells are an ideal manufactured good. Whether you are building a module for a calculator or a GW scale plant, the modules are the same. This is fundamentally different for steam turbines. On the "concrete-internal combustion engine" spectrum of complexity, solar modules are closer to concrete and turbines are closer to ICEs. Shouldn't this have led to a special interest in advancing solar module research? Or widespread understanding that eventually the unique set of attributes that define a solar module would lead to it's takeover of a significant portion of global energy generation? Shouldn't that have been apparent from the earliest days of photovoltaic research as a sort of philosophical truth before the advances in material science, extraction or manufacturing of the last fifty years?

justanotherjoe 2y ago

In terms of resource extraction needed for the batteries and the panels, how sustainable is it? The way I understand it is that you can't really repair broken panels and batteries... Can we still make these after, let's say, 500 years? I have no conception at all in this topic...

pjc50 2y ago
No, but I don't see a good reason why you can't recycle the cells especially given they contain a thin layer of silver. Google already finds local recycling firms, since it's required by WEEE. (The 500 years question has issues for all the other sources of energy as well!)
- deleted 2y ago
  [deleted]
ZeroGravitas 2y ago
Yes, batteries are getting better at such a rate that you can recycle old batteries at end of life, lose 10% of the material in that process and build a new battery with new tech and less material that is better than the original. The resource extraction issue is more than these are so useful we're going to build an ever growing amount of them. Luckily they're made from widely available materials, with even more widely available substitutions possible e.g sodium batteries.
adgjlsfhk1 2y ago
You can't repair, but you can recycle (although doing so likely isn't very profitable until the exponential price decrease stops)
ben_w 2y ago
The resources all start off chemically bound in rocks that aren't famous for spontaneously generating or storing electricity. I don't see it being meaningfully more expensive to process smashed up old PV or batteries than starting from the natural state, and my expectation is that it would be easier. The exception would be if some of the chemical pathways turn into low-concentration atmospheric gasses that then diffuse all over the world, which is how we got the problem with CO2 (and unrelated problems with CFCs).
pfdietz 2y ago
Aside from silver for contact wires, PV panels are made (or could be made) with mundane materials available in essentially unlimited amounts. The total mass flowing through new PV panels each year if the US were fully solar powered would be much less than the volume of mundane material flowing through the system already. For example, the EPA estimated that in 2018 the US generated 600 million tons of construction and demolition waste (of which 143 million tons went to landfills.) https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/construction-and-demolition-debris-material https://www.epa.gov/facts-and-figures-about-materials-waste-...

angleofrepose 2y ago

Thank you and other commenters for the great rundowns here. I'm interested in a related question and I wonder if you or others could point me in the right direction: why was the mainstream consensus around solar power (and/or batteries) apparently so wrong for so long? More specifically -- and maybe a better question -- why didn't progress in solar and batteries happen sooner? I'm less interested in blame than in a systems analysis of how in the last half century powerful players seem to have missed the opportunity to start earlier investment in solar and battery technology. Solar and batteries are unique in energy infrastructure, as even any casual observer knows by now, and is certain to change many aspects of politics, industry and culture. It seems an inevitability that energy infrastructure will evolve from large complex components towards small and simple components, and I'm interested in engaging with the history of why "now" is the moment, rather than decades ago.

mjamesaustin 2y ago
It's a false assumption that technological progress happens automatically or even that it's based upon the passage of time. Progress happens as a result of many choices made by individuals to invest time and energy solving problems. Why is solar rapidly improving now? Because way more people are invested in making it better. Nascent technologies almost always face an uphill battle because they compete against extremely optimized legacy technologies while themselves having no optimization at first. We only get to the current rapid period of growth because enough people pushed us through the early part of the S curve.
- angleofrepose 2y ago
  Sure, that makes sense. This is where I'm coming from with my interest in history: I heard an interesting argument somewhere that solar cells are an ideal manufactured good. Whether you are building a module for a calculator or a GW scale plant, the modules are the same. This is fundamentally different for steam turbines. On the "concrete-internal combustion engine" spectrum of complexity, solar modules are closer to concrete and turbines are closer to ICEs. Shouldn't this have led to a special interest in advancing solar module research? Or widespread understanding that eventually the unique set of attributes that define a solar module would lead to it's takeover of a significant portion of global energy generation? Shouldn't that have been apparent from the earliest days of photovoltaic research as a sort of philosophical truth before the advances in material science, extraction or manufacturing of the last fifty years?