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I've been intrigued by used solar panels for sale, seems like you can get an amazing price for ones that are only lightly degraded. Is there a downside, or do y

I've been intrigued by used solar panels for sale, seems like you can get an amazing price for ones that are only lightly degraded. Is there a downside, or do you just mean that it isn't popular currently?

jeffbee 1y ago
I think they were referring to the fact that the chief reason there is not large-scale PV panel recycling is that very few panels have ever been retired. It turns out that short of physical destruction by hail etc a PV panel does not degrade beyond economic usefulness simply by being out in the sun. In fact some panels actually get more powerful. The surprising-to-some conclusion of NREL's PV Lifetime Project is that the economic lifetime of a PV panel is basically forever.
hnaccount_rng 1y ago
In addition to my sibling comment: The cost of the panels is a rather small fraction of the total cost of a typical installation. Most of that cost ist labor, some regulatory requirements and the inverter. Whether you pay a factor of 2 for the panels or not typically doesn't matter. In other words: Reusing used panels will only ever be able to safe you a minuscule amount.
- pfdietz 1y ago
  The low cost of the modules themselves has led to the suggestion of cost optimized DC-coupled PV systems being used to directly drive resistive heaters. The cost per unit of thermal energy in a cost optimized system moderate scale system (> residential, < utility scale) may be in the range of $3-5/GJ, very competitive with natural gas. Low cost maximum power point trackers would be useful; inverters would not be needed. Low cost modules allow one to do away with things like optimally tilted modules and single axis tracking. The modules can also be tightly packed, reducing mounting and wiring costs.
  - maxerickson 1y ago
    What's the proposed system design? For example, in January, I get about 9 hours of sunlight and have an average daily high of 25 F. I'm gonna need to store heat somehow or another.
    - pfdietz 1y ago
      The place I saw this most clearly described was in Standard Thermal's concept, which will store the heat in huge piles of dirt heated to 600 C. The thermal time constant of such piles can be many years. https://www.orcasciences.com/articles/standard-thermal-copy https://www.orcasciences.com/articles/standard-thermal-copy https://austinvernon.substack.com/p/building-ultra-cheap-energy-storage https://austinvernon.substack.com/p/building-ultra-cheap-ene... https://news.ycombinator.com/item?id=45012942 https://news.ycombinator.com/item?id=45012942
      - mjevans 1y ago
        I'm going to want that pile hot enough to kill all the bugs and pets that want to get near it.
        pfdietz 1y ago
        The surface will always be only slightly hot. Heat will be stored inside, insulated by overlying dirt. Dirt isn't the best insulator by thickness, but it's a very good insulator by $.
      - cyberax 1y ago
        I ran the numbers on that, and it just doesn't work. Stone has rather lousy specific heat capacity (less than 1kJ/kg/K, compared to 4.2kJ for water). A typical house in Midwest needs around 22,000kWh (7.913×10^10 J) over the winter (75 million BTU - https://www.eia.gov/todayinenergy/detail.php?id=57321 https://www.eia.gov/todayinenergy/detail.php?id=57321 ). If we assume the delta of 550 degrees (600 down to 50), you'll need: 7.913×10^10 J / (550K * 1000Jkg^-1K^-1) = 143,872,727 kg of material in your pile. This is a ridiculously stupid number. And I don't see any obvious mistakes?
- hinkley 1y ago
  These days it’s a stack of microinverters. Which are not cheaper but do improve array efficiency outside of idea conditions. But that’s another up front cost.
  - dzhiurgis 1y ago
    They are still pretty unpopular. Solves niche problem (small roof, shade) for a quite a bit more money.
- ericd 1y ago
  Yeah, we paid more for the little bits of metal that held up the panels than for the panels themselves (aluminum, but still).
  - dzhiurgis 1y ago
    IDK sounds like you got ripped off. I diy'd and panels were cheap of course, but fittings were perhaps 3-5x cheaper. Inverter is typically same as your panels (hybrid, grid-tied are quite a bit cheaper).
    - namibj 1y ago
      For all of your context/reference, if you buy whole pallets from a central European port warehouse, glass-glass modules run around $0.11/Wp plus shipping. Unless you're just bolting them to the floor or to an uninsulated wall, mounting will (sadly) run you a sizable fraction of that cost in the best case.
    - ericd 1y ago
      Maybe, but these aren’t fittings, they’re ground mounts with large screws that screw into the ground to hold the entire array down, including under high wind (and have to come with PE stamped system-level engineering drawings talking about things like rated wind load of the whole array to pass building inspections). But yeah, at the end of the day, just bent bars of aluminum with ground screws and bolts to hold the corners of the panels, versus the technological marvels of the solar panels they hold.
duskwuff 1y ago
How much of a difference does it actually make in terms of the all-inclusive price of installation (e.g. panels, inverters, mounting hardware, and labor)? (Asking because I genuinely don't know, not because I have a specific answer in mind.)
- hinkley 1y ago
  Find an installer who will warranty work using third party let alone used solar panels and then we can talk.
- Rebelgecko 1y ago
  Labor is by far the top cost. But I'm intrigued by the economics of a small setups paired with like a <5kwh battery. And for something like that where you literally just throw 4-6 panels out, you can just brute force by buying more panels instead of optimizing angles. Basically a slightly beefier version of a European balcony setup
bityard 1y ago
Used panels are cheap because of where we are in the improvement curve. Let's say you're a large business with a factory rooftop full of 100W panels that was installed installed 10 years ago. Today, you can upgrade that rooftop to 300W panels without any additional footprint and often for less than the original deployment cost (adjusted for inflation). Those old panels have to go somewhere and still have at least 2/3 of their life left. Probably more because we're finding out that well-made panels do not degrade as quickly as previously thought. The used panel market (in the US anyway) might dry up soon if the tariffs stay in place, as that will make a lot of customers reluctant to upgrade due to greatly increased costs. But I guess we'll see. I've been wrong before.

jeffbee 1y ago

I think they were referring to the fact that the chief reason there is not large-scale PV panel recycling is that very few panels have ever been retired. It turns out that short of physical destruction by hail etc a PV panel does not degrade beyond economic usefulness simply by being out in the sun. In fact some panels actually get more powerful. The surprising-to-some conclusion of NREL's PV Lifetime Project is that the economic lifetime of a PV panel is basically forever.

hnaccount_rng 1y ago

In addition to my sibling comment: The cost of the panels is a rather small fraction of the total cost of a typical installation. Most of that cost ist labor, some regulatory requirements and the inverter. Whether you pay a factor of 2 for the panels or not typically doesn't matter. In other words: Reusing used panels will only ever be able to safe you a minuscule amount.

pfdietz 1y ago
The low cost of the modules themselves has led to the suggestion of cost optimized DC-coupled PV systems being used to directly drive resistive heaters. The cost per unit of thermal energy in a cost optimized system moderate scale system (> residential, < utility scale) may be in the range of $3-5/GJ, very competitive with natural gas. Low cost maximum power point trackers would be useful; inverters would not be needed. Low cost modules allow one to do away with things like optimally tilted modules and single axis tracking. The modules can also be tightly packed, reducing mounting and wiring costs.
- maxerickson 1y ago
  What's the proposed system design? For example, in January, I get about 9 hours of sunlight and have an average daily high of 25 F. I'm gonna need to store heat somehow or another.
  - pfdietz 1y ago
    The place I saw this most clearly described was in Standard Thermal's concept, which will store the heat in huge piles of dirt heated to 600 C. The thermal time constant of such piles can be many years. https://www.orcasciences.com/articles/standard-thermal-copy https://www.orcasciences.com/articles/standard-thermal-copy https://austinvernon.substack.com/p/building-ultra-cheap-energy-storage https://austinvernon.substack.com/p/building-ultra-cheap-ene... https://news.ycombinator.com/item?id=45012942 https://news.ycombinator.com/item?id=45012942
    - mjevans 1y ago
      I'm going to want that pile hot enough to kill all the bugs and pets that want to get near it.
      - pfdietz 1y ago
        The surface will always be only slightly hot. Heat will be stored inside, insulated by overlying dirt. Dirt isn't the best insulator by thickness, but it's a very good insulator by $.
    - cyberax 1y ago
      I ran the numbers on that, and it just doesn't work. Stone has rather lousy specific heat capacity (less than 1kJ/kg/K, compared to 4.2kJ for water). A typical house in Midwest needs around 22,000kWh (7.913×10^10 J) over the winter (75 million BTU - https://www.eia.gov/todayinenergy/detail.php?id=57321 https://www.eia.gov/todayinenergy/detail.php?id=57321 ). If we assume the delta of 550 degrees (600 down to 50), you'll need: 7.913×10^10 J / (550K * 1000Jkg^-1K^-1) = 143,872,727 kg of material in your pile. This is a ridiculously stupid number. And I don't see any obvious mistakes?
hinkley 1y ago
These days it’s a stack of microinverters. Which are not cheaper but do improve array efficiency outside of idea conditions. But that’s another up front cost.
- dzhiurgis 1y ago
  They are still pretty unpopular. Solves niche problem (small roof, shade) for a quite a bit more money.
ericd 1y ago
Yeah, we paid more for the little bits of metal that held up the panels than for the panels themselves (aluminum, but still).
- dzhiurgis 1y ago
  IDK sounds like you got ripped off. I diy'd and panels were cheap of course, but fittings were perhaps 3-5x cheaper. Inverter is typically same as your panels (hybrid, grid-tied are quite a bit cheaper).
  - namibj 1y ago
    For all of your context/reference, if you buy whole pallets from a central European port warehouse, glass-glass modules run around $0.11/Wp plus shipping. Unless you're just bolting them to the floor or to an uninsulated wall, mounting will (sadly) run you a sizable fraction of that cost in the best case.
  - ericd 1y ago
    Maybe, but these aren’t fittings, they’re ground mounts with large screws that screw into the ground to hold the entire array down, including under high wind (and have to come with PE stamped system-level engineering drawings talking about things like rated wind load of the whole array to pass building inspections). But yeah, at the end of the day, just bent bars of aluminum with ground screws and bolts to hold the corners of the panels, versus the technological marvels of the solar panels they hold.

duskwuff 1y ago

How much of a difference does it actually make in terms of the all-inclusive price of installation (e.g. panels, inverters, mounting hardware, and labor)? (Asking because I genuinely don't know, not because I have a specific answer in mind.)

hinkley 1y ago
Find an installer who will warranty work using third party let alone used solar panels and then we can talk.
Rebelgecko 1y ago
Labor is by far the top cost. But I'm intrigued by the economics of a small setups paired with like a <5kwh battery. And for something like that where you literally just throw 4-6 panels out, you can just brute force by buying more panels instead of optimizing angles. Basically a slightly beefier version of a European balcony setup

bityard 1y ago

Used panels are cheap because of where we are in the improvement curve. Let's say you're a large business with a factory rooftop full of 100W panels that was installed installed 10 years ago. Today, you can upgrade that rooftop to 300W panels without any additional footprint and often for less than the original deployment cost (adjusted for inflation). Those old panels have to go somewhere and still have at least 2/3 of their life left. Probably more because we're finding out that well-made panels do not degrade as quickly as previously thought. The used panel market (in the US anyway) might dry up soon if the tariffs stay in place, as that will make a lot of customers reluctant to upgrade due to greatly increased costs. But I guess we'll see. I've been wrong before.