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Stupid question I've been curious about. What happens to a PV panel, receiving sunlight, with no load? Does it degrade or suffer ill effects in any meaningful

by ethbr1 2y ago

Stupid question I've been curious about. What happens to a PV panel, receiving sunlight, with no load? Does it degrade or suffer ill effects in any meaningful way? Or does it just have a potential between its outputs but otherwise isn't impacted?

lompad 2y ago
A small current is going to flow internally, but nothing else happens. It's quite normal to have solar panels running with zero load in regions with lots of PV - reason being, that the carriers need to keep their electricity nets stable and have to carefully balance electricity entering and leaving the net. At least in Germany, every PV installation of certain size (> 30kW peak) is mandated to be able to be shutdown remotely by the carrier if you supply electricity for the net and aren't just using it for yourself. (You get paid the same during shutdowns, just like it were running. Otherwise it would be quite damaging and likely reduce adoption of PV) Point being: no, it doesn't hurt the panels and is a regular ocurence.
antisthenes 2y ago
The generated power will be dissipated through the panel as heat, AFAIK. Which means that in winter, probably nothing, because it's cold, but on a hot summer day with peak sun, the heat might start damaging the cells. How much exactly you'd have to look at studies. My guess is the output will permanently degrade by a few % per year if the panel is not connected. Might go down to 80% way quicker than normal (25-yr)
- addaon 2y ago
  > The generated power will be dissipated through the panel as heat, AFAIK. Solar panels are not constant-power devices. In an open circuit, they will generate their open circuit voltage at nearly zero current (except minor internal leakage), and thus nearly zero power. In a short circuit, they will generate nearly zero voltage, and thus also nearly zero power. To get maximum power out of a solar panel requires maximum power-point tracking (MPPT), where the load is adjusted such that the product of voltage and current (that is, power) is optimized for the current conditions; while significant power can be delivered to a fixed load, there's no real power being generated without a load.
  - CorrectHorseBat 2y ago
    Where's the power going to then? Either it's heating the panels or it's reflected back, no?
    - dzhiurgis 2y ago
      Given ~20% efficiency it's almost negligible amount of heat.
    - Dylan16807 2y ago
      The sunlight heats the panel a bit more than usual but there isn't really generation/dissipation going on. And since heat radiates away at temperature to the fourth power, the increase shouldn't be particularly much.
    - addaon 2y ago
      The thermal power of the sun will heat the panel, to the extent that it is not reflected. But no electrical power (or any power) is being "generated" by the panel, the panel is just absorbing photons like anything else with low albedo.
      - CorrectHorseBat 2y ago
        That's just nitpicking. There is thermal power generated from the electromagnetic power from the sun and GP is right that a solar panel turned off will be hotter than one turned on.
        addaon 2y ago
        And if that was the original poster's intent, I apologize for nitpicking. My impression was that the use of "generating power" in the given (open circuit) context suggested a fundamental misunderstanding of the behavior of solar cells in this situation on behalf of the poster, and thought I might clarify; and perhaps even if the original poster understood this already, someone else learned something.
    - 2y ago

by ethbr1 2y ago

lompad 2y ago

A small current is going to flow internally, but nothing else happens. It's quite normal to have solar panels running with zero load in regions with lots of PV - reason being, that the carriers need to keep their electricity nets stable and have to carefully balance electricity entering and leaving the net. At least in Germany, every PV installation of certain size (> 30kW peak) is mandated to be able to be shutdown remotely by the carrier if you supply electricity for the net and aren't just using it for yourself. (You get paid the same during shutdowns, just like it were running. Otherwise it would be quite damaging and likely reduce adoption of PV) Point being: no, it doesn't hurt the panels and is a regular ocurence.

antisthenes 2y ago

The generated power will be dissipated through the panel as heat, AFAIK. Which means that in winter, probably nothing, because it's cold, but on a hot summer day with peak sun, the heat might start damaging the cells. How much exactly you'd have to look at studies. My guess is the output will permanently degrade by a few % per year if the panel is not connected. Might go down to 80% way quicker than normal (25-yr)

addaon 2y ago
> The generated power will be dissipated through the panel as heat, AFAIK. Solar panels are not constant-power devices. In an open circuit, they will generate their open circuit voltage at nearly zero current (except minor internal leakage), and thus nearly zero power. In a short circuit, they will generate nearly zero voltage, and thus also nearly zero power. To get maximum power out of a solar panel requires maximum power-point tracking (MPPT), where the load is adjusted such that the product of voltage and current (that is, power) is optimized for the current conditions; while significant power can be delivered to a fixed load, there's no real power being generated without a load.
- CorrectHorseBat 2y ago
  Where's the power going to then? Either it's heating the panels or it's reflected back, no?
  - dzhiurgis 2y ago
    Given ~20% efficiency it's almost negligible amount of heat.
  - Dylan16807 2y ago
    The sunlight heats the panel a bit more than usual but there isn't really generation/dissipation going on. And since heat radiates away at temperature to the fourth power, the increase shouldn't be particularly much.
  - addaon 2y ago
    The thermal power of the sun will heat the panel, to the extent that it is not reflected. But no electrical power (or any power) is being "generated" by the panel, the panel is just absorbing photons like anything else with low albedo.
    - CorrectHorseBat 2y ago
      That's just nitpicking. There is thermal power generated from the electromagnetic power from the sun and GP is right that a solar panel turned off will be hotter than one turned on.
      - addaon 2y ago
        And if that was the original poster's intent, I apologize for nitpicking. My impression was that the use of "generating power" in the given (open circuit) context suggested a fundamental misunderstanding of the behavior of solar cells in this situation on behalf of the poster, and thought I might clarify; and perhaps even if the original poster understood this already, someone else learned something.
  - 2y ago