3 ms·

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.
teamonkey 2y ago
Think of what happens to a normal roof tile in the sun: it absorbs solar energy as heat and also reflects some and radiates some away. A solar panel is the same (though a bit more reflective), but when a load is connected some of the solar energy is converted to current instead of being absorbed as heat. Therefore the panel is a little cooler when a load is applied.
rfrey 2y ago
There is no power. Power is IV, current times voltage. The voltage will be the rated voltage of the panel at that sunlight level, but the current is 0 (minus some very, very small (microamp) internal currents). Alternately, power can be expressed as V^2/R. But in an open circuit R is infinite, so again, zero power.
- CorrectHorseBat 2y ago
  There is ~1000W/M2 of electromagnetic power from the sun, and if it's not turned into electrical power it will be turned into thermal power, thus heating up the panel.
  - ethbr1 2y ago
    But as noted by sibling comment, that heated panel will then begin to transfer that heat back into its environment, as a function of its temperature difference with its environment. So as long as manufacturers engineer their panels to be tolerant of the maximum heat at a site (i.e. full sun, maximum temperature), the panels won't be harmed in any meaningful way. They'll just heat up a bit faster than if they were providing current.
  - sangnoir 2y ago
    Is ther a difference between "electromagnetic power" and "thermal power" here? If a panel is not connected, there is no conversion and the surface is warmed - just like any other surface exposed to the sun gets warmed. PV panels are just like charged capacitor or a chemical battery with no loads: just holding unused potential differences with no damage to the unit.

Given ~20% efficiency it's almost negligible amount of heat.

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.

teamonkey 2y ago

Think of what happens to a normal roof tile in the sun: it absorbs solar energy as heat and also reflects some and radiates some away. A solar panel is the same (though a bit more reflective), but when a load is connected some of the solar energy is converted to current instead of being absorbed as heat. Therefore the panel is a little cooler when a load is applied.

rfrey 2y ago

There is no power. Power is IV, current times voltage. The voltage will be the rated voltage of the panel at that sunlight level, but the current is 0 (minus some very, very small (microamp) internal currents). Alternately, power can be expressed as V^2/R. But in an open circuit R is infinite, so again, zero power.

CorrectHorseBat 2y ago
There is ~1000W/M2 of electromagnetic power from the sun, and if it's not turned into electrical power it will be turned into thermal power, thus heating up the panel.
- ethbr1 2y ago
  But as noted by sibling comment, that heated panel will then begin to transfer that heat back into its environment, as a function of its temperature difference with its environment. So as long as manufacturers engineer their panels to be tolerant of the maximum heat at a site (i.e. full sun, maximum temperature), the panels won't be harmed in any meaningful way. They'll just heat up a bit faster than if they were providing current.
- sangnoir 2y ago
  Is ther a difference between "electromagnetic power" and "thermal power" here? If a panel is not connected, there is no conversion and the surface is warmed - just like any other surface exposed to the sun gets warmed. PV panels are just like charged capacitor or a chemical battery with no loads: just holding unused potential differences with no damage to the unit.