Solar panels operating and not operating...

[Externet]

Greetings.
Disconnected (no current flowing) solar panels on a roof get heated by ambient temperature plus sun rays exposure, reaching a temperature plateau.

If then are connected and current flows operating a load; will solar panels get hotter or cooler ?

 

[KlausST]

Hi,

a collegue and I have discussed the same, too. With no result.

The problem is:
let´s say you have a sun radiation of 1000W/m²
the panel is OPEN
--> then some radiation gets reflected
--> some radiation gets absorbed = heat that warms the panels ang gets spread by air.
I don´t think there`s much more..

Same situation, but you connect a load to the panel that draws 150W.
Since the incoming radiation is identical:
* either the reflection grade needs to change
* or the absorption grade needs to change
(or both)

Klaus

 

[FvM]

Presumed reflection/emission coefficient stays constant, it gets cooler when it sources electrical power.

 

[Externet]

Thanks, gentlemen.
The thermal energy at the solar panels is moved to the load and dissipated there when current flows; so panels get cooler; the energy conservation in the system is partially transferred to the load somewhere else causing cooling of the panels...
Is that valid in my very poor wording ?

Now, with mathematics... If a set of solar panels receives 5KW of solar energy and delivers/powers 1KW to a load; how many watts of cooling do the panels get ?

 

[FvM]

Without electrical load, solar panel is dissipating full 5 kW, if 1 kW is extracted, dissipated power reduces to 4 kW. How much panel temperature reduces depends on dissipation mechanism. Assuming it's mostly convective, we can expect overtemperature reduction slightly below 20 %.