I agree with tpi. If 1000 w/m^2 is striking the panel then 1000 w is heating the panel assuming no reflection. If a 15% efficient panel shuttles away 150 w there is only 850 w left to heat the panel. Should be 15% cooler than an open panel if everything is linear. Now assume the panel could be 100% efficient. All 1000 w are shuttled away. What is left to heat the panel?
The panel temp is an equilibrium between how much energy is absorbed and how much is transferred or rejected to the environment.
The panel producing power won't look any different but should be slightly cooler than an open panel.
