> Electric power is the product of voltage and current. If there is no external circuit, there can be no current and thus no electric power can be delivered by the panel, i.e., the "electricity" is never developed and thus, there is no need to consider "where it goes".
There's also an interesting discussion in the linked post in more depth about electron hole-pairs.
My takeaway is that the temperature in the panel will not rise due to it absorbing any power that would otherwise go down the wires were the circuit complete.
"The equilibrium temperature of the connected panel should be slightly lower than the disconnected panel, because those hole recombinations introduce heat. But the efficiency is only something like 12% to begin with. So the temperature difference isn't like the difference between a white and black surface. More like the difference between a dark and slightly darker surface"
I guess the process is somehow invertible, and once reached a certain static charge each panel stops absorbing energy?
In which case you're sort of already dumping the (non)produced energy in the environment- as heat, on each single panel?