An energy collector mk3 set on the same level as a solar panel will provide that panel with sunlight.
As you can see in this next photo, the furthest panel to the left is in fact getting sunlight.
With a setup like this, new underground solar farms are made possible.
Edit: Does not work with regular solar panels. It only works on arrays.
Edit: The Solar Arrays get sunlight, yet they produce no power. I will be testing this further.