I see solitude in the first image thus:
The object experiencing solitude (to me at least) is the lamp post.
The lamp post is itself a light emiting object, and it’s being singled out in this painting, the shadow of a single lamp post being cast by the bright light of what appears to be the setting sun (colour of the wall on the left and the long, shallow shadows imply this).
The sunlight is of a similar nature to the lamp in that they both emit light, but yet it’s not, because the lamp provides light, when the sun is down. Even so, after the sun sets, this lamp post will be alone, casting it’s light in to an open space (There are no other shadows near this lamp post, so one must assume that it is alone, in a vast open space, for the setting sun to be casting such a shadow on the wall to the left)
The colour of the shadow itself in contrast to the colour of the sun hitting the wall, sets it apart from the middle ground of the painting, but ties it with the foreground. The foreground of the painting ties the alley and the lampost together. The shadows in the ally, are where this lampost should be.
This lampost is alone, in solitude. Maybe it won’t be alone when the sun sets, and it can spead it’s light and joy across the courtyard, and into the alley, where it can reach in and play it’s light against the brick walls in the alley, as the sun does at the present time in this painting.
Very great painting, conveys solitude to me.