My favorite opportunities for silhouettes happen in the barn. Two barn doors open at either end--it's easy to stand with your back to the one with the sun on it and take a photo of whatever is at the other, more shadowed end.
So silhouette isn't just about a dark, shadowy image that you can just see the outline of, although it could be (like those old farmer silhouettes standing against a tree in some folks' yards). There can be elements of light in a silhouette. But for the most part, a large portion of the image will be darker than the surrounding elements.
Here's one more, of my cat Gus, who has been particularly cooperative about photos lately. This is a much newer photo (albeit not this past week) of him enjoying his time in his window seat, with half of his body silhouetted against the one and only sunny day we had last month. (Okay, okay, maybe we had two sunny days...)