Zhou Tai Chi Elbow as stated in the 13 Kinetic Postures post is about using the elbow with full body weight behind it. If you look at the Tai Chi set are there any moves where the elbow is the primary obviously intended application of the move?
For the most part the answer is no.
Yet, having thought about it you will probably have thought of some moves where the elbow is fairly prominent or could easily be brought to bear. Now you are at least closer to thinking about Zhou Tai Chi Elbow the way that it is done as a movement in the form. Zhou Tai Chi Elbow is in almost every move of the set. To bring it into your Tai Chi practice you could easily move a little bit differently so that emphasis is on the elbow. Get your full body weight and structure behind it and you are really moving in the right direction.
Last but not least the real way that most Zhou Elbow techniques are done is that you don’t really move your elbow into a different position as much as you make sure to utilize the elbow whenever contact is made with it and put your mind intent and body weight and structural support into your elbow so that the recipient / opponent feels and gets the effect of that mind intent and whole body power / weight.
Practice techniques with this and you might be surprised at the number of applications that you discover for Zhou Tai Chi Elbow.
Was always told to keep the elbow down during the movement of the forms.
Yet when I visualize moving the elbow to a different angle in each posture I see where it could be used in numerous postures.
Wave hands like clouds comes to mind immediately. Hit Tiger on Left and Right also comes to mind. On–would be one as well. List is too numerous to mention.