Practitioners of tai-chi may have heard about the square-form (方拳) of tai-chi. My understanding is that it was first developed by late Wu-style lineage Master Wu GongYi （吳公儀) and was later better popularized by late Wu-Cheng style Grandmaster Cheng TianHung （鄭天熊). Of course, I might be wrong about the origin, but the interesting thing is that both Masters had competed in the ring, and with good results (which was quite unusual for tai-chi masters of those days, or even nowadays)! Unlike general workout that most tai-chi enthusiasts practise nowadays, ring combat requires more power-training, in addition to other strenuous workout regimes.
The question is: How is the square form related to power generation, if at all?
The physics of punching dictates that a strong power needs two things to accomplish: firstly, a strong structure and secondly, an effective power generation mechanism. And I shall use punching as an example.
The answer to the above question is, in a nutshell, the square form can help building a stronger structure as well as allowing a practitioner to feel the internal path of power transmission in the body.
The square form requires a practitioner to freeze momentarily between each single movement. And therefore sometimes it looks rather robot-like. The "negative" aspect to do the square form is that it is rather difficult to sustain the chi (and of course, the proper requirement is "to sustain one's chi despite having to stop momentarily between single movements"). Actually from the outward appearance, it really doesn't look like "doing tai-chi"!
But what is the benefit of having to stop momentarily between each movement? Or a better question will be: What should a practitioner do or pay attention to when he stops momentarily between movement?
The answer is he has to finely adjust his joints (in particular his ball-and-socket shoulder and hip joints) to the correct positions (together with mind point-focus) during the "freezing" moment. Then he should subtly redirect his chi at the required points of his joints (again in particular his ball-and-socket joints), so that a strong structure is set up. And in the next movement, he can then subtly direct his chi to deliver better power (i.e. better power transmission) WITH a more aligned stronger structure. With good practice of the square-form, power can be delivered naturally.
PS: As with other tai-chi (or meditation) explanations, it is oftentimes difficult to explain in writing: because most things happened inside one's body, and these things are "managed" primarily by a practitioner's mind!