Alright!!. Now where were we...
I have to interject, the concept of negative power.
Positive power is power dissapated.
Negative power is power generated otherwise...
If you had a 10 MW generator and 1 million customers consuming 10,000 W
10 MW = 1000 * 1,000,000
0 = -10MW + 1000 * 1,000,000
or
Power consumed = power generated
All very true. However:
Any motor, for instance, by its very nature, while turning, is also a generator. Electric Motive Force (EMF) is said to be the "power" that causes the motor to turn. All well and good. But as it turns, it's also
generating what's called a Counter-EMF (CEMF) that flows in
opposition to the EMF (this can set up so called "Standing Waves", [which are
really bad for causing energy losses] but that really is down the road).
Anyway, as in KISS's example, yes, there is power generated that does no useful work due to losses that are abundant. But keep in mind that a 10MW plant does not always produce at full capacity. The main power producing apparatus is throttled to the load. This does not eliminate losses, but it does reduce unnecessary loses. And, in essence, CEMF
can be a power
saving phenomenon.
So, for DC, since by way of a bridge rectifier system (and other ways) we can move the negative element of the sine wave to the positive side of ground we are, thereby, now making it part of the "power" side of the equation. This is as you saw in the excepts you introduced in a previous post.
It's good to see that that your curiosity is leading you to search out the answers to some of the questions you have.
Sometimes it's necessary to explain a fundamental concept in such a way is isn't
exactly complete or in all cases true. Certainly in a number of fields thee are ambiguities and nuances that are difficult to grasp until a certain underlying concept is understood.
That's when you know better what questions to ask.
And you are rapidly getting there.