Is dark energy something we have known for a long time now?

"Is it possible that the whole universe is rotating creating huge centrifugal force we call the dark enegry?"

Not really. If this were the case then assuming the universe were rotating uniformly, like a solid, then the force would be greater the further you went out (because a = ω²r). Now, this IS consistent with our observation that the further away something is, that the more red-shifted it is and thus, the faster AWAY it's moving (perhaps it's accelerating away faster). HOWEVER, to believe this model with the observational evidence would mean that the Earth is the center (or near center) of the universe. That is highly unlikely. Otherwise we should observe that some galaxies move faster away in some directions and move much slower away in other directions (because we are almost certainly off-center of the center of rotation).

I think it is a huge possibility. There are many theories. This so called, "dark matter", is just one theory. It is pretty cool how everything in the universe revolves around something bigger than itself. I just hope we can find it one day