Q.  What is Dark Energy, really?

A.  Dark Energy was a theoretical substance invented by cosmologists to explain a putative acceleration in the expansion of the Universe.

Q.  Has it ever been detected?

A.  No, it was purely theoretical.

Q.  So does it actually exist?

A.  No. Now that the Big Bang theory and expansion of the Universe have been disproved, there is no need to consider it further.

Q.  Where can more about this be found?

A.  Look at R.I.P. Expanding Universe (b. 1930, d. 2012): (The Big Bang never happened).