Energy is the activity of God, for lack of a better term. When God “touches” something it is Divine Energy, so when God creates, blesses, speaks, Graces, it is called Divine Energy. There is one simple, singular Divine activity, but it is manifold to us because of our mode of being.
Another way to look at it is that Divine Essence is “God within God”, the core definition of God, and Divine Energy is “God doing”. Accident/substance is really a different thing, though in creatures some energies are accidents (for example my moving from one room to another), this really doesn’t apply with God because all energy is essential and eternal with Him.
Peace and God bless!