From memory, there are about 4-5 different ways that Nova/Nova's can absorb or manipulate energy. Keep in mind that a vital part of energy absorption for a Nova Prime is compatiblity. They can absorb ANY form of energy, but some exotic types can cause a massive feed back so they have to be careful. Also, the absorption power is dynamic in that the more energy an opponent puts into an attack, the easier it is for a Nova syphon to absorb, amp and redirect.
1) The most basic form of energy absorption a Nova can do is the classic absorb and redirect as seen here:
And here;
When you think about it, even though its basic, its easily used in a combat situation in real time and it can phuck people up.
Another use is a direct leech to amp their own physical stats or to recover quickly from injury. They can do it to humans or to machines as well. All that's needed is direct contact. Once contact is made they can keep on leeching even from a distance. Powerhouse was the best at this imo.
Steals some of the sphinxs' strength.
A weakened Nova uses energy from Strangler to boost his depleted energy, then breaks free:
Supernova does it to Rich. Arrogant prick.
Establishes contact here:
From then on, its a simple rope a dope until Rich has nothing left: