If he can only absorb heat based attacks not all energy that is a bit better. I think you need to state that more clearly though because it does no come across that way and energy manipulation is a big power most of the time. The limitation of certain powers does help with some of my worries on the matter since you already did well in stating how the power is released and that releasing all of it is bad and doesn't last long. 

The big worry now has to do with this question, what side will he be on? It is retaliative and important, I will explain why in a moment.