Several energy-based attack powers (Energy Ray,Energy Stun, etc.) use a particular energy type determined by your "active energy type". However, I can't find any reference to how you are supposed to choose an active energy type. The power descriptions say that "A kineticist does not need to select an energy type for this power when he gains psionic focus", which presumably means that the active energy type is chosen somehow when you gain psionic focus.
Is active energy type something that can be chosen freely whenever you gain psionic focus? Is there a restriction to what energy type you pick? Do you need to have psionic focus to manifest the power? If you have psionic focus already, is there any way to change your active energy type without expending your focus first? In general, how does picking an active energy type work?