Psychic energy was a type of energy that powered (or was powered by) mental processes.
Both the Nestene Consciousness (TV: Spearhead from Space) and the planet Siralos were made of pure psychic energy. (GAME: Destiny of the Doctors) Silverberg energy was present when there were signs of psychic energy. (PROSE: Alien Bodies)
The destruction of other planets by Zanak liberated energy of many different kinds, including some on the psychic spectrum. This powered the psychic abilities of the Mentiads. K9 Mark II had the power to track mental wavelengths of psychic energy. (TV: The Pirate Planet)
Psychic energy was harnessed on Hakol and used in combination with technology. The Malus, an war-machine from Hakol, was able to manifest psychic projections that were corporeal enough to interact with their environment. It may also have used psychic energy as a way to connect time zones. (TV: The Awakening)