«Empire (Serapis Classics)» by Clifford Simak

In a future time, the solar system is powered by one energy source, controlled by one huge organisation, which has plans to use this control to dominate the planets. Unknown to them, a couple of maverick scientists accidentally develop a completely new form of energy supply and threaten the corporation's monopoly. Naturally, the corporation can't allow this to happen… A stunning story about the manipulation of pure energy, climaxing in interstellar conflict.