The search for extra-terrestrial intelligence (SETI) has been conducted for 60 years. Although there is only negative result hitherto, individuals' curiosities have been evoking. We assume that a civilisation which develop the technology between Type II and Type III civilisation (the Alien) in the universe. The Alien must have collected the energy from their parent star for a while and start to absorb or start absorbing the energy from the nearby stars. However, the black holes could be the power stations for the Alien or not has sparked much debates since there is no direct light could be collected from black holes. In this study, we discuss and conclude that the collectable energy from cosmic wave background (CMB) and Hawking radiation would be too small to maintain the civilisation regardless of present or future. Nevertheless, if the Alien have the technology advanced enough to afford the strong radiation from accretion disk and the relativistic jests, they can absorb huge energy comparing to the same size star in main sequence even if the efficiency is low. Moreover, if the Alien can not only collect the light radiation and also the other type of energy (e.g., kinetic energy), the resource would be larger. In a nut shell, although it is unworthy to collect the energy from CMB and Hawking radiation, accretion disk and relativistic jets could be the promising energy source. Our results also suggest this structure is measurable in the UV, optical and IR.