Examination of power supply options for communication sites operating in grid-islanded environments

This paper discusses technological alternatives to operate communication sites without a grid connection. Two cases are the focus of this discussion: systems that are normally operating connected to the grid and they need to operate in islanded mode due to an involuntary event, such as a natural disasters, and systems where islanded operation is a desired choice, usually, for economic reasons. For the former, the performance of NTT-Facilities micro-grid in the city of Sendai after the March 11, 2011 earthquake is commented and lessons are drawn. For the latter case a new concept of data networking using distributed modular data centers is presented. The paper also discussed the availability model of these systems with particular focus on lifelines and sources modeling, including availability models for fuel delivery and for combination of renewable energy sources and batteries.