Modeling, realization and test on field of a fuel cell - Na/NiCl2 battery hybrid system as a base transceiver station power supply

The telecommunications sector has grown exponentially in recent years due to mobile communications and internet diffusion. This trend seems to continue in near future driven by both further increase of mobile communications in less developed areas and likely diffusion of IoT (Internet of Things). Radio base stations (RBS) need a power grid that is stable and reliable. The approach of the project presented in this work is to replace the UPS and stabilizers with a hybrid fuel cell (SOFC) - Na/NiCl2 batteries capable of high quality energy performances. This kind of system can ensure power delivering where the electric grid is absent or weak or provide a wide range of power and energy services if installed where the grid is present. In particular, the system developed is able to supply both on-grid and off-grid RBS (1-10 kW) and medium sized data centers (+50 kW), integrated with RES (e.g. solar PV, wind), minimizing their unpredictability, and is consistent with future smart grids/smart cities infrastructures. The hybrid approach guarantees energy and power supply while the fuel cell works at a fixed power set point, so that the batteries follow rapid load variations. SOFC systems have too slow dynamics to follow the load power variations without compromising its own lifetime. The integration of this hybrid system in the RBS has been studied and designed by using customized power electronics converters. A modelling tool has been developed in MATLAB environment to help in evaluating size, performance, and operative algorithms of this type of hybridization. The real system has been assembled and tested at the CNR ITAE Laboratories. Then it has been moved to a real telecommunication site, in Palermo, to work directly coupled to an operating load.