Lithium-Ion Batteries in PV off-grid systems: Comparison of 3 battery systems and their effects on system efficiency

摘要

In PV off-grid systems energy storage is a key factor for maintaining system operability. Lithium-Ion Batteries offer an alternative to commonly used Lead-Acid Batteries with promising properties such as a high energy density, high cell efficiency and high lifetime expectation. Nevertheless their impact on the system performance of an existing off-grid system remains questionable. Ambiguous effects on the system-efficiency could occur, mainly due to a necessary additional Battery Management Systems (BMS) and a difference in voltage levels. While neglect able in larger-scaled energy supply systems, the consumption of the BMS can play a major role influencing the system efficiency of small PV based systems. A reduced system performance could lead to a limited benefit from the promising properties. Aiming at an energy supply system for a small remote satellite telecommunications system, three Lithium-Ion and one Lead-Acid Battery System are examined in order to find the most promising system set-up of components for a prototype of the energy supply system. To achieve this they are examined regarding cell efficiency, self-consumption and BMS consumption. Based on these findings, the system performance for the different solutions is compared.