Energy Efficiency of the Passive Hybrid Battery Supercapacitor System: An Analytical Approach

Abstract

Under dynamic load, passive hybrid battery supercapacitor systems (HBSSs) have numerous advantages compared to stand-alone battery systems (SABS). The highlighted benefits include a lower voltage drop at the HBSS terminals, lower current and thermal stress on the battery, and higher energy efficiency. A novel set of analytical expressions is introduced for the analysis of energy efficiency of the passive HBSS in relation to the SABS. Using these expressions, energy efficiency of the passive HBSS was analyzed for different dynamic load parameters. Compared to existing approaches, the proposed approach that uses the introduced analytical expressions provides a better insight into the impact of battery and supercapacitor parameters on the energy efficiency of the passive HBSS in relation to the SABS. Additionally, the proposed approach is suitable for quick determination of HBSS behavior and energy efficiency under dynamic load. This contributes to the advancement of the sizing of HBSS components and optimization practices, ultimately leading to improved energy use. The analysis showed that in cases where the dynamic component of the load current is a very small part of the total load current, or slowly varying load currents, the passive HBSS in relation to the SABS has no advantages in terms of energy efficiency. The analysis showed that the HBSS is more suitable than the SABS in applications where the dynamic component of the load current is significant. The findings also indicate that there is an interval of the battery and supercapacitor parameters which is optimal for the sizing of the passive HBSS from a techno-economic aspect.