Optimal Lithium‐Ion Battery—Supercapacitor Energy Storage System Capacity for Off‐Grid Intermittent Renewable Energy Mini‐Grids

ABSTRACT Deployment of off‐grid intermittent renewable energy mini‐grids (IREMGs) instead of fossil fuels for electricity generation positively contributes to reduction of greenhouse gas emissions. However, in off‐grid IREMGs power supplied by renewable energy sources as well as demanded by loads fluctuates. These fluctuations accelerate aging of lithium‐ion battery (LB) energy storage systems (ESSs) installed in such systems. This study focused on designing optimal LB and supercapacitor (Sc) ESS capacity for deployment in off‐grid IREMGs. In this regard, an aging‐based controller was utilised to design optimal LB‐Sc hybrid ESS (HESS) and optimal LB single ESS (SESS) capacities for an off‐grid IREMG. Data were collected from an existing off‐grid IREMG system. Simulation results show that optimal LB‐Sc HESS improves the annualised cost of the system (ACS) of the ESSs by 33.15% in relation to optimal LB SESS. Furthermore, LB daily utilisation fractions improve by 1.02% in LB‐Sc HESS as compared to LB SESS. Also, the loss of power supply probability is less than the defined 5% in all simulations for both systems. Finally, the study recommends experimental validation of the performance results. It also recommends designing an overall optimal size of an off‐grid IREMG using a similar controller to further improve the ACS.