Design and Simulations of RT Na-S Battery/Supercapacitor Energy Storage Systems Integrated in Grid/Microgrid with Renewables

A sustainable non-lithium battery is proposed, integrated with renewables to cater for the intermittency and differences between daily supply and demand. A room temperature sodium–sulfur (RT Na-S) battery presented in this study offers a promising energy density of 177 Wh/kg of the pouch cell. A framework is introduced for the design of an RT Na-S battery system, alone and combined with a supercapacitor, and its operating schedule for two case studies: (a) a photovoltaic (PV) system for a household and (b) a wind turbine for an industrial site. Daily power supply and demand profiles are included in both cases. In the first design step, the required mass and volume of the battery cells are determined. In the second step, the system architecture is designed, and simulations of the renewable-energy storage system–demand are carried out for four consecutive days. An RT Na-S battery–supercapacitor system is recommended in association with the wind turbine that involves high frequency and high power pulses, where the supercapacitor caters for power exceeding 0.1 C. A standalone RT Na-S battery is recommended for the PV system. The simulations predicted that each storage system covered all the net power and energy demands without any contributions from the grid.