Lead-Acid Versus Lithium-Ion Battery Energy Storage System: Usable Energy Density and Storage Capacity Analysis

Abstract

A challenge for industries nowadays is to optimize the functionality of their critical assets; they rely on a sturdy power supply to increase their operational availability and the robustness of their critical assets against the damaging effect of power disturbances. An increase in load shedding in the past few years also highlights the country’s low energy availability and quality factor. An uninterruptible power supply (UPS) and its battery energy storage system (BESS) will be called up to condition or maintain the supply of electrical energy to critical loads during power disturbance incidents or in the event of a power outage. The backup energy system must be securely stored and promptly accessible whenever required, and once depleted, must effortlessly be refilled upon the restoration of the main power supply. The best-suited and optimally selected BESS for the UPS system application must, therefore, be made available. This paper presents a practical comparative analysis between lithium-ion and lead-acid BESSs vis-à-vis their storage or amp-hour capacity and usable energy density. This analysis follows the replacement of a legacy 3-phase online lead-acid based rotary UPS system with a newer high-performance static lithium-ion-based alternative. The comparative analysis approach is facility-based on requirements each BESS possesses to support the full power presented by critical loads.

Keywords: UPS, lithium-ion battery, lead-acid battery, battery energy storage system, usable energy density, storage capacity.