Stationary applications: II. Load levelling

This chapter discusses the significance of stationary applications of secondary battery systems. Multiple central power plants generate electric power and supply it to transmission systems. The transmission systems transfer large amounts of electric power to distribution systems. The distribution systems supply it to loads in consumers at appropriate voltage levels. The growth of power systems is the result of scale merits and location conditions of power plants. The reduction in the fluctuating proportion of the total demand is also one of the prominent advantages. Sodium/sulfur battery systems are available not only for daily load leveling but also for short-duration peak load shaving; however, the operational pattern needs to be determined before the module type is selected. The storage capacity of the NaS battery decreases gradually and irreversibly with the accumulation of the discharge and charge cycles, and the deep discharges steeply decrease the cycle life. The cell of vanadium redox flow (VRF) batteries is based on the electron transfer between different ionic forms of vanadium. The electrolyte is sulfuric acid at the same acidity level as that found in a lead/acid battery. It is stored in external tanks and pumped as required to the cells. The cell is divided into two half-cells by a proton exchange membrane, which separates the two different vanadium-containing electrolyte solutions and allows the flow of ionic charges (IV ions) to complete the electric circuit. The chapter also reviews the disadvantages of lead/acid batteries, such as low specific power and energy, short life cycle, high maintenance requirements, and environmental hazards associated with lead and sulfuric acid. Continuous improvements in design and techniques have mitigated many of these disadvantages, and lead/acid batteries remain the most popular energy storage system for most large-scale applications.