## 2 Battery and Hydrogen Energy Storage System  
### Battery Energy Storage Systems (BESSs)  
Battery energy storage systems (BESSs) store electrical energy using a variety of forms and technologies. Lithium-ion batteries are the most widely used because of their high energy density, high efficiency, and falling costs, which have made them the market leaders [26; 27; 28]. Lead-acid batteries are also utilized due to their reliability and cost-effectiveness, despite having lower energy density and shorter lifespans. Nickel-based batteries such as nickel-cadmium and nickel-metal hydride offer good performance but are less popular due to higher costs and environmental concerns [29; 30; 31]. Emerging technologies like solid-state batteries and flow batteries promise advancements such as higher energy densities, longer lifespans, and improved safety, positioning them favorably for future applications. Each type of battery (Table 1) offers distinct advantages tailored to specific requirements, like energy capacity, discharge rates, and operational longevity [32; 33; 34; 35; 36].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**No** & **Type** & **Details** \\ \hline
1 & Lithium-ion Batteries & High efficiency, high energy density, and declining costs. \\ \hline
2 & Lead–acid Batteries & Reliable, cost-effective, lower energy density, shorter lifespan. \\ \hline
3 & Nickel-based Batteries & Higher expenses, environmental issues, and good performance \\  & & (nickel–cadmium, nickel–metal hydride, etc.). \\ \hline
4 & Solid-state Batteries & Higher energy density, longer lifespan, improved safety, \\  & & emerging technology. \\ \hline
5 & Flow Batteries & Scalable, long lifespan, emerging technology. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Types and Technologies.  
BESSs are essential for energy storage, load balancing, and grid stabilization in contemporary grid management (Table 2). By storing excess energy during times of low demand and releasing it during peaks, they play a major role in peak shaving by lowering the need for expensive peaking power plants. Furthermore, BESSs are essential for frequency management since they can quickly modify power injectors to keep the grid stable. It is essential that they are able to include intermittent renewable energy sources like wind and solar. By storing surplus energy produced under ideal circumstances and supplying it during unfavorable ones, BESSs guarantee a steady supply of electricity. Furthermore, BESSs are crucial for remote locations and vital infrastructure since they provide a dependable backup power supply during grid disruptions [37; 38; 39; 40; 41; 42].  
Despite their manifold benefits, BESSs encounter challenges that hinder broader adoption. One significant obstacle is the initial high cost, particularly for lithium-ion batteries, which can be prohibitive for large-scale installations. However, ongoing advancements in manufacturing processes and economies of scale are progressively reducing these costs. Another challenge lies in battery lifespan and degradation over time, leading to diminished efficiency and capacity. Continuous research aims to enhance battery longevity and performance. Safety concerns such as thermal runaway and fire risks necessitate improved battery designs and management systems. Recent innovations such as solid-state batteries offer heightened safety and energy densities, while flow batteries provide scalable storage solutions with extended lifespans. These advancements are anticipated to address current challenges and propel (Table 3) the future expansion of BESSs in grid management [43; 44; 45; 46].