Energy Storage Technologies for Modern Power Systems: A Detailed Analysis of Functionalities, Potentials, and Impacts

Power systems are undergoing a significant transformation around the globe. Renewable energy sources (RES) are replacing their conventional counterparts, leading to a variable, unpredictable, and distributed energy supply mix. The predominant forms of RES, wind, and solar photovoltaic (PV) require inverter-based resources (IBRs) that lack inherent synchronous inertia desired for the grid and thereby warrant additional interventions for maintaining grid stability by organizing various contingency planning. Such scenarios become more pertinent in the wake of rapid decarbonization objectives adopted by different countries, stringent grid code compliance, and improved grid resilience milestones. Energy storage technologies can potentially address these concerns viably at different levels. This paper reviews different forms of storage technology available for grid application and classifies them on a series of merits relevant to a particular category. The varied maturity level of these solutions is discussed, depending on their adaptability and their notion towards pragmatic implementations. Some specific technologies that require particular mention are - hydrogen (
$H_{2}$
) storage with fuel cells (FC) as the reconversion medium, molten metal, and gravity batteries due to their highly scalable and siteable characteristics participating in load shifting; batteries and
$ H_{2}$
FC due to their high flexibility for peak shaving; and flywheels and supercapacitors for quick response applications, such as frequency regulation and voltage support. Various performance metrics are critically evaluated by comparing them on their usability scale, thus helping readers make a subjective judgment on a particular technology while being aware of the forthcoming limitations. Finally, the paper delves into some emerging trends that decide the selection of a particular technology based on life cycle assessment, economic viability, and commercial and environmental considerations that are presented under the given circumstances. The paper is believed to offer a broad overview of possible directions for the electric grid business, eventually emphasizing the need for more hybrid solutions with opportunities for short and long-term storage options.