*Review* **A Comparative Review on Energy Storage Systems and Their Application in Deregulated Systems**

**Mitul Ranjan Chakraborty 1, Subhojit Dawn 2,\*, Pradip Kumar Saha 3, Jayanta Bhusan Basu <sup>1</sup> and Taha Selim Ustun 4,\***


**Abstract:** Electrical energy is critical to the advancement of both social and economic growth. Because of its importance, the electricity industry has historically been controlled and operated by governmental entities. The power market is being deregulated, and it has been modified throughout time. Both regulated and deregulated electricity markets have benefits and pitfalls in terms of energy costs, efficiency, and environmental repercussions. In regulated markets, policy-based strategies are often used to deal with the costs of fossil fuel resources and increase the feasibility of renewable energy sources. Renewables may be incorporated into deregulated markets by a mix of regulatory and market-based approaches, as described in this paper, to increase the systems economic stability. As the demand for energy has increased substantially in recent decades, particularly in developing nations, the quantity of greenhouse gas emissions has increased fast, as have fuel prices, which are the primary motivators for programmers to use renewable energy sources more effectively. Despite its obvious benefits, renewable energy has considerable drawbacks, such as irregularity in generation, because most renewable energy supplies are climate-dependent, demanding complex design, planning, and control optimization approaches. Several optimization solutions have been used in the renewable-integrated deregulated power system. Energy storage technology has risen in relevance as the usage of renewable energy has expanded, since these devices may absorb electricity generated by renewables during off-peak demand hours and feed it back into the grid during peak demand hours. Using renewable energy and storing it for future use instead of expanding fossil fuel power can assist in reducing greenhouse gas emissions. There is a desire to maximize the societal benefit of a deregulated system by better using existing power system capacity through the implementation of an energy storage system (ESS). As a result, good ESS device placement offers innovative control capabilities in steady-state power flow regulation as well as dynamic stability management. This paper examines numerous elements of renewable integrated deregulated power systems and gives a comprehensive overview of the most current research breakthroughs in this field. The main objectives of the reviews are the maximization of system profit, maximization of social welfare and minimization of system generation cost and loss by optimal placement of energy storage devices and renewable energy systems. This study will be very helpful for the power production companies who want to build new renewable-based power plant by sighted the present status of renewable energy sources along with the details of several EES systems. The incorporation of storage devices in the renewable-incorporated deregulated system will provide maximum social benefit by supplying additional power to the thermal power plant with minimum cost.

**Keywords:** regulated system; deregulated system; energy storage devices; modern power system; profit; compressed air energy storage

**Citation:** Chakraborty, M.R.; Dawn, S.; Saha, P.K.; Basu, J.B.; Ustun, T.S. A Comparative Review on Energy Storage Systems and Their Application in Deregulated Systems. *Batteries* **2022**, *8*, 124. https:// doi.org/10.3390/batteries8090124

Academic Editors: Luis Hernández-Callejo, Jesús Armando Aguilar Jiménez and Carlos Meza Benavides

Received: 10 August 2022 Accepted: 7 September 2022 Published: 10 September 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

#### **1. Introduction**

Electrical energy storage (EES) systems have demonstrated unique skills in coping with several important aspects of electricity, for instance, hourly changes in demand and pricing [1]. Firstly, EES saves power costs by storing electricity obtained during off-peak hours when its price goes down, for use at peak hours, rather than electricity purchased then at higher costs [2]. Second, in order to increase power supply stability, EES systems assist users when electricity network disruptions occur as a result of natural catastrophes, for example. Thirdly, it preserves and enhances power quality, frequency, and voltage [2]. Electric vehicles with batteries are the most potential off-grid method for replacing the conventional sources with renewable energy [3]. Smart grid relates to power grid updates. Smart grid technology integration makes the grid more adaptable and responsive, with the potential to provide real-time feedback by sharing data among electricity producers and consumers to provide a more sustainable and efficient power supply. EES is one of the key elements in developing a smart grid [4].
