# Progress in Energy Storage Technologies and Methods for Renewable Energy Systems Application
## 1 Introduction  
The demand for additional energy in the modern world seems to be rising steadily. Both businesses and households require large amounts of power. New issues are simultaneously presented to the current energy production methods [1; 2]. International agreements seek to control pollution levels, global warming calls for measures to cut carbon dioxide emissions, and several nations have decided against constructing new nuclear power stations in favor of decommissioning existing ones [3]. Additionally, the price of conventional energy sources has increased considerably, and the need for a consistent and undistorted supply of these sources has become vital due to the enormous global increase in energy consumption [4; 5; 6]. A result of this evolution is the requirement to switch to new energy production methods. Renewable energy sources and other types of potential distribution generation sources are becoming more prevalent on a global scale. These energy sources, which include wind power, solar power, and hydroelectricity in all its forms, frequently depend on the weather or climate to function effectively [7; 8; 9]. The rate of growth of renewable energy generation capacity has been exponential over recent years, and data from IRENA put it that there was a global renewable energy generation capacity of 3083.929 GW in 2021.The largest share of this is hydropower, which accounts for a total capacity of 1360.524 GW (excluding pure pumped storage), followed by wind energy (824.874 GW), solar energy (849.473 GW), bioenergy (143.731 GW), geothermal energy (15.644 GW), andmarine energy (524 MW). In terms of installation capacity, wind energy accounted for the largest share of the global total, with a capacity of 623 GW; solar energy accounted for the second largest share, with 586 GW; and wind and solar energy continued to dominate the addition of renewable capacity in 2021, according to the generation capacity of RESs. However, the supply of energy from these sources is frequently disrupted by the intermittency of weather, for example, a lack of wind or sunshine. As a result, it is essential to maintain the power fluctuations of a power system that incorporates a lot of RESs such as solar and wind. Additionally, renewable energy usually is located in a remote site that is far away from the city, which will consume a lot of energy in the process of electricity transmission. The stated challenges of renewable energy sources show the importance of energy storage technology. Energy storage mitigates power quality concerns by supporting voltage, smoothing output variations, balancing network power flow, and matching supply and demand. Governments and private energy institutions globally have been working on energy storage technologies for a long time [10; 11]. The U.S. has positioned large-scale energy storage technology as an important supporting technology to revitalize the economy, realize the New Deal for energy, and ensure national energy and resource security. Large-capacity energy storage technology has been listed as the highest priority demand technology in the Grid 2030 plan [12]. Similarly, Japan has also positioned energy storage as a safeguard technology for its post-abandonment energy strategy (after the Fukushima nuclear meltdown) and promoted the application of the energy storage market through subsidies [13]. Additionally, Europe has over time supported energy storage technology as a strategic new industry in the energy sector [14]. China does not yet have a specific policy or large-scale use of energy storage [15]. However, it is in a critical period of energy and economic development transformation, and the proportion of renewable energy is increasing, which has an increasingly significant impact on grid reliability, grid peaking, and unit energy efficiency, thus energy storage will have a great market demand and necessity. [PERSON] et al.