# Progress in Energy Storage Technologies and Methods for Renewable Energy Systems Application
## 4 Research Classification
### Application Scenarios of Energy Storage System  
The storage energy is mainly in the three scenes, which are named the generation side, system operators, and user side. From the perspective of the power generation side, the demand endpoint of the energy storage is the power plant. Due to the different impacts of different power sources on the grid and the dynamic mismatch between power generation and power consumption caused by the difficulty of prediction at the load side, there are more types of demand scenarios for energy storage on the power generation side, including six types of scenarios such as energy time shifting, capacity units, load tracking, system frequency regulation, standby capacity, and renewable energy grid connection [97]. The application of energy storage on the grid side is mainly to relieve transmission and distribution blockage, delay transmission and distribution equipment expansion, and reactive power support. Compared with the application on the power generation side, there are fewer types of applications on the grid side, while the effect is more of a substitution effect from the perspective of the effect. The customer side is the terminal of electricity use, and the customer is the consumer and user of electricity. The cost and benefit of power generation and transmission and the distribution's side are expressed in the form of electricity price, which is translated into the cost of the customer; thus, the price of electricity will affect the demand of the customer. The role of the different statuses of energy storage in the power system is summarized in Table 8.  
A detailed description of the operating principles and technical and economic characteristics of mechanical, electrochemical, and hydrogen technologies is presented to derive potential EES utilization [116]. [PERSON] et al. [117] researched commercial battery technologies for EES applications. The feasibility and capabilities of stationary EES systems were considered in terms of obtaining more efficient electrochemical energy storage by comparing efficiency, lifetime, discharge time, and scalability, etc. [PERSON] and [PERSON] [118] studied various electrochemical hydrogen storage technologies. They were fuel storage, battery, and fuel cell supercapacitors. It was finally found that the optimal promising materials for electrochemical hydrogen storage were magnesium alloys and carbon nanocomposites. [PERSON] et al. [119] showed that ESS was a solution for the reliable operation of smart power systems, and the application of each type in the field of power systems was studied, emphasizing the cooperation of these entities with renewable energy. \begin{table}
\begin{tabular}{c c c c} \hline  & **Power Generation Side** & **Grid Side** & **Customer Side** \\ \hline Program tracking [98] & \(\surd\) & & \\ \hline Smoothing control [99; 100] & \(\surd\) & & \\ \hline Peaking [101] & \(\surd\) & \(\surd\) & \\ \hline Primary frequency modulation [102] & \(\surd\) & \(\surd\) & \\ \hline Automatic generation control & & & \\ (AGC) [103] & \(\surd\) & \(\surd\) & \\ \hline Automatic Voltage Control & & & \\ (AVC) [103; 104] & \(\surd\) & \(\surd\) & \\ \hline Reactive support [105] & \(\surd\) & \(\surd\) & \\ \hline Rotating/non-rotating & & & \\ standby [106] & & & \\ \hline Transmission and distribution & & & \\ congestion relief [107; 108] & & & \\ \hline Black start [109] & \(\surd\) & \(\surd\) & \\ \hline Peak shaving and valley & & & \\ filling [110] & & \(\surd\) & \(\surd\) \\ \hline Demand management [37; 111] & & & \(\surd\) \\ \hline Demand-side response [112] & & & \(\surd\) \\ \hline Backup power [113] & & & \(\surd\) \\ \hline Electrical energy leveling [114] & \(\surd\) & \(\surd\) & \(\surd\) \\ \hline Delayed transformer & & & \\ expansion [115] & \(\surd\) & \(\surd\) & \(\surd\) \\ \hline \end{tabular}
\end{table} 
Table 8: The role of energy storage projects. An efficient daily DC safety-constrained optimal tidal model was proposed to ensure the safe operation of wind power with the transmission grid [120].