Energy storage technology refers to the technology that stores energy and uses it when needed. Energy storage technology converts difficult-to-storage energy forms into technically easier and lower-cost forms for storage. For example: solar water heaters store light energy (radiation) in hot water (heat energy), and batteries store electrical energy in electrochemical energy.

Generally, when the proportion of renewable energy power generation is low (for example, less than 20%), the load-following power plant (for example: gas-fired power generation and hydropower generation) in the original power grid as a peak-off-peak power regulation can cope with the intermittent renewable energy. Changes in power supply. However, when the proportion is high enough, an additional adjustable system is required to maintain the balance of power supply [1]. Energy storage is an important technology, along with demand-side management and grid interconnection).

Energy storage has many uses, for example: emergency energy, it can also be used for energy storage when the grid load is low, and output energy when the grid load is high, for peak shaving and valley filling, and to reduce grid fluctuations. Stored energy comes in many forms, including mechanical, thermal, electrochemical, chemical, and electronic [2]. Energy storage involves converting energy from a form that is difficult to store into a more convenient or economically storable form. Bulk energy storage currently consists mostly of generating dams, either conventional or pumped.

The length of time suitable for each technology to store is different, for example: hot water can be stored for several hours, while hydrogen energy storage can be stored for several days to several months. At present, large-scale energy storage systems are mainly hydroelectric power generation and pumped storage power generation. Grid energy storage refers to large-scale energy storage devices used in the grid.

Energy storage technology can be seen everywhere in our daily life. The electrochemical energy stored in the battery can be converted into electrical energy to supply electronic products. The reservoir stores the gravitational potential energy of water, which is converted into electrical energy through hydroelectric power generation. The cold storage system uses off-peak electricity to make ice cubes, and the stored heat can be used during peak hours to reduce electricity consumption for cooling. Organisms grow by absorbing solar energy, and after death, they are buried underground for a long time, and become fossil fuels after transformation. Food stores chemical energy, which can supply human body heat after digestion and absorption.