Concept and classification of energy storage technology

The concept of energy storage technology

Broadly speaking, energy storage refers to the storage of energy. That is, through a medium or equipment, the current remaining energy is stored in its own form, or converted into another form of energy, and released in a specific form of energy according to the needs of future use. Energy storage in the narrow sense refers to the storage of electrical energy, that is, the technology that uses physical or chemical methods to store electrical energy.

The concept of energy storage is gradually formed in the process of purposeful use and control of energy by humans. In primitive society, people moved stones to high places and used mechanical energy to attack intruders, which was one of the earliest forms of energy storage. With the continuous development of society, human dependence on and demand for energy has gradually changed, prompting corresponding changes in the content and form of energy storage.

At the end of the 18th century, the “Volt Stack” connected energy storage with “electricity” for the first time. With the outbreak of the industrial revolution, electric power has become more and more widely used in people’s production and life, and people’s reliance on electric power has continued to increase. Batteries that can store electrical energy have become a convenient source of electricity, and battery technology development and utilization have become the core of the energy storage industry, but battery energy storage has always been limited to traditional small-scale applications. After the development of large-scale power systems in the 20th century, thanks to the development and utilization of new energy sources and the promotion of smart grids, the development and utilization of large-scale energy storage technologies have re-entered people’s vision. At present, energy storage is widely used in power systems, electric vehicles, rail transit, uninterruptible power supplies (UPS), power tools, and electronic products.

Large-scale application in the power system is the future development direction of the energy storage industry. Its applications in the fields of power generation, power transmission and distribution, user terminals, auxiliary services, new energy grid-connected fields, distributed power generation and micro-grid fields are the focus of attention. Energy storage is an important part of the smart grid. The development of energy storage technology is conducive to promoting the large-scale application of renewable energy. It can cut peaks and fill valleys in the power system, improve grid efficiency, reduce or delay investment in power construction, and improve the ability to respond to emergencies to ensure the safe operation of the power system.

Classification of energy storage technology

According to whether a chemical reaction occurs during the energy storage process, energy storage technology can be roughly divided into physical energy storage and chemical energy storage.

Physical energy storage refers to the conversion of one kind of energy into another form of energy storage without changing the composition of the medium, and releasing the energy when needed. According to different working principles, it can be divided into pumped water storage, compressed air energy storage, flywheel energy storage and superconducting energy storage.

Chemical energy storage refers to the technology in which the energy storage medium converts one kind of energy into another form of energy through a chemical reaction, and can release the energy through a chemical reaction when needed. The chemical energy storage process is accompanied by a chemical reaction of the medium. According to the different chemical substances that react, they can be divided into lead batteries, lithium ion batteries, flow batteries, molten salt batteries, nickel-hydrogen batteries, fuel cells, metal-air batteries, and super capacitors. Supercapacitors are also called electrochemical capacitors. Although some supercapacitors do not undergo chemical reactions during charging and discharging, their structure and performance are similar to those of batteries, so they are classified as chemical energy storage technology in this site.

According to the narrow definition of energy storage, because fuel cells and metal-air batteries do not have the characteristics of “charging”, they cannot be equated with energy storage in the narrow sense. However, the characteristics and application fields of this technology are similar to those of energy storage products. In the current general consensus, fuel cells and metal-air batteries can also be regarded as chemical energy storage categories.