Energy storage is divided into three major systems

These classifications lead to the division of energy storage into five main types: i) mechanical energy storage, ii) chemical energy storage, iii) electrochemical energy storage, iv) electrostatic and electromagnetic energy storage, and v) thermal energy storage, as illustrated in (Figure 2).

There are several approaches to classifying energy storage systems. The most common approach is classification according to physical form of energy and basic operating principle: electric (electromagnetic), electrochemical/chemical, mechanical, thermal.

It was classified into three types, such as sensible heat, latent heat and thermochemical heat storage system (absorption and adsorption system) (65). (Figure 14) shows the schematic representation of each thermal energy storage systems (66). Figure 14. Schematic representation of types of thermal energy storage system. Adapted from reference (66).

They are divided among the three energy storage processes: charging (converting energy), storing (holding energy), and discharging (converting energy). In the following discussion, these parameters are categorized and defined in terms of power, energy, and other criteria.

The most common chemical energy storage systems include hydrogen, synthetic natural gas, and solar fuel storage. Hydrogen fuel energy is a clean and abundant renewable fuel that is safe to use. The hydrogen energy can be produced from electrolysis or sunlight through photocatalytic water splitting (16,17).

Electricity storage systems include those that store electrical energy directly; for example, electrostatically (in capacitors) or electromagnetically (in inductors) (Kap. 6).