The different types of energy storage can be grouped into five broad technology categories: Within these they can be broken down further in application scale to utility-scale or the bulk system, customer-sited and residential. In addition, with the electrification of transport, there is a further mobile application category. 1. Battery storage
Mechanical energy storage systems are classified into the following types based on their working principles: pressurized gas, forced springs, kinetic energy, and potential energy. Mechanical energy storage systems have the advantage of being able to readily deliver the energy whenever required for mechanical works.
2. Regarding the type of energy to be stored (received by the storage system) and produced (the output of the system), any energy carrier (electricity, mechanical work of shaft or reciprocating pistons, thermal energy, fuels, etc.) could be the case.
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.
Chemical energy storage systems are sometimes classified according to the energy they consume, e.g., as electrochemical energy storage when they consume electrical energy, and as thermochemical energy storage when they consume thermal energy.
Electrochemical storage systems can be classified into four categories based on the principle of operation: primary cells or batteries, secondary cells or batteries, reserve cells, and fuel cells. The existing types of electrochemical storage systems vary according to the nature of the chemical reaction, structural features, and design.