It is common practice to classify energy storage systems according to the physical form of energy stored. The following are the basic forms of stored energy: 1. Electrical energy, including electrical power as well as electrostatic or electromagnetic energy. 2. Chemical energy, including. Electricity storage systems store energy in electrostatic fields, such as bi-layer capacitors, and in magnetic fields, such as superconducting. Mechanical storage systems exploit the energy stored in gaseous, liquid, or solid media due to their position (potential), speed (kinetic), or thermodynamic state (pressure). They include CAES, pumped-storage plants, flywheels, mechanical stored energy, and. Chemical storage systems contain primary or secondary energy converted into energy carriers with high energy-densities. They include gases. Thermal-energy storage systems are secondary energy storage systems that store heat. They can be grouped by the technology used: 1. Sensible-heat storage system s store energy within a medium, changing in temperature before and after charging, which can.