Key EES technologies include Pumped Hydroelectric Storage (PHS), Compressed Air Energy Storage (CAES), Advanced Battery Energy Storage (ABES), Flywheel Energy Storage (FES), Thermal Energy Storage (TES), and Hydrogen Energy Storage (HES). 16 PHS and CAES are. Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an accumulator or battery. Energy can be stored in various forms, including: When people talk about energy storage, they typically mean storing. As global renewable energy deployment accelerates, energy storage systems (ESS) have evolved from optional add-ons into core infrastructure for modern power systems. The first battery, Volta's cell, was developed in 1800.