# Outline of energy storage

The following outline is provided as an overview of and topical guide to energy storage:

Energy storage – accomplished by devices or physical media that store some form of energy to perform some useful operation at a later time. A device that stores energy is sometimes called an accumulator.

## History of energy storage

Main article: History of energy storage

## General energy storage concepts

1. Using a high density magnetic field. Energy ${\displaystyle E}$ in terms of magnetic field strength ${\displaystyle B}$ is

${\displaystyle E={\frac {1}{2}}B^{2}={\frac {1}{2}}Li^{2}}$

where ${\displaystyle L}$ is the inductance of the electromagnet and ${\displaystyle i}$ is the current.