Clean energy is generated when the wind blows, the sun shines, when it rains, when the waves rise, or the tide falls. If many sources are used, and they are spread over a wide area, then the supply will be steady enough to suit the needs of electricity users.
However when demand and supply are out of step, it would be extremely useful to be able to store electricity, or the energy needed to produce it.
The following pages explore the options.
Heat is under Kinetic Energy because that is what it is on a molecular level.