Why is it that alternating current cannot be stored?
1 Answer
Devices used to store electrical energy are DC. Batteries and Capacitors store electrical charge electrostaticly or electrochemically. This involves a polarization of a material or a chemical change in the material. One does not store electrical current. One stores electric charge. A current only exists when there is a moving electric charge.
Or course, there are devices which allow you to convert an AC current into a DC current. Energy could then be stored. Subsequently, the energy could be used and converted back to AC.
AC can also be stored is a dynamic way using capacitors and inductors. Like a resonance in an organ pipe or a violin string, a series a small pulses causes an oscillation which can store a lot of energy. All of these systems do lose energy. Resistance in the wires will cause the oscillation to fade away once the source is removed. This is not unlike the sound of a violin string after the performer lifts the bow from the string. The string will still produce sound for some time, but it will fade from hearing.
