An energy storage power supply is a device capable of converting electrical energy into other forms of energy and converting it back into electrical energy when needed.It is primarily used to store unstable or intermittent energy sources to provide energy in situations of peak energy demand or when conventional power supplies are not available.

Energy storage power supplies are usually classified into the following types:

1. Electrochemical energy storage: common electrochemical energy storage systems include lithium-ion batteries, lead-acid batteries and sodium-sulfur batteries. These batteries can convert electrical energy into potential energy through a chemical reaction and reverse the change to produce electrical energy when needed.

2. Mechanical energy storage: Mechanical energy storage usually uses heavy lifting, energy storage springs, compressed air or liquid energy storage to store energy. When electrical energy is needed, these storage systems can release the stored energy to generate power.

3. Thermal energy storage: Thermal energy storage typically uses the high or low temperature state of a thermal medium (such as molten salt, rock or water vapour) to store energy. When electrical energy is required, these storage systems convert the stored thermal energy into electrical energy through a thermal cycling process.

4. Compressed air energy storage: Compressed air energy storage systems take electrical energy and compress it using a compressor and store it in a storage tank. When electrical energy is needed, the compressed air in the tank is released through an expander and drives a generator to produce electrical energy.

These energy storage power sources can be used to balance the difference between energy supply and demand, increase energy utilisation, reduce energy waste and play an important role in renewable energy and smart grids.