An energy storage system includes at least one heterogeneous pressure media and interactive actuation module (“module”), a liquid source, a pump, a converter, a first pipeline, and a second pipeline. The module includes a first container storing an initial gas and a second container storing an initial liquid. The liquid source stores a working liquid. The pump regulates the working liquid from the liquid source into the module. The initial liquid is driven by the working liquid to continuously compress the initial gas so that the first container stores a first pressure energy, and the initial gas is continuously expanded to drive the initial liquid to convert the first pressure energy into a second pressure energy. The second pressure energy through the first pipe drives the converter to generate an electrical energy, and the working liquid after driving the converter is returned to the liquid source through the second pipeline.