Seoul metropolitan government
Electrical energy is high-quality form of energy, and thus it is beneficial to store the excessive electric energy in the Electrical Energy Storage (EES) rather than converting into a different type of energy. Like memory devices, no single type of EES element can fulfill all the desirable requirements. Despite active research on the new EES technologies, it is not likely to have an ultimate high-efficiency, high-power/ energy capacity, low-cost, and long-cycle life EES element in the near future. The authors propose an HEES system that consists of two or more heterogeneous EES elements, thereby realizing the advantages of each EES element while hiding their weaknesses.