It was verified that a new kind of energy is caused by “Spillover-Deuterium” generated in a double structure (DS)-cathode with “Pd-black”. Using this cathode, the authors confirmed the sustained production of a significantly abnormal amount of energy over a period of several months that could not be ascribed to chemical reaction energy. The chemical reaction energy of 0.1[mol] Pd-black used is only 4[kJ], but more than 200[MJ] of excess energy was continuously produced for over 3000[hr] at an average rate of 50-100[kJ/hr] using a DS-cathode with a same quantity of Pd-black. Intermittent operation over a period of two years using this structure proved the complete reproducibility of these results.