Abstract: An energy box includes a container, and an electric power generation device housed therewithin. The electric power generation device includes a number of thin-film based thermoelectric modules, each of which is less than or equal to 100 ?m in dimensional thickness and includes pairs of N-type thermoelectric legs and P-type thermoelectric legs electrically in contact with one another on a flexible substrate, a number of hot plates, and a number of cold plates. The each thin-film based thermoelectric module further includes a first surface and a second surface in surface contact with a hot plate and a cold plate respectively to form the electric power generation device. The energy box is configured to generate electric power at utility scale through the electric power generation device based on a temperature difference maintained between the first surface and the second surface of the each thin-film based thermoelectric module.