NOVELTY - The device (10) has two containers (12, 14) connected to a connecting line (20), where the connecting line comprises three line sections (21-23). The first line section and the third line section form a heat exchanger (30) e.g. cooling device (70) or heating device (75), and are guided with respect to each other such that a working medium (16) e.g. liquid methane and liquid carbon dioxide, flows along opposite directions in the first and third line sections. A turbine (40) or a piston engine is arranged in the second line section to drive a generator for electricity generation.    USE - Device for converting heat energy of industry water or environment (all claimed) into electrical power.    ADVANTAGE - The first line section and the third line section form the heat exchanger, and are guided to each other such that the working medium e.g. liquid methane and liquid carbon dioxide, flows along the opposite directions in the first line section and the third line section in the heat exchanger so as to ensure effective heat transfer between the line sections, and to maintain pressure in a closed system in a constant manner, so that the movement of the working medium does not take place against the pressure, thus reducing the energy consumption of the device, and increasing the efficiency of the device. The liquid or the liquefied gas with large thermal expansion is used as the working medium, so that high volumetric flow of the working medium is ensured, thus enhancing efficiency of the device. The volume of the containers can be adapted to the volume of the working medium and the flow of the working medium, so that the device can be realized in a simple and inexpensive manner.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of an energy converting device.'(Drawing includes non-English language text)'    Energy converting device (10)    Containers (12, 14)    Working medium (16)    Connecting line (20)    Line sections (21-23)    Heat exchanger (30)    Turbine (40)    Cooling device (70)    Heating device (75)