A device for converting thermal energy into electric energy intended to be used in combination with a hot source including: a capacitor of variable capacitance, including two electrodes separated by an electrically-insulating material, one of these electrodes being deformable and being associated with an element forming a bimetallic strip, said bimetallic strip including at least two layers of materials having different thermal expansion coefficients, said bimetallic strip being free to deform when it is submitted to the heat of said hot source; a second capacitor having a first electrode connected to a first electrode of said capacitor of variable capacitance; a harvesting circuit electrically connected between the second electrode of the capacitor of variable capacitance and the second electrode of the second capacitor, said harvesting circuit being capable of conducting the current flowing between said second electrodes.