A system for generating electrical power supply signals includes at least one heat engine having a chamber that undergoes heating/cooling cycle and corresponding pressure variations. At least one piezoelectric transducer is deformed in response to the pressure variations of the heat engine. A power converter transforms the electric signals generated in response to deformation of the piezoelectric transducer(s) to a desired electrical power supply signal. The heat engine preferably uses a geothermal source of cold and an ambient source of hot or vice-versa. Hydrogen can be used as a working fluid, and metal hydride material can be used for absorbing and desorbing hydrogen during the cycle of heating and cooling of the heat engine. A phase change material can also be used. The power converter preferably includes an electromechanical battery with a flywheel storing rotational energy and possibly an electrostatic motor that adds rotational energy to the flywheel.