Nanoelectromechanical systems utilizing nanometer-scale assemblies are provided that convert thermal energy into another form of energy that can be used to perform useful work at macroscopic level. Nanometer-scale beams are provided that reduce the velocity of working substance molecules that collide with this nanometer-scale beam by converting some of the kinetic energy of a colliding molecule into kinetic energy of the nanometer-scale beam. In embodiments that operate without a working substance, the thermal vibrations of the beam itself create the necessary beam motion. Automatic switches may be added to realize a regulator such that the nanometer-scale beams only deliver voltages that exceed a particular amount. The output energy of millions of these devices may be efficiently summed together.