A downhole electric power generator is disclosed in one embodiment of the invention as including an inlet channel formed in a bore of a downhole tool string component for conveying a moving downhole fluid and a turbine coupled to the inlet channel to receive the downhole fluid. The turbine converts the energy of the moving downhole fluid into rotational energy where it is stored using a flywheel. The flywheel may then be coupled to an electrical generator to convert the rotational energy to electrical energy. In certain embodiments, a continuously variable transmission may be inserted between the turbine and the flywheel. The entire generator may, in certain embodiments, be designed small enough to reside in the wall of a downhole tool.