A Flywheel Energy Storage System (FESS) can be a succesful alternative of an electromechanical battery, in order to achieve intermediate energy storage (buffering) in RES_based stand-alone systems. Although based on a mature idea, these stationary applications are found in an early stage. In all FESSs can be found: 1) a generator motor, 2) a rotational mass which transforms the electrical energy into kinetic (usually housed in a sealed vacuum enclosure and stabilized by nearly frictionless magnetic bearings). In the present project, the mass is rotated in the open air, based on simple mechanical bearings while an electromagnetic clutch is used to engage / disengage the rotational axle with the electric motor. To reduce the friction, the highest rotational speed has to be succeeded for the maximization of the kinetic energy. The rotating mass is actually a hallow aluminum cylindrical mass where an electric motor of 1 hp power is used to spin it up and an electromagnetic clutch is used for the transmission (see above). The system is controlled by an automatic relay under continuous voltage inspection.