Abstract: Buoyancy forces [N] and gravitational forces [N] of buoys in fluids are used as drive forces. Buoys are placed in one or more water-filled container/s. To use the buoyancy force [N], the buoys are connected to an energy storage device, herein springs. In addition, the buoys are temporarily connected to a reference system by either the container or a movable frame within the container. Upon fastening the containers to a movable system, both buoyancy and gravitational forces [N] are exerted via a short working stroke, producing effective energy. To repeat said energy supply, the movable system must resume the starting position. For this process to occur, internal and external energy may be used. In a technical application, this invention can supply electric energy via a gyrating mass, propel hydraulic or compressed air cylinders, or enable other repetitive motions (pumps.) The described system can also be used for energy storage.