A number of flywheel units are arranged in a geometric pattern. Each of the flywheel units is enclosed in a containment unit. The containment unit includes a cylindrical tube, a cover, a bottom support, resting on the ground, on which the containment unit is mounted, and a fill medium surrounding each containment unit. The containment unit may also include a horizontal plate, mounted to the base of tube, which extends outward or radially from the base of tube a pre-determined length. In this case, the fill medium rests directly on top of the portion of the plate that extends outward from tube.