Variation 3

Variation 3 shows a variation in which the water level of the larger reservoir is below the water level in the energy storage plant. In contrast to Variations 1 and 2, the direction of energy conversion is reversed. For this purpose the hydraulic energy storage plant is equipped with buoyant bodies within the structure, that are underneath the water reservoir, which raise the bottom of the water reservoir above the water level of the outer reservoir.

In turbine operation mode the floating structure rises, working against gravity. The potential energy is converted into electric energy and released. In pump operation mode the floating plant is lowered, thereby converting the electric energy into potential energy and storing it.