Variation 4

Variation 4 depicts the variation that is insusceptible to waves of water lapping over the plant and influencing the amount of water inside. The water level of the large reservoir is below the water level inside the storage plant. Just like Variation 3, Variation 4 contrasts Variations 1 and 2 in that the direction of the energy conversion is reversed. For this purpose the hydraulic energy storage plant is equipped with buoyant bodies within the 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.

During pump operation mode an extremely flexible material is deformed, in relation to the water pressure inside. As a result the potential energy, now deformation energy, can be stored and released in turbine operation mode. The flexible material in its most basic design can be realized as an air cushion. Consequently the floating energy storage has to be designed as an air-tight tank.