(US4808029-A)      The system for subterranean storage of energy comprises a lower and a higher cavern formed in a subterranean salt formation, both caverns being partially filled with salt soln. and a gas supply for pressurising a head space in each cavern. A channel interconnects the liquid filled portions of the caverns, a second channel interconnects the pressurised head spaces, and a pumping-generating plant at the ground surface connected between two vertical branches of the first channel. The plant is operable for pumping liquid through the first channel from the lower to the higher cavern when supplied with energy, or for generating energy when driven by liquid flowing through the first channel from the higher to the lower cavern.    The gas supply maintains a pressure equal or greater to the hydrostatic pressure differential between the liquid filled spaces in the caverns and also sufficient for driving the liquid from the lower cavern to the ground surface.    USE/ADVANTAGE -   Electrical power generation. Optimises heat source.    (EP247690-B)      A system for subterranean storage of energy, in which in a subterranean salt formation, caverns are formed by washing by means of water the lower sides thereof being interconnected by means of a first channel, and the upper sides by means of a second channel, from which caverns, by introducing gas under pressure, a part of the salt solution has been removed, the liquid spaces thereof being interconnected by means of the first channel, and the gas spaces by means of the second channel, in which first channel an assembly is included which is adapted for pumping liquid through the first channel from the lower towards the higher cavern when energy is supplied, and, on the other hand, producing electric energy by liquid flowing back through the first channel from the higher toward the lower cavern, which gas pressure is, furthermore, such that at this assembly, the difference between the gas pressure and the hydrostatic pressure difference between both liquid spaces is at least equal to zero, said channels being made so wide that the pressure drop in the flowing liquid becomes negligible, the assembly (21) being located at the ground surface (1) and is connected, by means of two branches (8, 9; 26, 27) of said first channel to the lower sides of the lower and higher cavern (4, 5) respectively, the gas pressure being chosen such that the liquid is driven upwards form the lower cavern (4) towards the surface (1), and no cratering towards the ground surface (1) from said higher cavern (5) can occur, and that cased boreholes (9, 26) which are subjected to the high gas and/or liquid pressures extend to a depth that is sufficiently deep to avoid cratering of gas and/or liquid to the ground level. (7pp)