Embodiments provide systems and methods for taking power from an electric power grid and converting it into higher-pressure natural gas for temporary storage. After temporary storage, the higher-pressure natural gas may be expanded through an expansion engine to drive a generator that converts energy from the expanding natural gas into electrical power, which may then be returned to the electric power grid. In this way, the disclosed systems and methods may provide ways to temporarily store, and then return stored power from the electric power grid. Preferably, the components of the system are co-located at the same natural gas storage facility. This allows natural gas storage, electrical energy storage, and electrical energy generation to take place at the same facility.

A method for storing an energy-storage fluid within a subterranean formation having suppressed microbial activity includes injecting a high-salinity aqueous solution into the subterranean formation via at least one injection wellbore extending from a terranean surface and penetrating the subterranean formation, such that at least a portion of the high-salinity aqueous solution is held within the subterranean formation. The high-salinity aqueous solution includes water and an inorganic salt, and is configured to suppress microbial activity in the subterranean formation. The method also includes injecting the energy-storage fluid into the subterranean formation via the at least one injection wellbore to store at least a portion of the energy-storage fluid within the subterranean formation.

Embodiments provide systems and methods for taking power from an electric power grid and converting it into higher-pressure natural gas for temporary storage. After temporary storage, the higher-pressure natural gas may be expanded through an expansion engine to drive a generator that converts energy from the expanding natural gas into electrical power, which may then be returned to the electric power grid. In this way, the disclosed systems and methods may provide ways to temporarily store, and then return stored power from the electric power grid. Preferably, the components of the system are co-located at the same natural gas storage facility. This allows natural gas storage, electrical energy storage, and electrical energy generation to take place at the same facility.

A novel method for storing high purity hydrogen into a salt cavern is provided. Particularly, the storage process involves confining the high purity hydrogen at a certain pressure in a salt cavern without seepage or leakage of the stored hydrogen through the salt cavern walls. The pressure in the cavern is maintained during storage of the high purity hydrogen.

A method for forming and maintaining a fundamentally impervious boundary to very high purity hydrogen stored in a salt cavern is provided. The cavern includes a salt cavern wall. The method includes introducing a compressed very high purity hydrogen gas into a salt cavern, thereby producing a stored very high purity hydrogen gas; forming a fundamentally impervious boundary to the very high purity hydrogen along at least a part of the perimeter of the salt cavern, and maintaining the fundamentally impervious boundary to the stored very high purity hydrogen gas at a pressure greater than 1.0 psi per linear foot of height within the cavern, and less than 4.0 psi per linear foot of height within the cavern and thereby retaining within the salt cavern over 95% of the stored very high purity hydrogen over a period of time of at least 72 hours.

A novel system for operating a hydrogen storage cavern is provided. Particularly, the system involves storing high purity hydrogen into a salt cavern without seepage or leakage of the stored hydrogen through the salt cavern walls, by confining the high purity hydrogen gas within the storage cavern under certain pressure conditions.

A method and system for storing and supplying hydrogen to a hydrogen pipeline in which a compressed hydrogen feed stream is introduced into a salt cavern for storage and a stored hydrogen stream is retrieved from the salt cavern and reintroduced into the hydrogen pipeline. A minimum quantity of stored hydrogen is maintained in the salt cavern to produce a stagnant layer having a carbon dioxide content along the cavern wall and the top of a residual brine layer located within the salt cavern. The compressed hydrogen feed stream is introduced into the salt cavern and the stored hydrogen stream is withdrawn without disturbing the stagnant layer to prevent carbon dioxide contamination from being drawn into the stored hydrogen stream being reintroduced into the hydrogen pipeline. This allows the stored hydrogen stream to be reintroduced into the hydrogen pipeline without carbon dioxide removal.

A method for subsurface gas storage including injecting a hydrogen stream into a subsurface reservoir for storage during periods of low sales demand, mixing the hydrogen stream in the subsurface reservoir with a stored gas, and removing the hydrogen from the subsurface reservoir during high sales demand.

A method for controlling the pressure in an underground storage volume, wherein the underground storage volume is at least in part filled with an incompressible fluid, the pressure is monitored, a compressible fluid can be introduced into and extracted from the underground storage volume, if the pressure reaches a predetermined upper pressure limit incompressible fluid is extracted from the underground storage volume for reducing the pressure in the underground storage volume; if the pressure volume reaches a predetermined lower pressure limit incompressible fluid is introduced into the underground storage volume for increasing the pressure in the underground storage volume. The method according to the present invention allows the increase the amount of compressible fluid like helium stored in an underground storage volume, e.g. a salt cavern, by adjusting the pressure by the introduction or extraction of an incompressible fluid like brine.

A method of pad gas management in an underground storage volume including storing a first compressible fluid, determining a transient minimum operating pressure (P.sub.trans), measuring the pressure (P.sub.act), removing at least a portion of the first compressible fluid, concurrently, introducing an incompressible fluid, thereby producing a transient pressure condition controlled by the flow rate of the incompressible fluid, such that P.sub.trans<P.sub.act. The method may also include a length of casing, permanently cemented into the surrounding rock formations, with a final cemented casing shoe defining the practical endpoint at an approximate depth (D.sub.casing), determining a transient pressure gradient (G.sub.trans) for the underground storage volume, wherein P.sub.trans<D.sub.casingG.sub.trans. The maximum removal of the first compressible fluid is controlled such that P.sub.min<P.sub.act, and wherein the transient pressure condition has a duration (D) of less than 7 days, more preferably less than 5 days.