NOVELTY - The method comprises compressing a feed stream of hydrogen to produce a compressed hydrogen feed stream, injecting the compressed hydrogen feed stream into a salt cavern (4) to produce stored hydrogen within the salt cavern through a conduit and then withdrawing a stored hydrogen stream, composed of the stored hydrogen, from the salt cavern through the conduit, introducing the stored hydrogen stream into a pipeline, and maintaining a minimum quantity of the stored hydrogen within the salt cavern before, during and between times at which the compressed hydrogen feed stream is injected.    USE - The method is useful for storing and supplying hydrogen to a hydrogen pipeline.    ADVANTAGE - The method is capable of economically and simply storing and supplying the hydrogen to the hydrogen pipeline.    DETAILED DESCRIPTION - The method comprises compressing a feed stream of hydrogen to produce a compressed hydrogen feed stream, injecting the compressed hydrogen feed stream into a salt cavern (4) to produce stored hydrogen within the salt cavern through a conduit and then withdrawing a stored hydrogen stream, composed of the stored hydrogen, from the salt cavern through the conduit, introducing the stored hydrogen stream into a pipeline, maintaining a minimum quantity of the stored hydrogen within the salt cavern before, during and between times at which the compressed hydrogen feed stream is injected and at which the stored hydrogen stream is withdrawn such that a stagnant layer of hydrogen is maintained that borders an interior region of the salt cavern and has a bottom portion overlying the residual brine layer and a lateral portion situated along side regions of the salt cavern, where the stagnant layer has a carbon dioxide content that is a potential source of carbon dioxide contamination to the stored hydrogen stream, and limiting the flow rates and the velocities at which the compressed hydrogen feed stream is injected into the salt cavern and the stored hydrogen stream is withdrawn from the salt cavern such that the stagnant layer is not disturbed and the carbon dioxide contamination of the stored hydrogen stream from the stagnant layer is inhibited. The salt cavern has a residual brine layer located at a bottom region of the salt cavern, where the side regions extend upwardly from the bottom region of the salt cavern. The conduit has a lower end that is located in the interior region of the salt cavern and spaced above the brine layer and from the side regions of the salt cavern, an injection conduit, and a withdrawal conduit, where the compressed hydrogen feed stream is injected into the salt cavern through the injection conduit and the stored hydrogen stream is withdrawn from the salt cavern through the withdrawal conduit. The lower end of the conduit is: spaced below a top region of the salt cavern at an upper vertical distance of greater than 50 feet, from the residual brine layer at a lower vertical distance of greater than 250 feet, and spaced from the side regions of the salt cavern at a lateral distance of greater than 40 feet from a vertical line extending 10-250 feet below the lower end of the conduit; located opposite to the bottom region of the salt cavern; and open. The stagnant layer has a top portion that extends along the top region of the salt cavern and is situated opposite to the bottom portion of the stagnant layer. Water is removed from the stored hydrogen stream prior to injection into the pipeline. The hydrogen feed stream: is compressed to pressure above the pipeline pressure within the pipeline; and contains less than 0.1 ppmv of carbon dioxide and less than 0.6 ppmv of carbon monoxide, where a sum of a carbon dioxide content and carbon monoxide content in the stored hydrogen stream is less than 1.0 ppmv. The stored hydrogen has a cavern pressure that is above the pipeline pressure. The stored hydrogen stream is removed from the salt cavern as a consequence of the cavern pressure and reduced to the pipeline pressure prior to injecting the stored hydrogen stream into the pipeline. The injection conduit has a flow diffuser from which the compressed hydrogen feed stream is injected into the salt cavern. The minimum volume of the hydrogen stored within the salt cavern is maintained at a volume ratio equal to a stored volume of the hydrogen to the actual cavern volume of greater than 29 standard cubic feet (scf)/cubic feet (cf). The flow rates and velocities are limited such that, as measured at the lower end of the conduit, the compressed hydrogen feed stream is injected at an injection ratio equal to an injection flow rate of the compressed hydrogen feed stream to the actual cavern volume of less than 7.5 scf day/cf and at an injection velocity of the compressed hydrogen feed stream of less than 100 feet per second and the stored hydrogen stream is withdrawn at a withdrawal ratio equal to the withdrawal flow rate of the stored hydrogen stream to the actual cavern volume of less than 10.0 scf day/cf and at a withdrawal velocity of the stored hydrogen stream of less than 150 feet per second. An INDEPENDENT CLAIM is included for a system for storing and supplying hydrogen to a hydrogen pipeline.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a system for storing and supplying hydrogen to a hydrogen pipeline.    System (1)    Hydrogen pipeline (2)    Flow network (3)    Compression side (3a)    Salt cavern. (4)