Integration of industrial gas site with liquid hydrogen production

A method for producing liquid hydrogen, the method comprising the steps of:

• introducing pressurized natural gas from a high pressure natural gas pipeline to a gas processing unit under conditions effective for producing a purified hydrogen stream;
• and
• introducing the purified hydrogen stream to a hydrogen liquefaction unit under conditions effective to produce a liquid hydrogen stream, wherein the purified hydrogen gas is sent from the gas processing unit to the hydrogen liquefaction unit, wherein there is an absence of a motor-driven compressor downstream the PSA unit and upstream the liquefaction unit, such that the purified hydrogen gas is sent from the PSA unit to the liquefaction unit without using the motor-driven compressor,
• wherein the hydrogen liquefaction unit provides a warm temperature cooling and a cold temperature cooling to the purified hydrogen stream,
• wherein the warm temperature cooling is provided by utilizing letdown energy of a pressurized stream selected from the group consisting of a nitrogen stream sourced from a nitrogen pipeline, liquid nitrogen, a natural gas stream sourced from the high pressure natural gas pipeline, an air gas sourced from an air separation unit, and combinations thereof,
• wherein the cold temperature refrigeration is provided by utilizing letdown energy of the purified hydrogen stream.