Integrated industrial unit

An integrated industrial unit comprising:

• a nitrogen source configured to provide liquid nitrogen;
• a hydrogen source configured to provide gaseous hydrogen at a pressure of at least 15 bar(a);
• a hydrogen liquefaction unit, wherein the hydrogen liquefaction unit comprises a precooling system, and a liquefaction system;
• and
• a liquid hydrogen storage tank,
• wherein the precooling system is configured to receive the gaseous hydrogen from the hydrogen source and cool the gaseous hydrogen to a temperature between 75 K and 100 K,
• wherein the precooling system comprises a primary refrigeration system and a secondary refrigeration system,
• wherein the liquefaction system is in fluid communication with the precooling system and is configured to liquefy the gaseous hydrogen received from the precooling system to produce liquid hydrogen,
• wherein the liquid hydrogen storage tank is in fluid communication with the liquefaction system and is configured to store the liquid hydrogen received from the liquefaction system,
• wherein the primary refrigeration system comprises compressors and expanders configured to compress and expand, respectively, a primary refrigerant, wherein the expanders are configured to have an outlet pressure of Pi,
• wherein the secondary refrigeration system provides refrigeration to the precooling system by vaporization of liquid nitrogen at pressure P2, wherein the primary and secondary refrigerants are not in fluid communication.