This paper describes a part of our feasibility study on the storage of hydrogen in the form of clathrate hydrates. The specific objective of this paper is to present conceptual designs of hydrogen-hydrate production plants applicable to large-scale in situ storage of hydrogen produced in an industrial complex area or to smaller-scale urban-area storage of hydrogen which is to be transported from the industrial complex area by container trucks. The plants were so designed as to produce either a simple hydrogen hydrate under a pressure of 35 MPa and a temperature of 140 K or a mixed hydrogen + tetrahydrofuran hydrate under a pressure of 30 MPa and a temperature of 223 K. In either case, the rate of hydrogen uptake into the hydrates during their production in each plant was targeted for 3000 Nm(3)/h (for use in an industrial complex area) or 500 Nm(3)/h (for use in an urban area). For each type of plant, we have prepared a process flow diagram accompanied by material-balance, heat-balance, and machinery specifications. The energy consumption in plant operation has also been evaluated, assuming that the cool energy generated by adjacent LNG facilities may or may not be available for cooling the hydrate-forming assemblies in each plant.