The Japan hydrogen project, WE-NET (World Energy Network), has shown that high-density LH
2 (liquid hydrogen) is the most promising medium for transporting and storing large-mass hydrogen efficiently and economically. In the future, large-mass liquid hydrogen storage technology for ground tanks and ocean tankers will be needed, and the commercial scale may be the same as existing LNG storage systems, which have a storage capacity of several hundreds of thousands of cubic meters. The conceptual designs of 200,000 m
3 LH
2 tankers and 50,000 m
3 LH
2 ground tanks were studied in WE-NET Phase I (1993-1998). This study has concluded that the optimized thermal insulation structure for a large storage tank should be developed. Therefore, in Phase II of WE-NET (1999-2002), we tested the thermal conductance and cryogenic compressive strengths of insulation materials in order to develop various insulation structures. Their conceptual designs were reviewed by analyzing experimental results. To realize the government target of introducing 50,000 fuel-cell vehicles by 2010 and 5 million vehicles by 2020, a hydrogen supply infrastructure must be constructed. Since LH
2 is applicable for the hydrogen infrastructure, we have developed a high-performance LH
2 container, a key component of the system. This paper describes the conceptual designs of LH
2 tankers and LH
2 ground tanks, elementary tests of various insulations, and also the LH
2 infrastructure for fuel-cell vehicles.
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