Research and Development of Liquid Hydrogen-Cooled Superconducting Energy Apparatus

A hydrogen based energy infrastructure, where liquid hydrogen (LH2) is one of the important energy carriers, has recently been being developed in support of a future carbon-free society. Effective utilization of LH2 cold energy is one of the key issues. We have been developing a hydrogen-cooled energy apparatus under a grant from the Japan Science and Technology Agency (JST). LH2 has good physical properties for cooling, including a low boiling point, a high latent heat, a high specific heat and low viscosity properties. Moreover, its low boiling point (20.3 K) is advantageous in view of the excellent electromagnetic properties of high-critical-temperature superconductors, such as YBCO, BSCCO and MgB2, which have been under development for many years. It is important to understand the heat transfer characteristics of LH2 in order to design LH2 cooled superconducting devices. For this purpose, we have designed and constructed basic experimental facilities, such as a thermal-hydraulics experimental system for LH2, in order to carry out systematic investigation of the forced-flow heat transfer, set up experiments for investigating the electro-magnetic properties of superconductors or superconducting magnets, and introduced an LH2 supply and exhaust test system for superconducting rotating machines. Using these facilities, we have conducted systematic experiments relevant to LH2 cooling properties, and LH2-cooled superconductor and superconducting magnet properties, and hence, have accumulated operational experience for handling LH2 safely throughout over 25 test events.