MgB2 wires with Tc ~ 39 K has been developed for the applications such as various coils. Considering hydrogen society in the future, MgB2 coils for the Superconducting Magnetic Energy Storage (SMES) devices under conduction cooling are worth serious consideration. First, the authors evaluated critical current density in commercially available MgB2 wires as a function of magnetic field and temperature (Ic-B-T) under conduction cooling. Ic of these MgB2 wires aligned in straight and curve lines under an external magnetic field up to 3.5 T by superconducting magnets was measured at 20-30 K. And then, the authors analyzed bending strain of MgB2 cable and coil, and designed double-pancake coils for several tens of kJ class SMES system. Finally, the authors produced a prototype pancake coil (200 mm inner diameter, 269 mm outer diameter, and thickness 7 mm) experimentally and evaluated coil properties under an external magnetic field. These results suggest can allow us to construct the robust energy storage system using MgB2 wires.
Acknowledgements: This work was supported by Advanced Low Carbon Technology Research and Development Program (ALCA) of Japan Science and Technology Agency (JST).