Design optimization of superconducting magnetic energy storage coil

•We modeled the optimization formulation that minimizes overall refrigeration load into the SMES cryostat.•Higher the operating current reduces the dynamic load but increases static heat load into the cryostat.•Higher allowable hoop stress reduces both coil volume and refrigeration load.•The formulation can be in general be utilized for any arbitrary specification of SMES coil and conductor type.

An optimization formulation has been developed for a superconducting magnetic energy storage (SMES) solenoid-type coil with niobium titanium (Nb–Ti) based Rutherford-type cable that minimizes the cryogenic refrigeration load into the cryostat. Minimization of refrigeration load reduces the operating cost and opens up the possibility to adopt helium re-condensing system using cryo-cooler especially for small-scale SMES system. Dynamic refrigeration load during charging or discharging operational mode of the coil dominates over steady state load. The paper outlines design optimization with practical design constraints like actual critical characteristics of the superconducting cable, maximum allowable hoop stress on winding, etc., with the objective to minimize refrigeration load into the SMES cryostat. Effect of design parameters on refrigeration load is also investigated.