Superconducting magnet design for magnetic liquefiers using total cost minimization

Abstract The Active Magnetic Regenerator (AMR) cycle can liquefy cryogens with high efficiency, however the system economics have not been investigated. The computational complexity of AMR modeling tools has limited the parameter space of numerical investigations, and the correlations between the cryocooler and cryogen cost have yet to be resolved. To address these issues, we present a system-level cost optimization of a magnetic liquefier with a Rare-Earth Barium Copper Oxide (ReBCO) high temperature superconducting (HTS) magnet. Using the semi-analytic AMR element model, the capital and operating costs of the cryocooler, superconducting tape and AMR system are optimized in a nested genetic-differential evolution algorithm and explored as a function of the cryocooler temperature. It is shown that a 20 K HTS magnet is several times cheaper than its 70 K counterpart, and in the optimized system, the cost to liquefy natural gas approaches 0.24 $/kg with a 3.57 tonne-per-day capacity and a plant cost of $350,000.