Investigations on Forced Flow Cooling Strategy for Solenoid Superconducting Magnetic Energy Storage (SMES) Devices Using High Temperature Superconducting (HTS) Cables Cooled by Supercritical Nitrogen (SCN)

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Raja Sekhar Dondapati

Abstract

Superconducting Magnetic Energy Storage (SMES) devices are the most reliable and promising in terms of energy density and energy security. However, the challenges encountered by these devices can be overcome by adapting suitable cooling strategies. Instead of using superconducting tapes on the Mandrel, High Temperature Superconducting (HTS) power cables can be wound on the mandrel due to higher energy density and due to higher energy storage capacity. While operating, SMES encounter few losses such as Alternating Current (A.C) losses in the superconducting tapes, dielectric losses in the dielectric material and thermal losses in the cryostat. The HTS cables wound on the mandrel mainly comprise of conductor phase consisting of HTS tapes enveloped in cryostat (two concentric corrugated pipes). The inner corrugated pipe is used as former in which the coolant flows to maintain the superconductivity of HTS tapes. The outer corrugated pipe of cryostat is wrapped with XLPE (Cross-Linked Poly Ethelene) to prevent the heat-in-leaks from the ambient. The thermal losses in HTS cables are mainly due to axial heat-in-leak from current leads, radial heat leak through insulating materials, cryostat-pipes and heat generation in the superconducting tapes. It is therefore necessary to investigate the effect of different heat flux on pressure drop and heat transfer. In the present work, an attempt has been made to propose Supercritical Nitrogen (SCN) as an alternative coolant for futuristic high temperature superconductors such as Hg (Mercury) based HTS tapes having critical temperature greater than 134K. Moreover, the effect of various heat fluxes and mass flow rates on pressure drop and heat transfer phenomenon in the futuristic SMES is also investigated using Computational Fluid Dynamics (CFD) algorithm. Finally, the pressure drop and heat transfer results of SCN are then compared with those of Liquid Nitrogen (LN2) experimental and computational results available in the literature.

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