Speaker
Description
Cryogenic gaseous helium circulation has been demonstrated as a viable option for some high temperature superconducting (HTS) power system applications, particularly when lower operating temperatures (T < 65 K) are needed to achieve very high power densities. The feasibility of a superconducting integrated power system (SIPS) will depend on the development of necessary technologies that support power distribution such as high power terminations, circuit breakers, cryocoolers, and improved thermal insulation. Potential cryocooler failures and fault currents could lead to excessive heat loads at the cable terminations that need to be mitigated to maintain operability of the cable while contingency plans are activated. Gaseous helium cooled systems are particularly vulnerable for unexpected heat loads due to the low volumetric heat capacity. This study explores the possibility of designing the terminations with sufficient cryogenic thermal storage to mitigate unexpected heat loads. Incorporation of solid nitrogen storage anchored to the copper terminals of superconducting cables in the terminations is being studied as a solution. The thermal storage would maintain the operations of the cable for 5-10 minutes after a system contingency. The latent heat of the stored solid nitrogen and the heat capacities of both the solid and liquid phases are utilized for the required thermal storage. A self-contained system of thermal storage that utilizes activated charcoal in the external buffer to store nitrogen gas that condenses and solidifies during the normal operating conditions and evaporates during a heat surge is being studied as an option. This paper will present the results of cryogenic thermal modelling efforts using finite element analysis techniques. Experimental results on a model thermal storage system are used to validate the modelling results. The benefits of such cryogenic thermal storage on GHe cooled high temperature superconducting power distribution network for SIPS will be presented.