1) Heat Exchange measurements and modelling between HTS-CCs tapes and LN2 bath.
A technique to measure real time heat exchange between a High Temperature Superconducting Coated Conductors (HTS-CC) and the liquid Nitrogen (LN2) bath at 65 -77 K has been developped in our lab. This technique uses a unique current pulser developped by EPFL and Polytechnique Montréal, the temperature is measured using intrinsec properties of specially prepared HTS-CC. The project aimed to measure the heat transmission coefficient in various power and temperature condition. This coefficient will be tested and used in COMSOL 3D Finite Elements Modelling.
This project is proposed in the framework of FastGrid project (http://fastgrid-h2020.eu/en/Home-2.html) which aims is a significant and impacting enhancement on the effective cost of high temperature superconductor coated conductors for the application on SuperConducting Fault Current Limiters (SCFCL). HTS-CCs are a really promising technology for future technologies in many fields (power systems, fusion reactors, high-energy physics, medical applications etc). Because of intrinsic defects of the tapes and of the principle of working of an SFCL the protection of the device and the cryogenic aspects are critical for the project. One of the tasks of which EPFL is in charge of, is to study the heat exchange between HTS-CCs FastGrid tapes and LN2 bath.
The student will use unique instrumentation able to pulse current in ms range up to 3.2 kA, used for NZPV characterization. He will work in contact with a team of the bests European laboratories in that field.
2) Evaluation of 2nd generation superconducting tapes as FCL elements.
Recently, our team succeeds in FEM modeling of high temperature superconducting fault current limiters (FCL) elements. By introducing a saturated E-J relation and taking into account the temperature dependence of the electrical parameters, the current limitation phase had been numerically simulated and results are in good agreement with measurements made on real samples. Based on our numerical modeling knowledge, we want now to study the electrical and thermal behavior of FCL elements made with emerging “commercial” coated conductors. The aim of this proposed project is to first identify the conductors resulting of different manufacturing process, and collect their electric and thermal properties. Then the work would be to simulate these conductors as FCL elements. The results will be decisive for the choice of the conductor in future FCL projects.
The student will be familiar with last conductors fabrication techniques, and will practice multiphysics Finite Element Modeling.