New second-generation high temperature superconducting coated conductors (2G HTS CC) with greatly-improved thermal stability

点击翻译按钮获取中文摘要

Unlike earlier generations of commercial superconducting wires, which require expensive liquid helium refrigerant near 4.2 K, second-generation high temperature superconducting coated conductors (2G HTS CC) merely need cheap liquid nitrogen at 77 K as the coolant. The refrigeration overhead costs are therefore at least 20 times lower; this technology is poised to invade electric power industries, an annual market place of close to a trillion dollars. A particular application addressed by this proposal is the superconducting fault current limiter (FCL), a security device for overloaded electric power grids world-wide. Unfortunately, currently available commercial "YBCO" (rare-earth cuprate)-based 2G HTS CC tapes have a major handicap, namely the danger of developing destructive "hot-spots" during a superconducting-to-normal quench event. It is the aim of the proposed research to help resolve this shortcoming: we have recently demonstrated that deliberately introducing a "flow diverter" (in the form of a highly-resistive interface between the superconductor and the outer normal metal stabilizer) has the effect to greatly (ca. 30-fold) enhance the normal zone propagation velocity (NZPV). The resulting "quench" (sudden loss of superconductivity) thereby becomes homogeneous throughout the volume of the superconductor, greatly reduces the possible appearance of hot spots, and thus prevents destruction of the tape and the device. We propose several approaches for introducing a flow diverter, based on surface modification or on the deposition of resistive thin film coatings, for example P-doped nano-crystalline silicon (nc-Si:P). Evidently, a prerequisite for successful implementation by the manufacturers of 2G HTS CC must be ease of adding the new step(s) into existing high-volume (km/day) fabrication processes. The applicants have filed a provisional patent application on their invention, in collaboration with Gestion Univalor, L.P., the commercialization partner of École Polytechnique, who will assist in eventual commercial licensing of this new technology to 2G HTS CC tape producers. A potential user based in Ontario is supporting this current I2I proposal, as it plans to implement it in their products.