No abstract

In an attempt to eliminate solid insulation challenges in cryogenic superconducting power cables, a new design concept for liquid cryogen cooled superconducting power cable was investigated. The design is based on superconducting gas insulated line (S-GIL). The design used liquid cryogen as the sole insulation medium. The suitability of the design for medium voltage power cables is discussed and the benefits of eliminating a solid insulation were identified. Experiments on 1-m long model cables with insulator tubes as spacers showed that the design is suitable for cables at 50 kV or higher. The actual limits could not be identified because of the experimental limitations originated from limited standoff distances in the measurement setup used. On a fundamental level, the investigations presented in the study showed a direct correlation between the intrinsic dielectric strength of the cryogen used and the maximum tolerated voltage for a given diameter of the cable system. The results show the promise for liquid nitrogen (LN2) and liquid hydrogen (LH2) cooled cables for various medium voltage applications, including electric aviation and electric ships.

The paper is a review of the opportunities and challenges of cryogenic power devices of electric aircraft, and the ongoing research and development efforts of the government agencies and the industry. Liquid Hydrogen (LH2) and Liquefied Natural Gas (LNG) are compared to support high temperature superconducting (HTS) and normal metal devices, respectively. The power devices were assumed to operate at the normal boiling point of the fuel used. The efficiencies of the electrical devices are estimated based on state-of-the-art technology. The mass flow rates and total fuel requirements for both the cryogenic fuels required to maintain the operating temperatures of the devices were simulated using thermal network models. A twin-aisle, 300 passenger aircraft with a 5.5 h flight duration was used for the models. The results show that the required masses of LH2 and LNG are 744 kg and 13,638 kg, respectively for the cooling requirement. The corresponding volumes of LH2 and LNG required are 9,760 and 30,300 L, respectively. In both cases, the estimated mass of the fuel needed for the aircraft is more than what is needed to maintain the cryogenic environment of the power devices. It was concluded that an electric aircraft with LNG cooled normal metal devices is feasible. However, an aircraft with HTS devices and cooled with LH2 is more attractive if the ongoing R&D efforts on HTS devices and LH2 infrastructure are successful. The emission reductions would be substantially higher with LH2, particularly when H2 is produced using renewable energy sources.