What exactly is Hydrogen Electric Propulsion Systems (HEPS) propulsion ?

High-Temperature Superconducting (HTS) Generators

HEPS often utilize HTS generators, which are key components in reducing CO2 emissions. These generators work in tandem with hydrogen gas turbines, harnessing the cold energy of liquid hydrogen. This approach negates the need for additional refrigeration, thereby minimizing cooling costs. One ambitious goal in this field is the commercialization of a 600 MW-class liquid hydrogen-cooled HTS generator.

Such a generator requires an assembled conductor capable of conducting 6 kA at 20 K and 5 T. A notable aspect of these conductors is their ability to manage interlayer current distribution effectively, which is crucial for steady operation and rapid response to power demands​​.

Superconducting Coils and Magnetic Fields

Another important aspect of HEPS is the use of superconducting coils. These coils, when applied to a rotating magnetic field, have been studied for their alternating current losses at cryogenic temperatures. Such studies are vital to understanding the efficiency and functionality of HEPS under various operational conditions​​.

Advantages of Superconducting Machines

Superconducting rotating machines, integral to HEPS, offer advantages over conventional machines, including higher efficiency, reduced size and weight, and lower energy consumption. High-temperature superconducting materials simplify the cooling design compared to low-temperature superconductors. These machines have been categorized based on the form of superconductor used, including wires/tapes, bulks, and stacked tapes, and have been applied in various types of machines, such as synchronous, induction, and flux modulation machines​​.

The Role of Liquid Hydrogen

Liquid hydrogen plays a dual role in HEPS – as a fuel and as a coolant. Its use as a coolant is particularly advantageous in fully electric aircraft designs. The Moscow Aviation Institute’s research into fully superconducting aviation synchronous generators for electric propulsion systems has highlighted the importance of liquid hydrogen in increasing the linear load of the generator and reducing the cross-sectional area of the coils.

This approach has the potential to facilitate the placement of these coils in individual cryostats, further enhancing the system’s efficiency​​.

Hydrogen Hybrid Electric Propulsion Systems (H2EPS)

A collaboration between the Electric Aviation Group (EAG) and the University of Nottingham aims to develop and commercialize kW-MW class electric propulsion systems, both superconducting and non-superconducting, for aerospace and non-aerospace applications. These systems are intended to support the development of hybrid, all-electric, and hydrogen-electric aircraft, with the ultimate goal of decarbonizing the aviation sector.

The University of Nottingham brings to the table expertise in power electronics and electrical machines for aerospace applications, having previously demonstrated aircraft propulsion drive systems up to 4MW/5MVA​​.