Potential of metal hydride-based range extenders for commuter aircraft

Abstract

Using alternative fuels like hydrogen in electrified propulsion systems is one possible approach for reducing aircraft emissions. The development of safe hydrogen storage with acceptable energy densities is an essential challenge being addressed in current research. Metal hydrides enable inherently safe and long term hydrogen storage. While also offering high volumetric storage densities, they achieve only low gravimetric storage densities. These properties impede the use of metal hydrides as a primary hydrogen storage in aviation. Nevertheless, their application may still be favorable for secondary hydrogen storage devices. This paper analyses the applicability of hydrides for the range extension of a commuter aircraft to allow a diversion to an alternate airport. Therefore, various hydride types, such as complex hydrides, hydride slurry and metal hydrides combined with compressed hydrogen storage, are sized and benchmarked against competing energy carriers, such as compressed hydrogen, liquid hydrogen and batteries, to evaluate their potential and determine future research needs. Although the results of the evaluation show that hydride range extenders can be beneficial from the safety point of view, their application as a range extender for the diversion would entail a reduction of the flight mission's range or payload.