Expanding the Definition of the Degree of Hybridization of Fuel Cell Electric Vehicles 2023-01-1202

Fuel cell electric vehicles are expected to support the effort to overcome the economic and ecological challenges in the automotive sector. Just as battery electric vehicles, fuel cell electric vehicles also offer locally emission free mobility. The drive system of fuel cell electric vehicles consists of a fuel cell system, an electric motor, power electronics, a hydrogen storage system as well as a rechargeable energy storage system, typically a battery. The quantified power ratio between the fuel cell system and the rechargeable energy storage system is referred to as the degree of hybridization, although inconsistent definitions are used. As these existing definitions of the degree of hybridization of fuel cell electric vehicles don’t support a distinct differentiation and characterization of the vehicles, a new definition of the degree of hybridization is proposed considering the ratio of the energy contents of the hydrogen storage system and the rechargeable energy storage system, effectively adding a second dimension. The degree of hybridization is then evaluated for existing fuel cell electric vehicles using the proposed definition and enables the characterization and clustering of the different vehicles. While this two-dimensional degree of hybridization can be used as optimization criteria during the design and optimization of fuel cell drive systems, the aforementioned clusters can be assigned to already established qualitative degree of hybridization definitions used to describe types of hybrid electric vehicles. This supports customers to be able to more easily distinguish between different types of fuel cell electric vehicles while also increasing the suitability of the degree of hybridization as an optimization criterion in drive system development.