*6.2. Sizing of the Energy Storage System in the Hybrid Cases*

The hybridization of energy storage systems enables the enhancement of autonomy and reliability in multirotor aerial vehicles. By combining batteries, hydrogen fuel cells, and supercapacitors, the specific energy to specific power ratio of the energy storage system is significantly improved compared to the case of a single energy source. This, coupled with in-flight energy management algorithms, extends the flight time of the aerial vehicle [29,39]. Figure 13 illustrates the Ragone plot, which depicts the distribution of different energy storage systems based on their specific energy to specific power ratios [40]. From this figure, it is evident that the combinations of Bat/HFC, Bat/SC, or Bat/SC/HFC allow for an improvement in specific energy while maintaining an adequate level of specific power. In this case, the energy storage sizing process remains similar to the single-source case, where the objective is to maximize the flight time while considering the GTOW constraint. However, there are additional variables to consider, particularly the hybridization coefficient of the energy sources.

**Figure 13.** The Ragone chart.
