**3. Results**

Sections 3.1 and 3.2 will describe the procedure in the medium-term scenario in more detail. The approach to determining energy demand, emissions and ticket prices is similar for all time horizons. Therefore, the methodology described in Section 2 is carried out once here. However, the different aircraft configuration already indicated in Table 1 was used. The fuel mix ratio in the medium-term (ICE + Battery) is 75% kerosene and 25% SAF, and the infrastructure is shown in Figure 4.

For the aircraft configuration PEMFC + Battery, the infrastructure was considered as in Figure 5. The results for an HEA with FC and battery are also described in Sections 3.1 and 3.2. A PEMFC is used for the fuel cell technology. This allows a direct comparison between the operation of an ICE + Battery and a PEMFC + Battery HEA.

#### *3.1. Determining Energy Demand ICE + Battery and PEMFC + Battery HEA*

Based on information from the relevant commercial flight and the configuration of the HEA, an overview of the fuel requirements for the eligible flights was made. To determine the maximum fuel and electricity supplies, one of the busiest days was selected for flights up to 1111 km to the destination.

For the medium term, based on these assumptions, the amount of electricity which the HEA flights would potentially require on a busy day at a regional airport is reported in Table 5. The departure airport in this study is Rotterdam. Table 5 lists the destinations and the amount of kerosene, SAF and electrical energy or LH2 and electrical energy required for the HEA in parentheses. The electrical energy demand for ICE + Battery HEA is listed as "Electric ICE [kWh]". The electrical energy demand for PEMFC + Battery HEA is listed as "Electric ICE [kWh]" in Table 5. These destinations are determined from the number of PAX and the distance, as already described in Section 2.3. It can be seen that several flights would have to take off at the same time. This is, of course, not possible, but it should serve here as an introduction to show the potential energy demand of the HEA. Energy consumption per flight is high in the morning and evening for the London destination and average for European flights. The total capacity required is highest in the late afternoon, shown in Figure 6. This high capacity is because three flights with many passengers depart in the afternoon. Figure 6 illustrates the high capacity of the period from 16:30 to 17:04. The initial calculations and simulations show that the short-term scenario requires a daily kerosene demand of 13.37 tonnes, an SAF demand of 4.39 tonnes and an electrical energy demand of 46.68 MWh (yellow line).


**Table 5.** Daily fuel and electricity amount per hybrid-electric flight, 2040.

**Figure 6.** Daily fuel and electricity amount per hybrid-electric flight, 2040.

To compare the impact of LH2, based on the combination of information from the respective RTHA traffic flight and the configuration of the newly developed medium-term HEA with PMFC + Battery, an overview of the fuel requirements for the considered flights is shown in Table 5 as "LH2" and "Electric PEMFC". Initial calculations and simulations show that the HEA in the medium-term scenario with PMFC + Battery no longer requires the daily kerosene demand of 23.5 tonnes (short-term) and 13.37 tonnes (medium-term-ICE + Battery). Similarly, the SAF demand of 2.55 tonnes (short-term) and 4.39 tonnes (medium-term-ICE + Battery) is no longer needed. Instead, a liquid hydrogen requirement of 5.523 tonnes is now determined to fuel the aircraft. In addition, the PEMFC + Battery medium-term HEA will be fitted with a battery of higher capacity and power, increasing the demand for electrical energy from 26.05 MWh (short-term) and 46.68 MWh (mediumterm-ICE + Battery) to 50.425 MWh (black line).

In order to replace these flights with hybrid-electric flights, a new flight schedule with new departure times must be created. This new flight schedule is presented in Table 6. In this table, the old departure times of the original flight plan are listed again. New departure times are introduced in the column to the right with the destination abbreviation. These new departure times are based on the original time, and an average time of 10 min assumed between the departure times. These 10 min are for taxiing from the gate to the runway and subsequent take-off. The kerosene, SAF and electrical energy consumption of each HEA is given and composed of typical mission (200 nmi) and design mission (600 nmi) flights. The maximum number of passengers per flight is 50. The maximum range of the potential flights was kept below 1111.2 km to represent a realistic scenario.


**Table 6.** Possible replacements through HEAs, 2040.

As in the scenarios before, PEMFC + Battery HEA should replace conventional aircrafts in this medium-term scenario. These energy requirements are also listed in Table 6 on the right side as "LH2" and "Electric PEMFC".

Figure 7 shows the new flight plan's results and the energy required. It is apparent that in the early morning, for the flights to London (LO), 1525 kWh of electrical energy is required to charge the aircraft and refuel them for the flight. The kerosene quantity is 306 kg, and the SAF quantity is 100 kg, with the previously defined specifications of 75% kerosene and 25% SAF. The equalisation of the flights to Pula (PU), Vienna (VIE) and Montpellier (MO) show an electrical energy demand of 2220 kWh to 2021 kWh. The flight schedule was equalised, and the electrical energy required from 16:00 to 17:29. The kerosene/SAF requirement of a maximum of 683 kg/flight can also be easily provided. Four take-offs to Pisa (PI) are required in the evening, with an electrical energy quantity of 2175 kWh and a kerosene quantity of 669 kg/flight. As soon as the last flight at 20:26 to London has taken off with an electrical energy quantity of 1525 kWh and 306 kg of kerosene, the electrical energy consumption of the airport can be reduced again.

As in the scenarios before, the HEA's kerosene, SAF and electrical energy consumption are now eliminated. Figure 7 shows the results of the new flight plan for required LH2 (blue) and electrical energy (black). Early morning flights to London (LO) require 1644 kWh of electrical energy in the medium term to recharge the aircraft and refuel for the flight. This is because a more powerful battery is installed in the PEMFC aircraft than in the previous time horizon. The liquid hydrogen quantity is 105 kg instead of the paraffin quantities of 306 kg (medium-term) and 557 kg (short-term). The reconciliation of the flights to Pula (PU), Vienna (VIE) and Montpellier (MO) resulted in an electrical energy demand of 2399 kWh to 2184 kWh, which is significantly higher than in the previous scenarios, as expected. The flight schedule was adjusted, and electrical energy is required from 16:00 to 17:29. The kerosene/SAF requirement of a maximum of 1191 kg/flight in the short term and a maximum of 683 kg/flight (medium-term) is now also omitted here. A maximum of 290 kg of liquid hydrogen is required for the flight to Pula. Four take-offs to Pisa (PI) are required in the evening, with an electrical energy quantity of 2351 kWh. The paraffin amounts of 1167 kg/flight in the short-term horizon and 669 kg/flight in the medium horizon with ICE + Battery are omitted, and 284 kg liquid hydrogen per flight is required. Once the last flight has taken off at 20:26 to London with an electrical energy quantity of 1644 kWh and 105 kg of liquid hydrogen, the electrical energy consumption of the airport can be reduced

again. In the long term, storing electrical energy not needed in large batteries or converting it into liquid hydrogen can be considered.

Finally, the annual energy demand for the short-term scenario is given in Table 7. Table 7 shows the energy demand for hybrid-electric flights in 2030 per month to determine the loading and refuelling energy for one year in 2030. It was concluded that 3215 tonnes of kerosene, 1056 tonnes of SAF and 11.704 GWh of electrical energy would be required in the short-term horizon to operate the HEA. These calculations were made with a fuel mix ratio of 75% kerosene, 25% SAF and an HEA configuration.

**Table 7.** Charging and refuelling HEA energy requirements per month, 2040.


For the PEMFC + Battery aircraft, the energy demand is listed on the right side of Table 7 as "LH2 [tons]" and "Electric PEMFC" [MWh]. This table shows the energy demand

**Figure 7.** Possible new flight plan with HEAs, 2040.

for HEA flights in 2040 per month to determine the loading and refuelling energy for one year in 2040. It was found that, instead of 3215 tonnes (medium-term-ICE + Battery), 1291 tonnes of liquid hydrogen are now required to operate the HEA in the medium-term scenario. The requirement of 1056 tonnes of SAF in the medium-term horizon are eliminated accordingly. The demand for electrical energy of 11.704 GWh (medium-term-ICE + Battery) increases to 12.640 GWh (black line). The demand for electrical energy is 74% higher than for the short-term horizon (Table 13). The demand for electrical energy in the medium-term with PEMFC is almost 8% higher than in the medium-term scenario with ICE + Battery. This is due, on the one hand, to the increased battery capacity in the PEMFC aircraft, and on the other hand to the use of liquid hydrogen. The charging and refuelling energy for the HEA is shown in Figure 8.

**Figure 8.** Charging and refuelling HEA energy requirements, 2040.
