*3.3. Results over All Time Horizons*

This section summarises all data for the operation of a regional airport for the different time horizons and aircraft configurations. The results for the short-term scenario (ICE + Battery—2030) follow the procedure described in Sections 3.1 and 3.2, but here the fuel composition is, as already mentioned, 90% kerosene and 10% SAF. In addition, a lower powerful battery is installed. The results for the long-term scenario (PEMFC + Battery— 2050) are obtained according to the procedure also described in Sections 3.1 and 3.2. Here, a further developed PEMFC and further developed battery are included in the aircraft configuration. For more detailed information on the aircraft configuration, please refer back to [10] or [13].

The already-presented results of the medium-term scenario (ICE + Battery) and medium-term scenario (PEMFC + Battery) are taken up in the following tables. They can be classified as short-term (ICE + Battery—2030) and long-term (PEMFC + Battery— 2050). Table 13 shows the annual energy demand for the process of the HEA in different time horizons. It was found that, instead of 5608 tonnes of paraffin (short term), 3215 tonnes (medium term ICE + Battery) and 1291 tonnes of liquid hydrogen (medium term PEMFC + Battery), 1234 tonnes of liquid hydrogen would now be required to operate the HEA in the long-term scenario. The electrical energy demands of 7233 GWh (short term), 11,704 GWh (medium term -ICE + Battery) and 12,640 GWh (medium term -PEMFC + Battery) are now 11,622 GWh. The demand for electrical energy is 60% higher than in the short term. The demand for electrical energy in the medium-term scenario with PEMFC is almost 0.7% lower, and thus almost identical to the medium-term scenario ICE + Battery. Overall, the demand for electrical energy in the medium-term scenario with PEMFC + Battery is 8.1% lower than in the short-term scenario.

**Table 13.** The yearly amount of energy for HEA 2025–2055.


Table 14 shows the expected and extrapolated ticket prices for the different time horizons. The approach was the same as in Sections 2.2, 3.1 and 3.2. The HEA ticket price is expected to be 49.4% cheaper for typical mission flights and 45.7% for design mission flights in the long-term PEMFC + Battery scenario. The list was compiled without the high investment, research and operating costs. As described in the respective sections, the price calculations considered environmental aspects and expected inflation rates.


**Table 14.** Costs for typical mission flights—forecast summary.

However, the high savings in the expected ticket price per passenger offer an excellent field to make these investments lucrative for airlines and passengers through hybrid-electric typical and design mission flights. This fact confirms the previously established thesis that hybrid-electric flights have the potential to be financially attractive and environmentally friendly. The assumed costs for CO2 compensation are justified here, as more and more institutions, such as FAU, are obliged to pay CO2 compensation on ticket prices for business trips.

Table 15 summarises the extrapolated and expected emissions of the different time horizons and aircraft types. The mentioned reference aircraft (ATR 42 with a Pratt and Whitney PW127 engine) is listed first under the 2012 category for comparison purposes.


**Table 15.** The yearly missions HEA flights forecast estimation compared to the reference aircraft— Summary 2025–2050.

#### **4. Conclusions**

This paper presents the results of an energy demand analysis for a future regional airport over three different time horizons. This study presents different options for the ground power supply of a regional airport and possible solutions for the airport infrastructure with a short (2030), medium (2040) and long (2050) time horizon. The results include estimating the future energy demand per day, month and year and the energy demand. To accommodate the increasing number of flights, the flight plan was adapted to the needs of a 50-PAX regional aircraft. This new flight plan provides the opportunity to present an overview of the results for the energy demand of a regional airport, broken down by individual time horizons. The result of this work describes the energy demand for the airport's operation, the expected emissions and an estimate of ticket prices. The findings confirm that airports will require an enormous amount of electrical energy due to the electrification of air traffic. Accordingly, the infrastructure of airports will also have to change. Furthermore, the study shows that the transition to sustainable hybrid-electric aviation is attractive due to lower emissions and adjusted ticket prices.

In future work, a full-fledged prospective Life Cycle Assessment (LCA) in accordance with the methodology proposed by [29] needs to be performed to consider all relevant life cycle stages and additional environmental impacts besides climate change. The inclusion of additional emerging propulsion systems (e.g., direct H2 use in the gas turbine), aircraft types (besides the regional HEA), and other means of reducing airport/aircraft emission (e.g., air traffic management) would broaden the scope and enrich the discussion of the transition of airports.

**Author Contributions:** This section reports the main contributions of each author according to the Contributor Roles Taxonomy (CRediT) (http://img.mdpi.org/data/contributor-role-instruction.pdf). Conceptualisation: M.M. (Markus Meindl), C.d.R. and F.H. Methodology: M.M. (Markus Meindl), C.d.R., V.M., M.D.S., M.R., F.H. and L.L. Data collection: M.M. (Markus Meindl), C.d.R., V.M., M.D.S. and M.R. Validation: M.M. (Markus Meindl), C.d.R., V.M. and M.D.S. Data maintenance: M.M. (Markus Meindl), C.d.R., V.M. and M.D.S. Writing—original draft preparation: M.M. (Markus Meindl). Writing—review and editing: M.M. (Markus Meindl), C.d.R., V.M., M.D.S., M.R., F.N., F.H., N.T., K.S.-R., A.L. and M.M. (Martin Maerz). Supervision: M.M. (Martin Maerz). Project administration: A.L. and M.M. (Martin Maerz). Funding acquisition: M.M. (Martin Maerz). All authors have read and agreed to the published version of the manuscript.

**Funding:** This study is part of the GENESIS project (https://www.genesis-cleansky.eu/ (9 March 2023)). The GENESIS project has received funding from the Clean Sky 2 Joint Undertaking (JU) under Grant Agreement n◦ 101007968. The JU receives support from the European Union´s Horizon 2020 research and innovation programme and the Clean Sky 2 JU members other than the Union. This study only reflects the authors' views; the JU is not responsible for any use that may be made of the information it contains.
