Evaluation of batteries for all-electric aircraft: a combined experimental and simulative study
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Date
2025-04-16
Authors
Hoenicke, Pia
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Dissertation
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Abstract
To meet the current trend of aircraft electrification, batteries as energy carriers are promising. Before implementing batteries in an aircraft, they have to be tested for the special conditions. NCA (Ni, Co, Al), NMC (Ni, Mn, Co) and LFP (Fe, P) lithium-ion batteries are favorable either with regards to specific energy or safety. Therefore, three commercial lithium-ion battery cells of these types were measured and characterized. The NCA and LFP types were cylindrical cells and the NMC type was a pouch cell. The measurements included current, temperature, humidity and pressure variations. Strong temperature dependency on the cell performance (up to 55 % specific energy loss from +60 to -30 °C) as well as strong current dependency (up to 63 % specific energy loss between 0.2C and maximum current) was found for all three cell types. None of the cells showed any humidity dependency. During the low-pressure tests, the NMC cell showed a slight pressure influence in their impedance spectra. An ohmic resistance increase of around 0.1 mΩ per 25 kPa and an impedance increase for low state of charge levels at 25 kPa was observed. The cylindrical cells (LFP and NCA) did not show pressure dependency. The hard cylindrical containers probably prevent the cell inside to be exposed to lower pressure. However, none of the cells showed strong pressure dependency.
Assessing aircraft suitability with a battery model instead of building and integrating a real battery stack is more efficient and economical since resources and time can be saved. A battery model based on RC circuits was built and parameterized using real measurements like pulse tests, electrochemical impedance spectroscopy and open circuit voltage measurements of all three battery types. RC-parameters obtained from pulse tests showed better accuracy than parameters from electrochemical impedance spectroscopy and were therefore implemented into the battery cell simulation. This battery cell model was extended to a battery system model and connected to an inverter-motor-model to build a battery-only aircraft. The simulation showed that the NMC battery is the most suitable to build a battery-only aircraft since the NMC cells have the highest specific energy as pouch cells which leads to a larger flight range at the same weight. However, the examined battery-only aircraft cannot fulfill the flight reserve for the used specific flight profile and even small distance extensions lead to large weight increase.
Hybrid aircraft using batteries and fuel cells are more suited for longer distances due to the high specific energy of hydrogen. Therefore, a fuel cell battery hybrid-electric aircraft model was built by adding a fuel cell model and a self-developed power distribution system to connect battery, fuel cell and inverter-motor system in a direct hybrid. For the hybrid aircraft, the NCA battery was most suitable for the specific flight profile since the combined powering of fuel cell and battery via the power distribution system was balanced best and therefore led to lowest weight. The simulation further showed this hybrid aircraft using a fuel cell and an NCA battery system even has SOC flight reserves and still works at lower temperatures like 0 °C where the battery capacity is decreased.
Description
Faculties
Fakultät für Ingenieurwissenschaften, Informatik und Psychologie
Institutions
Institut für Energiewandlung und -speicherung
Citation
DFG Project uulm
EXC 2154 / POLiS / POLiS - Post Lithium Storage Cluster of Excellence / DFG / 390874152
EU Project THU
MAHEPA / Modular Approach to Hybrid Electric Propulsion Architecture / EC / H2020 / 723368
Other projects THU
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CC BY 4.0 International
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DOI external
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DFG Project THU
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Keywords
Battery, Hybrid-Electric Aircraft, Batterie, Flugzeug, Hybridantrieb, Brennstoffzelle, Energiespeicherung, Airplanes; Batteries, Fuel cells, Lithium ion batteries, Energy storage, Aerospace engineering, DDC 620 / Engineering & allied operations