Dimensioning of a direct fuel cell battery hybrid system for an all-electric aircraft

Graf, Tobias; Fonk, Robin; Bauer, Christiane; Willich, Caroline

doi:10.2514/6.2023-4536

Cited by 2 publications

(3 citation statements)

References 11 publications

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“…The efficiency achieved by Hoenicke et al [14] was above 99% during cruise and take-off which is higher than the usual efficiencies of DC/DC, which usually has efficiencies somewhere between 85% and 98%. Graf et al examine the influence of the battery SOC [25] and the influence of the low ambient pressure [26] at high altitudes on the direct hybrid system and the resulting implications for dimensioning of a fuel cell and a battery [27] is investigated. A power unit combining a fuel cell and a battery in a direct hybrid can be used flexibly with the help of a power management system (PMS) as proposed by Hoenicke et al [14] and already used in the previously described test-airplane HY4 [28].…”

Section: Direct Hybrid Powertrain Of a Fuel Cell And A Batterymentioning

confidence: 99%

“…With the help of the power management system and an intelligent switching logic for it, different modes (fuel cell, battery, hybrid, charging, landing) can be used in different flight phases. This enables the fuel cell and the battery to be dimensioned according to the required power in each flight phase and reduces the weight of the system as much as possible [27].…”

Section: Direct Hybrid Powertrain Of a Fuel Cell And A Batterymentioning

confidence: 99%

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Switching Logic for a Direct Hybrid Electric Powertrain

Fonk,

Graf,

Paeßler

et al. 2024

Aerospace

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Hybrid electric aircraft with a powertrain based on fuel cells and batteries can reduce climate-active emissions in aviation. In a direct hybrid powertrain, the fuel cell and the battery are connected in parallel, without a DC/DC converter balancing their voltage levels. Switches make it possible to select different operational modes (fuel cell only, hybrid or battery charging) depending on the power demand during different flight phases. To exploit the high specific energy of hydrogen, the system should change from Hybrid Mode during take-off to Fuel Cell Mode in cruise. During descent, the battery can be charged if Charging Mode is selected. To avoid voltage and current peaks and consequent damage to components when switching between modes, certain conditions must be fulfilled. Those switching conditions were defined, and switching procedures for changing from one mode to the other during flight were developed and tested in a lab system. In a direct hybrid, the system voltage depends on the required power. When switching from Hybrid Mode to Fuel Cell Mode, a short reduction in power of 65% is necessary for the examined system to meet the switching requirements. It is also shown how this power loss can be reduced to 25% by distributed propulsion with a second powertrain or even eliminated by a change in the hybrid ratio.

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Section: Direct Hybrid Powertrain Of a Fuel Cell And A Batterymentioning

confidence: 99%

Section: Direct Hybrid Powertrain Of a Fuel Cell And A Batterymentioning

confidence: 99%

Switching Logic for a Direct Hybrid Electric Powertrain

Fonk,

Graf,

Paeßler

et al. 2024

Aerospace

Self Cite

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“…Figure 3 shows the voltage over power curves for one single fuel cell at different operating pressures (based on the HD10 stack) [36]. The pressures shown correspond to altitudes between ground level (950 mbar) and 25,000 ft (376 mbar).…”

Section: Fuel Cellmentioning

confidence: 99%

Optimal Sizing of Fuel Cell and Battery in a Direct-Hybrid for Electric Aircraft

Graf,

Fonk,

Bauer

et al. 2024

Aerospace

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The climate impact of aviation can be reduced using powertrains based on hydrogen fuel cells and batteries. Combining both technologies in a direct-hybrid without a DC/DC converter is a promising approach for light-weight systems. Depending on the power demand, both the fuel cell and battery are used to provide power or only the fuel cell is connected to the powertrain. The system voltage in a direct-hybrid is determined by the fuel cell and battery, but the performance of fuel cells is affected by low-ambient pressure at high altitudes and the battery voltage is affected by state of charge and discharge rate. Taking this into account, the presented work demonstrates how a direct-hybrid system must be designed based on a scaled mission profile of a 40-seater aircraft. The fuel cell and battery are configured and sized according to the power demand in different flight phases while considering voltage limits given by the powertrain. The energy requirement from the fuel cell and the battery is calculated for a flight based on a realistic mission profile and different battery and fuel cell configurations are evaluated. By optimizing the battery and fuel cell size, the energy required from the battery was reduced by 57% and the total weight of the fuel cell and battery was reduced by 11%.

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Dimensioning of a direct fuel cell battery hybrid system for an all-electric aircraft

Cited by 2 publications

References 11 publications

Switching Logic for a Direct Hybrid Electric Powertrain

Switching Logic for a Direct Hybrid Electric Powertrain

Optimal Sizing of Fuel Cell and Battery in a Direct-Hybrid for Electric Aircraft

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