Researchers at the Florida A&M University-Florida State University College of Engineering have engineered a practical liquid hydrogen storage and delivery system that brings zero-emission aviation significantly closer to reality. Their innovative design addresses multiple engineering challenges simultaneously, enabling hydrogen to serve as both a clean fuel and an integrated cooling medium for critical power systems in next-generation electric aircraft.
The comprehensive study introduces a scalable system specifically designed for 100-passenger hybrid-electric aircraft. The new design integrates hydrogen fuel cells with hydrogen turbine-driven superconducting generators, demonstrating how liquid hydrogen can be efficiently stored, safely transferred and strategically used to cool onboard systems during all flight phases.
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‘Our goal was to create a single system that handles multiple critical tasks: fuel storage, cooling and delivery control,’ said Professor Wei Guo (pictured below, at right), from the joint college’s Department of Mechanical Engineering. ‘This design lays the foundation for real-world hydrogen aviation systems.’
Hydrogen emerges as aviation’s most promising clean fuel alternative, packing more energy per kilogram than conventional jet fuel while producing zero carbon dioxide emissions. However, its ultra-low density requires storage as a super-cold liquid at –253°C, presenting significant engineering challenges for aircraft applications.
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The FAMU-FSU team tackled this challenge through comprehensive system-level optimisation, developing an innovative approach that goes beyond traditional tank design. They introduced a new gravimetric index – the ratio of fuel mass to total fuel system mass – that accounts for all system components, including hydrogen fuel, tank structure, insulation, heat exchangers, circulation devices and working fluids.
Through methodical optimisation of key design parameters such as vent pressure and heat exchanger dimensions, the team identified a configuration that achieves a remarkable gravimetric index of 0.62. This means 62 per cent of the system’s total weight consists of usable hydrogen fuel – a significant advancement over conventional designs that could accelerate commercial hydrogen aviation deployment.
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The system’s dual-function approach represents a paradigm shift in aircraft design. Rather than installing separate cooling systems, the innovative design routes ultra-cold hydrogen through strategically positioned heat exchangers that remove waste heat from superconducting generators, motors, cables and power electronics. This thermal integration process naturally preheats the hydrogen to optimal temperatures for fuel cell and turbine operation.
Delivering liquid hydrogen throughout aircraft presents unique challenges, as mechanical pumps add weight, complexity and potential failure points under cryogenic conditions. The research team developed an elegant pump-free system that utilises tank pressure regulation to control hydrogen flow.
The system employs two pressure control methods: injecting hydrogen gas from high-pressure cylinders to increase pressure and venting hydrogen vapour to decrease it. Advanced feedback loops connect pressure sensors to the aircraft’s power demand profile, enabling real-time pressure adjustments that ensure correct hydrogen flow rates across all flight phases.
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Simulations demonstrate the system can deliver hydrogen at rates up to 0.25 kilograms per second – sufficient to meet the 16.2-megawatt electrical demand during take-off or emergency go-around procedures, critical phases that require maximum power output.
The heat exchangers operate in a carefully orchestrated sequence that maximises efficiency while minimising hardware complexity. As hydrogen flows through the system, it first cools high-efficiency cryogenic components such as high-temperature superconducting generators and cables. Subsequently, it absorbs heat from higher-temperature components, including electric motors, motor drives and power electronics, before reaching optimal fuel cell inlet conditions.
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‘Previously, people were unsure about how to move liquid hydrogen effectively in an aircraft and whether you could also use it to cool down the power system component,’ Guo explained. ‘Not only did we show that it’s feasible, but we also demonstrated that you needed to do a system-level optimisation for this type of design.’
While this study focused on design optimisation and system simulation, the research team is preparing for the crucial next phase: experimental validation. Guo and his team plan to construct a prototype system and conduct comprehensive testing at FSU’s Center for Advanced Power Systems, a critical step toward commercialisation.
The project operates within NASA’s Integrated Zero Emission Aviation programme, a collaborative initiative that brings together leading institutions across the USA to develop comprehensive clean-aviation technologies.
Potential applications for the research extend beyond aircraft to other transportation sectors that require efficient hydrogen storage and thermal management solutions.
The research has been published in Applied Energy.