Despite widespread discussion about a hydrogen economy, kerosene will remain the one and only aviation fuel for the coming decades. The key problem of applying fuel cells on board an aircraft will be to generate hydrogen from the on-board kerosene fuel. To this end, various processes such as autothermal or catalytic partial oxidation have already been investigated. The EU-funded project GREENAIR (Generation of hydrogen by kerosene reforming via efficient and low emission new alternative, innovative, refined technologies for aircraft application) dealt with two alternative solutions that promise to be better suited to aircraft application. GREENAIR explored two novel reforming technologies, namely partial dehydrogenation fuel (PDh) processing and plasma-assisted fuel (PAF) processing. The former, as its name suggests, takes kerosene from the fuel tank and strips off hydrogen from the hydrocarbon molecules. The hydrogen is delivered to fuel cells and the depleted kerosene is sent back to the fuel tank or directly to the engine. The latter totally converts the kerosene to a hydrogen-rich gas. The gas is used to power a fuel cell and no fuel is returned to the tank or engine. Scientists also investigated fractionation, a process that delivers components (fractions) from kerosene that may be more favourable for hydrogen production. Except for developing the PDh and microwave reformer design prototypes over the first project period, scientists also designed and assembled a 5 kW PAF system. The prototype exhibited around 50 % conversion efficiency that was lower than expected, probably limited by the microwave power source. The level of hydrogen produced should enable supplying a 1.5 kWe fuel cell. Further tests were performed to evaluate the system's tolerance to vibrations. Thanks to GREENAIR technology, a new generation of hybrid aeroplanes capable of using both hydrogen gas and conventional jet fuel may be just around the corner.
Hydrogen, kerosene, fuel cells, aircraft, partial dehydrogenation fuel, plasma-assisted fuel