A peculiar-looking plane with one engine, two fuselages and room for a single human has completed a test flight in Slovenia that – its designers claim – could pave the way for guilt-free flight on routes as long as Rome to London. The H2FLY plane uses liquefied hydrogen (at minus 253 degrees C) and a fuel cell that turns the gas into electricity and water. The power drives a propeller; the water is vented like mist. The heavily insulated liquid H2 tank is so large in relation to the rest of the aircraft that it occupies its own pod to the left of the central propeller while the pilot sits in a third pod to the right. The upside is that unlike compressed hydrogen, the liquid version is almost as energy-dense as jet fuel, which is what lets the H2FLY team boast of a range in principle of up to 1500 kilometres. Airbus and others are also experimenting with hydrogen-powered flight, but so far only with compressed H2. Either way it would have to be produced by electrolysis of water with renewable energy for the H2 to be green. Aviation meanwhile accounts for 2 to 3 per cent of global CO2 emissions.
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