HY4 claims to be first zero-emission plane
A team of engineers, backed by the German Aerospace Center (DLR), are developing the HY4, the world's first zero-emissions passenger plane. A combination of four fuel cells and a high-performance lithium battery give the four-seater plane a range of around 100km. Josef Kallo, coordinator for energy system integration at DLR, said the HY4 could be used for "shuttle flights between airports and from cities to more remote regions", but it's still 20 years away from happening.
This is the HY4, claimed to be the world's first passenger aircraft to emit zero carbon into the atmosphere. With two fuselages positioned left and right, each with two seats beneath a perspex canopy, it has a wing section with a propeller in between, and a wingspan of 21.36m. With partners including the German Aerospace Center (DLR), the team has spent the past 18 months working towards electromobility, from the road to the air. In the wake of Solar Impulse 2's successful solar-powered circumnavigation of the globe in summer 2016, a fossil-fuel future looks set to be the aviation industry's next big thing.

The HY4 uses no fossil fuels. Four fuel cells, which convert hydrogen and oxygen into water and electric power, are the hybrid aircraft's main source of energy. About 1.2kg - stored in a carbon-fibre-reinforced high-pressure tank - is enough for a flight of around 100km. A new fuel-cell system developed by DLR, and a refuelling pressure of 700 bar, should eventually extend a flight to as much as 1,500km. The craft also carries a high-performance lithium battery on board, which provides sufficient power for the take-off and initial climb.

An aircraft that is emission-free in normal operation would be a massive first step into the post-fossil-fuel era for the aviation industry. If the world is serious about a future without oil, aircraft manufacturers will have no choice but to find alternatives.

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Josef Kallo is the co-ordinator for energy system integration at DLR and, for the past year, the director of the Institute for Energy Conversion and Storage at the University of Ulm. Before then, he was a driving force behind the development of fuel-cell technology for cars at General Motors. To test the viability of fuel cells for aviation, DLR teams in Hamburg and Stuttgart worked in parallel on small and large engines. When the Antares DLR-H2, the world's first single-seater fuel-cell-powered plane, took to the skies in 2009, it was the university team that was responsible for developing its propulsion system.

In 2011, in Hamburg, DLR's own Airbus A320 ATRA used a fuel-cell-powered nose wheel. As a result, the aircraft was able to manoeuvre on the ground without producing any emissions. A new fuel-cell concept is currently being developed for the A320's auxiliary power unit, which is normally a gas turbine.