Prof. Kallo presented HY4

Professor Josef Kallo has been working for years on realizing his dream: the use of zero-emission fuel cell aircraft in passenger transport. On Sept. 29, 2016, he came a huge step closer to his vision, when the first flight of a four-seat, propeller-driven and hydrogen-run airplane was completed successfully. During the World of Energy Solutions, Kallo talked about the flight, the technology used and presented “his” HY4 to all interested attendees.

Ten years ago, the German Aerospace Center (see Launch of Emission-Free Passenger Aircraft Hy4https://www.h2-international.com/2016/02/04/launch-of-emission-free-passenger-aircraft-hy4/) took the lead in developing small fuel cell-driven airplanes. Since then, Josef Kallo, coordinator of the Energy Systems Integration Group at the Institute of Engineering Thermodynamics, has been pursuing the goal of making air travel by fuel cell available to as many people as possible.

The mid-section of the Pipistrel aircraft houses a low-temperature PEM fuel cell (45 kW) by Hydrogenics. The tanks, which store up to eight kilograms of hydrogen gas, are located in the back of the two passenger cabins and supply enough energy for around 750 kilometers or 466 miles. A high-performance lithium battery – likewise installed behind the passenger sections – supplies additional power during peak loads (e.g., during takeoff or climb). The fuel cell-battery combination provides the aircraft with an acceleration speed of up to 200 kph or 124 mph.

Energy recovery ups efficiency

Similar to electric cars on the road, the HY4 is to be the first aircraft to use energy recovery. This means that the propeller still turns in the same direction, but slows down the airplane to allow for the electric motor to generate power. The HY4 project manager believes that the overall highly efficient propulsion system is one the aircraft’s distinct advantages which make this way of travelling so attractive. Assuming a consumption of around 400 grams of hydrogen for each person on 100 kilometers or 62 miles, total fuel cost would be a mere four euros per person at current price levels.

Kallo, who is also head of the Institute for Energy Conversion and Storage at Ulm University, intends to test the technological platform over the coming years before the target will be upped to six or eight seats. He explained: “Recent studies on commercial aviation show that there are indeed feasible propulsion designs for regional air travel with up to 40 seats and a range of 700 kilometers or below, even though the technical challenges are significant. […] In our view, electric aircraft are particularly suited for air taxi use to improve the links between regional airports or between regional and large ones. In both cases, the airports may be one to two hundred kilometers apart.”