HY4, © DLR

Although the aviation industry was the starting point for hydrogen developments, commercial applications in that industry have been few and far between. 1783 marked the launch of the first hydrogen-filled hot-air balloon; later, hydrogen-powered airships crossed the Atlantic. But since the Hindenburg disaster in Lakehurst in 1937, the most lightweight element of all has fallen out of favor in every field except for the space industry. But it is not as if H₂ aviation didn’t have his proponents who have continued their research and have meanwhile developed much-promising concepts.

Almost twenty years ago, a multi-million euro grant program funded research into the Cryoplane, a hydrogen-powered passenger aircraft. In retrospect, the mostly theoretical work in those days mainly proved one thing, namely that there is little chance for realizing such a project before 2025.

The situation reminds one of the issues surrounding Growian, a large wind power plant set up in the north of Germany in 1983, which has never seen regular operation. Both ideas were bound to fail, as their development was rushed toward the next breakthrough. The wind power industry, however, ultimately succeeded by gradually increasing the size of the systems until Growian was no longer “a breath of fresh air.” H₂ passenger airplanes could take the same route: Work on developments such as the HY4 (see p. 33) may mean that small passenger planes could soon transport not just four, but forty people.

DACAPO, DIANA and Diehl

Another R&D focus besides H₂-based propulsion is the fuel cell, which could supply at least part of the energy required on board. NOW supported BRIST – Fuel Cells, Integration and System Testing – with EUR 7.3 million for over five years. One of its outcomes was the creation of a Fuel Cell Test Center in Hamburg, Germany.

Additionally, BRIST partner Diehl Aerospace based in Überlingen is working on a portable energy supply system for passenger airplanes. Their main power consumer is the onboard galley, which prompted Diehl to develop a movable fuel cell unit. Similar to conventional airline trolleys, it is connected in the kitchen to supply power to galleys and cabins independently of the onboard power supply. Apart from a fuel cell and a fuel container, the trolley includes a reformer developed in-house. Its energy transfer medium is not a gas cylinder but propylene glycol, a non-flammable and non-toxic liquid when mixed with water. It has already been in use in aircraft for cooling and deicing and contains a great deal of hydrogen, which can be extracted through catalysts …