This is potentially neat, but I’m not seeing where the hydrogen is coming from. Carrying compressed bottles would probably be a lot heavier than a conventionally fueled APU.

Boeing in fuel-cell project-05/06/2007-Flight International
Boeing is collaborating with Sandia National Laboratories to determine the feasibility of using a hydrogen-powered fuel cell to provide back-up in aircraft. This is a new task under a co-operative research and development deal between the aircraft manufacturer and the laboratory signed in 2002.

The project focuses on use of a polymer electrolyte membrane fuel cell instead of an auxiliary power unit, batteries or ram-air turbine to provide emergency electrical power for critical aircraft systems. Livermore, California-based Sandia is leading evaluations of electrical and environmental requirements, fuel cell efficiency, and hydrogen storage options and issues.

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