Lightweight hardware design for regenerative fuel cells

Practical use of a RFC for solar powered winged aircraft and lighter-than-air craft has been limited due to weight constraints and the paucity of test data from and practical experience with closed loop RFC hardware. The lightweight cells and endplates developed in Phase I of this program will be applied to the practical implementation of a closed-loop regenerative fuel cell. This RFC will build upon the successfully developed and demonstrated unitized regenerative fuel cell from the DARPA/NRL Water Rocket program. Although that hardware has been developed for operation in a zero gravity environment (for space applications) it is quite applicable for high altitude aircraft (HAA) or terrestrial applications. The requirements in terms of mission profile and duration, maximum operating pressure, etc. may be different. The impact of these differences will be investigated. Furthermore, the trade study between discrete and unitized regenerative fuel cells will be undertaken early in Phase II. For the high altitude airship application with charge and discharge cycles varying between 8 and 16 hours each, the optimal cell stack configuration will be investigated. Moreover, if the performance of the unitized regenerative fuel cell proves to be limiting, the discrete regenerative fuel cell option will be considered.