Passive Unitized Regenerative Fuel Cell for Very High Altitude Long Endurance Solar Aircraft

Practical use of a unitized regenerative fuel cell (URFC) for solar powered aircraft and similar applications has been limited due to a lack of proven technology designed for the mission requirements. The concept of the static feed unitized regenerative fuel cell, successfully demonstrated in the laboratory in the DARPA/NRL Water Rocket program and two NASA SBIR contracts provides a strong basis for a derivative technology for the high altitude long endurance (HALE) aircraft application. Three critical technology areas need to be addressed before a URFC can be applied to the HALE platform. First, the membrane-electrode assembly must be demonstrated that allows the URFC to operate with little or no performance penalty compared to the discrete electrolyzer and fuel cell components. Second, a thermal management system internal to the cell stack must be developed to allow the cell area and number of cells to be scalable to the power ranges required by the HALE application. Third, the passive water management technology must be demonstrated to be stable over extended durations of continuous operation.