Energy Storage Systems for Very High Altitude Very Long Endurance Solar Aircraft

The purpose of the proposed solid oxide fuel cell (SOFC) development effort is to demonstrate the feasibility of achieving a high specific power (1000 W/kg) SOFC stack capable of operating both as a power generator and an electrolyzer while achieving high electrochemical efficiency (approximately 70%) and long operating life (one to two years). A SOFC stack achieving these performance characteristics enables the development of a regenerative power system with a system average specific energy of over 2000 W-hr/kg for use in a high altitude, long endurance (HALE) aircraft with multi-month endurance. Based on Versa Power Systems’ well-established SOFC technology baseline, the approach for demonstrating feasibility is based on deconstructing technical issues into deterministic engineering problems while avoiding fundamental changes to the technology baseline. The work encompasses a preliminary design of a high specific power stack, an empirical evaluation of innovative interconnect materials, and an empirical evaluation of the impact of electrolysis on component durability. Subsequent development will focus on the physical implementation of the components identified in Phase I, including ground-based functional stack and power system testing and eventual incorporation into a flight-test vehicle.