Unitized regenerative fuel cells (URFCs) are promising candidates for power sources for future Mars and crewed lunar missions, as they offer added benefits of reduced mass and footprint compared to the traditional regenerative fuel cell (RFC) systems. NASA seeks development of high pressure reversible or unitized proton exchange membrane RFC stacks that can meet (i) 2,500 psig balanced pressure operation, (ii) Round-trip efficiency of > 48% based on higher heating value measured at 500 mA/cm2 in fuel cell mode and 1,500 mA/cm2 in electrolyzer mode, and (iii) > 170 cycles with a target of up to 366 hours of operation per cycle in each mode (meaning ~ 62,000 hours operational durability!). To address these requirements, Lynntech will leverage its prior URFC stack design, catalyst and membrane materials experience, and develop advanced URFC stacks with emphasis on materials selection for high-pressure hydrogen and oxygen compatibility, amphiphilic corrosion resistant diffusion layer for reversible oxygen electrode, and stack design for balanced high-pressure operation. In the Phase I project, Lynntech will target the demonstration of stack and components at the single or short cell stack level and establish the stack design for a multi-kW URFC stack for the Phase II prototype demonstration.
URFC technology can be used by NASA for future surface exploration of the Moon and Mars. RFCs provide a lightweight alternative to batteries, especially to support energy storage requirements for long lunar nights. RFCs provide the possibility of integration with ISRU systems, as it involves the same feedstocks/products such as water and oxygen used for the life support systems. URFCs provide a more compact and lightweight version of RFCs where the system can be significantly simplified with elimination of several balance of plant systems.
The specific energy of URFCs can easily beat batteries for large energy storage requirements. Hence URFCs can find applications in stationary energy storage systems using renewable energy where the specific energy for the URFC systems is much greater than 200 Wh/kg, or that of current battery systems