Fuel cells have played an important role in NASA's space program starting with the Gemini space program. However, improved fuel cell performance will be needed to enable demanding future missions. An advanced fuel cell (FC) using liquid fuel and oxidizer is being developed by U of IL/ NPL team to provide air independence and to achieve higher power densities than normal H2/O2 fuel cells (Lou et al., 2008; Miley, 2007). Hydrogen peroxide (H2O2) is used in this FC directly at the cathode (Lou and Miley, 2004). Either of two types of reactant, namely a gas-phase hydrogen or an aqueous NaBH4 solution, is utilized as fuel at the anode. Experiments with both 10-W single cells and 500-W stacks demonstrate that the direct utilization of H2O2 and NaBH4 at the electrodes result in >30% higher voltage output compared to the ordinary H2/O2 FC (Miley, 2007). Further, the use of this combination of all liquid fuels provides - from an operational point of view - significant advantages (ease of storage, reduced pumping requirements, simplified heat removal). This design is inherently compact compared to other fuel cells that use gas phase reactants. This results in a high overall system (including fuel tanks, pumps and piping, waste heat radiator) power density. Further, work is in progress on a regenerative version which uses an electrical input, e.g. from power lines or a solar panel to regenerate reactants.
Experimental results to date and design studies confirm the original motivation that this new type of fuel cell offers great potential for enabling aggressive next set missions. This type of fuel cell also has the advantage that it can scale over a wide range of powers. Thus, it becomes a viable candidate for use in satellites, for component power in spacecraft, rovers, and base power. Since the NaBH4 fuel can be shipped as a compact solid and mixed with a small amount of startup water (e.g. initial water from indigenous sources), additional operational water is recycled from that generated in the cell reactions. This conservation of water removes the need to transport water to the fuel cell greatly simplifying operational logistics. The fuel supply and water strategy will be discussed in detail in the presentation.
