Regenerative Fuel Cells (RFC)
Low Mass, High-Energy Storage Capability
Unmanned high altitude aircraft and airships with long mission durations over fixed targets (persistence) have increased interest in the development of regenerative fuel cells. These devices combine an electrolyzer that converts photovoltaic energy into stored chemical energy (pressurized hydrogen (H2) and oxygen (O2) gas), with a fuel cell that can convert the chemical energy back to electric power and water. Doing so completely closes the system (no fluids are lost) and a regenerative fuel cell (RFC) results. The low-mass, high-energy RFCs offer significant advantages over batteries, as the RFCs have the ability to repeatedly undergo near 100% charge and discharge cycles.
In order to store the gaseous fluids in reasonable volumes with minimal mass, the electrolyzer portion of the system must operate at significant pressures. Typical system designs require the use of separate stacks for efficient high pressure electrolysis and high efficiency power production at low pressure in a fuel cell stack. As the acknowledged leader in high pressure electrolyzer technology, GES has worked with private and public sector organizations to design, fabricate, and operate lightweight high-pressure electrolyzers capable of producing high purity gas streams at pressures of 0 to 80 bar. We are currently developing designs for 140 bar operation for NASA’s Mars/Lunar exploration programs. Key in all our designs is world-class efficiency at high current density to electrolyze the most water possible, with the least electrical energy and the lowest total system mass.
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