A novel variable altitude Venus interior probe is currently under development that uses in-situ power and propulsion to lower a balloon down into Venus’s atmosphere, approximately 20 km from the surface, and then bring it back up above the clouds and hover at approximately 60 km from the surface. One of the biggest challenges is finding an energy storage solution that can withstand Venus’s harsh atmosphere. At 20 km the probe will experience temperatures close to 325°C, pressures around 20 atm, and an atmosphere composed of CO₂, with trace amounts of sulfur containing compounds. Conventional energy storage technologies, like batteries, are not an option under these conditions. The only technology that can survive under these conditions are solid oxide fuel cells (SOFCs), which operate in a temperature range between 600 – 1000 °C.

Fuel cells are devices that convert chemical energy, in this case from hydrogen and oxygen, into electricity with the only byproducts being heat and water. Solid oxide fuel cells can be run reversibly as an electrolyzer, taking the byproduct water and splitting it into hydrogen and oxygen that can then be used to run the fuel cell. A regenerative fuel cell system may therefore be built around a single SOFC stack. The goal is to run the SOFC to power the probe at 20 km and then reverse the SOFC to an electrolyzer when the probe is back above the clouds and use solar power to produce hydrogen and oxygen.

The data presented in this work shows the successful operation of a regenerative SOFC. Figure 1A shows a SOFC that was run in H₂/O₂ as an electrolyzer. Figure 1B shows a SOFC run as a fuel cell in different conditions including H₂/O₂ (red line) and H₂/Air at different flow rates (blue lines). The goal of this work is to pinpoint the exact conditions a SOFC would need to operate at in order to successfully store energy for an interior probe in the Venus atmosphere.

This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA) and NASA’s Innovative Concepts (NIAC) Program: “Venus Interior Probe Using In-situ Power and Propulsion (VIP-INSPR).