Production of Oxygen from Water by Electrolysis


Oxygen is produced from water by electrolysis aboard the Russian Mir Space Station. The Russians use a dedicated water processor to reclaim water from urine as a feed to the electrolysis cells.

As can be seen from the plots of enthalpy and Gibbs Free Energy vs. Temperature shown below, the reaction is both endothermic and endergonic. Electrical energy must be consumed for the reaction to proceed. The thermodynamics shown below indicate the minimum energy requirements for the production of oxygen (assuming an efficiency of 100%).

The Oxygen Generation Assembly (OGA) baselined for ISSA consists of 18 electrolysis cells constructed using ion exchange membranes and a conducting polymer termed a Solid Polymer Electrolyte. Oxygen is produced at ambient pressure and vented to the cabin. Hydrogen is produced at slightly elevated pressure as a potential supply source for a carbon dioxide reduction system (Sabatier Reactor).


REFERENCES

Butler, R., McElroy, J., and Smith, W., SPE* Electrolysis for Current and Future Space Applications, SAE Technical Paper Series No. 961524, presented at 26th International Conference on Environmental Systems, Monterey, CA, July 8-11, 1996.

Erickson, A.C., Roy, R.J., Mason, R.K., and Tatara, J.D., Solid Polymer Electrolysis Oxygen Generator Testing at MSFC, SAE Technical Paper Series No. 961518, presented at 26th International Conference on Environmental Systems, Monterey, CA, July 8-11, 1996.

Erickson, A.C., and McElroy, J.F., Space Station Life Support Oxygen Generation by SPE* Water Electrolyzer Systems, SAE Technical Paper Series No. 860949, presented 16th Intersociety Conference on Environmental Systems, San Diego, CA, July 14-16, 1986.

Grigger, D.J., Chang, B.-J., and Kovach, A.J., Summary of Static Feed Water Electrolysis Technology Developments and Applications for the Space Station and Beyond, SAE Technical Paper Series No. 901293, presenated 20th Intersociety Conference on Environmental Systems, Williamsburg, VA, July 9-12, 1990.

Hoadley, J.K., and Ginter, J.F., Polyphenylene Sulfide (PPS) as a Membrane in Electrolysis Cells, SAE Technical Paper Series No. 961438, presented at 26th International Conference on Environmental Systems, Monterey, CA, July 8-11, 1996.

Larkins, J.T., Wagner, R.C., and Gopikanth, M.L., A Space Station Utility - Static Feed Electrolyzer, SAE Technical Paper Series No. 860920, presented 16th Intersociety Conference on Environmental Systems, San Diego, CA, July 14-16, 1986.

Larkins, J.T., and Kovach, A.J., Static Feed Electrolysis System for Space Station O2 and H2 Generation, SAE Technical Paper Series No. 851339, presented 15th Intersociety Conference on Environmental Systems, San Francisco, CA, July 15-17, 1985.

McElroy, J.F., Molter, T.M., and Roy, R.J., SPE* Water Electrolyzers for Closed Environment Life Support, SAE Technical Paper Series No. 911453, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Samsonov, N.M., Farafonov, N.S., Gavrilov, L.I., Korolev, V.P., Pshenichnikov, A.G., Grigorjev, J.I., Gusenberg, A.I., and Rjabkin, A.M., Engineering Problems of Developing Systems for Water Electrolysis for Providing the Crew with Oxygen Aboard Space Stations, SAE Technical Paper Series No. 951559, presented at 25th International Conference on Environmental Systems, San Diego, CA, July 10-13, 1995.

Schubert, F.H., Wynveen, R.A., and Jensen, F.C., Developement of an Advanced Static Feed Electrolysis Module, ASME Paper No. 75-ENAS30, presented 5th Intersociety Conference on Environmental Systems, San Francisco, CA, July 21-24, 1975.



Copyright © 1996, James E. Atwater