Small Spacecraft Electric Propulsion (SSEP) Technology Suite
Pressurized Oxygen via Solid Oxide Electrolysis (LEW-TOPS-85)
Small, simple device produces pure, dry, pressurized oxygen
Innovators at NASA's Glenn Research Center have developed a method for producing pure high-pressure oxygen via an electrochemical pumping process through a solid oxide electrolysis (SOE) cell stack. Glenn's device can either concentrate the oxygen in the ambient atmosphere or extract the oxygen via the chemical reduction of carbon dioxide, water, or any combination of these substances. This solid-state device does not use any moving parts or any extra separation processes to purify the delivered oxygen. Instead, Glenn's technology relies on a multi-stage stack design and an SOE process that includes an oxygen-ion-conducting ceramic membrane to generate high-pressure oxygen within a compact, noiseless device. This process has great potential for use in industrial, medical, and recreational applications.
Originally conceived as a method to generate pressurized pure oxygen for extravehicular activity (EVA) suits worn on the International Space Station, Glenn's technology represents a significant breakthrough. The generator is an all-solid-state device that separates oxygen from air, water, or carbon dioxide and electrochemically pumps it to a high pressure in a multi-stage process. Glenn's design features a solid oxide electrolysis (SOE) stack, based on bi-supported cell design, that is structurally supported by two electrode layers. Sandwiched between the cathode and anode sides is an oxygen-ion conducting solid-state electrolyte membrane, made of yttria-stabilized zirconia (YSZ). These membranes form the individual SOE cells within the stack, and each cell carries out a single stage of the multi-stage process, with each stage incrementally pressurizing the oxygen. A voltage (1.5 to 2 volts) is applied across the cell, and the air or other input is supplied to the cathode side, where the oxygen dissociates into oxygen ions. The YSZ membrane will conduct only the oxygen ions, producing pure, dry oxygen. The entire stack is wrapped in a glass ceramic seal, providing a pressure vessel for the device. Glenn's novel stack design allows hermetic sealing and does not require a compression sealing mechanism or other spring-loaded hardware. Each cell is wired in parallel so the voltage can be controlled across each cell to avoid electrochemical reduction of the electrolyte. In addition, each cell is electrically insulated from other cells in the stack using a non-electronically conducting, ceramic-woven cloth YSZ layer. Because Glenn's process resists fouling from water containing impurities or other debris, it does not require a high-purity water source, as do other water electrolysis technologies. The oxygen product is also sterile for medical applications because of the high temperature (in excess of 600°C) at which the process operates.
- Simple: Eliminates pumps and rotary compressors and does not require compression sealing
- Green: Uses only air, water, or carbon dioxide to generate pure oxygen
- Reliable: Contains no moving parts, increasing reliability and requiring minimum maintenance
- Compact: Reduces device mass and volume compared to current oxygen-generation devices
- Stable: Avoids large pressure changes across individual cells
- Refining systems (e.g., fluid catalytic cracking regenerators)
- Syngas generation for gas to liquids (GTL) plants
- Industrial processes (e.g., smelting iron)
- Specialized medical oxygen systems