Solid-State System Efficiently Generates Purified O2

This engineering system is essentially solid state. Other than an external circulation fan, there are no moving parts, rotating equip-ment, multistep distillation process, or selector valves like those required for pressure swing adsorption systems. Additionally, there are no concerns about hydrogen permeability, which can occur in classical membrane separation systems. The system design uses multiple electrochemical cell stacks in a segmented, serial configur-ation, and it can be connected into a single DC circuit. System sizing calculations project that the energy use for a moderate scale system, producing between 10-30 standard-liters-per-minute (slpm) of purified oxygen and compressing it to upwards of 300 psig, is less than 75 W/liter O2. This system’s thermal tower design enables a fast sweep of “free-heated” process air, but it requires significantly less energy to do so over current systems that rely upon electrical preheating. At a 700-degree C system operating temperature, approximately 15% of the current performs electrochemical work, but 85% of the current results in waste heat. This system design incorporates a heat exchanger to transfer heat from the already-circulated and oxygen-depleted process air, to the fresh ambient process air feed. The waste heat generated by the lower, or first cell stack, preheats the second cell stack, and the temperature of the cell stack increases with each successive layer. With a sufficient number of layers, the temperature increase is substantial enough to enable the waste heat from the top cell stack to preheat the incoming air using the heat-exchanger, without the need of supplemental heaters. This efficient oxygen separation and compression technology could have applications other than space systems, such as terrestrial life-support systems, cabin air-supply for confined environments, medical health and veterinarian clinics in remote locations where commercially produced bottled oxygen is not readily available, and remote pure oxygen production for oxy-fuel welding. This technology could replace pressure swing absorption methods for small-scale distributed oxygen generation due to its greater efficiency and higher purity oxygen output. Although this specific system design and process is for separating oxygen from an ambient air feed, at substantially higher voltages some solid oxide systems can disassociate CO2 into CO and oxide ions and electrochemically transport the oxide ions across a cell membrane. The Solid State, Energy Efficient Method of Oxygen Separation and Compression technology has a technology readiness level (TRL) 4 (component and/or breadboard validation in laboratory environment), and it is now available for patent licensing. NASA does not manufac-ture products itself for commercial sale. Please note that the main image above shows a single cell stack technology demonstrator referred to as, “The Recirculator". Innovators at NASA Johnson Space Center, in collaboration with inno-vators at American Oxygen, have developed a solid-state system and process that separates oxygen from ambient air and compresses the resulting purified oxygen – with a significant reduction in power con-sumption compared to prior state-of-the-art. It is based upon a proven solid oxide electrochemical oxygen separation and compression tech-nique that derives purified oxygen from ambient air and compresses it using an electrochemical pumping method. This electrically driven technology relies upon the high operating tem-perature of electrochemical cell stacks for maximum efficiency. An inverse relationship exists between high temperature and electrical resistance; thus, a heated system requires less energy to drive oxide ions across a cell membrane and compress the resulting purified oxy-gen. Ambient air that is fed and circulated for processing through the system also helps to stabilize high system operating temperatures. To prevent the ambient air from overcooling the electrochemical pro-cess, the incoming air is preheated. However, in existing systems, this pre-heating incurs a large cost penalty in power consumption. The new solid-state system design performs electrochemical reactions to generate purified oxygen but uses an embedded heat exchanger to preheat the incoming air with system waste heat without the need for supplemental heaters, significantly boosting efficiency.