ABSTRACT
MOXIE [Mars Oxygen In Situ Resource Utilization (ISRU) Experiment] is the first demonstration of ISRU on another planet, producing oxygen by solid oxide electrolysis of carbon dioxide in the martian atmosphere. A scaled-up MOXIE would contribute to sustainable human exploration of Mars by producing on-site the tens of tons of oxygen required for a rocket to transport astronauts off the surface of Mars, instead of having to launch hundreds of tons of material from Earth's surface to transport the required oxygen to Mars. MOXIE has produced oxygen seven times between landing in February 2021 and the end of 2021 and will continue to demonstrate oxygen production during night and day throughout all martian seasons. This paper reviews what MOXIE has accomplished and the implications for larger-scale oxygen-producing systems.
ABSTRACT
Solid oxide cells can play a vital role in addressing energy and environmental issues. In fuel cell mode they are capable of producing electric energy at high efficiency using hydrocarbon fuels and in the electrolysis mode can produce hydrogen from steam or synthesis gas from a mixture of steam and carbon dioxide. The solid oxide electrolysis cells (SOECs) can operate at a wide range of conditions. A capable means by which to select operating conditions in the application of solid oxide electrolyzers is a necessity for successful commercial operation. Power and efficiency can be determined over a wide range of operating conditions by applying fundamental electrochemical principles to a SOEC system. Operating conditions may be selected based on power requirements or with efficiency as a priority. Operating cost for electricity which is a function of both power and efficiency can also be used to determine optimal operating conditions. Performance maps based on closed form isothermal parametric models for both hydrogen and natural gas fueled SOFC stacks have been demonstrated previously. This approach applied to a SOEC stack is shown. This model was applied to generate performance maps for a solid oxide cell stack operated in the electrolysis mode. The functional form of the model and the boundaries of the operating envelope provide useful insight into the SOEC operating characteristics and a simple means of selecting conditions for electrolysis operation.
