Integrated Energy Production Using a Fuel Cell System for a Crewed Space Base Station EERC Energy & Environmental Research Center ®

EERC ® Objective Develop and evaluate a concept for an integrated fuel processing and fuel cell power system for a crewed space base station. Background Fuel cell: an energy conversion tool which creates electric energy by separating out electrons from hydrogen and sending them on a path through the membrane to be combined with oxygen and the original hydrogen molecule creating water and electricity from hydrogen and oxygen. Reforming: reforming converts a fuel into hydrogen through a process like steam reforming, catalytic partial oxidation, or autothermal reforming.

EERC Energy & Environmental Research Center ® Fuel Source Options Sweet potatoes will be present on the station and would make a good fuel source. The Sabatier process on the solid and liquid waste streams produces methane and water as fuels. Fuel can come from a combination of different sources, or supplemental fuel can be brought along.

EERC Energy & Environmental Research Center ®

EERC ® System Description Fuel will be supplied by grown sweet potatoes and waste gases off the Sabatier process in the waste system. The sweet potatoes will be converted to ethanol. Ethanol will be reformed into hydrogen through autothermal or catalytic partial oxidation reforming. The methane gas stream from the Sabatier process can be reformed in a reformer or on the anode of the solid oxide fuel cell (SOFC). The resulting hydrogen will pass through an SOFC producing electricity to power the station.

EERC Energy & Environmental Research Center ®

EERC ®

EERC ® Integrated Energy Production System Concept

EERC Energy & Environmental Research Center ® Hydrogen Production at 0.1 moles O 2 / mole EtOH and Varied Water Feed Rates

EERC Energy & Environmental Research Center ® Carbon Formation at 0.1 moles O 2 / mole EtOH and Varied Water Feed Rates

EERC Energy & Environmental Research Center ® Conclusions The SOFC system is an attractive choice for a crewed space station. –It can operate at higher temperatures (to match the reformer). –It can tolerate CO and it allows for some internal reforming. –It requires less complicated fuel processing systems. Autothermal reforming or catalytic partial oxidation are good options for the power on a space station. –The outlet temperatures match requirements for the SOFC. –Both are relatively small (minimizing the transport weight). –Neither involves combustion. –Operation is straightforward. Ethanol is a premium fuel for this application. –No sulfur to poison the reformer and fuel cell. –Ethanol contains oxygen within the molecule.

EERC Energy & Environmental Research Center ® Recommendations It is recommended that other types of fuel cells be evaluated for use aboard a space station. Evaluation of electrolysis powered by solar or wind energy should continue. It provides pure forms of hydrogen and oxygen, which work well in fuel cells. NASA should keep evaluating nuclear, solar, and wind energy as other possible ways to power the station. NASA is currently looking at nuclear energy for the base because of its low weight-to-power output ratio.