High-temperature electrolysis for hydrogen production from nuclear energy

Full text of publication follows: Currently there is strong interest in the large-scale production of a secondary energy carrier for the non-electrical market. Hydrogen is of particular interest as the secondary energy carrier because it has the potential to be storable, transportable, and environmentally benign. Hydrogen can be used as a fuel for heating, electrical production (using fuel cells), and vehicles. It is also used as a raw material for many chemical processes, such as ammonia and methanol synthesis, iron ore processing, petroleum processing, and others. Currently hydrogen is produced primarily via steam reforming of methane. From a long-term perspective, methane reforming is not a viable process for large-scale production of hydrogen as a major energy carrier since such fossil fuel conversion processes consume non-renewable resources and emit greenhouse gases to the environment. Consequently, there is a high level of interest in production of hydrogen from water splitting via either thermochemical or electrolytic processes. High-temperature nuclear reactors have the potential for substantially increasing the efficiency of hydrogen production from water, with no consumption of fossil fuels, no production of greenhouse gases, and no other forms of air pollution. Thermal water-splitting for hydrogen production can be accomplished via high-temperature electrolysis or thermochemical processes, using high-temperature nuclear process heat. In order to achieve competitive efficiencies, both processes require high temperature operation (∼ 850 deg. C). Thus these hydrogen-production technologies are tied to the development of advanced high-temperature nuclear reactors. High-temperature electrolytic water splitting supported by nuclear process heat and electricity has the potential to produce hydrogen with an overall system efficiency near those of the thermochemical processes, but without the corrosive conditions of thermochemical processes and without the fossil fuel consumption and greenhouse gas emissions associated with hydrocarbon processes. Specifically, a high-temperature advanced nuclear reactor coupled with a high-efficiency high-temperature electrolyzer could achieve a competitive thermal-to-hydrogen conversion efficiency of 45 to 55%. A research program is under way at the Idaho National Laboratory (INL) to simultaneously address the research and scale-up issues associated with the implementation of planar solid-oxide electrolysis cell technology for hydrogen production from steam. We are conducting a logical progression of electrolysis stack testing activities, at increasing scales, along with a continuation of supporting research activities in the areas of materials development, single-cell testing, detailed computational fluid dynamics (CFD) and systems modeling. Single- and multiple-cell experimental studies are being performed. In addition, a conceptual design for large-scale nuclear production of hydrogen via planar solid oxide electrolysis technology is being developed. The design effort is addressing solid oxide cell materials and configuration, performance, durability, operating conditions, economics, and safety. Interim experimental results indicate that this technology performs close to theoretical predictions and remains a viable means for hydrogen production using nuclear energy. (authors)