Abstract:The Department of Energy, Office of Nuclear Energy, has requested that a Hydrogen Technology Down-Selection be performed to identify the hydrogen production technology that has the best potential for timely commercial demonstration and for ultimate deployment with the Next Generation Nuclear Plant (NGNP). An Independent Review Team (IRT) has been assembled to execute the down-selection. This report has been prepared to provide the members of the Independent Review Team with detailed background information on t… Show more
“…Figure 2b shows the corresponding electrolysis efficiencies. Electrolysis efficiency quantifies the heat value of the hydrogen produced by electrolysis per unit of electrical energy consumed in the stack 18. The electrolysis efficiency was calculated based on the following equation 18: …”
A 30‐cell solid oxide electrolysis (SOE) stack consisting of 30‐cell planar Ni–YSZ hydrogen electrode‐supported single cell with La0.6Sr0.4Co0.2Fe0.8O3–δ–Ce0.9Gd0.1O1.95 (LSCF–GDC) composite oxygen electrodes, interconnects, and sealing materials was tested at 750 °C in steam electrolysis mode for hydrogen production. The direction of gas flow in the stack was a cross‐flow configuration, and the stack configuration was designed to open gas flow channels at the air outlet. The electrolysis efficiency of the stack was higher than 100% at 90/10H2O/H2 ratio under <0.5 A cm−2 current density. During hydrogen production, the stack was operated at 750 °C under 0.5 A cm−2 constant current density for more than 500 h with 4.06% k h−1 degradation rate. Up to 73% steam conversion rate and 91.6% current efficiency were obtained; the net hydrogen production rate reached as high as 361.4 NL h−1. Our results suggested that the SOE stack that was designed with LSCF–GDC composite oxygen electrode could be used to conduct large‐scale hydrogen production.
“…Figure 2b shows the corresponding electrolysis efficiencies. Electrolysis efficiency quantifies the heat value of the hydrogen produced by electrolysis per unit of electrical energy consumed in the stack 18. The electrolysis efficiency was calculated based on the following equation 18: …”
A 30‐cell solid oxide electrolysis (SOE) stack consisting of 30‐cell planar Ni–YSZ hydrogen electrode‐supported single cell with La0.6Sr0.4Co0.2Fe0.8O3–δ–Ce0.9Gd0.1O1.95 (LSCF–GDC) composite oxygen electrodes, interconnects, and sealing materials was tested at 750 °C in steam electrolysis mode for hydrogen production. The direction of gas flow in the stack was a cross‐flow configuration, and the stack configuration was designed to open gas flow channels at the air outlet. The electrolysis efficiency of the stack was higher than 100% at 90/10H2O/H2 ratio under <0.5 A cm−2 current density. During hydrogen production, the stack was operated at 750 °C under 0.5 A cm−2 constant current density for more than 500 h with 4.06% k h−1 degradation rate. Up to 73% steam conversion rate and 91.6% current efficiency were obtained; the net hydrogen production rate reached as high as 361.4 NL h−1. Our results suggested that the SOE stack that was designed with LSCF–GDC composite oxygen electrode could be used to conduct large‐scale hydrogen production.
The current energy system is subject to a fundamental transformation: A system that is oriented towards a constant energy supply by means of fossil fuels is now expected to integrate increasing amounts of renewable energy to achieve overall a more sustainable energy supply. The challenges arising from this paradigm shift are currently most obvious in the area of electric power supply. However, it affects all areas of the energy system, albeit with different results. Within the energy system, various independent grids fulfill the function of transporting and spatially distributing energy or energy carriers, and the demand-oriented supply ensures that energy demands are met at all times. However, renewable energy sources generally supply their energy independently from any specific energy demand. Their contribution to the overall energy system is expected to increase significantly. Energy storage technologies are one option for temporal matching of energy supply and demand. Energy storage systems have the ability to take up a certain amount of energy, store it in a storage medium for a suitable period of time, and release it in a controlled manner after a certain time delay. Energy storage systems can also be constructed as process chains by combining unit operations, each of which cover different aspects of these functions. Large-scale mechanical storage of electric power is currently almost exclusively achieved by pumped-storage hydroelectric power stations. These systems may be supplemented in the future by compressed-air energy storage and possibly air separation plants. In the area of electrochemical storage, various technologies are currently in various stages of research, development, and demonstration of their suitability for large-scale electrical energy storage. Thermal energy storage technologies are based on the storage of sensible heat, exploitation of phase transitions, adsorption/desorption processes, and chemical reactions. The latter offer the possibility of permanent and loss-free storage of heat. The storage of energy in chemical bonds involves compounds that can act as energy carriers or as chemical feedstocks. Thus, they are in direct economic competition with established (fossil fuel) supply routes. The key technology here -now and for the foreseeable future -is the electrolysis of water to produce hydrogen and oxygen. Hydrogen can be transformed by various processes into other energy carriers, which can be exploited in different sectors of the energy system and/or as raw materials for energy-intensive industrial processes. Some functions of energy storage systems can be taken over by industrial processes. Within the overall energy system, chemical energy storage technologies open up opportunities to link and interweave the various energy streams and sectors. Chemical energy storage not only offers means for greater integration of renewable energy outside the electric power sector, it also creates new opportunities for increased flexibility, novel synergies, and additional optimizatio...
“…At the Idaho National Laboratory (INL) there have been a number of studies (Harvego, et.al. 2009 andO'Brien, et.al. 2010) evaluating different power conversion cycles, including supercritical CO 2 power cycles, for use in the production of hydrogen using high-temperature steam-electrolysis.…”
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