In this study, Solar Energy Demand (SED), Cumulative Exergy Extraction from the Natural Environment (CEENE), and LCA-ReCiPe 2016 (using both midpoint and endpoint modeling) life cycle impact assessment methods has been used to assess the performance of hydrogen (H 2) production with renewable and non-renewable electricity sources via high-temperature Solid Oxide Electrolysis Cells. The analysis identified most relevant impact categories, life cycle stages, and processes, both from a thermodynamic and an environmental viewpoint. Electrolysis with nonrenewable energy is characterized by the greatest environmental burdens, however, renewable energy systems also have considerable environmental impacts, some of which are significant. While no perfect electricity source exists, a growing portion of the renewable-based electricity production in the grid mix is an attractive option to lower environmental impacts of H 2 production. Irrespective of the evaluation method, the contribution analysis from different life-cycle stages shows and confirm that the major contributor to the environmental burdens is the electricity supply. The manufacturing stage has high relevance for mineral and metal resources and toxicity-related impacts. Calculations of grid-based electrolysis life cycle environmental impacts in some European countries showed that significant variations. For example, global warming potential per kgH 2 produced vary between 3.31 and 48.24 kgCO 2. Trade-off analysis between the midpoint and endpoint indicators revealed that water consumption, global warming, and particulate matter formation, play a major role in the ranking of electricity supply options. The findings suggest that all potential impacts both at the midpoint and endpoint level should be considered to ensure robust results of the LCA evaluation, a fair comparison between pathways towards more transparent and evidence-based decisions. Towards that end, a further country site-specific assessment with optimization strategies and integration of traditional LCA with resource accounting (thermodynamic metrics) will need to be developed to explore additional valuable insights towards sustainable electrolytic H 2 production systems.

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A series of SOC (Solid Oxide Cell) short stacks from identical production batches was operated in 3 different modes for the systematic assessment of performance according to experimental protocols being harmonized across 7 institutes in Europe and Asia. The operation modes were: Solid oxide fuel cell (SOFC) operation under electrical current profiles and thermal cycling conditions for stationary applications (micro-chp and distributed power generation) and mobile application (SOFC-APU). Solid oxide electrolysis (SOEC) operation under dynamic current profiles for H2 production in a power to gas system. Combined SOFC/SOEC operation for electricity storage in a power-to-gas-to-power system. Each of these cases includes both steady state and dynamic operations. The measurements carried out were current-voltage curves, electrochemical impedance spectroscopy and galvanostatic performance, each executed according to agreed and fully developed protocols. These will be established and experimentally validated. The test modules and programs will consider all relevant operating conditions of the complete SOC test system, e.g. input gases, pressure levels, temperatures, current loads, voltage level, mechanical loads, dynamic transients etc. In order to systematically study these effects, a sound understanding of the interaction of the test object with the test bench shall be developed. It needs to include test bench specifications (e.g. temporal resolution of sensor signals or time constants associated to actuators) and the associated limits to the data analysis. Analysis of the short stack response allowed us to map different parameters with the aim to systematically investigate performance dependency in all the operation modes considered, including: Power density versus current density, fuel utilization, gas phase composition; Efficiency versus temperature, inlet pressure, fuel utilization or gas phase composition Degradation versus time The outcome of the campaign is a clearer assessment of SOC performance dependencies as well as a set of harmonized, rigorous, easy-to-understand and user-friendly procedures for univocal testing of SOC stacks in representative application areas of SOC. Preliminary results underline good performance and repeatability of the tested stacks, strong dependence on gas (H2 and air) inlet temperature, strong instability effects in SOEC modes due to high steam contents and imperfect steam supply etc. The test results will lead to recommendations on test procedure execution and instrument specifications for the benefit of reliable characterization of SOC stacks in multiple, application-representative modes.

Reversible Solid Oxide Cell (Re-SOC) technology has attracted great interest in recent years and is considered to be one of the most promising energy conversion and storage systems. The same Re-SOC cell, can work as a power generator (SOFC) and as an electrolyser (SOEC) by simply reversing the sense of the electric current. The possibility to work in both ways guarantees multiple benefits: fuel flexibility, insignificant emissions, silent operation and affordability. These characteristics are the pillars on which this technology sustains for overriding the current power and substance generation systems in terms of flexibility, environmental sustainability and efficiency. This paper focuses on the effects of test bench system architecture characterization for Re-SOC devices. Preliminary results underline good performance and repeatability of the tested stacks, strong dependence on gas (H 2 and air) inlet temperature, strong instability effects in SOEC modes due to high steam contents and imperfect steam supply. The test results will lead to generate a set of harmonized, rigorous and user-friendly procedures for International Electrochemical Commission (IEC).