Periodic Reporting for period 3 - AD ASTRA (HArnessing Degradation mechanisms to prescribe Accelerated Stress Tests for the Realization of SOC lifetime prediction Algorithms) Reporting period: 2022-01-01 to 2022-08-31 Summary of the context and overall objectives of the project Considering the useful lifetimes that are expected for commercial Solid Oxide Cell (SOC) stacks of up to 80000 hours (both for stationary CHP and energy storage applications), the current state-of-art durability is still a long way from meeting market requirements. Apart from more reliable system design, that provides better control and safeguard of the SOC stack during operation, the intrinsic degradation of the cell assembly still needs to be adequately addressed.Generally, a great number of operational parameters influence SOC degradation during lifetime, each contributing according to characteristic times and intensities, often in convoluted or even contrasting fashion. Furthermore, the closely knit processes in a working SOC often lead to domino-effects, whereby acute degradation occurring in one component or area can trigger or accelerate degradation elsewhere in the stack. Thus, it is crucial to identify the critical locations and dominant mechanisms that curtail SOC lifetime. Then, in order for development cycles to be shorter and to obviate the need for one-to-one lifetime testing, accelerated testing of improved components could speed up the overcoming of critical degradation and achieving significant lifetime improvements. Accelerated Stress Test (AST) protocols thus allow shortening stack qualification and time-to-product cycles and bridge current gaps in testing procedures worldwide.The overall objective of AD ASTRA is the development of AST protocols that allow quantitative identification and prediction of critical degradation mechanisms, correlating them with overall performance variables in selected solid oxide fuel cell/electrolyser (SOFC/SOEC, or SOC) stack components (fuel electrode, oxygen electrode and interconnect). These protocols will build firstly on the analysis of numerous field-tested samples of SOC stacks provided by the industrial partners, followed by applying existing and developing improved testing and modelling methods based on ex-situ component ageing and aggravated stack testing. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far The starting point of the AD ASTRA project was to shed light on the degradation effects on field-tested samples. Through the post-operation analysis and characterization of a large number of samples coming from stacks operated in the field for periods ranging between 2000 up to 40000 hours (both in fuel cell and electrolysis mode), provided by both Sunfire and SolidPower (SolydEra), an inventory of failure effects has been established. Specific investigations, particularly addressing the effects perceived in the inlet, outlet and intermediate areas of the cell or interconnect, have been carried out to achieve a comprehensive operating history of these samples, aiming to define coherent correlations between the stressing of one or more operating parameters and the induced effects.The core of the AD ASTRA project was the definition and validation of Accelerating Stress Test (AST) procedures for the main cell and stack components (fuel electrode, air electrode and interconnects). Relying on the accumulated information (from experiments, post-mortem analysis and modelling activities), a design of experiments (in 3 cycles) for accelerated tests of SOC have been established to systematically address, harness and accelerate the failure modes of the aforementioned SOC components through a testing approach consisting of both in-situ aggravated tests of cells/stacks and ex-situ artificial ageing of components. This experimental approach, based on well formulated targets and selected stressors, ensured the establishment of a quantitative relation between the real-life aging data and the AST aging data that replicate the calendar aged state, presented as acceleration factor (AF). As a final outcome of the project, related to this extensive experimental campaign, 12 AST protocols have been elaborated, including high temperature, high steam, high current density, high pressure, redox treatments and cycling operation as stressors. AST procedures will be available on the project website and public repositories for further use by the scientific community and will contribute to the standardisation of accelerated stress test procedures by International Electrotechnical Commission, Technical Commitee 105 in the next future.Another key result achieved within the AD ASTRA project has been the design of mathematical transfer functions that can correlate applied operating conditions to degradation rate of SOC units. The design process of these functions was summarized into a general procedure that takes into account experimental evidence and model design through multiscale modelling approach, involving high-level, low-level, stochastic and statistical models. As final result, the transfer functions have been achieved by summarizing the degradation models information into performance models and conceiving the transfer functions design approach, ultimately leading to the possibility of predicting the Remaining Useful Lifetime (RUL).The dissemination and exploitation of all the results achieved by the AD ASTRA project has led to a total number of 28 presentations at events and 27 papers published on peer-reviewed journals. Accessibility to the open access publications has been guaranteed via selected public repository, and datasets related to publications have been made available for download. A dedicated workshop was jointly organized between AD ASTRA and RUBY projects, and it was held in Lucerne as an official side event of the 15th European SOFC & SOE Forum, bridging together project partners, researchers and industries representatives. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) The project helped significantly increasing knowledge and understanding of degradation phenomena, contributing to the future improvement of the technology by finding new strategies for limiting the loss of performances on long-term operation. The progress achieved towards the definition of AST protocols, as well as in definition of transfer functions and predictive algorithm for RUL estimation, will pave the way in the near future for the implementation of established procedure at industrial level capable of reducing resources and costs for the validation of the technology. For instance, a 1000h stack test incurs approximately 10 k€ operational costs and typical testing times are 15 kh for industry qualification. By reducing testing times to 3kh, 120k€ can be saved per test. AST procedures, tackling single specific degradation phenomena, will therefore positively speed up the innovation concerning new formulation of SOC components, decreasing at the same time the risks of investing in SOC development.The goals achieved within the AD ASTRA project would also raise awareness of the SOC as a rapidly maturing solution for CHP and P2X applications, among students, researchers and industries, and the increased confidence in manufacturing and validating SOC systems that AST procedures would provide, would enable European SOC industries to invest more in job creation and market cultivation. The resulting increase in SOC deployment would then benefit the environment, given the recognized efficiency, flexibility and low environmental impact of this technology. The process flow in AD ASTRA
