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SECOND ACT Sintesi della relazione

Project ID: 621216
Finanziato nell'ambito di: FP7-JTI
Paese: France

Periodic Report Summary 1 - SECOND ACT (Simulation, Statistics and Experiments Coupled to develop Optimized aNd Durable µCHP systems using ACcelerated Tests.)

Project Context and Objectives:
Second Act (Simulation, statistics and Experiments Coupled to develop Optimized aNd Durable µCHP systems using ACcelerated Tests) was proposed to address the topic: “Improving understanding of cell & stack degradation mechanisms using advanced testing techniques, and developments to achieve cost reduction and lifetime enhancements for Stationary Fuel Cell power and CHP systems”.
Second Act aims at improving understanding of stack degradation in order to propose solutions enabling significant lifetime improvements for µCHP systems using PEMFC (Proton Exchange Membrane Fuel Cell), operating under Hydrogen or Reformate, or DMFC (Direct Methanol) technology. The project is founded and focused on two efforts: degradation understanding and durability improvement. These efforts are oriented towards existing systems available in the project thanks to the involvement of three industry partners willing to enhance lifetime and hence competiveness for market deployment.

The main double objective of Second Act is to improve understanding of stack degradation and propose durability improvements for µCHP systems using PEMFC or DMFC. The project aims at:
• Analysing long term lifetime tests data from existing systems to identify main causes for failure related to system operation and quantify performance degradation of the stacks, over the long term (at least 10,000 hrs and more than 20,000 hrs for some systems considered)
• Conducting lifetime tests to investigate degradation at cell and stack levels and to better understand mechanisms involved. Common degradation mechanisms in stack components (electrodes mainly) will be particularly considered to help identifying similar type of improvements on materials and processes to be implemented for lifetime extension.
• Developing, applying and validating accelerated stress tests (AST) and specific tests representative of failures in harsh conditions for the different Fuel Cell technologies
• Developing and applying in-situ and ex-situ investigation techniques for better identification and local resolution of the degradation mechanisms. Heterogeneities in degradation over the cells surface and across the stacks will be particularly tackled, with regards to local operation and local conditions (including fuel composition)
• Developing new statistical approach and models for better understanding and description of systems stochastic/deterministic degradation, reversible/permanent degradation and heterogeneities of degradation in single cells and stacks.
• Demonstrating stack lifetime improvements increased tolerance to applications’ relevant cycling or operating modes (e.g. start/stop or idle), mainly through stack components modifications (in materials, components design, manufacturing processes…) for Pure H2, Reformate PEMFC and DMFC. For the improvements of Membrane Electrodes Assemblies that will be particularly considered as core components, two routes will be followed, one on raw materials and manufacturing processes to face mainly defects and one on structured (non-homogeneous) electrodes and GDL to face mainly degradation heterogeneities.
The overall strategy is based on degradation understanding based on lifetime tests information followed by durability improvement thanks to the exploitation of all degradation investigations. The approach is an iterative process with proposal of improvements at two periods: near mid-term and again before the end for final demonstration.
First period was thus focused on ageing investigations and degradation understanding. Proposal, selection, implementation of components modifications in cells and stacks for their characterisation during ageing and final demonstration of improvement will be done during the next period.

Project Results:
The activities of the first period have been conducted in three technical work packages dedicated to “specification of reference components and degradation data” (WP1), “Investigation of degradation processes” (WP2), and “Statistical analysis and simulation of stack performance degradation” (WP3).
Summary of main actions and results are listed below.
• Definition and description of systems, stacks, cells and reference components… And
• Preparation and delivery of reference components, cells, stacks
More than 400 MEAs have been assembled in small (25 cm²) or stack size (200 cm²) single cells for tests at 6 partners lab, in short low power (8 cells) or higher power stacks (up to 75 cells) for tests by 3 partners on test stations or directly on real systems (incl. a 70kW power plant reaching total of 50000 hrs of operation).
• Available degradation and durability data at systems, stacks, cells
Previous experiences have been summarized and data have been provided as input for further understanding and statistical analysis.
For the three technologies, the overall decay includes permanent and reversible contributions. Irreversible cathode electrochemical active surface area loss is a common cause of degradation. Then additional specific causes have been identified for each technology (contaminants, CO, catalysts modifications, systems’ operation mode).
• Planning of the whole experimental activities to ensure data statistical significance
• Application of advanced testing techniques and procedures 

Improved tools from new segmented cells to reformate CHP prototype and new specific diagnostics.
• Characterization by state of art technologies
H2, Reformate and Methanol fuelled single cell or stacks have been tested under reference, cycling or accelerated conditions. Effects of overall conditions and of particular cases such as impurities in Air or Fuel, have been characterized. Impact of operation modes such as load cycles, start-up/shut-down, flow orientation have been investigated.
Both temporary and permanent degradation are thus considerably affected by materials applied in anode catalyst layers.
• Quantification of local degradation and heterogeneities effects
Heterogeneities are strongly affected by initial local conditions. Current redistribution over time is observed; it appears caused by local temporary degradation phenomena related to catalysts surface.
• Analysis of induced failure
• Development and validation of AST for specific failure modes 

• Ex-situ analysis of degradation mechanisms in pristine and aged samples 

Fluoride ion detection, Infrared Thermography, XPS and Electrochemical and Transmission Electron Microscopy analyses have been carried out on aged samples.
Numerical tools for the simulation of degradation mechanisms at the MEA and cell levels have been developed. First simulations have been performed and model validation is on-going. For PEMFC and DMFC reversible mechanisms are addressed. Especially in the case of DMFC, specific experiments have been proposed for the model validation and calibration. Simulations analysis and sensitivity studies will allow to propose specific experiments for the calibration and validation of the mechanisms involved in PEMFC.
Main expected outcome was to identify major performance degradation related to heterogeneous operation in a cell. The simulation performed at the MEA and cell levels for reversible degradation show a strong heterogeneous degradation through the thickness of the catalyst layer, or between the inlet and the outlet of the cell. As degradation mechanism strongly depend on local condition, the degradation rate will obviously be heterogeneous over the surface of the cell.

Outcomes from WP1, WP2 and WP3 result suitable to prepare the list describing main causes for failure or performance losses to be used as a basis of first set of improvements for next period.

Potential Impact:
Concerning components, cells and stacks to be investigated: the second period of the project more samples will be supplied.
Concerning experimental investigations of degradation, the next steps can be summarised as:
• Additional ageing tests in different conditions and consolidation of degradation mechanism understanding combining in operando and ex-situ analyses.
• Based on ageing data, experimental and modelling investigations: identification of major causes for performance degradation related to heterogeneous operation
• Identification of first set of possible improvements, selection and implementation of more relevant in single cells or stacks
• Selection of the more relevant tests to be applied for improvements validation
• Application of the ageing experimental and modelling tools to the proposed improved components for evaluation and further understanding.

Major expected findings for the end of the project are modifications of materials, design or manufacturing process of stacks core components allowing systems’ lifetime improvement.

Potential impact will be first related to the exploitation of results by the partners.

Industrials (IRD, Nedstack, ICI) plan to exploit project results to improve the durability of their future generations of DMFC and PEMFC. They will then be able to reinforce their share on the market of stationary power generation and CHP.
For the three fuel cell technologies considered (pure H2 PEMFC, reformate PEMFC and DMFC), SECOND ACT will propose improvements on core components to be integrated in stacks to increase their durability in the conditions imposed by the systems. To be consistent with the exploitation targets of partners, applicability at industrial level (e.g. availability of raw materials or manufacturability for large scale production) will always be taken into account when considering the components selected for demonstration of durability improvements.
The insights obtained by the project will be used by industrials as follows:
• to help MEA suppliers to improve MEAs
• to improve their stack design
• to avoid conditions that are detrimental for stack life
• to improve stack life forecasts for customers

Improvement in stack life leads to lower maintenance costs for customers. This will lead to a more favourable position of the fuel cell systems compared to other technologies with which industrials compete.

For research groups, skills and knowledge acquired will be used for their expertise enhancement and thus allow further valuable developments for the whole community in the field of fuel cells. Of course, as far as possible results will be exploited to propose patents or publications.

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