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SOCTESQA Report Summary

Project ID: 621245
Funded under: FP7-JTI
Country: Germany

Periodic Report Summary 1 - SOCTESQA (Solid Oxide Cell and Stack Testing, Safety and Quality Assurance)

Project Context and Objectives:
The aim of the project is to develop uniform and industry wide test modules and programs for solid oxide cell and stack (SOC) assembly units. New application fields which are based on the operation of the SOC cell/stack assembly in the fuel cell (SOFC), in the electrolysis (SOEC) and in the combined SOFC/SOEC mode are addressed. This covers the wide field of power generation systems, e.g. stationary SOFC µ-CHP, mobile SOFC APU and SOFC/SOEC power-to-gas systems.

The proposal builds on the experience and the methodology gained in previous European projects, e.g. “FCTESTNET” and “FCTESQA”. However, these projects focused mainly on single cell tests and system level tests under steady state conditions. On the other hand other relevant stack projects, e.g. the “STACKTEST” project, do not address the high temperature fuel cell technology. None of these projects focus on the development of test procedures of solid oxide cell/stack systems under dynamic operation conditions or in the electrolysis mode. Moreover, established advanced characterization techniques, e.g. the electrochemical impedance spectroscopy (EIS), have not yet been integrated in the test protocols of these previous projects. Only few results were validated by round robin tests.

It is intended to develop a full set of application specific testing modules and programs addressing function, performance, durability and degradation. Within the project, the test modules and test programs will be established and experimentally validated. The test procedures will be developed on stack relevant test specimens, e.g. on short stacks with 5 cells. 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 station shall be developed.

For the SOCTESQA project an organization and management structure has been built that suits the multitude of activities. In this project six European partners and one non-European partner are involved. These are DLR (coordinator, Germany), CEA (France), DTU (Denmark), ENEA (Italy), JRC (Belgium), EIFER (Germany) and NTU (Singapore). During the project there will be a close interaction with an industrial advisory board (IAB) in order to achieve an industrial relevant outcome of the project. Additionally, a continuous liaison with standards developing organizations (SDOs) is aspired with the aim to implement the outcome of the project successfully into international standards. The activities are organized in work packages (WP), which are coordinated by work package leaders. These are WP 1: Coordination (DLR), WP 2: Specifications and Procurement (JRC), WP 3: Testing Procedures (EIFER), WP 4: Solid Oxide Fuel Cell (DLR), WP 5: Solid Oxide Electrolysis Cell (CEA), WP 6: Combined SOFC/SOEC (DTU), WP 7: Dissemination and Liaison (ENEA). Each work package contains several tasks, which are coordinated by task leaders. In this project the work package leaders are also the leaders of the corresponding tasks in their WP.

For the achievement of the project objectives, two workflow paths have to be taken into account. The first path is the development of the test modules and programs. This path will have a clear structure based on an initial definition phase, the development of generic test modules which will be validated by experimental validation phases. The review of the test procedures will result in modified test procedures leading to a subsequent second validation loop. At the end of the project, the final test modules will be confirmed by round robin tests. As mentioned above, the second path of the project refers to the liaison activities to the industrial advisory board industry (IAB) and to standards developing organizations (SDO).

Project Results:
All specifications for the solid oxide stack assembly unit (SOC short stack) have been defined. Moreover, a survey of all existent SOC test procedures and nomenclatures for single cells and stacks including those from previous projects, from the open literature and from relevant standards developing organizations was performed. After having selected one stack supplier (ElringKlinger, Germany) short stacks with 5 repeat units were procured.

A test matrix containing altogether 18 test modules has been defined. Industrial stakeholders who are developing SOFC/SOEC products have been contacted to collect information regarding the required operation modes. A test program has been developed for the initial test station validation campaign. In this test program, all three operation modes of the SOC stack (SOFC, SOEC and combined SOFC/SOEC) have been considered. Five generic test modules have been developed and embedded in the test program. These are TM 02: Start-up, TM 03: Current-voltage characteristics, TM 04: Electrochemical impedance spectroscopy, TM 12: Operation under constant current and TM 16: Shut-down. In addition, a master document named TM 00: General SOC Testing Guidelines has been developed. Moreover, the test program for the next testing campaign has already been drafted. This program contains another 4 test modules: TM 07: Reactant utilization, TM 08: Reactant gas composition, TM 09: Temperature sensitivity and TM 13: Operation under varying current.

The test stations were adapted, particularly with regard to uniform test input parameters at the stack/test station interfaces. The adaptation of the test stations comprised mainly the integration of gas distribution plates for the stacks, thermocouples and gas preheating subsystems, the modification of the gas supply units, the integration of humidification units and voltage sources for SOEC operation, the upgrading of the electrochemical impedance spectroscopy and control/software adaptations.

After the test stations have been adapted successfully the initial tests station validation campaign dedicated to identify remaining differences among the test stations of all partners was started. The current-voltage characteristics of the stacks in SOFC and SOEC operation show a very high reproducibility between the different test laboratories. The OCVs of all partners are almost the same and the voltage curves are very similar. However, in electrolysis operation voltage fluctuations in the jV-curves appear which are caused by instabilities of the steam generating units. The improvement of the steam flow stability is very important in order to accurately determine the area specific resistance (ASR). A clear increase in performance with increase in gas inlet temperature was observed. Hence, the gas inlet temperature is one of the most important test input parameters.

The electrochemical impedance spectra in SOFC mode show uniform results among the partners. Especially in the high-frequency range the spectra are almost similar which indicates a high reproducibility for the determination of the ohmic resistance of the repeat units. In the low frequency range variations of the overall impedances among the partners can be observed, which are due to the high sensitivity of the gas concentration arc on the fuel gas composition. In SOFC mode the total resistances of the EIS spectra correlate very well with the ASRs calculated with the jV-curve which proves a good reproducibility of both methods. In contrast to SOFC, the voltage fluctuations in SOEC mode are crucial in the EIS spectra as they induce high instabilities especially at low frequencies.

The operations under constant current in SOFC and SOEC mode show different trends among the partners, resulting in different degradation rates. All test stations of the partners are able to follow the planned set points for reversible SOFC/SOEC operation and to perform switching between the operation modes within the specified 2 hours period.

Potential Impact:
The ultimate objective of the project is to come up at the end with test procedures that are not only validated inside the laboratory, but are already shaped towards the requirements of regulations codes and standards (RCS) as well as industrial productivity and reliability. The test procedures should incorporate the inputs from both entities and should foster worldwide discussion and awareness of the topic. In this way the maximum exploitation of the project outcome can be achieved. Therefore, the broad dissemination of the project results, the interaction with relevant industrial stakeholders and the liaison with standards developing organizations (SDO) are important issues in the project.

In order to create awareness of the hydrogen and fuel cell activities and to disseminate the project activities and results for interested parties the SOCTESQA project was intensively promoted with different items, e.g. the project website, posters at high-profile conferences, project newsletters and a project flyer. Moreover, interaction with other European funded projects was established by participating and exchanging of the results at project meetings.

Since the procedures of SOCTESQA are directed towards the use of SOFC/SOEC in real-life applications an Industrial Advisory Board (IAB) was established within the project. The aim is to incorporate requirements and preferences from key industrial stakeholders in SOC technology. Therefore, at the beginning of the project, fact sheets were compiled by SOCTESQA partners and sent out to the IAB for gaining technical input. These include mainly the operating conditions of SOC systems for combined heat and power generation (µ-CHP), auxiliary power units (APU) and electrolysis systems.

SOCTESQA has entered into contact and liaison with the main bodies currently working on regulations for hydrogen and fuel cell technologies. Essentially, these are grouped under the international bodies of the ISO Technical Committee 197 on hydrogen technologies – which looks mainly at safety issues of electrolyzers and hydrogen handling – and the IEC TC105 on fuel cell technologies. The latter is much more focused on the technology and the definition of practical guidelines in terms of system performance, installation and characterization. In order to intensify the interaction with this committee SOCTESQA was presented at the IEC TC105 plenary meeting in 2014. It was agreed to initiate a dedicated working group on procedures for testing fuel cells in reversing mode within TC105. This “Ad Hoc Group 6” (AHG 6) will develop three International Standards within a New Work Item Proposal (NWIP) by 2019. One of these standards focuses on “Solid oxide single cell and stack performance including reversing operation”. Since the convenor of this Ad Hoc Group 6 is the leader of work package 7 in SOCTESQA first-hand involvement is guaranteed and the best possible output pathway for SOCTESQA activities is enabled.

Simultaneously, CENELEC, the European technical standardization body, has also initiated a new working group on Hydrogen. DLR has joined this working group, namely task force 2: electrolyzers, and participated at several meetings with the background of transferring the results and experience so far achieved in SOCTESQA and to monitor the progress in this working group on behalf of the SOCTESQA consortium. The final objective of this working group is to set a long-term collaborative framework (liaison) with major bodies for strengthening cooperation between regulatory work, standardization work and RDI programs (e.g. European Commission, JRC, FCH2 JU, IEA, ISO, IEC). The formal liaison agreement between DLR and CENELEC was signed in Sept. 2015.

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