Tubular proton conducting ceramic stacks for pressurized hydrogen production

Project Information

PROTOSTACK

Grant agreement ID: 101101504

DOI

10.3030/101101504

EC signature date 7 December 2022

Start date 1 January 2023

End date 31 December 2026

Funded under

• Climate, Energy and Mobility

Total cost

€ 2 497 013,75

EU contribution

€ 2 497 013,75

Coordinated by

SINTEF AS
Norway

Periodic Reporting for period 1 - PROTOSTACK (Tubular proton conducting ceramic stacks for pressurized hydrogen production)

Reporting period: 2023-01-01 to 2024-06-30

Summary of the context and overall objectives of the project

The project aims to showcase the competitive edge of Pressurized Proton Ceramic Electrolysis (PCCEL) technology. At the heart of PROTOSTACK is a novel stack technology designed to tolerate high-pressure operations. The project seeks to experimentally validate its performance at pressures up to 30 bar in a 5kW stack panel. The stack design employs a tubular cell architecture, which is inherently more suitable for pressurized operations compared to planar stacks and allows for operation under differential pressures. This innovative, compact, and modular technology will be based on a 400W stack, which can be easily replicated and assembled into multiple stack panels to increase capacity. Each stack will comprise up to six Single Repeating Units (SRUs), electrically connected in series using specialized interconnects and integrated glass ceramic sealants. Each SRU will contain six tubular proton ceramic-based cells and other key enabling technologies (KETs) such as interconnects and seals. The short length of the individual cells and a specialized current collector system integrated with each electrode will address current collection challenges typically encountered in tubular systems. All processes will align with a sustainable value chain for stack manufacturing, based on eco-design principles aimed at reducing emissions and the consumption of energy and critical raw materials.
The stack design will integrate electrical feedthroughs, gas manifolds, and a steel pressure vessel. A key aspect of this design is its enhanced robustness against thermal gradients and thermal runaway propagation due to its geometric configuration. This stack design will be easily scalable by assembling the stacks into panels. The project will develop and demonstrate a scaled-up version of the tubular PCCEL technology, represented by a 5kW stack panel containing 12 stacks fully integrated into a hotbox with optimized stack arrangements for improved electrical efficiency and thermal management. PROTOSTACK will drive innovations in electrochemical stack design, stack components, processing methods for stack assembly, and hands-on knowledge of pressurized PCCEL technology.
Building on these advancements, the project will also evaluate the techno-economic viability of the PCCEL technology and explore three distinct business cases where thermal integration and the use of directly pressurized hydrogen from PCCEL stacks enhance the value proposition for decarbonization.
To achieve its ambitious goals, the project consortium brings together world-leading research and industry partners in proton ceramic technologies, with recognized expertise in the research and development of electrolysers, membrane reactors, materials, electrochemistry, and process engineering: SINTEF, Shell Global Solutions International B.V. CoorsTek Membrane Sciences AS, CSIC, ATENA, and DEMCON energy systems B.V.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the initial phase of the project, significant efforts were focused on validating and optimizing the tubular stack design using computational fluid dynamics (CFD) modeling. The impact of cell configuration, stack design, and specific operating conditions on thermal gradients, potential distribution, velocity profiles, and concentration distributions within the stack pressure was investigated to evaluate and minimize thermal and electrical losses throughout the stack configuration. Concurrently, a new hot-box design was conceived and engineered based on a replaceable cartridge concept, which mitigates thermal expansion between the hot and cold zones of the complete assembly. The hot-box design is finalized, and construction is currently in its final stages.
Production and acquisition of key components for stack production commenced in the first period. A total of 250 tubular half-cells have been manufactured to build up a stock for the initiation of stack production in the second half of the project. All key components for stack production—including steel materials for the pressure vessel, gas distribution, and current collection—have been validated for their chemical stability under PCCEL conditions: 30 bar total pressure with 75% steam in air at 600°C.
The project also developed and optimized a new production route for the deposition and annealing of the steam electrode, which is less labor-intensive and well-aligned with the existing manufacturing processes employed at CoorsTek Membrane Sciences. Single cells based on the optimized production protocol have been prepared and tested up to 10 bar for 300 hours, showing improved performance compared to the state-of-the-art, with no indications of degradation after pressurized operation.
Additionally, the project investigated a range of steel materials as current collectors for pressurized PCCEL operation and implemented various coating strategies to mitigate corrosion and reduce contact resistance at the electrode-current collector interface. A systematic study of contact resistance and chemical stability in pressurized operation identified promising candidate current collection assemblies with contact resistance below 0.05Ωcm² for over 500 hours in pressurized operation.
Prototype short-stacks were fabricated to validate the production process and the compatibility of different components (cells, interconnects, sealants, and electrical contacts). The Balance-of-Plant for integrating the new stack and hot-box design into the dedicated containerized test plant was re-engineered to facilitate the optimized stack design and expanded operating conditions. A HAZOP session was conducted to ensure the safe operability of the system.
Finally, a methodological framework for techno-economic and life-cycle analysis was developed and validated using a base-case stand-alone process flow layout for the PCCEL technology. This framework will be leveraged in the second period of the project with an optimized process flow and integration with downstream end-users to assess specific business case opportunities for the PROTOSTACK technology.

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)

In the first period of the project, the focus has been on establishing and validating the stack design and individual components as assemblies in terms of manufacturability and stability. The main technical results and outcomes are expected to emerge in the second period of the project.

However, significant progress has already been made. The project has developed and optimized a steam electrode material and implemented a scalable and robust deposition and annealing process, consistent with large-scale manufacturing and existing infrastructure for tubular PCCEL cell production. These optimizations have resulted in a significant reduction in the overall tubular cell resistance from 0.8 to 0.5 Ωcm², and an electrode polarization resistance below 0.2 Ωcm².

PROTOSTACK has also developed and investigated steel-based current collector systems under pressurized PCCEL conditions, an area not previously explored within proton ceramics. Through dedicated and systematic studies, the project has demonstrated a steel-based current collector system with a contact resistance below 0.05 Ωcm² for more than 500 hours in pressurized operation. Further improvements in processing parameters and material combinations will be pursued in the second half of the project, representing a major advancement for PCCEL technology.

Cell performance evolution across three subsequent EU-projects on tubular PCE technology

First prototype short-stack produced in PROTOSTACK