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Hydrogen Production in Pressurized 3D-Printed Solid Oxide Electrolysis Stacks

Periodic Reporting for period 1 - HyP3D (Hydrogen Production in Pressurized 3D-Printed Solid Oxide Electrolysis Stacks)

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

Water electrolysis for green hydrogen production, offers a promising solution for energy storage from renewable sources and for decarbonizing industrial sectors like: mobility, iron and steel, refineries, ceramics, and chemical plants. Among various electrolysis systems, high-temperature Solid Oxide Electrolysis Cells (SOECs) are the most efficient. However, SOECs face limitations in stable operation at high pressures, hindering their use in applications requiring pressurized hydrogen, such as gas grid injection (P2X) or high-pressure hydrogen storage at refuelling stations (HRS). These limitations arise from the fragile flat thin ceramic cells and issues with flat sealing joints under pressure conventionally involved in these devices. Current solutions involve costly, impractical high-pressure vessels.

The HyP3D project addresses this by utilizing 3D printing of functional ceramics to create robust cells with complex shapes, unachievable through traditional methods. HyP3D cells will feature increased active areas (up to twice that of conventional cells), withstand unbalanced pressures, include non-flat high-pressure sealing, and reduce the volume and weight of the cell stacks.

HyP3D aims to deliver an SOEC stack capable of operating at 5 bar and 850°C. The stack, consisting of 30 3D printed cells, will produce 2.14 kW in a 630 cm³ volume, achieving unprecedented power densities of 3.4 kW/L (three times the current standard) and 1.1 kW/kg (four times the current standard). Demonstrating robust pressurized SOEC technology will enable the efficient use of electrolysis in various hydrogen production scenarios, including storage and transportations. Additionally, HyP3D's additive manufacturing approach reduces the environmental footprint of stack production.
During the first half of HyP3D project, stereolithography paste formulations, printing, and post-printing processes were optimized to fabricate in a reproducible and robust way large-area (45cm2 of projected area) yttria-stabilized zirconia (YSZ) electrolytes with uniform shrinkage. The first produced cells were functionalized with electrodes and tested as single repeating units (SRUs) and three-cell sub-stacks. Additionally, the first full stack (18 cells) based on 3D printed cells demonstrated successful operation in SOEC mode at ambient pressure. HyP3D cells performance today can be summarized as: 20 A of injected current @ 1.4 V per cell, corresponding to 28 W per cell and to a current density of 450 mA/cm2.

The unique HyP3D design was proved to be suitable for using flat thin (200 µm) metallic interconnects. The spinel protective coating deposition and sintering on the interconnects were optimized, producing thick (>10 µm) and dense (>80%) protective layers.

New cell and sealing designs were conceptualized for high-pressure operations, featuring non-flat concepts like notches on cells for compressive sealants, controlled micro-structuration on sealing surfaces for optimized glass ceramic sealants, and sharp notches on cells for gas tightness via metal counterpart plastic deformation. Initial samples of these designs were successfully produced and are currently under high-pressure resistance tests.

A digital twin of the HyP3D stack is being developed. Fluid and mechanical analyses for two different cell geometries, including SRU, five, and twenty-two-cell stacks using the HPC Alya code, were performed. This numerical approach was validated against literature results and will serve as a reference to test new developments.
HyP3D progress beyond state of the art:

- HyP3D stacks will overcome reliability issues of SOEL systems operated inside pressure vessels.

- HyP3D will deliver ultra-compact lightweight stacks with significantly higher volume and mass specific power (3.14kW/L and 1.10kW/kg) from 3 to 4 times higher than commercial SOEC stacks.

- HyP3D will develop high-fidelity and a generate digital twins for real-time decision-making based on deep neural networks.

Expected potential impact:
- Publication of foundational papers on the use of 3D printing technologies for overcoming historical barriers of the SOC technology.
- The development of HyP3D digital twin will contribute to expected outcomes in the Clean H2 SRIA such as: i) improve the performance by design and ii) improve SOEC lifetime by implementing predictive-behaviour and real-time decision-making solutions.
- HyP3D concept will allow easy scaling of the technology resulting in profitable use cases like P2X and HRS.
- Creation of a new production paradigm based on ultra-low CAPEX 3D-printing technology.
- Robust pressurized SOEL technology opens the use of highly efficient electrolysis in a majority of hydrogen production scenarios.
- Reduction of the environmental footprint of the manufacturing of stacks.
- Electricity reduction for hydrogen production by approximately 27%, and reduced hydrogen cost (LCoH) to below €4.25/kgH2.
HyP3D cells and stack concepts
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