Gradient Meshed and Toughened SOEC (Solid Oxide Electrolyzer Cell) Composite Seal with Self-Healing Capabilities

Technology readiness levels (TRLs) of electrolysis systems have dramatically increased in recent years as the interest in clean hydrogen production and decarbonization of transportation, industrial and other sectors increases across the globe. This is especially true of high temperature steam electrolysis (HTSE) / solid oxide electrolysis cell (SOEC) systems which show promise of much higher system efficiencies than other more developed electrolysis technologies. This possibility of higher efficiencies of HTSE / SOEC systems has been previously assumed to be theoretically possible but in recent years it has become less theoretical and more realistic as an increasing amount of suppliers complete lab and pilot tests showing very promising results. Research in the areas of manufacturing techniques, material selection, electrode and electrolyte compositions, and balance of plant size and integration continues at a fast pace as an increasing number of suppliers both internationally and domestically become involved. The advantages of HTSE become more pronounced when HTSE is coupled with nuclear power plants (NPPs). This is because thermal energy produced by the nuclear reactor can be used in a series of heat transfer loops and heat exchangers to vaporize HTSE feedwater, which drastically improves the economics of the process. Idaho National Laboratory (INL) has been very involved in the research and modeling of HTSE systems for a number of years, in collaboration with other national laboratories, academia, and industry stakeholders both on the hydrogen production as well as the hydrogen demand side. The modeling completed over the years on a large variety of projects has led to a wealth of knowledge at INL including in the area of the technoeconomic assessment (TEA) of HTSE systems. TEAs include process modeling of the HTSE systems to calculate system energy requirements and equipment sizing, followed by estimation of capital and operating costs to enable calculation of the levelized cost of hydrogen (LCOH). The TEA work performed has produced incremental improvements and tuning of the methods, assumptions, models, and results of the analyses as well as providing some opportunities for validating these results. The purpose of this document is to record the current baseline HTSE analyses led by INL to show the current status of assumptions and costs of these systems. Given the rapid development of this technology, the variety of suppliers entering the space, and the increasing attention government and industry are giving to such systems, this document may be updated on a periodic basis with updated analysis and assumptions. This document compiles various analyses results and approaches completed over a period of years into a single document to be used as a baseline going forward. It represents what the INL HTSE analysis group assumes to be the internal best estimate of the current operation, costs, and landscape of the HTSE industry state of the art capability for current SOEC technology in an Nth-of-a-Kind (NOAK) plant, which in this study is defined as existence of the manufacturing capacity to support previous deployment of N = 100 count of 25 MWe modular HTSE blocks (with modular equipment component cost reductions specified as following a 95% learning curve). That said, Tthis is a public document and as such so no proprietary data was used or included in this report. There may be HTSE suppliers that have performance specifications, and cost estimates, and test data that differ from the analysisose presented in this document. This document is meant to be a best conservative estimate of the technology and not an absolute reference.

Stable solid oxide electrolysis cells with SSF-based symmetrical electrode for direct high-temperature steam electrolysis

An ongoing project at Idaho National Laboratory involves generating hydrogen from steam using solid oxide electrolysis cells (SOEC). This report describes background information about SOECs, the Integrated Laboratory Scale (ILS) testing of solid-oxide electrolysis stacks, ILS performance degradation, and post-test examination of SOECs by various researchers. The ILS test was a 720- cell, three-module test comprised of 12 stacks of 60 cells each. A peak H2 production rate of 5.7 Nm3/hr was achieved. Initially, the module area-specific resistance ranged from 1.25 Ocm2 to just over 2 Ocm2. Total H2 production rate decreased from 5.7 Nm3/hr to a steady state value of 0.7 Nm3/hr. The decrease was primarily due to cell degradation. Post test examination by Ceramatec showed that the hydrogen electrode appeared to be in good condition. The oxygen evolution electrode does show delamination in operation and an apparent foreign layer deposited at the electrolyte interface. Post test examination by Argonne National Laboratory showed that the O2-electrode delaminated from the electrolyte near the edge. One possible reason for this delamination is excessive pressure buildup with high O2 flow in the over-sintered region. According to post test examination at the Massachusetts Institute of Technology, the electrochemical reactions have been recognized as one of the prevalent causes of their degradation. Specifically, two important degradation mechanisms were examined: (1) transport of Crcontaining species from steel interconnects into the oxygen electrode and LSC bond layers in SOECs, and (2) cation segregation and phase separation in the bond layer. INL conducted a workshop October 27, 2008 to discuss possible causes of degradation in a SOEC stack. Generally, it was agreed that the following are major degradation issues relating to SOECs: • Delamination of the O2-electrode and bond layer on the steam/O2-electrode side • Contaminants (Ni, Cr, Si, etc.) on reaction sites (triple phase boundary) • Loss of electrical/ionic conductivity of electrolyte.

Through the carbon combustion process, the oxygen produced by solid oxide electrolysis cell (SOEC) in the purging gas can be consumed. And the purging gas with low oxygen partial pressure can be recycled into the anode of SOEC, which achieves ultra-low power consumption for hydrogen production. In this study, the I-V curve of steam electrolysis in SOEC with CO2 anode gas is analyzed and discussed. The results show that the cell voltage for hydrogen production can be reduced to 0.62 V at 400 mA/cm2 under CO2 atmosphere. A combined process coupled with carbon fuel combustion and SOEC hydrogen production is proposed. By comparing three different processes of single SOEC, SOEC with heat supply directly by combustion and SOEC coupled with combustion, the advantages of SOEC hydrogen production coupled with carbon fuel combustion are analyzed. The results show that the ultra-low power consumption of SOEC can be achieved by matching the anode circulating gas flow rate, carbon fuel usage and external oxygen amount. When considering the energy efficiency of electricity to hydrogen, carbon fuel combustion can significantly reduce the electrolysis voltage and improve the energy efficiency of the system, but it will lead to an increase in the amount of anode circulating gas.

Review: 22 refs.

In this paper, the integration of geothermal energy with high temperature electrolysis to produce low-carbon hydrogen is investigated. Geothermal energy provides a stable energy flux, allowing to achieve high electrolyzer utilization factors, the compatibility with industrial processes and reduced load oscillations on electrolyzers. If steam-fed high temperature electrolysis is employed a highly efficient low-temperature heat exploitation process is made possible, with an electrolysis electrical efficiency above 80 % on LHV basis. The study identifies the best design for the integration of high temperature SOEC (Solid Oxide Electrolysis Cell) electrolysis technology and geothermal energy and provides a techno-economic assessment, computing its performance and the Levelized Cost of Hydrogen (LCOH). To feed the 3 MW electrolyzer the system exploits a hot geothermal fluid, both to generate steam and power (via ORC). A model of the system is set up with Aspen Plus software. A set of low-enthalpy geothermal resources ranging from 85 °C to 160 °C are considered. The two technologies work synergistically, leading to an efficient and stable hydrogen production. The use of SOEC electrolysis allows to produce 34 % to 38 % more hydrogen than alkaline electrolysis. The economic evaluation shows an exponential increase in the geothermal plant specific Capex for decreasing geothermal resource temperature, leading to an analogous trend in the LCOH. A benchmark case is defined coupling a PEM electrolyzer with a PV plant. The LCOH grows from a value 15 % lower than the benchmark in the 160 °C geothermal brine case, to a value 20 % higher than the benchmark in the 85 °C case. The breakeven point is found at 98 °C. This promising result is even more valuable considering the high dispatchability and stability of the output.

Hydrogen energy has been hailed as a versatile energy of the future that could aid the transition to net-zero emissions. It has large potential as an alternate fuel source for mobility and power, heating and feedstock for the industry. The energy carrier is produced from water electrolysis technology using different types of electrolyzer (i.e., Proton Exchange Membrane (PEM) or Solid Oxide Electrolysis Cells (SOECs)) for hydrogen separation process. In this energy research journey, PETRONAS has jointly worked with SLB to evaluate the feasibility of using SOECs for green hydrogen production. The study's focus is to explore integrating SOECs into existing industrial facilities creating hybrid systems, specifically with available flue gas from combustion process e.g. power generation. This allows for the utilization of waste heat from existing processes to enhance overall energy efficiency in hydrogen production. To understand hydrogen production and its utilization in the existing facility, the full system including existing gas turbines, solid oxide electrolyzer cells (SOECs), a hydrogen compression train, and a temperate cooling water system were modeled in a process simulation software. The model also included a heat recovery steam generator (HRSG) to recover the energy from gas turbine exhaust gases to heat water feed to produce saturated steam which will be the feed to SOEC. Several configurations considering heat integrations were explored, including heat recovery from SOEC product stream. Various sensitivities were run for different configurations of the process to study hydrogen purity, hydrogen blending, overall power required, water required in the overall process, and power produced by the hydrogen generated from SOEC and CO2 emission values in all the configuration. The results were compared and evaluated to help assess how variation in parameters affect the performance or outcome. The results were evaluated for blending the produced hydrogen with the existing export gas before and after export gas compression and how it influences the hydrogen purity. Hydrogen blending with the fuel gas to the gas turbine also helped in overall reduction of CO2 emission. It was observed that additional cooling of the hydrogen stream to achieve better hydrogen purity did not significantly help in reducing CO2 emissions when hydrogen is used as fuel gas; therefore, cooling with temperate water system can be considered. All the cases were compared and evaluated for expanding the application of green hydrogen technologies in the facility considering viability and reduction in emissions. The study was a part of a collaborative research initiative by the industry players to accelerate the development and deployment of SOEC technologies in existing facilities. The results from the study provided an overall understanding of adding SOEC in the facility and valuable insights to the stakeholders to make well-informed choices on the configuration.

High temperature electrolysis is a promising option for carbon-free hydrogen production and huge energy storage with high energy conversion efficiencies from renewable and nuclear resources. Over the past few decades, yttria-stabilized zirconia (YSZ) based ion conductor has been widely used as a solid electrolyte in solid oxide electrolysis cells (SOECs). However, its high operation temperature and lower conductivity in the appropriate temperature range for solid electrochemical devices were major drawbacks. Regarding improving ionic-conducting electrolytes, several groups have contributed significantly to developing and applying LaGaO3 based perovskite as a superior ionic conductor. La(Sr)Ga(Mg)O3 (LSGM) electrolyte was successfully validated for intermediate-temperature solid oxide fuel cells (SOFCs) but was rarely conducted on SOECs for its high efficient electrolysis performance. Their lower mechanical strengths or higher reactivity with electrode compared with the YSZ electrolysis cells, which make it difficult to choose compatible materials, remain major challenges. In this field, SOECs have attracted a great attention in the last few years, as they offer significant power and higher efficiencies compared to conventional YSZ based electrolysers. Herein, SOECs using LSGM based electrolyte, their applications, high performance, and their issues will be reviewed.

Solid Oxide Electrolysis Cells (SOECs) are advancing toward global commercialization, driven by significant improvements in cell performance, extended lifetimes, and effective applications. Leading companies like Bloom Energy and Topsoe are demonstrating the feasibility of industrial-scale SOECs hydrogen production and synthetic fuel generation. Additionally, SOECs are being integrated with renewable energy and industrial heat sources to reduce green hydrogen cost and improving energy efficiency. Despite challenges like degradation and expensive costs, ongoing research are paving the way for SOECs to play a pivotal role in the global energy transition.China has been actively involved in the SOECs development since the early stages of this technology. However, the Chinese SOEC industry has not yet reached the same level of maturity as its international counterparts. Currently, SOEC technology in China remains in the research and small-scale demonstration phase, hindered by challenges such as expensive capital costs, poor lifespan, and unclear applications. Despite these barriers, China boasts the world's largest green hydrogen market, where alkaline electrolyzers (AECs) currently dominate due to their lower costs. However, SOECs known for their superior efficiency, have good potential application prospects in the future if key bottlenecks such as cost, and durability can be effectively addressed. This transition could significantly enhance global green hydrogen production capabilities and contribute to decarbonization goals.The primary objectives for the Chinese SOEC industry are: (1) enhancing durability, and (2) reducing hydrogen production costs. To achieve these goals, specific efforts are being directed at three key areas: (1) Material and cell: develop advancing surface defect theory and novel cell (micro-)structures to achieve higher current densities at lower temperatures; (2) Stack: design advanced stack structures and improve manufacturing procedures to enhance stack consistency, reliability, robustness, and performance; (3) System: develop cost-effective BoPs, enable high-value chemical production via effective integration. These targeted initiatives aim to address critical challenges and position the Chinese SOEC industry as a global leader in green hydrogen area. SOEC development is vital for building a green energy and chemical industry and promoting China's energy structure transformation.

B-site doped, A-site deficient perovskite oxide titanates with formula La0.4Sr0.4Mn+xTi1−xO3−γ−δ (M = Fe3+ or Ni2+; x = 0.06; γ = (4 − n)x/2) were employed as solid oxide electrolysis cell (SOEC) cathodes for hydrogen production via high temperature steam electrolysis at 900 °C. A-site deficiency provided additional driving force for the exsolution of a proportion of B-site dopants at the surface in the form of metallic nanoparticles under reducing SOEC cathode operating conditions. In the case of La0.4Sr0.4Fe0.06Ti0.94O2.97, this represents the first time that Fe0 has been exsolved from a perovskite in such a way. Exsolution was due in part to the inability of the host lattice to accommodate vacancies (introduced (δ) oxygen vacancies () and fixed A-site () and inherent (γ) oxygen vacancies) beyond a certain limit. The presence of electrocatalytically active Fe0 or Ni0 nanoparticles and higher concentrations dramatically lowered the activation barrier to steam electrolysis compared to the parent material (x = 0). The use of defect chemistry to drive the exsolution of less reducible dopant cations could conceivably be extended to produce new catalytically active perovskites with unique properties.

As the world progresses toward a sustainable energy future, green hydrogen emerges as an innovative solution in the global effort to achieve decarbonization. This study examines the performance of a photovoltaic (PV)-driven solid oxide electrolyzer cell (SOEC) in producing green hydrogen under dynamic and unpredictable solar energy conditions. High-temperature electrolyzers provide substantial advantages in conversion efficiency compared to their low-temperature counterparts. The study focuses on designing and analyzing the thermodynamic and electrochemical performance of an SOEC capable of generating hydrogen and oxygen from water using solar energy. The SOEC was evaluated in exothermic and endothermic modes to ensure autonomous operation without external heat sources. The heat exchanger network was optimized to enhance system performance. This approach equips the SOEC system to adapt to renewable hydrogen production, particularly within a PV system configuration. The PV system was analyzed using two modes: direct and indirect coupling. A parametric study explores the impacts of key operating conditions, such as temperature, pressure, and current density, on cell potential and overall performance. The SOEC achieved energy and exergy efficiencies of 88% and 78%, respectively. A PV system comprising eight panels in series and seven panels in parallel generates 27.72 kW of power directly supplied to the electrolyzer. With a total annual solar energy radiation of 2.36 MWh/m2, the electrolyzer produces approximately 1500 kg of hydrogen and 12 000 kg of oxygen while consuming 13 500 kg of water annually. The findings of this study highlight significant advancements in the efficiency and stability of PV-driven SOEC.

To support the development of hydrogen production by high temperature electrolysis using solid oxide electrolysis cells (SOECs), the effects of operating conditions on the performance of the SOECs were investigated using a one‐dimensional model of a cathode‐supported planar SOEC stack. Among all the operating parameters, temperature is the most influential factor on the performance of an SOEC, in terms of both cell voltage and operation mode (i.e. endothermic, thermoneutral and exothermic). Current density is another influential factor, in terms of both cell voltage and operation mode. For the conditions used in this study it is recommended that the SOEC be operated at 1,073 K and with an average current density of 10,000 A m–2, as this results in the stack operating at almost constant temperature along the cell length. Both the steam molar fraction at the inlet and the steam utilisation factor have little influence on the cell voltage of the SOEC but their influence on the temperature distribution cannot be neglected. Changes in the operating parameters of the SOEC can result in a transition between endothermic and exothermic operation modes, calling for careful temperature control. The introduction of air into the anode stream appears to be a promising approach to ensure small temperature variations along the cell.

Due to the random fluctuations in power experienced by high-temperature green electric hydrogen production systems, further deterioration of spatial distribution characteristics such as temperature, voltage/current, and material concentration inside the solid oxide electrolysis cell (SOEC) stack may occur. This has a negative impact on the system’s flexibility and the corresponding control capabilities. In this paper, based on the SOEC electrolytic cell model, a comprehensive optimization method using an adaptive incremental Kriging surrogate model is proposed. The reliability of this method is verified by accurately analyzing the dynamic performance of the SOEC and the spatial characteristics of various physical quantities. Additionally, a thermal dynamic analysis is performed on the SOEC, and an adaptive time-varying LPV-MPC optimization control method is established to ensure the temperature stability of the electrolysis cell stack, aiming to maintain a stable, efficient, and sustainable SOEC operation. The simulation analysis of SOEC hydrogen production adopting a variable load operation has demonstrated the advantages of this method over conventional PID control in stabilizing the temperature of the stack. It allows for a rapid adjustment in the electrolysis voltage and current and improves electrolysis efficiency. The results highlighted that the increase in the electrolysis load increases the current density, while the water vapor, electrolysis voltage, and H2 flow rate significantly decrease. Finally, the SOEC electrolytic hydrogen production module is introduced for optimization scheduling of energy consumption in Xinjiang, China. The findings not only confirmed that the SOEC can transition to the current load operating point at each scheduling period but also demonstrated higher effectiveness in stabilizing the stack temperature and improving electrolysis efficiency.

Electrolyte degradation in anode supported microtubular yttria stabilized zirconia-based solid oxide steam electrolysis cells at high voltages of operation

Increasing demand for long-term energy storage, reduced carbon emissions, more resilient grid, and the lowest cost grid balancing solutions promotes solid oxide electrolysis cell (SOEC) and reversible solid oxide cell (RSOC) technologies. These systems can achieve high hydrogen production rates with near 100 percent stack electrical efficiency while co-electrolysis of carbon dioxide and water leads to production of syngas. RSOC can serve as a grid storage device (hydrogen production) and power production plant (provide electricity during peak demand). With over 25 years’ experience building and testing solid oxide cell materials, components and stacks, Nexceris has a proven track-record of commercializing products to major OEMs. The established manufacturing platforms at Nexceris enable smooth expansion into new applications.In this talk, development of cells, stack components and stacks will be discussed. Performance and durability improvements from single cell to short stacks will be addressed. Cells with downselected electrode sets were implemented into short stacks with active cell area of 42 cm2 and 96 cm2. Stacks were operated continuously in SOEC mode at ~1.3 V for ≥ 500 hours with <5%/kh degradation and improving. The resulting short stack demonstrations show promising baseline performance and durability platform for future cell and stack development. RSOC tests were recently initiated with dynamic operation. Nexceris’ ChromLok coatings for bipolar plates were also integrated to stacks to enhance durability.