Development Strategy and Vision for Chinese Solid Oxide Electrolysis Cell Industry

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.

Green hydrogen production plants: A techno-economic review

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.

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.

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.

With the rapid development of hydrogen production technology by using solar energy, the research of Solid Oxide Electrolysis Cell (SOEC) and Photovoltaic/Thermal (PV/T) system have become popular. A design scheme of hydrogen production system based on PV/T technology was proposed. The electrolytic cell combined photovoltaic panels, trough solar collectors and multiple heat exchagers to improve the overall efficiency of the hydrogen production system. The efficiency was predicted based on empirical models. The results showed that the hydrogen production efficiency of SOEC increased with increasing temperature and with decreasing current density. However, the balance between energy efficiency and hydrogen production rate of SOEC needed to be taken into account. The predicted hydrogen production efficiency of SOEC and overall system efficiency also agreed well with the results available in literature.

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.

With the development of globalization and public increase awareness of the greenhouse effect, and there are strategic objectives of peak carbon emission and carbon neutrality that are realized, building a clean, low-carbon, safe, and efficient new energy system has become a consensus in the global world. Under this background, hydrogen, with its clean, zero-carbon emissions (especially carbon dioxide, which contribute to the greenhouse) and high energy density far exceeding that of traditional energy sources, is widely viewed as a key strategic alternative energy source that leads the future energy revolution. Among the numerous hydrogen production technologies, water electrolysis, particularly the "green hydrogen" production route that deeply integrates with fluctuating renewable energy sources such as wind, photovoltaics, and some other, is highly attractive because it can effectively address the storage and absorption issues of renewable energy. It is recognized as one of the core pillar technologies for achieving deep decarbonization and achieving green transformation of the energy system. Among the different routes for hydrogen production (through compare with the alkaline membrane electrolysis and the solid oxide electrolysis cell, later AWE and SOCE will be used respectively to refer to), water electrolysis is an attractive process for integration with renewable sources of energy like wind and photovoltaics and is considered one of the key technologies to allow a green transition of energy systems. Proton exchange membrane electrolysis (PEM) technology has attracted much attention from the academia and industry in the previous years because of its significant advantages, including a large current density, high dynamic response speed, high hydrogen purity, and direct production of high-pressure hydrogen, which is more fitted to the active and unstable renewable energy. Nevertheless, the development of this technology is still hindered by precious-metal reliance, high cost, and low durability. This paper is expected to offer theoretical reference and technical support for the large-scale applications and the industrialization of PEM water electrolysis for hydrogen production, by systematically analyzing the research work of material optimization, process improvement, and system integration.

A novel system for the production of pure hydrogen from natural gas based on solid oxide fuel cell–solid oxide electrolyzer

Water splitting coupled to renewable power systems is an attractive way to generate green hydrogen and achieve zero carbon emissions, and represents a strategic technology to meet the high demand of carbon-neutral development. Catalysts essentially determine the efficiency and cost of water splitting technologies, and are a class of key materials for green hydrogen production. In this review, we summarize the catalyst developments for the mainstream green hydrogen production technologies, including water electrolysis, water photolysis, and photoelectrocatalytic water splitting. We first present basic catalytic mechanisms of these water splitting pathways, as well as emphasize their current research status and challenges for practical application. We subsequently introduce the recent progress in representative catalysts and design strategies toward these photo(electro)catalytic technologies, paying particular attention to water electrolysis, including alkaline water electrolyzer (AWE), proton exchange membrane water electrolyzer (PEMWE), anion-exchange membrane water electrolyzer (AEMWE) and solid oxide electrolysis cell (SOEC). Finally, we propose future prospects to develop more desirable catalysts for green hydrogen production at a large scale.

Following EU carbon neutral and net-zero policies, Danish energy islands will use offshore wind power to produce green fuel. The solid oxide electrolysis cell (SOEC) is a potential green hydrogen production technology that can be installed on energy islands. Given the inherent variability of wind power, the SOEC plant on an energy island must contend with fluctuating energy inputs. This study investigates the energy and economic performance of an SOEC-based energy island, exploring various control strategies, operating temperatures, and hydrogen storage technologies. An optimization procedure based on the energy distribution principle is proposed, characterized by a limited set of decision variables and enhanced computational efficiency. The results confirmed that this procedure could successfully illustrate the dynamic energy distribution process.Our findings indicated that the most economically viable SOEC plant for the Bornholm energy island consists of two independent SOEC systems, each with a capacity of 187.7 MW, culminating in a combined output of 375.4 MW. These SOEC systems are optimized to operate at 800 °C with a constant conversion (CC) strategy and a synchronized (SYN) power strategy. Hydrogen products stored as compressed hydrogen instead of ammonia could be more cost-effective. Specifically, under 800 °C with CC-SYN strategy, the LCOH is projected to be $2.59/kg H2 (compressed hydrogen) and $3.12/kg H2 (ammonia). In another scenario, hydrogen tanks and batteries are included in the system for temporary energy storage. The economic analysis suggests that integrating energy storage systems is not financially reasonable for the SOEC-based energy island. It will be economically viable if the reduction in battery costs exceeds 75%. To conclude, SOEC-based energy islands have the potential to contribute significantly to green hydrogen production, with applications in the renewable energy sectors and maritime transportation. Realizing this potential, however, requires more research focuses on flexibility and durability, a comprehensive investigation of the synergies of system components, enhanced collaboration between business entities, and increased investments.

Comparative Life-Cycle-Assessment analysis of three major water electrolysis technologies while applying various energy scenarios for a greener hydrogen production

Increasing demand for long-term energy storage and reduced carbon emissions promotes solid oxide electrolysis cell (SOEC) technology. SOEC 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. With over 25 years’ experience building and testing solid oxide fuel cell (SOFC) materials, components and stacks, Nexceris has a proven track-record of commercializing SOFC products to major OEMs. The established manufacturing platforms at Nexceris enable smooth expansion into SOEC applications.In this talk, development of new SOEC electrode materials, stack components and stacks will be discussed. Over 50 down-selected air and fuel electrodes were electrochemically screened on 25 cm2 electrolyte-supported single cells and compared to baseline electrodes. Multiple electrode sets provided current density over -1.5 A/cm2 at 1.3 V and 800 °C with 75 percent steam/25% percent hydrogen fuel and air. The promising electrodes were implemented into short stacks with active cell area of 42 cm2. Stacks were operated continuously in SOEC mode at 1.3-1.4 V for ≥ 500 hours. The resulting short stack demonstrations show promising SOEC baseline performance and durability platform for future cell and stack development. Co-electrolysis and water electrolysis tests were also conducted and yielded comparable performance. Nexceris’ ChromLok coatings for bipolar plates were also integrated to stacks and tested under realistic conditions.

The depletion of fossil fuels in the current world has been a major concern due to their role as a primary source of energy for many countries. As non-renewable sources continue to deplete, there is a need for more research and initiatives to reduce reliance on these sources and explore better alternatives, such as renewable energy. Hydrogen is one of the most intriguing energy sources for producing power from fuel cells and heat engines without releasing carbon dioxide or other pollutants. The production of hydrogen via the electrolysis of water using renewable energy sources, such as solar energy, is one of the possible uses for solid oxide electrolysis cells (SOECs). SOECs can be classified as either oxygen-ion conducting or proton-conducting, depending on the electrolyte materials used. This article aims to highlight broad and important aspects of the hybrid SOEC-based solar hydrogen-generating technology, which utilizes a mixed-ion conductor capable of transporting both oxygen ions and protons simultaneously. In addition to providing useful information on the technological efficiency of hydrogen production in SOEC, this review aims to make hydrogen production more efficient than any other water electrolysis system.

In recent years, the application of machine learning methods has become increasingly common in atmospheric science, particularly in modeling and predicting processes that impact air quality. This study focuses on predicting hydrogen production from solid oxide electrolytic cells (SOECs), a technology with significant potential for reducing greenhouse gas emissions and improving air quality. We developed two models using artificial neural networks (ANNs) and support vector machine (SVM) to predict hydrogen production. The input variables are current, voltage, communication delay time, and real-time measured hydrogen production, while the output variable is hydrogen production at the next sampling time. Both models address the critical issue of production hysteresis. Using 50 h of SOEC system data, we evaluated the effectiveness of the ANN and SVM methods, incorporating hydrogen production time as an input variable. The results show that the ANN model is superior to the SVM model in terms of hydrogen production prediction performance. Specifically, the ANN model shows strong predictive performance at a communication delay time ε = 0.01–0.02 h, with RMSE = 2.59 × 10−2, MAPE = 33.34 × 10−2%, MAE = 1.70 × 10−2 Nm3/h, and R2 = 99.76 × 10−2. At delay time ε = 0.03 h, the ANN model yields RMSE = 2.74 × 10−2 Nm3/h, MAPE = 34.43 × 10−2%, MAE = 1.73 × 10−2 Nm3/h, and R2 = 99.73 × 10−2. Using the SVM model, the prediction error values at delay time ε = 0.01–0.02 h are RMSE = 2.70 × 10−2 Nm3/h, MAPE = 44.01 × 10−2%, MAE = 2.24 × 10−2 Nm3/h, and R2 = 99.74 × 10−2, while at delay time ε = 0.03 h they become RMSE = 2.67 × 10−2 Nm3/h, MAPE = 43.44 × 10−2%, MAE = 2.11 × 10−2 Nm3/h, and R2 = 99.75 × 10−2. With this precision, the ANN model for SOEC hydrogen production prediction has positive implications for air pollution control strategies and the development of cleaner energy technologies, contributing to overall improvements in air quality and the reduction of atmospheric pollutants.