Solid Oxide Co-electrolysis Research Articles

Modeling of a combined CH4-assisted solid oxide co-electrolysis and Fischer-Tropsch synthesis system for low-carbon fuel production

CH4-assisted solid oxide electrolyzer cells (SOECs) can co-electrolyze H2O and CO2 effectively for simultaneous energy storage and CO2 utilization. Compared with conventional SOECs, CH4-assisted SOECs consume less electricity because CH4 in the anode provides part of the energy for electrolysis. As syngas (CO and H2 mixture) is generated from the co-electrolysis process, it is necessary to study its utilization through the subsequent processes, such as Fischer-Tropsch (F-T) synthesis. An F-T reactor can convert syngas into hydrocarbons, and thus it is very suitable for the utilization of syngas. In this paper, the combined CH4-assisted SOEC and F-T synthesis system is numerically studied. Validated 2D models for CH4-assisted SOEC and F-T processes are adopted for parametric studies. It is found that the cathode inlet H2O/ CO2 ratio in the SOEC significantly affects the production components through the F-T process. Other operating parameters such as the operating temperature and applied voltage of the SOEC are found to greatly affect the productions of the system. This model can be used for understanding and design optimization of the combined fuel-assisted SOEC and F-T synthesis system to achieve economical hydrocarbon generation.

Economic and environmental assessment of current (2015) and future (2030) use of E-fuels in light-duty vehicles in Germany

While e-fuels offer a path towards large scale use of renewable electricity in transportation and improved energy security their economic effectiveness is unclear. To address this gap, an economic and environmental analysis of e-fuel production in Germany using renewable wind energy, different electrolysis technologies, and Fischer-Tropsch synthesis in 2015 and 2030 was performed. For current alkaline electrolysis and future solid oxide co-electrolysis using wind energy for electrolysis, e-fuel production costs and life cycle emissions were estimated to be 4.97 €/leq diesel and 64.07 gCO2-eq/MJ in 2015, and 3.24 €/leq diesel and 6.63 gCO2-eq/MJ in 2030. The critical parameters determining e-fuel cost are electricity cost, carbon dioxide (CO2) cost, electrolysis investment cost, and capacity utilization. Using optimistic estimates for all these parameters gives a production cost of 1.17 €/leq diesel (3.12 € ct/MJ). Abatement costs in the range 544–6424 €/tCO2-eq were estimated for e-fuels; much higher than those for competing vehicle-fuel technology options. While e-fuels are currently not a cost-effective method to reduce CO2 emissions they could be in the future if investment cost, capacity utilization, CO2 cost, and wind electricity cost can be improved by further research and development, or if fossil fuel prices increase substantially.

Synthetic Diesel Production as a Form of Renewable Energy Storage

Production of synthetic hydrocarbon fuels as a means for renewable energy storage has gained attention recently. Integration of solid oxide co-electrolysis of steam and carbon dioxide with the Fischer-Tropsch process to transform renewable electricity into Fischer-Tropsch diesel is one of the promising suggested pathways. However, considering the intermittency of produced renewable electricity such integration will have a low capacity factor. Besides, locating a reliable source of carbon dioxide near the installed integrated system may prove to be difficult. A novel integration for production of Fischer-Tropsch diesel from various renewable sources is suggested in this study. The proposed integrated system includes solid oxide electrolysis, entrained gasification, Fischer-Tropsch process and an upgrading system. Gasification is assumed to have a continuous operation which increases capacity factor of the integrated system. Carbon dioxide supplied via gasification of biomass provides a reliable source for on-site co-electrolysis. Technical capabilities of the proposed integrated system examined by investigating performance in relation with electricity, and diesel demand of four different European cities. Results show that the proposed system is capable of supplying Fischer-Tropsch diesel of between 0.9–32% of the annual diesel demand for road transportation respective to the location of installation, with a high emission savings (around 100%). Cost of produced diesel is not competitive with conventional diesel for all cases, even when all the other by-products were assumed to be sold to the market.

Production of syngas from H2O/CO2 by high-pressure coelectrolysis in tubular solid oxide cells

The conversion of CO2 and steam into syngas in a pressurized solid oxide coelectrolysis (SOC) cell is considered one of the most promising pathways towards the production of sustainable fuels. In this study, a high pressure tubular SOC system was designed and developed that can efficiently convert a mixture of steam and CO2 into valuable syngas fuel. Tubular SOC cells based on a Ni-yttria stabilized zirconia (Ni-YSZ) fuel electrode, scandia stabilized zirconia (ScSZ) electrolyte, and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF)-Ce0.8Gd0.2O1.9−δ (GDC) composite air electrode were fabricated and tested at various high pressure conditions to determine the electrochemical and syngas production characteristics. The pressurized tubular SOC cell was first operated at the ambient pressure for various inlet gas conditions and the electrochemical performance of the tubular SOC was studied by current-voltage curves combined with electrochemical impedance spectroscopy at different H2O and CO2 mole% in the inlet gas. The pressurized SOC cell was then operated between 1 and 8 bar pressure at 800 °C in both fuel cell and coelectrolysis modes. In the fuel cell mode, the SOC showed a 44.2% increase in the maximum power density to with a pressure increase of 1–8 bar. The increase in the performance of the cell in the fuel cell mode was attributed to the higher open circuit voltage (OCV) and reduced polarization resistance of the electrodes at higher pressures. In the coelectrolysis mode, the pressure dependency of the electrochemical characteristics on the tubular SOC cell was studied and the relation between different parameters of the system and the pressure conditions was derived. It was found that the higher open circuit voltage (OCV) and the reduced polarization resistance resulted in a significant improvement in the performance of the pressurized tubular SOC cell for the production of syngas. A post-test material characterization by electron microscopy did not show any significant degradation in the tubular SOC cell microstructure during the high pressure operation at 8 bar.

Syngas production in high performing tubular solid oxide cells by using high-temperature H2O/CO2 co-electrolysis

By using electricity from renewable sources, high-temperature solid oxide co-electrolysis cells (SOCs) can perform advantageous conversion of H2O/CO2 to high-value syngas. In this work, we investigated the performance of tubular solid oxide co-electrolysis cells for the production of syngas by electrochemical conversion of H2O/CO2. The tubular solid-oxide electrolysis cells comprise Ni-yttria stabilized zirconia (Ni-YSZ) based fuel-electrode supported cells, a yttria or scandia-stabilized zirconia (YSZ and ScSZ) electrolyte, and a composite air-electrode of (La0.85Sr0.15)0.9MnO3 (LSM) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF). The electrochemical performance of the tubular SOCs for various operating conditions was analyzed using I-V curves, EIS analysis, and gas chromatography. From the results, we confirm the correlation between the operating conditions and the electrochemical performance of the co-electrolysis process in the tubular SOCs. Furthermore, we found that the syngas yield of the ScSZ electrolyte-based SOC cell was better than that of the YSZ electrolyte-based SOC. The results show that using a tubular SOC offered highly efficient conversion of H2O/CO2, with high yield and good-quality syngas.

Characteristics of Electrochemical Conversion for Syngas Production by Tubular Solid Oxide Coelectrolysis Cell

The high temperature H2O/CO2 electrochemical conversion process using solid oxide coelectrolysis (SOC) cell is potentially an efficient way to reduce CO2 emission and to store renewable power simultaneously. In this study, the tubular solid oxide coelectrolysis (SOC) cell based on a general electrode support tube through an extrusion process, and the essential SOC cell, components, such as the electrolyte and the electrode, were then coated onto the surface of a ceramic support consecutively using a vacuum slurry and dip-coating method. The tubular SOC cell was operated while varying the operating temperature, cathode flow rate, and inlet H2O and CO2 composition. In this study, we have been conducted advanced and systematic experimental with the tubular SOC cell in order to experimentally approach. Electrochemical performance of tubular SOC cell is systematically investigated with various operating conditions such as operating temperature, inlet H2O or CO2 composition and analysis by I-V curve and EIS analysis. Finally, produced syngas is analyzed by gas chromatography through optimized operating conditions. The effect of operating conditions and syngas yields were discussed in detail.

High Temperature Co-Electrolysis of CO2 and Water on Doped Lanthanum Chromites

High temperature Solid Oxide Electrolysis Cells (SOEC) have recently attracted global research interest towards syngas (CO and H2) production [1-3]. Co-electrolysis of CO2 and water is a key element of power-to-chemicals and power-to-fuel strategies for green chemicals, CO2 recovery and electricity storage at large scale. High temperature solid oxide co-electrolysis of CO2 and H2O is highly efficient to CO and hydrogen production with high reaction rates. Additionally, this technology has the advantage of controlling syngas composition at the outlet by applying the proper potential. This is extremely important when the produced syngas will be fed in conventional Fischer-Tropsch catalytic fuel synthesis reactors [4]. The commercialization of co-electrolysis could provide a simpler and cost efficient way for the production of light-fuels compared to other conventional technologies, whereas it is advantageous in that the expected technology development can be based and use the progress of the existing more mature Solid Oxide Fuel Cells technology. At the same time, strategies to achieve technical targets and technology development are expected to lead to significant improvement of the system performance, e.g. thermal and mass integration with other units and components of a complete system (e.g. H2O vaporizer, CO2recovery and compressor, methanation reactor etc.). Several recent studies focus on technical development and operation of Solid Oxide Electrolysers, primarily for water electrolysis but also for the co-electrolysis and fuel conversion process. On the other hand, conventional materials used to construct SOFC cells are not offering the required performance to achieve high efficiency in SOEC devices. Therefore, studies concerning electrode materials and materials of cell structure or electrolytes, as well as cell design are on the top of the research agenda. This paper summarizes progress in materials aspects for the development and optimization of a solid oxide electrolyser based on perovskitic cathode electrodes able to efficiently perform co-electrolysis of CO2 and H2O for syngas production. Laboratory synthesized lanthanum strontium chromites doped with Fe [5] have shown adequate efficiency and remarkable stability during co-electrolysis compared to the commercial and state-of-the-art Ni-YSZ material. The study is conducted in the framework of the four-years EU Research project funded by the Fuel Cells and Hydrogen 2 Joint Undertaking, entitled SElySOs: “Development of new electrode materials & understanding of degradation mechanisms on Solid Oxide Electrolysis Cells”. Acknowledgements The authors would like to acknowledge financial support from the European Union’s Fuel Cells and Hydrogen 2 Joint Undertaking (SElySOs project, Grant Agreement No. 671481).

Methane assisted solid oxide co-electrolysis process for syngas production

Abstract In this study, methane assisted high temperature steam/CO2 co-electrolysis process is performed on symmetrical cells with a configuration of SFM-SDC/LSGM/SFM-SDC to produce high-quality synthesis gas (syngas, a mixture of H2 and CO). The Nernst potential has been evaluated for solid oxide cells in the methane assisted mode, which is reduced by nearly one order of magnitude through substituting the anode atmosphere from air to methane. The open circuit voltage (OCV) is −0.06 V at 800 °C, and an electrolysis current density of −242 mAcm−2 has been obtained at 850 °C and 0.3 V. Effects of operating conditions on products composition have been revealed by using the chemical equilibrium co-electrolysis model and HSC software. High-quality syngas with high conversion rate of CO2 to CO as well as ideal H2/CO molar ratio of 2 could be achieved in both electrode sides by adjusting appropriate operating conditions. The short-term cell voltage is slightly fluctuant less than 0.05 V at 850 °C and −120 mAcm−2, in which condition carbon deposition has been observed in the SFM-SDC anode due to the low O2-/CH4 ratio.

Efficient syngas generation for electricity storage through carbon gasification assisted solid oxide co-electrolysis

High temperature CO2 and H2O co-electrolysis is a promising way to produce syngas for the storage of electrical energy harvested from renewable energy sources. However, a significant portion of electricity input is consumed to overcome a large oxygen potential gradient between the electrodes in conventional solid oxide electrolysis cells (SOECs). In this study, we present a novel and efficient syngas generator integrating carbon gasification and solid oxide co-electrolysis to improve the system efficiency. The feasibility of this new system is demonstrated in La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte-supported SOECs. Both thermodynamic calculation and experimental results show that the potential barrier for co-electrolysis can be reduced by about 1V and the electricity input can be saved by more than 90% upon integration of SOECs with carbon gasification. On the anode side, “CO shuttle” between the electrochemical reaction sites and solid carbon is realized through the Boudouard reaction (C+CO2=2CO). Simultaneous production of CO on the anode side and CO/H2 on the cathode side generates syngas that can serve as fuel for power generation or feedstock for chemical plants. The integration of carbon gasification and SOECs provides a potential pathway for efficient utilization of electricity, coal/biomass, and CO2 to store electrical energy, produce clean fuel, and achieve a carbon neutral sustainable energy supply.

Electrochemical Performance of H2o-CO2 Co-Electrolysis with a Tubular Solid-Oxide Co-Electrolysis (SOC) Cell

The H2O-CO2 electrochemical conversion process in solid-oxide co-electrolysis (SOC) cells may be one of the most efficient ways to reduce CO2 emissions and to store renewable power simultaneously. In this study, a tubular solid-oxide co-electrolysis (SOC) cell based on a general electrode support solid-oxide fuel cell was fabricated and investigated. For this purpose, we fabricated tubular electrode support tubes through an extrusion process, and after which the essential SOC cell components, i.e., the electrolyte and the electrode, were coated onto the surface of the ceramic support consecutively using a vacuum slurry and dip-coating method. The cell was operated while varying the operating temperature, cathode gas flow rate, and the supplied amount of H2O. The results demonstrate that the fabricated tubular SOC cell is a promising candidate for many practical applications, such as technology to mitigate climate change and power fluctuations associated with renewable energy.

Electrochemical performance of H2O–CO2 coelectrolysis with a tubular solid oxide coelectrolysis (SOC) cell

The H2O–CO2 electrochemical conversion process in solid oxide coelectrolysis (SOC) cells is potentially an efficient way to reduce CO2 emissions and to store renewable power simultaneously. In this study, a tubular solid oxide coelectrolysis (SOC) cell based on a general electrode support solid oxide fuel cell was fabricated and investigated. We fabricated tubular electrode support tubes through an extrusion process, and the essential SOC cell components, i.e., the electrolyte and the electrode, were then coated onto the surface of a ceramic support consecutively using a vacuum slurry and dip-coating method. The cell was operated while varying the operating temperature, cathode gas flow rate, and the supplied amount of H2O. The results demonstrate that the fabricated tubular SOC cell is a promising candidate for many practical applications, such as technology to mitigate climate change and power fluctuations associated with renewable energy.

Electrochemical Characteristics and Gas Composition Generated by La0.8Sr0.2Cr0.5Mn0.5O3–δ Cathode at Electrolysis and Co-Electrolysis Modes

Ceramic materials with perovskite structure have recently attracted attention as possible redox stable, sulfur- and carbon tolerant cathode materials for solid oxide electrolysis cells. In this study ceramic SOE single cell was fabricated using impregnation method. La0.8Sr0.2Cr0.5Mn0.5O3–δ-Zr0.94Sc0.06O2–δ cathode was activated with CeO2 and Pd nanoparticles and investigated as potential solid oxide co-electrolysis cell cathode at various working temperatures, cell potentials and inlet gas compositions. Based on the electrochemical measurements data the single cell performed the same in co-electrolysis and water electrolysis modes having total polarization resistance 0.52 Ω cm2 (at 750°C at 1.3 V). Analysis of gas chromatography data shows that the ratio between produced H2 and CO gases decreased with increase of temperature, from 10.5 to 0.76 at 650°C and 800°C, respectively. Also the H2/CO ratio decreased with steam content in inlet gas.

A novel clean and effective syngas production system based on partial oxidation of methane assisted solid oxide co-electrolysis process

Development of the syngas production from solid oxide H2O/CO2 co-electrolysis is limited by the intensive energy input and low efficiency. Here, we present a new concept to efficiently generate syngas in both sides of the solid oxide electrolyzer by synergistically combining co-electrolysis with partial oxidation of methane (POM). Thermodynamic calculation and electrochemical measurements for the POM assisted solid oxide co-electrolysis processes on the SFM-SDC/LSGM/SFM-SDC cells exhibited an reduced electric input, increased energy conversion efficiency and decreased cathodic co-electrolysis polarization resistance in comparison with the conventional co-electrolysis. This method will be crucial to establish a clean and effective energy conversion system to meet global sustainable energy needs.

Production of Fischer–Tropsch liquid fuels from high temperature solid oxide co-electrolysis units

A model for high temperature co-electrolysis (HTCE) of carbon dioxide and water using solid oxide electrolytic cells (SOEC) for syngas production and subsequent conversion to liquid fuels by a Fischer–Tropsch (F–T) process is presented. The SOEC model is guided by experimental data from the literature, and the model is employed to explore the effect of temperature, pressure, and feedstock composition on syngas composition exiting the SOEC. The syngas is converted in a slurry bubble column F–T synthesis reactor in which the model approach of a once-through conversion of carbon monoxide is chosen, and the distribution of hydrocarbon products is determined by the Anderson–Schulz–Flory model. The overall system efficiency for liquid hydrocarbon fuels produced from electrical energy is found to be 54.8% HHV (51.0%-LHV). It is determined that operating the SOEC at low pressure (1.6 bar) versus higher pressure (5 bar) results in an efficiency gain of 2.6%. The economics of the production plant are evaluated for variations in electricity feedstock costs and operating capacity factors. The liquid fuels production costs range from 4.4 $/GGE to 15.0 $/GGE for electricity prices of 0.02 $/kWh to 0.14 $/kWh and a plant capacity factor of 90% to 40%, respectively.

Novel Structured Solid Oxide Co-Electrolysis Cells

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Results of recent high temperature coelectrolysis studies at the Idaho National Laboratory

For the past several years, the Idaho National Laboratory and Ceramatec, Inc. have been studying the feasibility of high temperature solid oxide electrolysis for large-scale, nuclear-powered hydrogen production. Parallel to this effort, the INL and Ceramatec have been researching high temperature solid oxide co-electrolysis of steam/CO2 mixtures to produce syngas, the raw material for synthetic fuels production. When powered by nuclear energy, high temperature co-electrolysis offers a carbon-neutral means of syngas production while consuming CO2. The INL has been conducting experiments to characterize the electrochemical performance of co-electrolysis, as well as validate INL-developed computer models. An inline methanation reactor has also been tested to study direct methane production from co-electrolysis products. Testing to date indicate that high temperature steam electrolysis cells perform equally well under co-electrolysis conditions. Process model predictions compare well with measurements for outlet product compositions. The process appears to be a promising technique for large-scale syngas production.