Solid Oxide Electrolysis Cells Stack Research Articles

Conceptual design of lead cooled reactor for hydrogen production

Hydrogen is considered as the most potential energy carrier in the near future and can be produced from nuclear energy by several means. Lead-based reactor is one of the advance reactors in hydrogen production. In this paper, a novel feasible system of lead cooled reactor coupled with solid oxide electrolysis cells (SOEC) is presented, which is named China LEAd-based Reactor for Hydrogen production (CLEAR-H). By taking advantage of the chemically inert and high density of lead–bismuth eutectic (LBE), the concept of LBE-water direct-contact steam generator is proposed to supply high temperature (up to 600 °C) and low pressure (0.1–0.2 MPa) steam for SOEC stack without additional decompression devices. The results show that 47 tons hydrogen and 3000 tons oxygen-enriched air are obtained per day, and the thermal-to-hydrogen efficiency can reach about 39%.

A techno-economic model of a solid oxide electrolysis system.

Solid oxide cells can play a vital role in addressing energy and environmental issues. In fuel cell mode they are capable of producing electric energy at high efficiency using hydrocarbon fuels and in the electrolysis mode can produce hydrogen from steam or synthesis gas from a mixture of steam and carbon dioxide. The solid oxide electrolysis cells (SOECs) can operate at a wide range of conditions. A capable means by which to select operating conditions in the application of solid oxide electrolyzers is a necessity for successful commercial operation. Power and efficiency can be determined over a wide range of operating conditions by applying fundamental electrochemical principles to a SOEC system. Operating conditions may be selected based on power requirements or with efficiency as a priority. Operating cost for electricity which is a function of both power and efficiency can also be used to determine optimal operating conditions. Performance maps based on closed form isothermal parametric models for both hydrogen and natural gas fueled SOFC stacks have been demonstrated previously. This approach applied to a SOEC stack is shown. This model was applied to generate performance maps for a solid oxide cell stack operated in the electrolysis mode. The functional form of the model and the boundaries of the operating envelope provide useful insight into the SOEC operating characteristics and a simple means of selecting conditions for electrolysis operation.

A comparative assessment on hydrogen production from low- and high-temperature electrolysis

In this work a comparative analysis between low- and high-temperature electrolysis for hydrogen generation is assessed. A hydrogen production system based on Solid Oxide Electrolysis Cells (SOEC) is designed and modeled and compared to the performance of a more mature system based on PEM technology. The SOEC system mainly consists of an SOEC stack, a heat recovery system and a hydrogen compression section. Experimental data measured in steam electrolysis tests performed on single solid oxide cells were utilized into the model to characterize the stack performance. The model carries out a thermodynamic analysis in order to calculate the energy efficiency and the exergetic consumption of the system; these performances are subsequently compared with those of a low-temperature hydrogen generation system evaluated from experimental data measured in test sessions performed on a complete BoP integrating a pressurized Proton Exchange Membrane (PEM) electrolyser. The comparison is carried out with the two electrolysis systems generating hydrogen at the same production rate and pressure. The results of this study show that the modeled SOEC hydrogen generation system can compete with the PEM electrolyser, achieving better performance than the low-temperature system at hydrogen production rate higher than 18.3 g h−1 (corresponding to 0.25 A cm−2) and showing an energy efficiency up to 14% higher than the PEM system at 1 A cm−2.

Electric Current Effects on the Corrosion Behaviour of High Chromium Ferritic Steels

The high-temperature corrosion behaviour of the Cr containing ferritic alloys Crofer 22 APU and Crofer 22 H were investigated for their potential application as interconnects in planar-type solid oxide electrolysis cells (SOECs) operating at 800 °C for syngas production in steam/CO2 co-electrolysis mode. To simulate the operating conditions for this application, oxidation tests in relevant atmospheres with and without electric current were conducted. The corrosion behaviour was influenced by the electric current resulting in accelerated oxidation on the negative side and suppressed oxidation on the positive side. The scale structure was influenced by a combination of atmosphere and electric current effects. The modified oxidation of the interconnect steels due to the electric current effect could have detrimental impact for the O2 side and beneficial effect for the CO2/H2O side in an SOEC stack operating in co-electrolysis mode.

Achieving Hydrogen Production through Solid Oxide Electrolyzer Stack by High Temperature Electrolysis

Based on the reversal reaction of solid oxide fuel cells (SOFC), high temperature electrolysis (HTE) is an effective way for large-scale and low cost hydrogen production. The problem restricted the development for HTE is the stability of steam supplying, conversion rate of steam to H2, hydrogen production rate and the durability of solid oxide electrolysis cells (SOECs) and stacks. To solve the problems mentioned above, a steam and gas fogged mixer (SGFM) was designed which can be used for not only experimental HTE but also large-scale hydrogen production. A 30-cell SOEC stack was tested combined with the mixer for 1000 hours at 800oC with an electrolysis current of 4 A. The steam-to-hydrogen conversion (SC) rate was calculated to be 70% by determining the water amount at the inlet and outlet of the hydrogen electrode. The hydrogen production rate was 99.3 NL/h.

An Innovative Electrochemical Model for Three-Dimensional Modeling of a SOFC Stack Used in Electrolysis Mode

A one-dimensional model has been developed to model the mass and charge transfer occurring in the water reduction on nickel-cermet. An artificial neural network (ANN) was identified and validated from this model. The ANN, in equation form, was used in a three-dimensional model of a serial repeat unit of a Solid Oxide Electrolysis Cell stack. The electrochemical processes can be modeled with acceptable accuracy with the one-dimensional model based on a two-step mechanism for the water reduction. The presented results show that the ANN could be employed to model electrochemical reactions and be implemented in a macro-scale model.

The Effects of Operating Conditions on the Performance of a Solid Oxide Steam Electrolyser: A Model‐Based Study

AbstractTo 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.

Degradation Mechanism in La0.8Sr0.2CoO3 as Contact Layer on the Solid Oxide Electrolysis Cell Anode

Detailed chemical and structural analyses are presented for the degradation mechanism of (LSC) as the contact layer of solid oxide electrolysis cell (SOEC) anodes. SOEC stack cells, which were operated in the presence of Cr-containing interconnects, and reference half-cells, which were tested with Pt interconnects, were investigated. The as-prepared surface chemistry of LSC showed a spatially uniform A-site (La and Sr) enrichment. Undesirable secondary phases of , , , and were identified in the contact layer of the SOEC stack cells, which had significantly reduced electrochemical performance after long-term testing. Auger electron spectroscopy and analytical transmission electron microscopy showed the presence of Cr throughout the layer cross section on the surface and in the bulk, respectively, with significant variations in the local chemistry at the micro- to nanoscale. Particularly, a long-range transport of Sr and Co cations out of the LSC phase to the top of the contact layer was evident. However, when tested with electrolytic potential and current without a Cr environment, the LSC contact layer composition remained stable. The dissociation of the LSC in the SOEC stack cells can be, most probably, driven by the La–Cr–O related thermodynamics under the electrolytic potential and oxygen pressure at the anode.

Improvement in ion transport biomarkers and spirometry with the investigational CFTR potentiator VX-770 in subjects with cystic fibrosis and the G551D-CFTR mutation

Hydrogen is considered as the most potential energy carrier in the near future and can be produced from nuclear energy by several means. Lead-based reactor is one of the advance reactors in hydrogen production. In this paper, a novel feasible system of lead cooled reactor coupled with solid oxide electrolysis cells (SOEC) is presented, which is named China LEAd-based Reactor for Hydrogen production (CLEAR-H). By taking advantage of the chemically inert and high density of lead–bismuth eutectic (LBE), the concept of LBE-water direct-contact steam generator is proposed to supply high temperature (up to 600 °C) and low pressure (0.1–0.2 MPa) steam for SOEC stack without additional decompression devices. The results show that 47 tons hydrogen and 3000 tons oxygen-enriched air are obtained per day, and the thermal-to-hydrogen efficiency can reach about 39%.

Hydrogen production through steam electrolysis: Model-based dynamic behaviour of a cathode-supported intermediate temperature solid oxide electrolysis cell

Hydrogen production via steam electrolysis may involve less electrical energy consumption than conventional low temperature water electrolysis, reflecting the favourable thermodynamics and kinetics at elevated temperatures. In the present paper, a one-dimensional model of a cathode-supported planar intermediate temperature solid oxide electrolysis cell (SOEC) stack is employed to study the dynamic behaviour of such an electrolyser. The simulations found that step changes in the average current density cause the stack temperature to alter during both exothermic and endothermic operation. However, the temperature control, by the variation of the air flow through the stack, was predicted to be capable of returning the stack temperature to the initial value. Furthermore, the proposed control strategy is observed to reduce the interim temperature excursions between the initial and final steady states, suggesting that such a control strategy has a good potential to prevent the issues of cell component fracture, and transitions in stack operating mode, which are related to the temperature fluctuations during dynamic operation of an SOEC stack.

Hydrogen production through steam electrolysis: Model-based steady state performance of a cathode-supported intermediate temperature solid oxide electrolysis cell

Hydrogen production via steam electrolysis may involve less electrical energy consumption than conventional low temperature water electrolysis, reflecting the improved thermodynamics and kinetics at elevated temperatures. The present paper reports on the development of a one-dimensional dynamic model of a cathode-supported planar intermediate temperature solid oxide electrolysis cell (SOEC) stack. The model, which consists of an electrochemical model, a mass balance, and four energy balances, is here employed to study the steady state behaviour of an SOEC stack at different current densities and temperatures. The simulations found that activation overpotentials provide the largest contributions to irreversible losses while concentration overpotentials remained negligible throughout the stack. For an average current density of 7000 A m −2 and an inlet steam temperature of 1023 K, the predicted electrical energy consumption of the stack is around 3 kW h per normal m 3 of hydrogen, significantly smaller than those of low temperature stacks commercially available today. However, the dependence of the stack temperature distribution on the average current density calls for strict temperature control, especially during dynamic operation.