Hydrogen Flow Rate Research Articles

Efficiency Optimization of SOFC Subject to Degradation and Minimum Power Constraint

Solid Oxide Fuel Cell (SOFC) is a developing energy conversion technology featuring high efficiency, power density, durability, and fuel compatibility. With these advantages, SOFCs are combined frequently with heat engines such as gas turbines, for higher system efficiency and power density.In practice, SOFCs are often required to deliver certain power. Considering economical aspects, power generation efficiency is critical to the running cost of energy conversion systems. However, high power and high efficiency are likely reached under different operating conditions. For example, to meet peak power demands, higher operating currents and fuel flowrates are necessary, while SOFCs are generally more energy efficient at lower current densities and fuel flowrates. Hence, the ideal operating condition is the solution to a power-constrained efficiency optimization problem. Moreover, SOFCs degrade as they operate, introducing gradual changes to SOFC characteristics. Thus, the optimization needs to be solved dynamically.To analyze the above-mentioned problem, a 10 cm by 10 cm planar SOFC was repeatedly tested for polarization characterizations and electrochemical impedance spectra. A 2-dimentional multi-physics model was developed and calibrated using both polarization and impedance data. To account for the lower open circuit voltage at lower fuel flowrates, an equivalent leakage current is included in the model. The model was thereafter employed for efficiency optimization given power constraints. At each required power output, the optimal fuel flowrate and the corresponding voltage, current, and efficiency was calculated. The electrical efficiency peaks globally at around 0.1 Standard Liter per Minute (SLM) hydrogen flowrate, while at higher power, the optimal efficiency is reached at fuel utilizations between 65% and 90%. Accounting for degradation in terms of growing ohmic resistance and decreasing electrode exchange current densities, the optimal efficiency is reached at lowering fuel utilization and lowering voltage, which may result in local oxidization of the anode.Moreover, an easy and straight-forward way was proposed to estimate the optimal fuel flowrate given polarization data. Further studies involving the safety constraints will be carried out in the future. Figure 1

Biofuel upgrading via catalytic deoxygenation in trickle bed reactor: Crucial issue in selection of pressure regulator type

Trickle bed reactors (TBRs) are commonly used in various chemical and associated processes. The selection of a proper back pressure regulator (BPR) is crucial for maintaining the system's upstream pressure. In this study, we investigate the impact of BPR selection on deoxygenation reaction in a TBR with two typical types of BPR, including gas-phase type back pressure regulator (Gas-BPR) and multiphase type back pressure regulator (Multi-BPR). Notably, Gas-BPR introduces interruptions and pressure drops during the sampling step, impacting the hydrogen flow rate, while Multi-BPR ensures more consistent hydrogen flow. To examine the performance of BPR systems, hydrotreating experiments were conducted at 330 °C, 50 bar of hydrogen over Ni/γ-Al2O3 catalyst using crude Pongamia pinnata oil as a feedstock and refined palm olein as a benchmark. Insignificant difference in the reaction performance between Multi-BPR and Gas-BPR systems was observed when using refined palm olein. Interestingly, there was a significant difference between the two systems when feeding with crude Pongamia pinnata oil. The multi-BPR system demonstrated superior performance, achieving 100% conversion of the feedstock over a prolonged period compared to the interrupted hydrogen flow in the Gas-BPR system. Further characterization of fresh and spent catalysts using N2 sorption, XRD, SEM-EDS and TGA-DTG-DSC techniques revealed that a gum and coke formation was a reason for the rapid catalyst deactivation. Furthermore, the interrupted flow in the Gas-BPR system led to substantial gum production, ultimately causing a blockage in the reactor bed. Consequently, for feedstocks with high impurities, a robust continuous flow of hydrogen is essential. Thus, the study strongly recommends selecting Multi-BPR for continuous operation in TBRs to enhance efficiency and avoid catalyst deactivation.

Investigation of the hydrogen production of the PACER fusion blanket integrated with Fe–Cl thermochemical water splitting cycle

In order to meet the energy demand, energy production must be done continuously. Hydrogen seems to be the best alternative for this energy production, because it is both an environmentally friendly and renewable energy source. In this study, the hydrogen fuel production of the peaceful nuclear explosives (PACER) fusion blanket as the energy source integrated with Fe–Cl thermochemical water splitting cycle have been investigated. Firstly, neutronic analyzes of the PACER fusion blanket were performed. Necessary neutronic studies were performed in the Monte Carlo calculation method. Molten salt fuel has been considered mole-fractions of heavy metal salt (ThF4, UF4 and ThF4+UF4) by 2, 6 and 12 mol. % with Flibe as the main constituent. Secondly, potential of the hydrogen fuel production as a result of the neutronic evaluations of the PACER fusion blanket integrated with Fe–Cl thermochemical cycle have been performed. In these calculations, tritium breeding (TBR), energy multiplication factor (M), thermal power ratio (1−ψ), total thermal power (Phpf) and mass flow rate of hydrogen (m˙H2) have been computed. As a results, the amount of the hydrogen production (m˙H2) have been obtained in the range of 232.24x106 kg/year and 345.79 x106 kg/year for the all mole-fractions of heavy metal salts using in the blanket.

Dynamic modeling and performance analysis of metal hydride hydrogen storage system

Metal hydride hydrogen storage has the advantages of high hydrogen storage volume density, high safety, and high hydrogen purity, which can meet the hydrogen storage and supply needs of fuel cells in both mobile and fixed scenarios. It has become one of the most promising hydrogen storage methods. This work studies the dynamic performance of metal hydride hydrogen storage systems under absorption and desorption process by establishing dynamic models and heat exchange models. The dynamic properties of metal hydride hydrogen storage system are analyzed in different reaction process with the experimental test. Results show that when the ambient temperature is within a certain range, low temperatures are conducive to hydrogen absorption, while high temperatures can improve hydrogen release dynamics. Besides, raising the flow rate of hydrogen and reducing the volume fraction of hydrogen storage materials can help to improve the efficiency of hydrogen absorption and desorption reaction.

Experimental studies on a closed cycle compressor operated metal hydride based cooling system with large hydrogen inventory

The current manuscript reports the experimental results of a closed loop metal hydride (MH) based compressor driven cooling system (CDCS) employing large-scale reactors. Two identical tube bundle reactors (TBR) with 19 MH tubes were designed, constructed and packed with 26.5 kg La0.8Ce0.2Ni5 alloy each for the experiments. The TBR modules were coupled with a custom-built compressor to provide cooling effect in quasi-continuous mode of operation. The compressor was tested to operate smoothly up to a hydrogen flow rate of 0.5 g. s−1 in the temperature range of 10–35 °C, yielding pressure ratio up to 12.8. Test runs were performed by altering refrigeration temperature (10–20 °C), sink temperature (30–35 °C), and half-cycle time (120–600 s). The maximum cooling power attained at 20 °C refrigeration temperature and 30 °C sink temperature was 1.44 kW, generating 537.3 kJ cooling within 600 s. The corresponding mean coefficient of performance (COP) and specific cooling power (SCP) were 0.95 and 36.4 W.kg−1 for 480 s half-cycle time. To avoid overheating of the compressor base, the half-cycle time was restricted to maximum of 600 s.

Analysis of polarization characteristics and optimal operating conditions for industrial-sized SOFC based on comparison with button cells

Although button solid oxide fuel cells (SOFCs) have been extensively used in fundamental research, practical commercial applications are developed on industrial-sized SOFCs. As the active area and fuel utilization increase, some issues that are not considered in button cells become essential. Therefore, it is necessary to focus on the differences between button cells and industrial-sized cells, including their polarization characteristics and performance evaluation. In this study, the polarization curves of both types of cells under different hydrogen flow rates are tested. Both types of cells experience a sudden increase in total area-specific resistance (Rtot) under high current density. However, the effects of hydrogen flow rate differs between cell types. Based on the equivalent circuit model (ECM) fitting of electrochemical impedance spectroscopy (EIS) measured under different DC biases and the theoretical calculation of gas diffusion and gas conversion resistances, it is demonstrated that the rapid increase in Rtot in button cells is primarily attributed to gas diffusion through the anode. In contrast, non-uniform gas distribution along the flow channel direction results in a dominant role of gas conversion resistance on Rtot in industrial-sized cells, especially at hydrogen flow rates below 0.4 L min−1. Although electrical efficiency is often overlooked in button cells, it is a crucial performance evaluation index in industrial-sized cells. The impact of operating parameters on power density and electrical efficiency is analyzed, revealing a trade-off between the two. With the critical Nernst electromotive force of Ni oxidation as the voltage lower limit, the optimal operating conditions with high electrical efficiency and prevention of Ni oxidation under different flow rates are obtained. It is investigated that operation should be carried out at a low flow rate below 0.3 L min−1 to achieve high electrical efficiency of over 50%. The selected operating parameters will change when the cell performance or load demand changes. However, the analysis method proposed in this paper can still provide a reference for selecting the operating parameters of a SOFC system.

Hydrogen-modulation method for wafer-scale few-layer single-crystal graphene growth

Single-crystal few-layer graphene films have potential applications in microelectronic and optoelectronic devices. Considerable efforts have been taken to prepare large-area bilayer graphene through chemical vapor deposition, but the growth of uniform graphene films with increased layers remains challenging. Herein, a hydrogen-modulation method for growing wafer-scale few-layer single-crystal graphene through chemical vapor deposition was proposed. By controlling the hydrogen flow rate at different stages, the dissolution amount and segregation process of carbon atoms in a CuNi substrate can be regulated separately. The hydrogen-modulation method fully exploits the effect of the dissolution–segregation mechanism, and the number of graphene layers can be controlled by modulating the hydrogen flow rate. Through the proposed method, the coverages of bilayer and trilayer graphene can reach more than 99% and 95%, respectively. The stacking and uniformity of few-layer graphene were evaluated by Raman and microstructure characterization, and bilayer and trilayer graphene were confirmed as AB and ABA stacks, respectively. Transmission line test structure and field effect transistor were prepared to verify the electrical properties of bilayer graphene. Results show that the square resistance of bilayer graphene is significantly lower than that of single-layer graphene, and it can also achieve high on-state current on field effect transistor.

Research on transient heat transfer of ball valves in high-pressure liquid hydrogen receiving stations

As one of the most important fluid control devices in the liquid hydrogen receiving station, the liquid hydrogen ball valve's performance directly affects the system's stability. Aiming at the problem of insufficient cold shrinkage compensation ability of ball valve under high-temperature difference and excessive flow rate during the working process, a high-pressure liquid hydrogen hollow ball valve with elastic compensation ability is designed. Based on the conjugate heat transfer method, the transient conjugate heat transfer and transient thermal stress analysis were carried out on the high-pressure hollow ball valve of the liquid hydrogen receiving station. The results show that the transient temperature of each part of the ball valve decreases under different flow rates, and the closer to the flow part of the medium, the faster the cooling. In the initial stage, the larger the flow rate of liquid hydrogen, the greater the heat flux density of the fluid-solid interface, but after a certain period, the large flow rate is cooled to a greater extent, the heat transfer is weakened, and the heat flux density is smaller. Under different flow rates, the transient thermal stress of the key components of the ball valve first increases sharply and then decreases. At large flow rates, the temperature change is more obvious, and the maximum stress of each component increases. The research results have guiding significance for designing and applying ball valves in high-pressure liquid hydrogen receiving stations.

An experimental investigation of hydrogen-enriched and nanoparticle blended waste cooking biodiesel on diesel engine

The hazardous effect of the pollution of fossil fuels has brought the necessity of shifting conventional energy sources to renewable and clean ones. In this study, the effect of hydrogen addition and CeO2 nanoparticle addition in waste cooking palm biodiesel on a CRDI engine is evaluated. The dosage of the nanoparticle is fixed at 75 ppm and a hydrogen flow rate of 10 L/min is selected for the engine operations. The crystalline structure of the nanoparticles is determined by XRD analysis. Results showed that on the addition of both H2 and CeO2 in a B20 biodiesel blend (80% diesel and 20% biodiesel) the performance, emission, and combustion parameters of the diesel engine improved compared to neat diesel. The brake thermal efficiency was improved by 3.53% and brake fuel consumption was reduced by 16.12% in comparison to diesel at 90% loading condition. The addition of both nanoparticles and hydrogen in the biodiesel blend lowered the emissions of CO by 30%, and HC and smoke by 50% and 42% respectively. However, NOx increased by 11% as compared to diesel. A 6% higher HRR values and 8% higher in-cylinder pressure were obtained while using hydrogen and CeO2 nanoparticle blended biodiesel. This blend also shows the lowest ignition delay period at full load condition which results in more engine power and efficiency. This experimental study has helped pave the way for the use of hydrogen-enriched and nanoparticle-blended biodiesel in place of fossil fuel for the applications of diesel engines.

Experimental evaluation of a 1 kW proton exchange membrane fuel cell with resistive, DC and AC loads

In this communication, an experimental investigation is carried out on a PEM (Proton Exchange Membrane) fuel cell. A small-scale standalone PEM fuel cell system of 1 kW capacity is demonstrated in the present study. The fuel cell is connected to the charge controller, and the charge controller is further connected to the DC and AC loads to study the fuel cell characteristics. A battery bank backup is also provided to account for the stable power output from the fuel cell. The purpose of the study is to determine the fuel cell's performance when operated with resistive, AC, and DC loads (home appliances within the rated power range). The effect of hydrogen flow rates on the power output is also presented in this paper. The DC and AC loads are connected to the fuel cell setup to study the characteristics of the fuel cell. From the study, it can be observed that the performance of the fuel cell is better at higher flow rates of hydrogen. The experimental results showed that the maximum power obtained was 986.8 W at a hydrogen supply rate of 15 LPM. The maximum fuel cell efficiency was found to be 44% at the flow rate of 8 LPM. The charge controller efficiency reported for DC and AC load connections is 94.97% and 96.98%, respectively. The inverter efficiency was observed to increase with the current value, with the maximum value reaching around 98.86%.

Comparison of the Electrochemical Performances of Solid Oxide Fuel Cells with Sputtered Thin Barrier Layers Fueled by Hydrogen or Ammonia

We investigated the influence of a fuel change from pure hydrogen to a hydrogen–ammonia mixture at different percentages on the electrochemical behavior of 50 mm in diameter Solid Oxide Fuel Cells (SOFCs) with sputtered thin buffer layers of Gd-doped ceria, varying the working temperatures from 800 °C to 650 °C. The results show that the performances of the cells are not affected by the fuel change for high working temperatures (800 °C and 750 °C). As an example, a power density value of 802 mW∙cm−2 at 1 A∙cm−2 is found when directly feeding the cell with 8 NmL∙min−1cm−2 of ammonia and with an equivalent flowrate of 12 NmL∙min−1cm−2 of H2. These power density output values are higher than those obtained in industrial state-of-art (SoA) SOFCs with screen-printed buffer layers fed with equivalent hydrogen flowrates, thanks to the improved electrochemical performances obtained in the case of cells with sputtered thin buffer layers of Gd-doped ceria. At lower working temperatures (700 °C and 650 °C), slight changes in the electrochemical behavior of the cells are observed. Nevertheless, in this temperature range, we also obtain an output current density value of 0.54 A∙cm−2 in a pure ammonia flowrate of 12 NmL min−1cm−2 at 800 mV and 700 °C, equal to the value observed in SoA button cells with industrial screen-printed GDC barrier layer fueled with 16 NmL∙min−1cm−2 of H2. These results pave the way towards the use of innovative SOFC structures with sputtered thin buffer layers fueled by ammonia.

The combined effect of EGR and hydrogen addition on a Syzygium cumini (jamun) liquid biofuel engine

Rapid depletion of fossil fuels required the development of alternate and sustainable fuel sources that could replace conventional fuel while having no negative environmental impact. Combining hydrogen induction with biodiesel ensures strict emission standards and lowers energy consumption compared to conventional fuels. In this study, the performance, emissions, and combustion of a CI engine for Syzygiumcumini (B20) were assessed and compared to diesel fuel while using a fixed amount of hydrogen flow rate (6L/m). Throughout the experiment, an exhaust gas recirculation (EGR) technology of 10% and 20% and a constant engine speed of 1500 rpm at varying engine load circumstances were used. When hydrogen is added to B20, it decrease the emissions of carbon monoxide (CO), unburned hydrocarbons (UHC), brake thermal efficiency (BTE), and brake specific energy consumption (BSEC). At maximum load, the use of the EGR system decreased the exhaust gas temperature (EGT) by 13.4% and nitrogen oxide (NOX) emission by 25%, but it had a negative impact on BTE, BSEC, as well as other emission parameters including CO and UHC. Therefore, using hydrogen in dual fuel mode in a CI engine enhances performance and lowers exhaust emissions, while using the EGR approach reduces NOX emissions.

Effect of hydrogen blending on the combustion performance, emission, and cycle-to-cycle variation characteristics of a single-cylinder GDI spark ignition dual-fuel engine

The effect of hydrogen addition on combustion, performance, emission and cyclic variation under different hydrogen flow rates (2, 5, 8, 11, and 14 LPM) were investigated based on a SI engine with hydrogen port induction and gasoline direct injection. The in-cylinder pressure increases by 52.04% with an 8LPM of hydrogen flow rate. The rate of pressure rise and heat release from the hydrogen-gasoline mixture combustion are more concentrated and 95.53% increase in the engine torque. For the specified hydrogen flow rate, brake specific energy consumption was reduced by 92.27% and brake thermal efficiency increased by 25%. Moreover, CO emission was improved after hydrogen addition under all operating conditions. CO2 and NOX emissions were continuously increased with hydrogen addition. The cyclic variation was increased with the increase in the hydrogen flow rate and reduced with the increase in gasoline injection quantity.

Physical model of non-adiabatic blowdown of cryo-compressed hydrogen storage tanks

This paper describes a model of hydrogen blowdown dynamics for storage tanks needed for hydrogen safety engineering to accurately represent incident scenarios. Heat transfer through a tank and pipe walls affects the temperature and pressure transients inside the storage vessel and at the nozzle exit, and thus the characteristics of the resulting hydrogen jet in the case of loss of containment. Current non-adiabatic blowdown models are validated against experiments performed with hydrogen storage tanks at only ambient temperature. The effect of heat transfer for cryo-compressed hydrogen is more significant due to a larger difference of temperature between the stored hydrogen and the surrounding atmosphere, especially in case of equipment insulation failure during an incident. Our previous work demonstrated that the heat transfer through a discharge pipe wall can significantly affect the mass flow rate of cryogenic hydrogen releases. Thoroughly validated models of non-adiabatic blowdown dynamics for cryo-compressed hydrogen are missing at the moment. This work develops further the non-adiabatic blowdown model at ambient temperature using the under-expanded jet theory developed at Ulster University, to expand it to cryo-compressed hydrogen storage tanks. The non-ideal behaviour of cryo-compressed hydrogen due to low temperatures is taken into account through the high-accuracy Helmholtz energy formulations. The developed model includes effect of heat transfer at both the tank and the discharge pipe walls. The model is thoroughly validated against sixteen tests on blowdown of hydrogen storage tanks with initial pressure 0.6–20 MPa ab and temperature 80–310 K, through release nozzle of diameter in the range 0.5–4.0 mm, performed within the PRESLHY project. The model well reproduces the experimental pressure and temperature recordings in the storage tank during the entire blowdown duration for the whole set of sixteen tests. In conjunction with the volumetric source model, explained in detail, the physical model allows to perform CFD simulations accurately reproducing the temperature distribution in time and space for the cryogenic hydrogen jet experiment.

Polyoxometalates as highly efficient adsorbents for ciprofloxacin removal: The key role of oxygen vacancies

In this study, various silver phosphomolybdates (x-y-z-AgPMo) with oxygen vacancies were successfully prepared through H2 calcination and subsequent chemical precipitation and used for the adsorption of ciprofloxacin (CIP) in water. The microstructures of x-y-z-AgPMo were analyzed by a series of characterization methods. The effects of calcination time, calcination temperature, hydrogen flow rate, and external adsorption conditions on the adsorption performance were investigated. The results showed that the adsorption performance of 1–0.1–250-AgPMo toward CIP could reach 91% within 20 min with a maximum adsorption capacity of 45.5 mg∙g − 1, which was about 1.7 times as that of silver phosphomolybdate (Y-AgPMo) without H2 calcination. The improved adsorption performance of 1–0.1–250-AgPMo was mainly attributed to the presence of oxygen vacancies, which induced more negative surface charges and larger specific surface area in 1–0.1–250-AgPMo. This work provided an excellent adsorbent for CIP removal and forcefully confirmed the important role of oxygen vacancies in the adsorption process.

Hydrogen flow rate control in a liquid organic hydrogen carrier batch reactor for hydrogen storage

Liquid Organic Hydrogen Carriers (LOHCs) feature a highly variable rate of hydrogen release if held at constant pressure and temperature, but in real-life applications hydrogen release must be controlled to match end-user demand. The aim of this paper is to provide an overall assessment of LOHC systems’ controllability, within a general framework regardless of the specific application field. Hydrogen discharge can be controlled through the reactor pressure and temperature; thus, a PI controller is introduced acting on three control variables independently: discharge pressure; thermal fluid inlet temperature; thermal fluid mass flow rate. A quantile analysis is performed on the uncontrolled hydrogen release: practical values of the energy-to-power ratios for LOHC systems are 2–6 h. A normalised release time is introduced to assess the efficiency of the control system. Temperature control leads to the best results, with an efficiency higher than 90% for the entire load range, while pressure control leads to satisfactory performance only at low loads. The mass flow rate control is the least effective, with efficiencies always below 80%. Sensitivity analysis highlights the temperature control strategy as the best fit to enhance controllability across the whole power range. Pressure control presents a more variable trend.

The Effect Of Acid Strength Of Bronsted Acid Site On The Ability Of The Catalyst To Break The Carbon Chain Bonds Of 1-Octadekenes Into Alkanes And Short Chain Alkenes As A Substitute For Fossil Fuels

Research has been carried out on the strength of acids on their ability to break carbon chain bonds. The preparation of the zeolite catalyst includes soaking the zeolite in distilled water for 24 hours, followed by calcination and oxidation, then followed by reduction. Further acid treatment with 6 M HCl. Then followed by washing with H2O until neutral pH (pH = 7), then dried in an oven with a temperature of 105 oC, then after becoming a zeolite catalyst used in the cracking reaction of 1-octadekenes into alkanes and short chain alkenes.The results obtained are as follows for the type of zeolite catalyst with code Z having a very low acidity level of 3.15 mmol NH3/mgZeolite, then the zeolite has been modified by a calcination process for 24 hours given the code ZCA which shows a moderate acidity level of 5, 76 mmol NH3/mg Zeolite, then the catalyst with the code ZCAO is zeolite which has been calcified and oxidized and shows a yield of 9.54 mmol NH3/mg Zeolite. Catalytic hydrocracking of 1-octadecene with ZCAO catalyst at a variation of the hydrogen flow rate of 20 mL/minute and a temperature of 450 oC resulted in alkanes and alkenes C12 which was 15.29% maximum, followed by a hydrogen flow rate of 10 mL/minute at temperatures of 500 and 400 oC.

Multiple-objective optimization on ammonia decomposition using membrane reactor

Ammonia plays a key role in the renewable hydrogen economy nowadays, thus, the efficiency of ammonia decomposition for hydrogen production becomes an important research topic. In this study, a numerical model was built to study the performance of ammonia decomposition using a membrane reactor and Ru/Al2O3 catalyst under various operating conditions such as feed NH3 temperature and volume flow rate as well as retentate side pressure. The reactor performance was characterized by ammonia conversion, hydrogen recovery, and recovered hydrogen flow rate. Pre-exponential factor and activation energy of ammonia reaction rate were obtained by equilibrium conversion and two-step parametric sweeping. It was found that ammonia conversion can be increased by about 33% compared to a conventional fixed-bed reactor under the same operating conditions. H2 recovery can be enhanced when the reactant inlet temperature and the pressure difference between the retentate and permeate sides increase. The increase in feed NH3 flow rate (gas hourly space velocity, GHSV) decreased the ammonia conversion and H2 recovery. An optimum GHSV that results in a maximum recovered H2 flow rate can be found. Finally, optimum operation conditions for maximizing the hydrogen recovery and recovered hydrogen flow rate were analyzed using the multi-objective Non-dominated sorting genetic algorithm-II (NSGA-II). It was found that maximum H2 recovery with a value of 79.7% can be obtained under the conditions of inlet temperature of 336 °C, GHSV of 900 h−1, and retentate side pressure of 9.9875 bar. The maximum recovered hydrogen flow rate with a value of 9.55×10−14(mol·s−1) can be obtained under the conditions of an inlet temperature of 394 °C, GHSV of 1315 h−1, and retentate side pressure of 9.9879 bar.

Influence of Process Parameters on SOEC Performance

Solid oxide electrolysis cells (SOECs) are highlighted as promising power-to-gas (P2G) devices that can provide a reliable supply of hydrogen gas to store renewable energy. Despite the potential of SOECs, there are many challenges facing their commercialization. In this work, the influence of process parameters and fuel electrode optimization on initial SOEC performance (500 hours) is investigated. Electrolysis experiments were performed with both GDC (gadolinia doped ceria)-infiltrated and uninfiltrated Ni-YSZ (yttria stabilized zirconia) fuel electrodes under various hydrogen flow rates with different ratios of H2-H2O and current densities. All cells marginally improve in performance initially, then undergo a brief period of rapid performance degradation followed by stabilization. The observed three stages of cell performance, in terms of length of time and rate of change, are found to be dependent on the type of fuel electrode and experimental process parameters used.

A Novel Online Diagnosis Method for Tubular Solid Oxide Fuel Cells Using Total Harmonic Distortion Analysis

Fast and accurate online prognostic technology is urgently needed for the long-term and stable operation of solid oxide fuel cell (SOFCs). Total harmonic distortion analysis (THDA) is a potential candidate that obtains the dynamic information of an electrochemical system by analyzing high-order signals and has been successfully utilized in PEMFC fault diagnosis. In this study, the THDA method is utilized in a tubular SOFC under fuel and air starvation conditions at different hydrogen and air flow rates. The total harmonic distortion spectra are obtained in the frequency range of 0.1~100 Hz. The effects of different excitation current amplitudes on the results accuracy are further investigated. As a consequence, the excitation amplitude range, frequencies with high sensitivity and appropriate threshold are chosen to diagnose different faults efficiently.