scholarly journals High Temperature Water Electrolysis Using Metal Supported Solid Oxide Electrolyser Cells (SOEC)

2010 ◽  
Vol 72 ◽  
pp. 135-143 ◽  
Author(s):  
Günter Schiller ◽  
Asif Ansar ◽  
Olaf Patz
Keyword(s):  
High Temperature ◽  
Fuel Cell ◽  
Current Density ◽  
Degradation Rate ◽  
Cell Voltage ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Metallic Interconnect ◽  
A Current

Metal supported cells as developed at DLR for use as solid oxide fuel cells by applying plasma deposition technologies were investigated in operation of high temperature steam electrolysis. The cells consisted of a porous ferritic steel support, a diffusion barrier layer, a Ni/YSZ fuel electrode, a YSZ electrolyte and a LSCF oxygen electrode. During fuel cell and electrolysis operation the cells were electrochemically characterised by means of i-V characteristics and electrochemical impedance spectroscopy measurements including a long-term test over 2000 hours. The results of electrochemical performance and long-term durability tests of both single cells and single repeating units (cell including metallic interconnect) are reported. During electrolysis operation at an operating temperature of 850 °C a cell voltage of 1.28 V was achieved at a current density of -1.0 A cm-2; at 800 °C the cell voltage was 1.40 V at the same operating conditions. The impedance spectra revealed a significantly enhanced polarisation resistance during electrolysis operation compared to fuel cell operation which was mainly attributed to the hydrogen electrode. During a long-term test run of a single cell over 2000 hours a degradation rate of 3.2% per 1000 hours was observed for operation with steam content of 43% at 800 °C and a current density of -0.3 Acm-2. Testing of a single repeating unit proved that a good contacting of cell and metallic interconnect is of major importance to achieve good performance. A test run over nearly 1000 hours showed a remarkably low degradation rate.

scholarly journals Performance Assessment of Single Electrode-Supported Solid Oxide Cells Operating in the Steam Electrolysis Mode

2011 ◽  
Author(s):  
X. Zhang ◽  
J. E. O’Brien ◽  
R. C. O’Brien ◽  
N. Petigny
Keyword(s):  
Fuel Cell ◽  
Single Cells ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Accelerated Degradation ◽  
Degradation Rates ◽  
Electrolysis Cells ◽  
Cell Test ◽  
Electrolysis Mode

An experimental study has been conducted to assess the performance of electrode-supported solid-oxide cells operating in the steam electrolysis mode for hydrogen production. Results presented in this paper were obtained from single cells, with an active area of 16 cm2 per cell. The electrolysis cells are electrode-supported, with yttria-stabilized zirconia (YSZ) electrolytes (∼10 μm thick), nickel-YSZ steam/hydrogen electrodes (∼1400 μm thick), and modified LSM or LSCF air-side electrodes (∼90 μm thick). The purpose of the present study is to document and compare the performance and degradation rates of these cells in the fuel cell mode and in the electrolysis mode under various operating conditions. Initial performance was documented through a series of voltage-current (VI) sweeps and AC impedance spectroscopy measurements. Degradation was determined through long-term testing, first in the fuel cell mode, then in the electrolysis mode. Results generally indicate accelerated degradation rates in the electrolysis mode compared to the fuel cell mode, possibly due to electrode delamination. The paper also includes details of an improved single-cell test apparatus developed specifically for these experiments.

Oscillation Phenomenon of the Cell Performance for an Anode-Supported Solid Oxide Fuel Cell with a Low-Porosity/High-Thickness Anode Structure

2015 ◽  
Vol 656-657 ◽  
pp. 124-128 ◽  
Author(s):  
Wei Xin Kao ◽  
Tai Nan Lin ◽  
Yang Chuang Chang ◽  
Maw Chwain Lee
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Current Density ◽  
Concentration Polarization ◽  
Cell Voltage ◽  
Solid Oxide ◽  
Constant Current ◽  
Oxide Fuel ◽  
Oscillation Phenomenon ◽  
Low Porosity

The anode-supported solid oxide fuel cell (SOFC) with low-porosity anode structure is fabricated and the electrochemical characteristics are investigated. The electrochemical characterization of the cell shows a periodic oscillation phenomenon of the cell voltage under the constant current density operation. The low-porosity anode structure results in the decrease in the effective diffusion coefficient and the accumulation of water vapor. The cell voltage oscillation is mainly caused by the concentration polarization as well as the boundary migration of the reaction zone. The profound influence on the concentration polarization can be observed when the cell test is executed with operation condition of higher current density, lower hydrogen concentration, and lower hydrogen flow rate in the anode side.

scholarly journals Measurement of polarization curve and development of a unique semi empirical model for description of PEMFC and DMFC performances

2011 ◽  
Vol 17 (2) ◽  
pp. 207-214 ◽  
Author(s):  
T. Selyari ◽  
A.A. Ghoreyshi ◽  
M. Shakeri ◽  
G.D. Najafpour ◽  
T. Jafary
Keyword(s):  
Experimental Data ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Current Density ◽  
Power Output ◽  
Cell Voltage ◽  
Operating Conditions ◽  
Cell Performance ◽  
Oxygen Stoichiometry ◽  
Semi Empirical

In this study, a single polymer electrolyte membrane fuel cell (PEMFC) in H2/O2 form with an effective dimension of 5?5 cm as well as a single direct methanol fuel cell (DMFC) with a dimension of 10?10 cm were fabricated. In an existing test station, the voltage-current density performances of the fabricated PEMFC and DMFC were examined under various operating conditions. As was expected DMFC showed a lower electrical performance which can be attributed to the slower methanol oxidation rate in comparison to the hydrogen oxidation. The results obtained from the cell operation indicated that the temperature has a great effect on the cell performance. At 60?C, the best power output was obtained for PEMFC. There was a drop in the cell voltage beyond 60?C which can be attributed to the reduction of water content inside the membrane. For DMFC, maximum power output was resulted at 64oC. Increasing oxygen stoichiometry and total cell pressure had a marginal effect on the cell performance. The results also revealed that the cell performance improved by increasing pressure differences between anode and cathode. A unified semi-empirical thermodynamic based model was developed to describe the cell voltage as a function of current density for both kinds of fuel cells. The model equation parameters were obtained through a nonlinear fit to the experimental data. There was a good agreement between the experimental data and the model predicted cell performance for both types of fuel cells.

scholarly journals Analysis of Fuel Cell Stack Performance Attenuation and Individual Cell Voltage Uniformity Based on the Durability Cycle Condition

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1199
Author(s):  
Chunjuan Shen ◽  
Sichuan Xu ◽  
Yuan Gao
Keyword(s):  
Fuel Cell ◽  
Current Density ◽  
Individual Cell ◽  
Cell Voltage ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Variation Coefficient ◽  
Fuel Cell Stack ◽  
Cycle Condition ◽  
Attenuation Rate

Based on the dynamic cycle condition test of a 4.5 kW fuel cell stack, the performance attenuation and individual cell voltage uniformity of the proton exchange membrane fuel cell (PEMFC) stack was evaluated synthetically. The performance decay period of the fuel cell stack was 180–600 h, the decrease of voltage and power was evaluated by rate and amplitude. The results show that the performance of the fuel cell stack decreased with the increase of test time and current density. When the test was carried out to 600 h, under rated operating conditions, the voltage attenuation rate was 130 μV/h, and the voltage reduced by 71 mV, with a decrease of 10.41%. The power attenuation rate was 0.8 W/h, with a decrease of 10.42%. The statistical parameter variation coefficient was used to characterize the voltage consistency of individual cells. It was found that the voltage uniformity is worse at the high current density point and with a long-running process. The variation coefficient was 3.1% in the worst performance.

Accelerated Degradation for Hardware in the Loop Simulation of Fuel Cell-Gas Turbine Hybrid

2014 ◽  
Author(s):  
Maria Abreu-Sepulveda ◽  
David Tucker ◽  
Nor Farida Harun ◽  
Gregory Hackett ◽  
Anke Hagen
Keyword(s):  
Fuel Cell ◽  
Real Time ◽  
Gas Turbine ◽  
Degradation Rate ◽  
Operating Conditions ◽  
Hardware In The Loop ◽  
Electrochemical Degradation ◽  
Term Stability ◽  
Long Term Stability

Solid oxide fuel cells (SOFCs) are a promising technology for clean power generation, however their implementation has been limited by several degradation mechanisms, which significantly reduce its lifetime under constant output power and inhibits the technology for commercialization in the near future. With the purpose of harnessing the capabilities offered by SOFCs, the U.S. DOE-National Energy Technology Laboratory (NETL) in Morgantown, WV has developed the Hybrid Performance (HyPer) project in which a SOFC 1D, real-time operating model is coupled to a gas turbine hardware system by utilizing hardware-in-the-loop simulation (HiLS). More recently, in order to assess the long-term stability of the SOFC part of the system, electrochemical degradation due to operating conditions such as current density and fuel utilization have been incorporated into the SOFC model and successfully recreated in real time for standalone and hybrid operation. The mathematical expression for degradation rate was obtained through the analysis of empirical voltage versus time plots for different current densities and fuel utilizations at 750, 800, and 850°C. Simulation results well reflected the behavior of SOFC degradation rates from which the long-term stability of the cell under various conditions was assessed. Distributed fuel cell parameters are presented for both standalone and hybrid configurations. The incorporation of the electrochemical degradation rate into the SOFC model provides a framework to study more realistically Fuel Cell-hybrid systems and set forth a mechanism to improve the long-term stability of SOFCs through the hybridization of such technology.

scholarly journals Long-Term Performance of Solid Oxide Stacks With Electrode-Supported Cells Operating in the Steam Electrolysis Mode

2011 ◽  
Author(s):  
J. E. O’Brien ◽  
R. C. O’Brien ◽  
X. Zhang ◽  
G. G. Tao ◽  
B. J. Butler
Keyword(s):  
Fuel Cell ◽  
Negative Electrode ◽  
Cell Voltage ◽  
Solid Oxide ◽  
Test Duration ◽  
Modes Of Operation ◽  
Performance Characterization ◽  
Dc Potential ◽  
Durability Testing

Performance characterization and durability testing have been completed on two five-cell high-temperature electrolysis stacks constructed with advanced cell and stack technologies. The solid oxide cells incorporate a negative-electrode-supported multi-layer design with nickel-zirconia cermet negative electrodes, thin-film yttria-stabilized zirconia electrolytes, and multi-layer lanthanum ferrite-based positive electrodes. The per-cell active area is 100 cm2. The stack is internally manifolded with compliant seals. Treated metallic interconnects with integral flow channels separate the cells and electrode gases. Stack compression is accomplished by means of a custom spring-loaded test fixture. Initial stack performance characterization was determined through a series of DC potential sweeps in both fuel cell and electrolysis modes of operation. Results of these sweeps indicated very good initial performance, with area-specific resistance values less than 0.5 Ω.cm2. Long-term durability testing was performed with a test duration of 1000 hours. Overall performance degradation was less than 10% over the 1000-hour period. Final stack performance characterization was again determined by a series of DC potential sweeps at the same flow conditions as the initial sweeps in both electrolysis and fuel cell modes of operation. A final sweep in the fuel cell mode indicated a power density of 0.356 W/cm2, with average per-cell voltage of 0.71 V at a current of 50 A.

Barium-Free Glass-Ceramic Sealants from the System CaO-MgO-B2O3-Al2O3-SiO2 for Application in the SOFC

2011 ◽  
Vol 695 ◽  
pp. 1-4 ◽  
Author(s):  
Apirat Theerapapvisetpong ◽  
Sirithan Jiemsirilers ◽  
Parjaree Thavorniti ◽  
Reinhard Conradt
Keyword(s):  
Fuel Cell ◽  
Flow Behavior ◽  
Glass Ceramics ◽  
Interfacial Strength ◽  
Solid Oxide ◽  
Cell Components ◽  
Metallic Interconnect ◽  
Glass Compositions ◽  
Free Glass

The planar solid oxide fuel cell (p-SOFC) is a promising configuration of a high-T fuel cell. Barium alumosilicate glass ceramics are suggested to use as sealants by many authors since these materials seem to meet the requirements to establish a hermetic and electrically insulating seal between the steel components of the SOFC. However, in long-term application, the formation of BaCrO4 may degrade the interfacial strength between glass-ceramics and metallic interconnect and disrupt the cell components. In this work, a series of barium-free glass-ceramics in the system of CaO-MgO-B2O3-Al2O3-SiO2 were prepared. The selected compositions were located within the constitutional range of åkermanite – forsterite –anorthite. The thermal properties including glass transition temperature (Tg) and crystallization temperature (Tc) of the produced glasses were measured. The effect of boron oxide additions was studied in order to optimize the softening and flow behavior. For the experiments, a hot – stage microscope was used. Some glass compositions were mixed with high – CTE akermanite powder in order to increase their CTE after sintering. The CTE of the investigated materials after sintering at 900 °C, 2 h, ranged from 10.5 to 11.8 10−6 K−1.

A Practical Method for Modeling of Solid Oxide Fuel Cell Stack Degradation

2009 ◽  
Author(s):  
Wei Dong ◽  
Michael Pastula
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Current Density ◽  
Thermal Cycle ◽  
Degradation Rate ◽  
Operating Temperature ◽  
Practical Method ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Fuel Cell Stack

In this paper, the influences of area specific resistance (ASR), current density, temperature and thermal cycle (TC) on solid oxide fuel cell (SOFC) degradation were analyzed and quantified. The cell degradation equation and its influence equations with ASR, current density, temperature and thermal cycles were derived. Based on these equations, several ideal cases were studied. Meanwhile, a practical method considering three types of SOFC stack degradation behaviors based on empirical data were employed. This was done using an inhouse SOFC dynamic-link library as an input into a computational fluid dynamics (CFD) tool for modeling voltage decay and end of life (EOL) performance. It allows for a detailed 3-D study of a solid oxide fuel cell stack. It is revealed that the operating current density and cell ASR are two factors directly determining the degradation rate of individual cells. In addition, the operating temperature has a significant influence on the lumped ASR, thus also influencing cell degradation rate. The influence of contact ASR on cell degradation can be superior to that of temperature in that a contact resistance increment due to a thermal cycle, or other event, can cause a step change with a cell temperature increase and cell voltage decrease. It is suggested to run a stack below a certain critical peak internal temperature is favored, and if the contact loss is around 0.1 Ωcm2, one may offset the cell degradation by increasing operating temperature about 30°C. However, if the stack is operated above the cell critical peak temperature, it may cause an ineluctable increase in degradation.

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