Real Stack Research Articles

Parametrical Coordinates and Microsamples to Investigate Real SOFCs in Operating Stacks

One of the issues defining the performance of an SOFC stack is to estimate and check during operation the behavior of all components, i.e.: the cell, the sealant, the interconnects and the scaffolding. Each component has at least one function which is not strictly related to the power or heat generation but all are strategic and fundamental because any degradation or change in properties may lead to the failure of the whole stack. The behavior of materials is strongly related to physical parameters like temperature, surrounding atmospheres, coupling among two or more materials (e.g. electrolyte, sealant, metal). A twofold approach by experimental (e.g. segmented cells or instrumented short stacks) and modelling sessions allows to predict a number of parameters (e.g. temperature, fuel utilization) by fixing the others. This procedure engages the creation of refining loops between the experimental measures and the predicted ones. The final result is that regardless the cell or layer taken into account in a stack most of the electrochemical and physical behaviors can be predicted in a zone defined by "parametrical coordinates" or, in other words, areas of the stack standing in a similar range of parameters have similar behaviors. To take advantage of such important achievements in the field of modelling applied to SOFC stacks it is important to consider all components being all inter-related, and working conditions as close as possible to the real ones. The experiments with real stacks or with segmented cells in short stacks are thus more and more important but at the same time quite expensive and mainly for long lasting sessions of durability and estimation of the degradation rate they are prone to as unpredictable as dramatic events leading to failure (e.g. black-out). In this paper an opportunity offered by experiments and samples specifically designed in the EU FP7 project ENDURANCE (contract FCH-JU 621207) is introduced. The samples have the shape and size of a button cell and contain all components present in a stack: the cell (cut from an industrial batch and treated as the real cells for stacking), the metal with coating (interconnects and scaffolding) and the sealant. These samples are tested in a test rig defined as Real Life Tester (RLT) meant to reproduce the same operating conditions (i.e. temperature, mechanical load, gases composition, polarization) as those inside a real stack with the possibility to smoothly and rapidly change parameters and thus "parametrical coordinates" so that the operator can virtually move the sample across the stack and check in real time the response of the sample in a specific zone. The sample and the experiment itself are cost effective and offer the opportunity to soundly contribute to the assessment of stack components behavior in the "real world". ACKNOWLEDGEMENTS The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) Fuel Cells and Hydrogen Joint Undertaking (FCH-JU-2013-1) under grant agreement No 621207.

Short Stack Kit for the Open Flange™ Set-up Using Soft Mica Seals

Fiaxell has been active since 2008 in the Solid Oxide Fuel Cells (SOFC) industry and has been developing components and products for SOFC research. Fiaxell is the inventor of the “2R-Cell”, an anode supported cell able to withstand full re-oxidation and thermal cycles. The 2R-Cell is robust and has demonstrated high fuel utilization (85-90%) and electrical efficiency up to 50% with pure hydrogen on button cells. Fiaxell has developed the Open Flange™ Set-Up in order to test SOFC and SOEC cells. The Set-Up allows researchers to do various experiments, such as current-voltage characteristics, polarization, impedance spectroscopy measurements, electrolysis, co-electrolysis and in situgas processing (POX, SR) thanks to its integrated steam generator. Fiaxell is now offering a complete short stack kit that can be directly mounted onto the Open Flange™ Set-Up platform. This kit allows researchers to perform a range of experiments and to study stack parameters such as flow distribution, electrical contact resistance, and to investigate protective coatings to avoid chromium evaporation, in situfuel processing and sealing gas tightness. Each parameter can be independently characterized and optimized by combining ideal and real stack conditions on both sides of the cell, for instance Crofer steel on the anode and gold mesh on the cathode. Fiaxell is proposing Crofer 22H interconnects with different flow pattern designs for 50 X 50 mm and 80 X 60 mm cells. Alternatively, customers can propose their own customized design which can then be chemically grooved and laser cut by Fiaxell. The short stack kit comes with soft mica sealing but can also be made gas tight with any glass paste or other sealants. The soft mica seals have been designs to be easily removed and replaced, contrary to the use of glass based sealants that require mechanical grinding to remove. Mechanical simulations and calculations have been made to ensure that the design of the end Flange™ is adequate to compress the entire stack without any distortion or stress concentration points, especially on the interconnect plates. In order to see the gas distribution in the interconnect pattern, Fiaxell has developed an alternative, and complementary method to simulation, which consists of direct visualization and image analysis of the real flow motion. Screen captures will be included and discussed. In this paper, we present the experimental results of the short stack tests using two different interconnect patterns and also discuss the effectiveness of the soft mica gasket seals. Image caption: Exploded view of two cells short stack showing the three bipolar plates (interconnect) and soft mica gaskets (in beige). The short stack has been designed as a kit to be integrated directly on the Open Flange™ Set-Up platform. Figure 1

Co-Electrolysis with CFY-Stacks

The efficient high temperature electrolysis is of high interest for potential application in a renewable energy system. The possibility to use high temperature heat for the electrolysis reaction makes the SOEC technology an attractive option for the integration in process concepts for the production of valuable chemicals from renewable energies. Moreover, the SOEC allows the electrolysis of water and carbon dioxide in a so-called Co-electrolysis. The produced syngas can be used in a subsequent synthesis step, e.g. a Fischer-Tropsch synthesis. The development of these power-to-product processes as well as of necessary components are in focus of current research activities at IKTS. The main component is the high temperature electrolyzer (SOEC). In collaboration with Plansee SE, the CFY stack technology has been developed. This stack technology can be applied for SOFC, SOEC and reversible operation (rSOC) and establishes an universal platform for different applications.Performance maps of a MK352 CFY stack in steam- (H2O) and Co- (H2O/CO2) electrolysis operation show a difference in electric power demand of less than 5 %. This low additional power demand of Co-electrolysis together with the advantages of direct syngas production makes it promising for highly efficient integration within a process concept for the production of valuable hydrocarbons. The output syngas can be directly adjusted by choosing appropriate operating conditions for the SOEC to typical compositions used for reactions like Fischer-Tropsch synthesis. Based on this approach the operating conditions were set and durability tests with stacks (>1500 h) were conducted. The results raised several scientific questions which were answered by splitting the “black box” of the stack in separate parallel investigated experiments in the fields of cell tests, tests of interconnect materials, contact resistances, protective layer and glasses. The surprising behavior of reversible degradation of the stacks was analyzed by single cell experiments and could be reduced by adjusting of operating conditions and resulted in a fine tuning of the electrode design. Nevertheless still an irreversible degradation of about 1%/1000 h was detected. Several material tests consolidated the common understanding of degradation phenomena and will be shown with comparison to the real stack tests. The results show the excellent suitability of the CFY stack for electrolysis applications and give an outlook on further improvements.Figure: 30-cell MK352 stack for SOFC/SOEC and rSOC operation Figure 1

Parametrical Coordinates and Microsamples to Investigate Real SOFCs in Operating Stacks

One of the issues defining the performance of an SOFC stack is to estimate and check during operation the behavior of all components (i.e. cell, sealant, interconnects). Each component has at least one function which is not strictly related to the power or heat generation but all are strategic due to their contribution to the degradation of the whole stack. The model based approach leads to identify zones of the stack by their operating parameters (e.g. T, j, P) corresponding to an univocal material response. In this paper an experiment combining the parametrical coordinates with real samples in order to contribute to the study of real stacks is presented. The sample and the experiment itself are cost effective and offer the opportunity to soundly contribute to the assessment of stack components behavior in the "real world". The research was carried out in the frame of the FCH-JU project ENDURANCE.

Steady-state performance evaluation of Linux TCPs versus TCP wave over leaky satellite links

Internet access is becoming even more heterogeneous, including different wireless backhauling links, with Ka-band satellites as a possible alternative. Since communication path is unknown a priori, adoption of PEP solutions to optimize TCP performance over satellite is discouraged to allow dynamic network reconfigurations. To opposite, an end-to-end TCP performance evaluation on such a challenging scenario, with possible large latency and transmission losses, is herein considered of paramount importance. Several TCP variants exist to tackle different aspects of communication networks. In Linux, the different TCP congestion control schemes differ from the theoretical formulations and RFC specifications, introducing a varying set of optimizations and options. This aspect makes difficult to identify a standard/reference TCP version for the proposed scenario, while testing with the real protocol stacks is deemed necessary to obtain consistent results. In addition, an innovative end-to-end TCP, namely TCP Wave, is introduced to replace the traditional window-based transmission with a burst-based strategy, representing a valid alternative to Linux TCP. To offer a fair, realistic and comprehensive evaluation, we configured a simulation setup where different Linux TCPs can be run within ns-3 network simulator and compared with TCP Wave.

Simulation Technology on SOFC Durability With an Emphasis on Conductivity Degradation of ZrO2-Base Electrolyte

Attempts have been made to simulate numerically the conductivity degradation of solid oxide fuel cell (SOFC) YSZ electrolyte; physicochemical model has been constructed on the basis of experimental conductivities of Pt/1%NiO-doped YSZ/Pt cells under OCV condition. The temperature effect was extracted from the time constant for degradation caused by one thermal activation process (namely Y-diffusion), whereas the oxygen potential effect was determined by those Raman peak ratios between the tetragonal and the cubic phases which linearly change in relation to the conductivity. The electrical properties of the YSZ electrolyte before and after the transformation are taken into account. The time constant is directly correlated with Y-diffusion with proper critical diffusion length (∼10 nm), while the Y-diffusion can be enhanced on the reduction of NiO; this gives rise to the oxygen potential dependence. The most important objective of simulating the conductivity degradation is to reproduce the oxygen potential profile shift on transformation. Detailed comparison between experimental and simulation results reveal that the shift of oxygen potential profile, therefore, the conductivity profile change inside the YSZ electrolyte can well account for the Raman spectra profile. This also reveals that with decreasing temperature, there appear other kinetic factors of weakening or diminishing enhancing effects by NiO reduction. This may be important in interpreting the ohmic losses in real stacks, because there are differences in time constant or in magnitude of degradation between the pellets and those industrial stacks in which transformation was confirmed by Raman spectroscopy.

Dual control of low concentration CO poisoning by anode air bleeding of low temperature polymer electrolyte membrane fuel cells

Fuel impurities, fed to a polymer electrolyte membrane fuel cell, can affect stack performance by poisoning of catalyst layers. This paper describes the dynamic behaviour of a stack, including state-of-the-art membrane electrode assemblies (MEA) of three different manufacturers, at different operating conditions. The voltage transients of the step responses to CO poisoning as well as air bleed recovery are compared, revealing differences in performance loss: slow poisoning versus fast recovery, incomplete recovery and voltage oscillation. The recorded behaviour is used to develop a model, based on Tafel equation and first order dynamic response, which can be calibrated to each MEA type. Using this model to predict voltage response, a controller is built with the aim of reducing the total amount of air bleed and monitoring upstream stack processes without the need of sensors measuring the poisoning level. Two controllers are implemented in order to show the concept from a heuristic, easy to implement, and a more technical side allowing more detailed analysis of the synthesis. The heuristic algorithm, based on periodic perturbations of the manipulated variable (air-bleed), is validated on a real stack, revealing a stabilized performance without the need of detailed stack properties knowledge.

Further Insights into PEMFC Stack Degradation Modes Depending on Operating Strategies

Proton Exchange Membrane Fuel Cell (PEMFC) technologies are considered as a promising and clean energy supply for both transportation and stationary applications. Whereas the overall electrical performances and power densities have now reached most of the targeted specifications for integration, the overall durability and cost are still major hurdles to the mass market. The mechanisms of performances loss under PEMFC operation on individual components (catalyst, membrane, gas diffusion layer) are well-known in the literature at the material or small electrode scales. However in real stack configuration, the degradations may be strongly accelerated and localized since all phenomena are highly inter-correlated and very dependent of both the stack/cell designs and the operating conditions. The decrease in performances (under continuous or cycling modes) is composed of both irreversible losses (essentially due to materials degradations) and reversible losses which are attributed to the evolution of cell water management and electrode pollution (CO-like contamination, Pt-oxide formation) over time. Long stop phases make it possible to rejuvenate these reversible degradations but may not always be convenient or possible according to the applications or user needs. Developing reliable operation strategies either to recover or avoid reversible performance loss are necessary to adjust system dimensioning and prevent from using oversized stacks. When considering particularly the reversibility losses hypothetically caused by PtOx formation at high cathode potential, a modification during a short period of local conditions enabling to remove the oxides can be proposed to stabilize the performances [1]. Air-starvation have already been studied at single cell level to regenerate the reversible losses in Direct Methanol Fuel Cell (DMFC) [2] but the impact on the long-term durability remains uncertain. Our work is thus on PEMFC stack operation under both automotive Fuel Cell Dynamic Load Cycles (FC-DLC) and stationary conditions at fixed load to evaluate and discuss the interest and reliability of transient and repeated air-starvation periods. Start-up and shut-down protocols must also be taken into account since they can cause harsh degradation phenomena in the fuel cell caused by the so-called reverse current mechanism arising from the H2|O2 (or air) front at the anode side. Since this configuration is hardly avoidable after long stops in real systems, mitigation strategies must also be developed to enhance the lifetime of the PEMFC stack despite the embedded system integration constraints. In this perspective, we determined in-situ current density distribution mapping using an S++® equipment inside our stack in order to localize the degradation under repetitive fuel starvation conditions. Based on the degradation mapping, we propose to discuss the possibility to tune and adapt the 2D/3D structure and composition of the Membrane Electrode Assembly to modify internal current distribution and mitigate corrosion phenomena within the cells.

Effect of polarization on Sr and Zr diffusion behavior in LSCF/GDC/YSZ system

To accurately evaluate the role as diffusion barrier of gadolinia-doped ceria (GDC) interlayer, often used in real stacks of solid oxide fuel cells, the cation diffusion behavior in a LSCF/GDC/YSZ system was investigated. Diffusion under open circuit voltage (OCV) and cathodic polarization conditions was evaluated using pellet-type cells in which a dense GDC interlayer, about 1μm in thickness, was prepared by pulse laser deposition (PLD). Results clearly show that under polarization, SrZrO3 formation along both LSCF/GDC and GDC/YSZ interfaces is accelerated. The enhancement of Sr diffusion during cathodic polarization is explained by a shift to higher values of the thermodynamic activity of Sr at the LSCF/GDC interface that also leads to a decrease in oxygen potential.

Glass coated compressible solid oxide fuel cell seals

With the growing footprint of solid oxide fuel cell stacks, there is a need to extend the operating range of compressible gaskets towards lower stress levels. This article describes a method to manufacture SOFC seals by coating a compressible sealing material (Thermiculite 866) with glass to obtain good sealing performance even at compression stresses as low as 0.1 MPa. Glass layer can be coated using an organic carrier consisting of terpineol, ethanol and ethyl cellulose. The coated seals can be heat treated by simply ramping the temperature up to operating temperature at 60 Kh−1 and therefore no extra steps, which are typical to glass seals, are required. Coated seals were manufactured using this route and evaluated both ex-situ and in a real stack. Leak rates of 0.1–0.3 ml (m min)−1 were measured at 2–25 mbar overpressure using 50/50 H2/N2. A 30-cell stack was manufactured and tested using coated seals. At nominal operating conditions of 0.25 A cm−2 and 650 °C average cathode temperature, 46% fuel utilization and 20% air utilization the stack had a total hydrogen cross leak of 60 ml min−1 corresponding to 0.7% of the inlet hydrogen flow rate.

Effect of Contact Method between Interconnects and Electrodes on Area Specific Resistance in Planar Solid Oxide Fuel Cells

AbstractIn this work, interconnect/electrode sheet/interconnect sandwiches are assembled by designing interfacial contact between interconnects and electrodes for planar solid oxide fuel cells (SOFCs). Their area specific resistance (ASR) values of different contact methods under isothermal oxidation and thermal cycling are recorded by four‐point method. The ASR of SUS430/Ni–YSZ/SUS430 anode sandwich with NiO current collecting layer is close to that of anode sandwich without NiO current collecting layer during isothermal operation, but smaller and more stable during thermal cycling. Meanwhile, the lowest ASR is obtained in SUS430/LSM–YSZ/SUS430 cathode sandwich with LSM coated interconnect and LSM current collecting layer among various contact methods between interconnects and cathodes, and remains constant under isothermal oxidation and thermal cycling. Contact resistance between cathodes and interconnects is the main source of the SOFC stack resistance. A real stack with three anode‐supported cells is assembled and tested under thermal cycling to verify the effect of different contact methods between interconnects and electrodes on performance of stack repeating unit. The degradation rate and ASR values of repeating unit inside the stack indicate that the contact between LSM coated interconnect and LSM current collecting layer on cathode side is the optimized contact.

Peak load prediction of multi-pin joints FRP laminates by limit analysis

The paper presents a wide range of numerical findings aimed at validating a design methodology founded on the application of two Finite Element based limit analysis numerical procedures, namely the Linear Matching Method and the Elastic Compensation Method. Such methodology is here used to determine upper and lower bounds to the peak load multiplier of multi-pin joints composite laminates. In modeling the composite orthotropic material a Tsai–Wu type yield criterion is utilized, while the real stacking sequence of the laminate is considered applying the limit analysis procedures at lamina (layer) level. The obtained results on real prototypes, by comparing numerical tests against experimental (laboratory) ones, seem to prove the ability of the proposed approach to bracket the real peak load value of the examined structural elements.

Influence of protective layers on SOFC operation

Corrosion kinetics of ferritic alloys/steels (Crofer22APU, ITMLC, ZMG232L) were studied at high temperature. An extent of corrosion was evaluated by measuring the oxide scale thickness and the weight gain as a function of heating time. It is shown that even porous layer applied to interconnect can significantly reduce the rate of the steel oxidation. Contribution of the “oxide component” into the total degradation of the SOFC stack performance is estimated. Different protection materials and combinations were tested to analyze their influence on the processes of high temperature oxidation and long-term degradation of Fe-Cr steels. It has been shown that “more soft” materials on the basis of spinels (Mn(Co1 − x Fe x )2O4, Cu1 − x Ni x Mn2O4) are most suitable materials for the use as protective layers in comparison to perovskites. The efficiency of different protective materials was also tested in the real SOFC stacks designed in cooperation with company Staxera GmbH. It has been shown that applied spinel materials can effectively increase the long-term stability of the SOFC stacks.

Current Status of NEDO Project on Durability/Reliability of Solid Oxide Fuel Cell Stacks/Systems

Fundamental investigations on the durability and reliability of SOFC modules/stacks have started as one of the new NEDO SOFC project from 2008 to 2013. The main target is to make sure the long term durability in the range of 40,000 h and reliability during 250 times of starting up and ending operation mode; for this purpose, it needs to adopt the accelerating methods for establishing durability and reliability. This project consists of industrial developers, public research institutes and universities. Investigations will be made using real stacks, real cells and single model cells to facilitate the cooperation among three parties. Industrial developers will focus on the test of durability and reliability using real stacks, whereas universities and research institutes will focus on the fundamental understanding on degradation using various kinds of cells from various different approaches based on thermodynamic, chemical, and mechanical aspects; since three phase boundaries are important in understanding of degradation in electrochemical performance, special emphasis will be paid on this research topics. Prediction of life is also important topics in this project on durability and reliability.

Phase Transformation of Stabilized Zirconia on SOFC Stacks

The phase transformation of cubic stabilized zirconia in real SOFC stacks, especially in regions along the anode/electrolyte interface, was investigated by micro-Raman spectroscopy. In some real stacks, phase transformation of cubic stabilized zirconia into tetragonal phase was observed at the electrolyte/anode interface and/or in the anode after long time operation. On the other hand, in electrolyte, phase transformation was rarely observed. Bearing in mind the possible effect of Ni dissolution on phase transformation of zirconia, in parallel, a study was also carried out. NiO doped cubic zirconia was partially transformed into tetragonal phase, but transformation was not observed for cubic zirconia without NiO dissolution. It was clear that phase transformation was enhanced by NiO dissolution into the cubic stabilized zirconia.

SOFC 5 kWe CHP Field Unit: Effect of the Methane Dilution

AbstractTurboCare and Politecnico di Torino (Italy) have installed an SOFC laboratory in order to analyse the operation of two SOFC generators (Project EOS‐100 kW and EBE‐5 kW) built by Siemens Power Corporation (SPC). In the EBE project the installation of the SFC5 SOFC generator (3.5 kWe and 3 kWth) was carried out. To date, it has operated in the workshop canteen for more than 15,984 h with very high reliability.The real stack is a complex system not installed in a laboratory environment, and has several effects of non‐homogeneity in terms of electrochemical response to fuel or air management modifications. Moreover, many of the parameters of the stack are not directly measurable, and have to be inferred by indirect measurements.In this paper, the analysis of the non‐homogeneous behaviour of the different segments of the complete stack is performed, through an experimental session using a non‐conventional fuel.The obtained data have been analysed using the ANOVA for every dependent variable and a non‐linear regression model for the voltage. Those models were used to evaluate the effect of the fuel modification on the local fuel utilisation in different sectors of the stack.

RedOx study of anode-supported solid oxide fuel cell

The common technology for solid oxide fuel cells (SOFC) is based on a cermet anode of nickel with yttrium stabilized zirconia (YSZ), often used as the supporting structure. One of the main limitations of this anode technology is the redox tolerance. In this study, two techniques are used to quantify the anode expansion after one redox cycle at different temperatures. First, the increase of porosity is measured using scanning electron microscopy (SEM) image quantification. The second method considers the anode expansion above the electrolyte fracture limit by measuring the crack width in the electrolyte layer. An influence of redox cycling temperature on anode volume expansion was already observed by Ettler et al. but not fully understood. Here a model based on nickel oxidation mechanisms is proposed to explain the relation between redox temperature and volume expansion. The same methods are used to quantify anode expansion after consecutive redox cycles at constant temperature. In particular, small cracks caused at low oxidation temperature (600°C) were closed again after a subsequent reduction. The quantifying technique is then applied to cells tested in real stack conditions. The cell corners can undergo redox cycles depending on stack design and fuel utilization. The study of this location can give information on the number of cycles experienced by the anode support. Moreover, cracks in the electrolyte show infiltration of NiO that close the openings. Important infiltration can produce a short circuit between anode and cathode. The presence of strontium chromate on the infiltrated NiO was observed.

Thermofluid-Dynamic Analysis of Circular-Planar Type Intermediate-Temperature Solid Oxide Fuel Cells

This work presents a computational thermofluid-dynamic analysis of circular-planar type intermediate-temperature solid oxide fuel cells (SOFCs), based on the Hexis design. A single cell, representative of the average conditions of a real stack, is simulated in detail considering the real anode and cathode channel design, featuring an array of square pegs supporting the interconnection layers. The analysis is developed starting from cell operating data assumed from real test experimental information for an anode-supported SOFC with a 100cm2 active area, fed with pure hydrogen, and is extended to different reactant flow rates and generated heat flux power densities to evidence a generalized correlation for the thermofluid-dynamic behavior of the fuel cell under variable operating conditions. Aiming to provide a set of general results for the calculation of the heat transfer coefficient, which is applicable for the purpose of a complete thermal and electrochemical finite volume analysis, the simulation calculates local temperature distributions depending on radial and angular positions. The fluid-dynamic analysis evidences the existence of preferential flow paths and nonuniformity issues of the gas flow field, which may affect significantly the cell performances, and indicates possible cell design improvements.

Development of a Three-Dimensional Molten Carbonate Fuel Cell Model and Application to Hybrid Cycle Simulations

In this paper, a three-dimensional finite volume model of a molten carbonate fuel cell (MCFC) is presented. The model applies a detailed electrochemical and thermal analysis to a planar MCFC stack of given geometry and assigned input flows conditions, material properties and assigned external heat losses, calculating global energy balances and reactant utilization, as well as internal temperature and chemical composition profiles, pressure profiles, polarization losses, and current density and voltage distribution over the stack. The model is calibrated on the available data for an experimented MCFC stack manufactured by Ansaldo Fuel Cells. The comparison of 2D versus 3D simulations is first discussed, showing the importance of the 3D model for an accurate analysis of real stack operation under significant heat loss conditions, but also showing the mutual influence of heat transfer between adjoining cells and evidencing the variable electrical performances between different cells of the same stack. As a counterpart, application of the 2D model, which takes advantage by much shorter calculation time while keeping a reasonable accuracy in the overall energy balances, is anyway indicated for complex cycle analysis and cycle optimization, where a complete 3D stack analysis may be limited to selected cases. Then, the model is applied to the off-design analysis of hybrid cycles based on a recuperated gas turbine arrangement where variable pressure ratios and fuel supply conditions are assumed for the fuel cell. The effects of the operating pressure and of the adoption of different fuel compositions are considered, with a cycle layout that may include natural gas reforming or is directly fed by a syngas provided by an external source, simulating different fuel feedstocks (e.g., coal gasification). Complete results are presented, in terms of fuel cell and overall cycle performances.

Optimizations of stacking sequence and number of plies for laminated cylinders using GA with intron genes

For the method to optimize stacking sequences and number of plies of composites, the present paper proposes a new intron method. The intron method is developed from the recessive gene like repair method that is employed for implements of stacking-sequence constraints without causing decrease of the design reliability of GA. The intron method is attempted for the optimizations of laminated cylinders to maximize the buckling load and to minimize the number of plies. As a result, the intron method successfully obtained the real optimal stacking sequences and the number of plies without decrease of design reliabilities.