Stack System Research Articles

Deep Reinforcement Learning Guided Cascade Control for Air Supply of Polymer Exchange Membrane Fuel Cell

The power consumption of an electric air compressor becomes the major parasitic energy waste leading to the deterioration of net efficiency of the fuel cell system (FCS). Optimal control of the oxygen excess ratio (OER) is recognized as a feasible way to resolve the paradox of stack health and system efficiency. Herein, a novel cascade control scheme that leverages model predictive control (MPC), fuzzy Proportion Integral control (FPI), and deep reinforcement learning technique is proposed to regulate the OER for a 75 kW FCS. The master‐slave control structure is adopted, and a reference air mass flow rate and the motor voltage of the air compressor are taken as control targets, respectively. A deep deterministic policy gradient (DDPG) algorithm is used as a parameter tuner for MPCProportion Integral (PI) controller. The results indicate that both MPCFPI and DDPGMPCPI can achieve better control performance indices in comparison to classic controller under step response and a typical driving cycle. The DDPG‐guided cascade controller is also capable of regulating the OER tracking error and the derivative of rotation speed of the air compressor, which reveals the potential for extending the longevity of the FCS.

Ground simulation of fuel cell/battery hybrid propulsion system for small unmanned air vehicles

PurposeThe endurance of small unmanned air vehicles (UAVs) is directly associated with the energy density of the propulsion system used. As the batteries commonly used in small UAVs have a relatively low energy density, they are not sufficient for long-term endurance tasks. The purpose of this paper is to offer a solution to increase the endurance of a concept small UAV with combination of different power sources. The design, construction and ground tests of fuel cell-powered hybrid propulsion systems are presented in this paper.Design/methodology/approachThe power requirements of a concept UAV were calculated according to aerodynamic calculations and then, hybrid propulsion system sources are determined. The hybrid system consists of a 100 W scale proton-exchange membrane (PEM) type fuel cell stack, lithium-polymer battery, solar cells and power management system (PMS). Subsequently, this hybrid power system was integrated with the new design of PMS and then series of ground tests were carried out.FindingsThis experimental study proved that it is theoretically possible to obtain an endurance of around 3 h for concept UAV with the proposed hybrid system.Practical implicationsThe research study shows that fuel cell-based hybrid propulsion system with the proposed PMS can be widely used to obtain extended endurance in small UAVs.Originality/valueA hybrid propulsion system with a novel PMS unit is proposed for small UAVs and the ground tests were implemented.

Results of the measurement of SOFC fuel cell stacks under pressure conditions

Results from the measurement of SOFC fuel cell stacks under pressure conditions are presented. As part of a measurement campaign, the operation of a stack system is investigated, particularly under the operating conditions of a recuperated micro gas turbine. Above all, the performance and effectiveness of selected stack types at various operating pressures and operating temperatures are measured. With the test facility set up for such investigations, cell systems could be examined under atmospheric conditions and with pressures of up to 5 bar.It is shown that in operating conditions under pressure, the output of the fuel cell systems are improving. From a gauge pressure of 4 bar, the performance curve is flattened and higher pressures only produced a marginal increase in performance. Furthermore, the cells tested at overpressure show a steady-state behavior more quickly under load change requirements than in atmospheric operation. This means that more flexible operating modes with faster response behavior can be realized. By choosing a suitable operating temperature, the efficiency of the system is further increasing. Care was taken to select the operating conditions of the cell systems so that coking can be prevented.Finally, a statement can be made about the pressure dependence of the fuel conversion rate. Parasitic reactions at the anode can be related to the power output. The tests carried out have shown that the high-temperature fuel cell is a promising service provider of the future. A combination of SOFC high-temperature fuel cells and micro gas turbines in one machine could, in addition to the internal provision of the required pressure, also lead to better dynamics of the entire system and increase the energy yield from the primary energy source.

ALC中層集合住宅専用排水立て管システムの提案と性能評価 （その2）排水横主管の拡径に伴う適用階数の検討

ALC中層集合住宅専用排水立て管システムの提案と性能評価 （その2）排水横主管の拡径に伴う適用階数の検討

ALC中層集合住宅専用排水立て管システムの提案と性能評価 （その1）通気方式の違いによる排水性能への影響

ALC中層集合住宅専用排水立て管システムの提案と性能評価 （その1）通気方式の違いによる排水性能への影響

Model identification of the Proton Exchange Membrane Fuel Cells by Extreme Learning Machine and a developed version of Arithmetic Optimization Algorithm

The major purpose of this study is to provide a proper approach for model identification of the Proton Exchange Membrane Fuel Cells (PEMFCs) to use in different applications. The method introduces a modified version of the Extreme Learning Machine (ELM) model for identification purposes. The modification is based on proposing and designing a new improved metaheuristic, called the developed Arithmetic Optimization Algorithm (dAOA). The algorithm is then verified by various algorithms to demonstrate its effectiveness and is then employed for optimizing the ELM configuration with the aim of minimizing the sum of the square error between the output voltage of the real PEMFC data and the output voltage achieved by the network. Simulation results of the proposed system are validated based on four scenarios that their results are as follows: for 3/5bar with 353.15 K, the maximum training error for dAOA and AOA are 6.01 and 9.899, respectively. For 1/1bar with 343.15 K, the maximum training error for dAOA and AOA are 0.0045 and 0.012, respectively. For 2.5/3bar with 343.15 K, the maximum training error for dAOA and AOA are 0.0132 and 0.0177, respectively, and for 1.5/1.5 bar with 343.15 K, the maximum training error for dAOA and AOA are 0.01and 0.01584, respectively. This shows the better results of the proposed dAOA to provide accurate parameters of the PEMFC stack system.

Control system of 4-DOF palletizing robot based on improved R control multi-objective trajectory planning

To realize efficient palletizing robot trajectory planning and ensure ultimate robot control system universality and extensibility, the B-spline trajectory planning algorithm is used to establish a palletizing robot control system and the system is tested and analyzed. Simultaneously, to improve trajectory planning speeds, R control trajectory planning is used. Through improved algorithm design, a trajectory interpolation algorithm is established. The robot control system is based on R-dominated multi-objective trajectory planning. System stack function testing and system accuracy testing are conducted in a production environment. During palletizing function testing, the system’s single-step code packet time is stable at approximately 5.8 s and the average evolutionary algebra for each layer ranges between 32.49 and 45.66, which can save trajectory planning time. During system accuracy testing, the palletizing robot system’s repeated positioning accuracy is tested. The repeated positioning accuracy error is currently 10−1 mm and is mainly caused by friction and the machining process. By studying the control system of a four-degrees-of-freedom (4-DOF) palletizing robot based on the trajectory planning algorithm, the design predictions and effects are realized, thus providing a reference for more efficient future palletizing robot design. Although the working process still has some shortcomings, the research has major practical significance.

Microfluidic Overhauser DNP chip for signal-enhanced compact NMR

Nuclear magnetic resonance at low field strength is an insensitive spectroscopic technique, precluding portable applications with small sample volumes, such as needed for biomarker detection in body fluids. Here we report a compact double resonant chip stack system that implements in situ dynamic nuclear polarisation of a 130 nL sample volume, achieving signal enhancements of up to − 60 w.r.t. the thermal equilibrium level at a microwave power level of 0.5 W. This work overcomes instrumental barriers to the use of NMR detection for point-of-care applications.

Experimental and numerical investigation on dynamic response of a four-tier container stack and lashing system subject to rolling and pitching excitation

This research aims to investigate the dynamic responses of the lashing force, twist lock force, and container stack displacement under conditions close to real, providing a better understanding of the mechanism behind container damage and loss. Based on Froude scaling laws, a four-tier 20-ft ISO freight container stack and lashing assembly scaled model was built. The rolling and pitching driving excitation is provided by a shaking table. Input variables for the experimental and numerical simulation include driving excitation (amplitude and frequency), lashing methods (internal and external), twist lock gap (horizontal and vertical), contact and friction between adjacent corner castings. Output variables of the system contain the lashing force, twist lock's tensile and shear force as well as displacement of the container stack. The results of the present study are compared via numerical simulation, experiments, and theoretical calculations, suggesting that the external lashing is superior to the internal lashing when encountering high stack and heavy stowage. There are mutual coupling effects between the lashing methods, lashing force, twist lock force and twist lock gap. Moreover, decreasing the gap can minimize the stack displacement and lashing force, while it is not a viable solution to reduce the twist lock force.

Numerical modeling and analysis of the effect of pressure on the performance of an alkaline water electrolysis system

Hydrogen is considered a promising green energy carrier due to its long storage period and zero harmful emissions. The green hydrogen produced by water electrolysis using renewable energy is indispensable for expanding the renewable energy grid and establishing a clean energy society. As renewable power sources are widely deployed, hydrogen can be utilized to connect the energy demand section with the energy supply section. To transport hydrogen to demand sites, one of the most common commercial methods is hydrogen compression. Notably, high-pressure water electrolysis does not need to additionally compress hydrogen, which can significantly diminish the cost of hydrogen production. In this study, to evaluate the effect of the operating pressure on the performance of an alkaline water electrolysis (AWE) system, a numerical model of the AWE system was developed using Aspen Plus®. The AWE system is comprised of the AWE stack, water pumps, heat exchangers, separator, condenser, and electric heat pump (EHP) system. The AWE stack model is validated by comparing the current–voltage polarization curve with experimental data. Simulation results show that an appropriate pressure makes the system more efficient due to decreasing the power consumption of the balance of plant (BOP). Furthermore, high-pressure water electrolysis has a large advantage for obtaining high-purity hydrogen (over 99.9%) without using a water adsorption device.

Polarization analysis of a micro direct methanol fuel cell stack based on Debye-Hückel ionic atmosphere theory

In this paper, a micro direct methanol fuel cell (μDMFC) stack model is developed in order to analyze the polarization characteristics. The model employed the Debye-Hückel ionic atmosphere theory to describe the charge conductions and electrochemical kinetics during the polarization coupling. The simulated current-power profiles of the model are verified experimentally. Compared with the μDMFC stack model based on conventional polarization theory, the error of the proposed μDMFC stack model reduces by about 8% at average. For every 10 mol · m−3 increase in cathodic oxygen concentration, the increase in polarization coupling efficiency alone can improve the output power by about 2% on average. The increase of operating temperature from 293 K to 333 K weakens the coupling forces within the μDMFC stack. The analyzing results of dynamic operation show that the polarization coupling causes a voltage peak during unloading. High loading current and unloading speed raise the voltage peak. The energy loss caused by methanol crossover decreases during dynamic operating process. The dynamic energy conversion efficiency of the μDMFC stack is relatively high. The proposed μDMFC stack model solves the polarization coupling problem and makes it possible to analyze the polarization coupling between μDMFC stack and modern microelectronic portable systems.

Thermal and Mechanical Analyses of Clamping Area on the Performance of Press-Pack IGBT in Series-Connection Stack Application

Press-pack insulated gate bipolar transistors (PP-IGBTs) are commonly connected in series and stacked together with heatsinks using an exterior clamping fixture in order to achieve high-voltage dc-link levels. A suitable contact area between the clamping fixture and the device is essential to ensuring optimal PP-IGBT thermomechanical performance, especially for the first and last devices in a stack. In this study, the effects of the clamping area on collector deformation, temperature, and stress distributions are investigated by means of the finite-element method (FEM). Moreover, this article analyzes the influence of heatsink thickness to maximize the stress evenness of the terminal PP-IGBT and reduce the overall length of the stack system. The results indicate that the collector lid is prone to warpage due to thermal expansion, which results in a decrease in the effective contact area between component layers. As the contact resistance increases, the chips accumulate considerable heat. Increasing the clamping area at this point can adequately compensate for the warp deformation and can also improve the stress uniformity of the chips. Finally, an experiment making use of stress-sensitive film has been carried out to verify the developed FEM models.

Experimental Study on The Performance of FCV in Standard Test Cycle

The experiments of one FCV (Fuel Cell Vehicle) are conducted in three standard cycle conditions of NEDC (New European Driving Cycle), WLTC (Worldwide Light-duty Test Cycle) and CLTC (China Light-duty vehicle Test Cycle), and the performance of stack power, temperature and system efficiency are compared and analysed. Results show that the variation range of fuel cell system efficiency is ordered as: WLTC > NEDC > CLTC. The efficiency of fuel cell system is highest in CLTC; the fuel cell stack power and temperature are relatively low; the hydrogen consumption is lowest(0.93kg/100km). According to the analysis on experimental data of FCV in NEDC, the output power of stack is proportional to accelerator pedal when the accelerator pedal opening is greater than 25%.

Performance analysis of solid oxide fuel cell and micro gas turbine top-level cycle

First, a simulation model of the SOFC-MGT top-level combined cycle was established through Matlab/Simulink, and then the effect of different methane flow rates on the performance of the stack and the SOFC-MGT system was analyzed. The research results show that with the increase of methane flow, the power of the stack and SOFC-MGT system gradually increases, but the efficiency of the SOFC-MGT system gradually decreases with the increase of methane flow.

Thermal management of open-cathode proton exchange membrane fuel cell stack with thin vapor chambers

Proton exchange membrane fuel cell (PEMFC) is one of the most promising electricity-generating devices with zero pollution. However, a large amount of waste heat will be generated during the operation. The waste heat must be dissipated in time to prevent performance deterioration and irreversible damage. In this paper, a novel cooling strategy is proposed and implemented. Five thin vapor chambers (VCs) are integrated into a 10-cell open-cathode PEMFC stack to enhance its heat dissipation effect. PEMFC stack with VCs has been successfully fabricated and tested experimentally. Results show that VCs can effectively reduce the operating temperature of PEMFC and the minimum in-plane temperature difference can be reduced to 0.5 °C, which provides a reliable and stable thermal environment for safe operation. The effects of VCs on the through-plane and in-plane temperature distribution is studied and analyzed in detail. In addition, when the cathode air flow is small, the thermal management of the stack is significantly affected by the inclination angle. This study has fully demonstrated the feasibility of integrating VCs in PEMFC stack to improve thermal management, and provides guidance for designing and developing a better cooling system of PEMFC stack.

Study on electrolyte supply strategy for energy storage system of multi zinc nickel single flow battery stack loaded with single pump

Zinc nickel single flow battery (ZNB) has the advantages of low cost, low toxicity and long life, which is considered as one of the ideal choices for large-scale fixed energy storage. The efficient operation of ZNB is a necessary condition for maximizing system efficiency and safe operation. In this paper, a dynamic model of ZNB of single pump loaded with multi stack considering electrochemical reaction, mass transfer and hydraulic loss is constructed. Based on the principle of minimizing charging energy and maximizing discharge energy, the effects of electrolyte flow rate and current density on potential window and morphology of zinc deposition are considered, an adaptively adjusted electrolyte flow supply scheme is proposed. By considering the effect of flow rate on zinc deposition, the optimized electrolyte supply strategy can not only improve the system efficiency, but also effectively extend the service life of ZNB.

Representative sampling analysis of radioactive airborne effluent for the stack system in a molten salt reactor

During the operation of the molten salt reactor, the radioactive gas and radioactive aerosol particles will be generated, and should be discharged into the atmospheric environment through ventilation ducts and stacks after filtration and adsorption. In order to determine whether the radioactive airborne effluent emissions would meet the requirements of the National management limits (ISO 2889–2010), it is necessary to calculate and monitor the radioactive airborne effluents in the stack system. Therefore, a three-dimensional computational fluid dynamics (CFD) model is built to evaluate the flowing and mixing state for radioactive airborne effluent in the stack system of the molten salt reactor. The uniformities of velocity, cyclonic flow, tracer gas concentration, and aerosol particle concentration at different sampling heights in the stack are analyzed by CFD-Fluent. The results show that, the airflow and concentration of tracer gas easily tend to blend well at high flow speed, while there is a little random distribution effect for the aerosol particles due to their large densities, which needs a longer transport process to increase the uniformity. When the sampling height is above 11 m from the bottom of the stack, the variation coefficients of velocity, cyclonic flow, tracer gas concentration, and aerosol particle concentration are below 11.6%, 4.4%, 0.4% and 20% correspondingly, which all meet the well-mixed criteria and the requirement of representativeness sampling location in ISO 2889–2010. If the variation coefficient of aerosol particle concentration can be allowed to be less than 30%, then sampling height above 6 m will satisfy the ISO standard. The results of this study provide a good reference for the detection, sampling and analysis of radioactive gases and aerosol particles in the stack of the molten salt reactor.

Detailed insight into processes of reversible solid oxide cells and stacks using DRT analysis

This study demonstrates applicability of the distribution of relaxation times (DRT) methodology to reveal more precise analysis of processes that occur in solid-oxide fuel (SOFC) and electrolysis (SOEC) cells of industrial-size as well as 10-layer stacks. Initially, we show that before starting to interpret the data observed, it is necessary to verify the quality of the impedance data measured in order to be used for further analysis. For the purpose of experimental study, operating parameters were varied and their impact on the system performance was determined. When operating cells and stacks very similar specific frequencies were identified, whereby for the stack one additional peak was observed. In the fuel cell mode the main frequency ranges to link with the processes that occur were identified to be 0.01–5 Hz and 50–100 Hz. In the electrolysis mode, the DRT amplitudes observed are lower, but specific frequencies higher, even by a factor of 10. In addition, specific behaviour of DRT-peaks could be correlated to the morphological changes of the Ni-based fuel electrodes that occurred during the stability tests performed. Summarizing this, the results presented in this study show how to: (i) distinguish different processes, (ii) link the knowledge gained from the analysis of single-cell level and subsequently, (iii) transfer it to real stack system. Thus, this study also represents a guideline for a detailed electrochemical performance characterization of high temperature fuel cell and electrolysis systems using the sophisticated DRT tool.

Investigations on the dynamics of container stack and securing system under rolling motion using a scaled model test

ABSTRACT Currently, most existing studies and specifications for container stack and securing system are corresponding to static conditions. In this paper, we attempt to investigate the dynamic effects caused by hull movement on the stack and securing system. Based on Froude scaling laws, the four-tier 20-ft ISO container stack and lashing equipment scaled models are constructed. The physical and structural characteristics of the scaled models are determined by two dimensionless parameters: the gravity force/inertia force ratio, and the elastic force divided by inertia force. By inputting the sinusoidal excitation on the excitation device, a series of rolling tests were performed to study the effect of excitation, twist lock gap and payload on the dynamic response of the system. The experimental results are in a good agreement with the numerical simulation results. The results indicate that decreasing gap size and the proper cargo configuration can enhance the safety of the container stack.

VISUALIZING MULTILAYERED GEOSPATIAL DATA IN VIRTUAL REALITY TO ASSESS PUBLIC LIGHTING

Abstract. With the improvement and proliferation of virtual reality devices, their use for research and professional activity is broadening, fostering the advent of the field of immersive analytics, as is their acceptance among consumers. Other than the heightened sense of immersion into visualized data they provide, they also make displays of much larger apparent size and different positioning practical than what would be possible otherwise. Drawing on these benefits, we implemented a development of Multiple and Coordinated Displays (MCVs) for geovisualization that stacks different layers of data above each other, tilted for legibility. In a formal experiment, we evaluated it and two other, comparable MCV methods implemented in VR for their usefulness in analyzing public perception and soliciting public feedback regarding urban street lighting. In that field, the direction has recently been shifting from purely systemic development to a participatory approach, thus our investigation was into how a system like this could facilitate participation that can yield actionable results. Previous analysis of interaction data and usability questionnaires reveals preferences for certain systems depending on user characteristics, with the stack system showing a slight advantage over a grid of layers and especially over temporal multiplexing. We show that regardless of MCV variation, participants were able to analyze and provide feedback on public lighting situations that can directly contribute to urbanist work. The MCV approach further aided in understanding their choices, as eye-tracking allowed us to analyze attention to individual data layers.