Concept for Temperature-Cascade Hydrogen Release from Organic Liquid Carriers Coupled with SOFC Power Generation

For a sustainable hydrogen economy, large-scale transportation and storage of hydrogen becomes increasingly important. Typically, hydrogen is compressed or liquified, but both processes are energy intensive. Liquid organic hydrogen carriers (LOHCs) present a potential solution for mitigating these challenges while making use of the existing fossil fuel transportation infrastructure. Here, we present a process intensification strategy for improved LOHC dehydrogenation and an example of clean power generation using solid oxide fuel cells. Four LOHC candidates???ammonia, biphenyl-diphenylmethane eutectic mixture, N-phenylcarbazole, and N-ethylcarbazole???have been compared as stand-alone and integrated systems using comprehensive process simulation. ???Temperature cascade??? dehydrogenation was shown to increase the energy generated per unit mass (kWh/kg LOHC) by 1.3???2 times in an integrated system compared to stand-alone LOHC systems, thus providing a possibility for a positive impact on a LOHC-based hydrogen supply chain. ?? 2020 The Author(s)Liquid organic hydrogen carriers (LOHCs) are a potentially safer alternative to conventional hydrogen storage processes. Here, Brigljevi?? et al. select four similar LOHC compounds and exploit differences in their physical chemistry, presenting the concept of a temperature-cascading process for a more energy-efficient dehydrogenation. ?? 2020 The Author(s

Quasi-three dimensional dynamic modeling of a proton exchange membrane fuel cell with consideration of two-phase water transport through a gas diffusion layer

Water management is one of the challenging issues for low-temperature PEMFCs (proton exchange membrane fuel cells). When liquid water is formed at the GDL (gas diffusion layer), the pathway of reactant gas can be blocked, which inhibits the electrochemical reaction of PEMFC. Thus, liquid water transport through GDL is a critical factor determining the performance of a PEMFC. In present study, quasi-three dimensional dynamic modeling of PEMFC with consideration of two-phase water transport through GDL is developed. To investigate the distributions of PEMFC characteristics, including current density, species mole fraction, and membrane hydration, the PEMFC was discretized into twenty control volumes along the anode channel. To resolve the mass and energy conservation, the PEMFC is discretized into eleven and fifteen control volumes in the perpendicular direction, respectively. The dynamic variation of PEMFC characteristics of cell voltage, overvoltage of activation and ohmic, liquid water saturation through a GDL, and oxygen concentration were captured during transient behavior. (C) 2015 Elsevier Ltd. All rights reserved.N

Dynamic simulation of a fuel cell hybrid vehicle during the federal test procedure-75 driving cycle

The dynamic behavior of a proton exchange membrane fuel cell (PEMFC) system is a crucial factor to ensure the safe and effective operation of fuel cell hybrid vehicles (FCHVs). Specifically, water and thermal management are critical to stabilize the performance of the PEMFC during severe load changes. In the present study, the FCHV dynamic model is developed. The dynamic model of the PEMFC system developed by Matlab-Simulink (R) is integrated into the electric vehicle model embedded in the Amesim (R). The dynamic model of the PEMFC system is composed of a PEMFC stack, an air feeding system, and a thermal management system (TMS). The component models of PEMFC, a shell-and-tube gas-to-gas membrane humidifier, and a heat exchanger are validated via a comparison with the experimental data. The FCHV model is simulated during a federal test procedure (FTP)-75 driving cycle. One system configuration and control strategy is adopted to attain optimal water and thermal management in the PEMFC system. The vehicle speed obtained from the FCHV model aptly tracks the target velocity profile of the FTP-75 cycle within an error of +/- 0.5%. The dynamic behavior and correlation of each component in the PEMFC system is investigated. The mass and heat transfer in the PEMFC, a humidifier, and a heat exchanger are resolved to determine the species concentration and the temperature more accurately with discretization in the flow's perpendicular direction. Discretization in the flow parallel direction of humidifier and heat exchanger model makes it possible to capture the distribution of the characteristics. The present model can be used to attain the optimization of the system and control design for the PEMFC system in FCHVs. (C) 2015 Elsevier Ltd. All rights reserved.N

A spatially resolved physical model of an ion transport membrane reactor for system development

The ion transport membrane (ITM) reactor has been developed as a potential novel syngas production technology that includes both air separation and fuel conversion. To successfully commercialize the ITM reactor, it is necessary to optimize its operation. In this study, a spatially resolved physical model of the ITM reactor for syngas production has been developed to investigate the ITM reactor characteristics using Aspen Plus((R)), which will be extended to the system level simulation. The approach captures spatial variations in the crucial physics of heat transfer, oxygen permeation and reaction kinetics in a manner that is simple enough to make the model amenable to ITM reactor system simulations development. To simulate the partial oxidation of methane (POM), methane oxidation, steam reforming of methane, and dry reforming of methane have been considered. By varying the carbon space velocity, CH4 conversion, CO selectivity, H-2-CO ratio, and species molar flow rates have been calculated. Moreover, oxygen partial pressure and temperature distribution on the feed and sweep sides are presented in the paper. This study provides the basic insight to establish the optimal system designs and operating schemes of the ITM reactor by analyzing the reaction kinetics distribution of the POM and oxygen permeation rates.N

Numerical analysis of an ion transport membrane system for oxy-fuel combustion

Ion transport membranes (ITM) have been studied as a promising air separation unit (ASU) technology for oxy-fuel combustion owing to their high oxygen permeability. Even though the power consumption of the ITM is lower than that of cryogenic ASU, it still consumes a high proportion of the overall system power. In this study, a numerical analysis of the ITM system has been conducted using Aspen Plus (R) to determine the optimal system design for minimizing the power consumption to separate oxygen from air. Since the oxygen permeation through the ITM is driven by the oxygen partial pressure gradient between feed and permeation side, three ITM systems that have different pressure gradients across the membrane have been presented and their performances compared. The effects of the contributing parameters, such as thickness, pressure, temperature, and air flow rate on the oxygen permeation rate have been investigated. ITM performances of the counter and parallel flow configurations have been compared. The system that operates under atmospheric pressure at the feed channel and under vacuum pressure at the permeate channel yields the lowest power consumption for obtaining the same oxygen permeation rate among other pressure conditions.N

Data from: Enhanced cycle stability of a NiCo2S4 nanostructured electrode for supercapacitors fabricated by the alternate-dip-coating method

Nanostructured nickel cobalt sulfide (NiCo2S4) electrodes are successfully fabricated using a simple alternate-dip-coating method. The process involves dipping a TiO2 nanoparticles-covered substrate in a nickel/cobalt precursor solution and sulfur precursor solution alternately at room temperature. The fabricated bimetallic sulfide electrode exhibits a synergetic improvement compensating for the disadvantages of the two single metal sulfide electrodes, i.e. the poor cycle stability of the nickel sulfide electrode and the low specific capacitance (C) of the cobalt sulfide electrode. The two capacitive properties are optimized by adjusting the ratio of nickel and cobalt concentrations in the metal precursor solution, reaching a C of 516 F/g at a current density of 1 mA/cm2 and its retention of 99.9 % even after 2000 galvanostatic charge-discharge cycles

Cycle life of nanostructured metal sulfide electrodes

Specific capacitance values after various numbers of galvanostatic charge-discharge cycles for the nanostructrued NiS, Co3S4 and NiCo2S4 electrodes

Dynamic modeling and verification of a proton exchange membrane fuel cell-battery hybrid system to power servers in data centers

Dynamic performance of a 10-kW proton exchange membrane fuel cell (PEMFC) battery hybrid system to power servers in data centers has been experimentally evaluated in our previous work [1]. The present work is a numerical study based on the previous work to identify the dynamic characteristics and present basic insights for the system control strategy during transients. The hybrid system dynamic model has been developed using the MATLAB Simulink, which consists of a one-dimensional, two-phase dynamic model of the PEMFC, lumped dynamic model of an air blower and a battery. The system model is verified by comparing the dynamic behavior of the power generated by the PEMFC and battery with the experimental data at the step change of the system demand power between 0 and 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 kW. During the step load increases, the system instantly obtained the total amount of external load power from the battery within 0.1 s in every case and gradually decreased until approximately 4 s or 6 s as the power generated by the fuel cell is gradually increased. The dynamic response of the system model is compared with the experimental data at various load profiles of three, six, and nine servers. (C) 2019 Elsevier Ltd. All rights reserved.N

Specific capacitance values measured at various current densities

Specific capacitance values measured at various current densities for the nanostructrued NiS, Co3S4 and NiCo2S4 electrodes fabricated by the alternate dip coating metho

Dynamic modeling of a proton exchange membrane fuel cell system with a shell-and-tube gas-to-gas membrane humidifier

The proton exchange membrane fuel cell (PEMFC) system with a shell-and-tube gas-to-gas membrane humidifier is considered to be a promising PEMFC system because of its energy-efficient operation. However, because the relative humidity of the dry air flowing into the stack depends on the stack exhaust air, this system can be unstable during transients. To investigate the dynamic behavior of the PEMFC system, a system model composed of a lumped dynamic model of an air blower, a two-dimensional dynamic model of a shell-and-tube gas-to-gas membrane humidifier, and a one-dimensional dynamic model of a PEMFC system is developed. Because the water management during transient of the PEMFC system is one of the key challenges, the system model is simulated at the step change of current. The variations in the PEMFC system characteristics are captured. To confirm the superiority of the system model, it is compared with the PEMFC component model during transients.N