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Article Citation - WoS: 9Citation - Scopus: 9Experimental and Modeling Studies of a High-Temperature Electrochemical Hydrogen Compressor(Pergamon-elsevier Science Ltd, 2024) Durmus, Gizem Nur Bulanik; Kuzu, Cemil; Devrim, Yilser; Colpan, C. OzgurSome non-technical factors such as economics and logistics prevent hydrogen (H2) tech-nologies from becoming more widespread in daily life. Today, the prevalence of H2 tech-nologies requires new technological developments. Electrochemical hydrogen compressors (ECHC) are of great interest due to their ability to pressurize and purify in one step. In this study, the electrochemical H2 compression performance of high phosphoric acid (PA) doped poly 2,2-m-phenylene-5,5-benzimidazole (PBI) membrane-based HT-ECHC under high temperature and non-humid conditions was investigated through both an experimental and a numerical approach. The H2 compression capacity of HT-ECHC at different operating voltages was examined by performance tests at 160 degrees C, and it was determined that the electrochemical compression performance increased with increasing operating voltage. It was observed that the current density values also increased with increasing voltage, and it was determined that a current density of 61.2 A was obtained at 1 V. As a result of the tests, H2 was successfully compressed from atmospheric pressure to 60 bar by HT-ECHC without any gas leakage. The results of the developed model were compared with the experimental performance test data, and the variation of molar flow, cell voltage, and cell efficiency over time was examined. It has been determined that the back diffusion from the cathode to the anode in the cell increases with the increasing operating voltage of HT-ECHC and therefore the cell efficiency decreases. It has been evaluated that the developed model and experimental results are in good agreement. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 13Citation - Scopus: 17Effect of hydrogen on fracture locus of Fe-16Mn-0.6C-2.15Al TWIP steel(Pergamon-elsevier Science Ltd, 2020) Bal, Burak; Cetin, Baris; Bayram, Ferdi Caner; Billur, ErenEffect of hydrogen on the mechanical response and fracture locus of commercial TWIP steel was investigated comprehensively by tensile testing TWIP steel samples at room temperature and quasi-static regime. 5 different sample geometries were utilized to ensure different specific stress states and a digital image correlation (DIC) system was used during tensile tests. Electrochemical charging method was utilized for hydrogen charging and microstructural characterizations were carried out by scanning electron microscope. Stress triaxiality factors were calculated throughout the plastic deformation via finite element analysis (FEA) based simulations and average values were calculated at the most critical node. A specific Python script was developed to determine the equivalent fracture strain. Based on the experimental and numerical results, the relation between the equivalent fracture strain and stress triaxiality was determined and the effect of hydrogen on the corresponding fracture locus was quantified. The deterioration in the mechanical response due to hydrogen was observed regardless of the sample geometry and hydrogen changed the fracture mode from ductile to brittle. Moreover, hydrogen affected the fracture locus of TWIP steel by lowering the equivalent failure strains at given stress triaxiality levels. In this study, a modified Johnson-Cook failure mode was proposed and effect of hydrogen on damage constants were quantified. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 25Citation - Scopus: 26Identifying the Potentials for Charge Transport Layers Free N-P Homojunction-Based Perovskite Solar Cells(Pergamon-elsevier Science Ltd, 2022) Khan, Danish; Sajid, Sajid; Khan, Suliman; Park, Jongee; Ullah, IhsanPerovskite solar cells (PSCs) with no charge transport layers (CTLs) could be one of the major device architectures for the production of simple and low-cost devices. However, CTLs-free PSCs based on n-p homojunction have yet to show high power conversion efficiency (PCE), which is most likely due to inadequate light-and charge-management in the p-type perovskite. The device operation is examined using Solar Cell Capacitance Simulator (SCAPS)-software, and a novel n-p homojunction design is proposed to attempt efficient CTLs-free PSCs. Several aspects of p-type layer that can affect device performance, such as acceptor density, photon harvesting capability, defects density, and resistances to the transport of charge-carriers are scrutinized and adjusted. Furthermore, the effects of different work-functions of metal electrodes are examined. A suitable acceptor concentration is required for oriented charge transport. It is determined that a p-type perovskite with a thickness of 0.3 mu m is advantageous for high performance. A metal electrode with a high work-function is essential for efficient device. Consequently, a PCE of 15.60% is obtained with an optimal defect density of E15 cm(-3), indicating that n-p homojunction-based CTLs-free PSCs are promising since they simplify the device design and fabrication process while retaining an acceptable PCE.Article Citation - WoS: 76Citation - Scopus: 76Composite Membrane by Incorporating Sulfonated Graphene Oxide in Polybenzimidazole for High Temperature Proton Exchange Membrane Fuel Cells(Pergamon-elsevier Science Ltd, 2022) Devrim, Yilser; Durmus, Gizem Nur BulanikThe objective of this work is to examine the polybenzimidazole (PBI)/sulfonated graphene oxide (sGO) membranes as alternative materials for high-temperature proton exchange membrane fuel cell (HT-PEMFC). PBI/sGO composite membranes were characterized by TGA, FTIR, SEM analysis, acid doping&acid leaching tests, mechanical analysis, and proton conductivity measurements. The proton conductivity of composite membranes was considerably enhanced by the existence of sGO filler. The enhancement of these properties is related to the increased content of -SO3H groups in the PBI/sGO composite membrane, increasing the channel availability required for the proton transport. The PBI/sGO membranes were tested in a single HT-PEMFC to evaluate high-temperature fuel cell performance. Amongst the PBI/sGO composite membranes, the membrane containing 5 wt. % GO (PBI/sGO-2) showed the highest HT-PEMFC performance. The maximum power density of 364 mW/cm(2) was yielded by PBI/sGO-2 membrane when operating the cell at 160 degrees C under non humidified conditions. In comparison, a maximum power density of 235 mW/cm(2) was determined by the PBI membrane under the same operating conditions. To investigate the HT-PEMFC stability, long-term stability tests were performed in comparison with the PBI membrane. After a long-term performance test for 200 h, the HT-PEMFC performance loss was obtained as 9% and 13% for PBI/sGO-2 and PBI membranes, respectively. The improved HT-PEMFC performance of PBI/sGO composite membranes suggests that PBI/sGO composites are feasible candidates for HT-PEMFC applications. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Review Citation - WoS: 120Citation - Scopus: 142Dynamic Thermal and Hygrometric Simulation of Historical Buildings: Critical Factors and Possible Solutions(Pergamon-elsevier Science Ltd, 2020) Akkurt, G. G.; Aste, N.; Borderon, J.; Buda, A.; Calzolari, M.; Chung, D.; Turhan, C.Building dynamic simulation tools, traditionally used to study the hygrothermal performance of new buildings during the preliminary design steps, have been recently adopted also in historical buildings, as a tool to investigate possible strategies for their conservation and the suitability of energy retrofit scenarios, according to the boundary conditions. However, designers often face with the lack of reliable thermophysical input data for various envelope components as well as with some intrinsic limitations in the simulation models, especially to describe the geometric features and peculiarities of the heritage buildings. This paper attempts to bridge this knowledge gap, providing critical factors and possible solutions to support hygrothermal simulations of historical buildings. The information collected in the present work could be used by researchers, specialists and policy-makers involved in the conservation of building's heritage, who need to address a detailed study of the hygrothermal performance of historical buildings thorugh dynamic simulation tools.Article Citation - WoS: 17Citation - Scopus: 18Optimal Design and Technoeconomic Analysis of On-Site Hydrogen Refueling Station Powered by Wind and Solar Photovoltaic Hybrid Energy Systems(Pergamon-elsevier Science Ltd, 2025) Ozturk, Reyhan Atabay; Devrim, YilserIn this study, a grid-connected on-site hydrogen filling station (HRS) integrated with renewable energy systems is designed and examined for different daily hydrogen refueling capacities. The installation location of the HRS is selected in Izmir (Turkey) and daily solar radiation and wind speed data are used in the calculations. The HRS station was integrated with a hybrid energy system using photovoltaic panels (PV), wind turbine (WT) and PV/ WT and five different daily refueling scenarios were investigated. A techno-economic analysis is conducted for the designed HRS system, considering the initial investment capital, installation and operating costs. The levelized cost of hydrogen (LCOH) is evaluated according to different refueling capacity scenarios, periods of operation and renewable energy installation capacities. The lowest LCOH is obtained as 4.5 /kg H2 in the PVintegrated HRS system for a 20-year investment scenario. The results prove the suitability of the HRS system for integrating renewable energy in the identified region. It is recommended to integrate analytical models for the system components to increase the reliability of the design and optimization process in future planned studies.Conference Object Citation - WoS: 30Citation - Scopus: 34Investigation of the effect of graphitized carbon nanotube catalyst support for high temperature PEM fuel cells(Pergamon-elsevier Science Ltd, 2020) Devrim, Yilser; Arica, Elif DamlaIn this study, it is aimed to investigate the graphitization effect on the performance of the multi walled carbon nanotube catalyst support for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. Microwave synthesis method was selected to load Pt nanoparticles on both CNT materials. Prepared catalyst was analyzed thermal analysis (TGA), Transmission Electron Microscopy (TEM) and corrosion tests. TEM analysis proved that a distribution of Pt nanoparticles with a size range of 2.8-3.1 nm was loaded on the Pt/CNT and Pt/GCNT catalysts. Gas diffusion electrodes (GDE) were manufactured by an ultrasonic spray method with synthesized catalyst. Polybenzimidazole (PBI) membrane based Membrane Electrode Assembly (MEA) was prepared for observe the performance of the prepared catalysts. The synthesized catalysts were also tested in a HT-PEMFC environment with a 5 cm(2) active area at 160 degrees C without humidification. This study demonstrates the feasibility of using the microwave synthesis method as a fast and effective method for preparing high performance Pt/CNT and Pt/GCNT catalyst for HT-PEMFC. The HT-PEMFC performance evaluation shows current densities of 0.36 A/cm(2)0.30 A/cm(2) and 0.20 A/cm(2) for the MEAs prepared with Pt/GCNT, Pt/CNT and Pt/C catalysts @ 0.6 V operating voltage, respectively. AST (Accelerated Stress Test) analyzes of MEAs prepared with Pt/GCNT and Pt/CNT catalysts were also performed and compared with Pt/C catalyst. According to current density @ 0.6 V after 10,000 potential cycles, Pt/GCNT, Pt/CNT and Pt/C catalysts can retain 61%, 67% and 60% of their performance, respectively. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 14Citation - Scopus: 14The Number of Failed Components in Series-Parallel System and Its Application To Optimal Design(Pergamon-elsevier Science Ltd, 2020) Eryilmaz, Serkan; Ozkurt, Fatma Yerlikaya; Erkan, T. ErmanThe number of components that are failed at the time of system failure is a useful quantity since it gives an idea of how many spares should be available to replace all failed components upon the system failure. In this paper, the number of failed components is considered at subsystem and system levels for the series-parallel system that consists of K subsystems. In particular, the joint behavior of the number of failed components in each subsystem is studied when each subsystem has identical components and different subsystems have different types of components. The results are then used to find the optimal number of components in each subsystem by minimizing an expected cost per unit of time upon the system failure.Article Citation - WoS: 45Citation - Scopus: 46Carbon Nanotube-Graphene Supported Bimetallic Electrocatalyst for Direct Borohydride Hydrogen Peroxide Fuel Cells(Pergamon-elsevier Science Ltd, 2021) Uzundurukan, Arife; Akca, Elif Seda; Budak, Yagmur; Devrim, YilserAt present study, carbon nanotube-graphene (CNT-G) supported PtAu, Au and Pt catalysts were prepared by microwave-assisted synthesis method to investigate the direct liquid-fed sodium borohydride/hydrogen peroxide (NaBH4/H2O2) fuel cell performance. Prepared catalysts were characterized by TGA, XRD, TEM, ICP-OES, cyclic voltammetry and rotating disc electrode (RDE) voltammetry. The catalysts were tested in a single NaBH4/H2O2 fuel cell with 25 cm(2) active area to evaluate fuel cell performance. The effects of temperature and fuel concentration on fuel cell performance were examined to observed best operating conditions. As a result of direct NaBH4/H2O2 fuel cell experiments, maximum power densities of 139 mW/cm(2), 125 mW/cm(2) and 113 mW/cm(2) were obtained for PtAu/CNT-G, Au/CNT-G and Pt/CNT-G catalysts, respectively. PtAu/CNT-G catalyst showed the enhanced NaBH4/H2O2 fuel cell performance, which was higher than the Pt/CNT-G catalyst and Au/CNT-G catalyst at 50 degrees C. The enhanced NaBH4/H2O2 performance can be attributed to synergistic effects between Pt and Au particles on CNT-G support providing a better catalyst utilization and interaction. These results suggest that the prepared PtAu/CNT-G catalyst is a promising anode catalyst for NaBH4/H2O2 fuel cell application. (c) 2020 Elsevier Ltd. All rights reserved.Article Citation - WoS: 36Citation - Scopus: 42Development of a Personalized Thermal Comfort Driven Controller for Hvac Systems(Pergamon-elsevier Science Ltd, 2021) Turhan, Cihan; Simani, Silvio; Akkurt, Gulden GokcenIncreasing thermal comfort and reducing energy consumption are two main objectives of advanced HVAC control systems. In this study, a thermal comfort driven control (PTC-DC) algorithm was developed to improve HVAC control systems with no need of retrofitting HVAC system components. A case building located in Izmir Institute of Technology Campus-Izmir-Turkey was selected to test the developed system. First, wireless sensors were installed to the building and a mobile application was developed to monitor/ collect temperature, relative humidity and thermal comfort data of an occupant. Then, the PTC-DC algorithm was developed to meet the highest occupant thermal comfort as well as saving energy. The prototypes of the controller were tested on the case building from July 3rd, 2017 to November 1st, 2018 and compared with a conventional PID controller. The results showed that the developed control algorithm and conventional controller satisfy neutral thermal comfort for 92 % and 6 % of total measurement days, respectively. From energy consumption point of view, the PTC-DC decreased energy consumption by 13.2 % compared to the conventional controller. Consequently, the PTC-DC differs from other works in the literature that the prototype of PTC-DC can be easily deployed in real environments. Moreover, the PTC-DC is low-cost and user-friendly. (c) 2021 Elsevier Ltd. All rights reserved.
