1,721,043 research outputs found
Comparative Study of Pv/Pem Fuel Cell Hybrid Energy System Based on Methanol and Water Electrolysis
No full textDEVRIM, YILSER/0000-0001-8430-0702; Budak, Yagmur/0000-0002-8443-1160In this study, we investigated the comparative analysis of a solar-fuel cell hybrid system based on water and methanol electrolysis. The proposed system comprises PV, electrolyzer and proton exchange membrane fuel cell (PEMFC). The hybrid system is designed to supply the hydrogen (H-2) needed of the PEMFC system and also to fulfill the H-2 requirement of other applications. The actual data of solar irradiation of Izmir, Turkey are used in the simulation. The methanol and water electrolyzers were designed for 1.2 kW PEMFC H-2 demand which were met a house-hold energy requirement. Analyzes show that the use of the methanol electrolyzer can produce 27% more H-2 than the water electrolyzer. According to the study, it was determined that the methanol-based hybrid system offered a viable option for self-sustaining in household application
Reliability and Optimal Replacement Policy for a <i>k</I>-out-of-<i>n< System Subject To Shocks
No full textDEVRIM, YILSER/0000-0001-8430-0702; Eryilmaz, Serkan/0000-0002-2108-1781Consider a k-out-of-n system which is subject to shocks that occur at random times. Each shock causes failure of random number of components, and hence the system's lifetime corresponds to one of the arrival times of shocks. The reliability and mean time to failure of the system are studied when the times between shocks follow a phase type distribution. The optimal replacement time problem which is concerned with the minimization of the total long-run average cost per unit time is also defined and studied
Enhancement of Pem Fuel Cell Performance at Higher Temperatures and Lower Humidities by High Performance Membrane Electrode Assembly Based on Nafion/Zeolite Membrane
No full textDEVRIM, YILSER/0000-0001-8430-0702This work reports the preparation of Nafion/zeolite composite membranes with different zeolite loading. The structure of the Nafion/zeolite composite membranes are investigated by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and by thermogravimetric analysis (TGA). The introduction of zeolite particles into the Nafion matrix helps to improve the water uptake, proton conductivity and thermal stability of the nanocomposite membranes compared to the virgin Nafion membrane. The SEM analyses have proved the uniform and homogeneous distribution of zeolite in composite membranes. The composite membranes are tested in a single PEMFC with a 5 cm(2) active area operating at the temperature range of 75-120 degrees C and in humidified under 50% relative humidity (RH) and fully humidified conditions. Single PEMFC tests show that Nafion/zeolite composite membrane is more stable and also performed better than virgin Nafion membrane at low humidity condition. The results indicate the Nafion/zeolite composite membranes could be utilized as the proton exchange membranes for PEMFC. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Atilim University Research project [ATU-LAP-SD-1314-02]This study is supported by Atilim University Research project ATU-LAP-SD-1314-02. The author gratefully acknowledge to TEKSIS (METU Technopolis, TURKEY) for their support during MEA preparation
Fabrication and Performance Evaluation of Hybrid Membrane Based on a Sulfonated Polyphenyl Sulfone/Phosphotungstic Acid/Silica for Proton Exchange Membrane Fuel Cell at Low Humidity Conditions
No full textDEVRIM, YILSER/0000-0001-8430-0702Sulfonated polyphenyl sulfone/phosphotungstic acid/silica ( sPPS/PWA/silica) hybrid membranes were prepared and characterized as alternative materials for PEMFC operation at high temperature and low humidity conditions. Polyphenyl sulfone polymer (PPS) was sulfonated with trimethylsilyl chlorosulfonate in 1,2 dichloroethane at ambient temperatures. The degree of sulfonation was determined by 1H-NMR analysis. Sulfonation levels from 25 to 45% were easily achieved by varying the content of the sulfonation agent. The hybrid membrane was composed of the mixture of sPPS solution, PWA/silica particles. The structures of the membranes were investigated by Scanning Electron Microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and by thermogravimetric analysis (TGA). The composite membranes gained good thermal resistance with insertion of PWA/silica. SEM results have proven the uniform and homogeneous distribution of PWA/silica in hybrid membrane. The existence PWA/silica has improved the water uptake, proton conductivity and oxidative stability of hybrid membrane. Gas diffusion electrodes (GDE) were fabricated by ultrasonic coating technique. Catalyst loading was 0.4 mg Pt/cm(2) for both anode and cathode sides. The membranes were tested in a single cell with a 5 cm(2) active area operating at the temperature range of 70 to 120 degrees C and 100 and 30% relative humidity conditions. Single PEMFC tests performed at different operating temperatures indicated that sPPS/PWA/silica hybrid membrane was more stable and also performed better than pristine sPPS membrane. At the overall, the sPPS/PWA/silica hybrid membrane seems to be a promising alternative membrane for the possible utilization in PEMFC. (C) 2014 Elsevier Ltd. All rights reserved
Development and Performance Analysis of Polybenzimidazole/Boron Nitride Composite Membranes for High-Temperature Pem Fuel Cells
No full textDEVRIM, YILSER/0000-0001-8430-0702In this research, polybenzimidazole/boron nitride (PBI/BN) based composite membranes have been prepared for high-temperature PEM fuel cell (HT-PEMFC). BN was preferred because of its superior thermal robustness, high chemical stability, non-conductor property, and high plasticizer characteristic. The loading of BN in the composite membrane was studied between 2.5 to 10 wt%. The composite membranes were characterized using TGA, DSC, XRD, SEM, mechanical tests, acid doping/leaching, and proton conductivity measurements. The highest conductivity of 0.260 S/cm was found for PBI/BN-2.5 membrane at 180 degrees C. It has been determined that the PBI/BN-2.5 membrane has higher performance than the PBI membrane according to the HT-PEMFC tests performed with Hydrogen and dry air. The heightened HT-PEMFC performance can be ascribed to interactive effects between BN particles and the PBI polymer matrix. PBI/BN composite membranes show a good perspective in the high-temperature PEMFC applications
Design of a Hybrid Photovoltaic-Electrolyzer Fuel Cell System for Developing Solar Model
No full textDEVRIM, YILSER/0000-0001-8430-0702The world's fossil fuel energy reserves have rapidly decreased, while the energy demand has increased due to industrial growth, population growth, and technology advances, all of which affect the environment by the production of greenhouse gases. Alternative energy sources such as solar, hydrogen, etc. are attracting more attention as an alternative of fossil fuels. We present in this study hybrid photovoltaic (PV) panels/PEM electrolyzer/high temperature proton exchange membrane fuel cell (HTPEMFC) system used in off-grid application. The purpose of a hybrid system is to produce as much energy from alternative energy sources to ensure the load demand. Solar energy is used as primary source and a fuel cell is used as backup power. The hybrid system is designed and analyzed according to the new solar radiation model. Firstly a new solar model is developed to determine solar radiation on horizontal surface. After that solar radiation on tilted surface is obtained by using solar radiation on horizontal surface model for PV panel calculations. The hybrid system is modelled and the obtained results presented and discussed. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Reliability-Based Evaluation of Hybrid Wind-Solar Energy System
No full textDEVRIM, YILSER/0000-0001-8430-0702; Eryilmaz, Serkan/0000-0002-2108-1781In this article, a hybrid system that consists of a specified number of wind turbines and solar modules is considered. In particular, the system is modeled using weightedk-out-of-nsystem which is also known as a threshold system in reliability literature. The system under concern consists ofn1identical wind turbines andn2identical solar modules, and each turbine and module can be in one of two states as working or failed. The probability that the entire hybrid system withn=n1+n2components produces power at minimum levelkis computed and evaluated. The importance of single-wind turbine and solar module is also calculated to measure which renewable energy component is more critical and important. Extensive numerical results that are based on real data set are presented to illustrate the model
Multi-Walled Carbon Nanotubes Decorated by Platinum Catalyst for High Temperature Pem Fuel Cell
No full textDEVRIM, YILSER/0000-0001-8430-0702In the literature, studies on platinum catalysts deposited on multi-walled carbon nanotube (Pt/MWCNT) have been mostly focused on low temperature fuel cell (LT-PEMFC) applications. In this study, we focus the synthesis and characterization of high temperature fuel cell (HT-PEMFC) performance of Pt/MWCNT in short and long term. The structural properties of the Pt/MWCNT electrocatalyst were analyzed by XRD, TGA, SEM and TEM measurements. The Pt/MWCNTs were also characterized by electrochemical measurements for durability estimation. Laboratory scale MEA with Pt/MWCNT was prepared by ultrasonic coating technique and has been tested in situ in single HT-PEMFC. Performance curves in dry Hydrogen/Air system were obtained that demonstrated performance comparable to commercial catalysts in that HT-PEMFC. The characterizations specified that the electrocatalytic and HT-PEMFC performance of the Pt/MWCNT catalysts are higher power density (0.360 W/cm(2)) than Pt/C (0.310 W/cm(2)) at 160 degrees C. The results obtained show that the synthesized catalysts are suitable for high temperature applications. In addition, the stability studies of MEAs prepared with Pt/MWCNT catalyst were performed by AST tests and compared with Pt/C based MEA. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
Carbon Nanotube-Graphene Hybrid Supported Platinum as an Effective Catalyst for Hydrogen Generation From Hydrolysis of Ammonia Borane
No full textDEVRIM, YILSER/0000-0001-8430-0702; UZUNDURUKAN, ARIFE/0000-0003-1104-1644In this study, we report the results of a kinetic study on the hydrogen (H-2) generation from the hydrolysis of ammonia borane (NH3BH3) catalyzed by Platinum supported on carbon nanotube-graphene hybrid material (Pt/CNT-G). Synthesized catalyst was characterized by TGA, XRD, CP-OES, TEM and SEM-EDX techniques. Characterization studies have shown that the CNT-G hybrid support material provides desired distribution of the Pt particles on the support material. The effect of various parameters such as catalyst loading, reaction temperature, effect of NaOH and the effect of NH3BH3 concentration are also determined. Experimental results showed that the Pt/CNT-G catalyst exhibited high catalytic activity on NH3BH3 hydrolysis reaction to release H-2. It has been found that Pt/CNT-G catalyst shows low activation energy of 35.34 kJ mol(-1) for hydrolysis reaction of NH3BH3. Pt/CNT-G catalyst also exhibited high catalytic activity with turnover frequency (TOF) of 135 (mol(H2)/mol(cat).-min). Therefore, the synthesized Pt/CNT-G catalyst is a potential candidate for enhanced H-2 generation through NH3BH3 hydrolysis. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.ATILIM University [ATU-LAP-C-1718-06]This study was supported by ATILIM University (Grant number: ATU-LAP-C-1718-06)
Evaluation of Hybridsolar-Wind System Based on Methanol Electrolyzer
No full textDEVRIM, YILSER/0000-0001-8430-0702;In this study, it is aimed to meet the annual electricity and heating needs of a house without interruption with the photovoltaic panel, wind turbine, methanol electrolyzer, and high temperature proton exchange membrane fuel cell system. The system results show that the use of the 2 WT with 18 PV was enough to provide the need of the methanol electrolyzer, which provides requirements of the high temperature proton exchange membrane fuel cell. The produced heat by the fuel cell was used to meet the heat requirement of the house with combined heat and power system. Electrical, thermal and total efficiencies of fuel cell system with combined heat and power were obtained as 38.54%, 51.77% and 90%, respectively. Additionally, the levelized cost of energy of the system was calculated as 0.295 $/kWh with combined heat and power application. The results of this study show that H(2)is useful for long-term energy storage in off-grid energy systems and that the proposed hybrid system may be the basis for future H-2-based alternative energy applications
- …
