فهرست مطالب

Hydrogen and Fuel Cell - Volume:4 Issue: 4, 2018
  • Volume:4 Issue: 4, 2018
  • تاریخ انتشار: 1396/10/30
  • تعداد عناوین: 6
|
  • Puriya Mohammad Gholy Nejad, Ali Reza Solaimany Nazar *, Zohreh Rahimi-Ahar, Zohreh Karami Pages 249-263
    An electrochemical analysis on a single channel PEM fuel cell was carried out by Computational Fuel Cell Dynamics (CFCD). The objective was to assess the latest developments regarding the effects of change in the current collector materials, porosity of electrodes and gas diffusion layer on the fuel cell power density. Graphite, as the most applicable current collector material, was applied followed by Aluminum and Titanium. It was found that titanium enhances the performance of the fuel cell as compared to the graphite and aluminum. Other results obtained were: the total porosity of electrode's layers does not have a significant effect on power density. At higher porosity of gas diffusion layer at voltages higher than 0.5 is favorable in gas diffusion, which leads to better performance. A numerical model, based on the assessment of basic best practice guidelines for CFCD, was developed that led to reasonably good agreement with the experimental results.
    Keywords: PEM fuel cell, Catalyst Layer, Gas Diffusion Layer, Power density, Performance
  • Ebrahim Afshari *, Nabi Jahantigh, Masoud Ziaei-Rad Pages 265-274
    In a polymer membrane fuel cell more than half of the chemical energy of hydrogen is converted to heat during generation of electricity. This causes an increase in the cell temperature. The Cooling field design has a significant role in cell cooling. The cell's performance and stability are reduced due to inappropriate heat dissipation. In this paper, the cooling flow and heat transfer in cooling plates with parallel channels in the polymer membrane fuel cell are simulated and a parametric study of the influence of cooling channels dimensions on the fuel cell thermal performance is performed based on three indexes: maximum surface temperature cooling (Tmax), the temperature uniformity on the surface (Ut), and pressure drop. Numerical results show that increasing the depth of the channels has an adverse effect on temperature characteristic; inaddition, the pressure drop decreases. Therefore, regarding constructional limitations and mechanical strength, use of channels with a depth of 1 mm is recommended. Increasing the width of the channels decreases the maximum surface temperature of the cooling plate, the temperature uniformity index, and the pressure drop. However, increasing the channel width more than 3 mm does not have a significant effect on the cooling performance. Increasing the distance between two channels adversely effects the thermal parameters as well as increases the pressure drop. Therefore, the distance between two cooling channels should not be more than 2 mm.
    Keywords: polymer membrane fuel cell, cooling flow field, The temperature distribution, Uniform temperature distribution, Pressure drop, Parametric study
  • Saber Sadeghi * Pages 275-287
    Conversion of fossil fuels to electrical power is the most popular method of electrical power generation. Due to the depletion of fossil fuels and the increase in air pollution, the necessity of using high efficiency power generation systems is increasing. High temperature fuel cells, such as solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MCFC), have high efficiency. According to the high operation temperature of these fuel cells, there is the possibility of combination of them with gas turbines (GT) to reach to a higher efficiency. In the present study, the SOFC-GT hybrid system, the MCFC-GT hybrid system, and the new SOFC-MCFC-GT hybrid system are compared from an energy and economic point of view. The results show that the MCFC-GT has the highest efficiency but its annualized cost is greater than the others. The new SOFC-MCFC-GT hybrid system is more efficient than the SOFC-GT hybrid system for low current density, high fuel utilization, and high air utilization. This new hybrid system has lower annualized cost than MCFC-GT hybrid system.
    Keywords: SOFC, MCFC, Hybrid system, energy analysis, economic analysis
  • Khaled Mammar *, Farid Saadaoui, Abdaldjabar Hazzab Pages 289-299
    The proton exchange membrane (PEMFC) fuel cell represents the energy of the future, in parallel with hydrogen. However, this technology must meet many technical challenges related to performance and durability before being sold on a large scale. It is well known that these challenges are closely linked to water management. This paper develops and implements a model of PEM fuel for simulation to make prediction on the water content. The proposed model includes a voltage evolution model based on the electrochemical and dynamics gases aspect, a water activity model to approximate relative humidity and a fuel cell spectroscopy impedance model to estimate the water content in order to make an accurate diagnosis. Furthermore, this work adopts a methods of modeling that presents a new solution to bring water into the fuel cell membrane, where it humidifies the Input gases (air and hydrogen) to a relative humidity over 0%. However, this solution causes a problem of flooding the membrane in the PEMFC. In this work, an Electrochemical Impedance Spectroscopy (EIS) is used to make the flooding and drying diagnosis in the fuel cell. The strengths of this proposed model are that it can be used at the same time in the field of power systems and for water diagnosis. This model predicts the response of step change in the load demand, and the water rate introduced by air into the fuel cell. The simulation results are presented with a qualitative interpretation of PEM fuel cell flooding and drying behavior.
    Keywords: PEMFC, Electrochemical model, impedance spectroscopy model, Water diagnosis, Flooding drying
  • Morteza Torabi, Mohammad Golmohammad, Hamid Abdoli, Hamed Mohebi, Khaled Azari, Alireza Mehranjani, Shahriar Bozorgmehri * Pages 301-306
    In this study, a solid oxide fuel cell (SOFC) stack has been successfully fabricated and tested by using direct natural gas. The main objective of this research was to achieve optimal long-term performance of the SOFC stack without carbon deposition by using low-cost natural gas as a fuel. The stack configuration was improved by a new interconnect design and made of cost-effective raw materials. In this respect, the stack showed maximum power of 31 W while 33 A current was applied at a flow rate of 1000 ccm for H2 (as fuel) and oxygen. Then, humidified natural gas was employed as an internal reforming technique, which showed degradation of 1.4% after 24 h. Maximum obtained power was 32 W under 33 A current at a flow rate of 1000 ccm. After 48 h of operation, 34 W of power was achieved at the current of 38 A. Therefore, the power was increased from 32 to 34 W after 48 h of operation in upper current. Finally, a suitable SOFC stack made of cost effective materials and using direct natural gas under appropriate conditions was fabricated and developed in this research.
    Keywords: Stack, SOFC, Internal Reforming, Natural gas
  • Masood Rahimi, Seyed Mojtaba Sadrameli, H Mohammadpoor, H. Kazerouni, M.D. Ghaffari Page 307
    The current importance of energy emphasizes the use of renewable resources (such as wastewater) for electricity generation by microbial fuel cell (MFC). In the present study, the native sulfate-reducing bacterial strain (R.gh 3) was employed simultaneously for sulfurous component removal and bioelectricity generation. In order to enhance the electrical conductivity and provision of a compatible bed, a complex electrode structure based on stainless steel-304 was prepared. Next, the electrode was coated with a composite of graphite and activated carbon solution. A new approach associated with increasing bacterial population was studied using two electron acceptors composed of iron and sulfate for respiration of sulfate-reducing bacteria. Finally, according to the maximum living cell number (nM = 20 ´108 cell ml-1) and the conditions of the bioreactor including the highly efficient anode electrode, a higher current generation (2.26 mA for the new structure as compared to 1.73 and 1.29 mA for graphite rod and carbon paper, respectively) was observed in the culture media.
    Keywords: Microbial fuel cell (MFC), electrode, bacterial growth, sulfate-reducing bacteria (SRB)