Effects of baffle position in serpentine flow channel on the performance of proton exchange membrane fuel cells

This study used a three-dimensional numerical model of a proton exchange membrane fuel cell with five types of channels:a smooth channel(Case 1);eight rectangular baffles were arranged in the upstream(Case 2),midstream(Case 3),downstream(Case 4),and the entire cathode flow channel(Case 5)to study the effects of baffle position on mass transport,power density,net power,etc.Moreover,the effects of back pressure and humidity on the voltage were investigated.Results showed that compared to smooth channels,the oxygen and water transport facilitation at the diffusion layer-channel interface were added 11.53%-20.60%and 7.81%-9.80%at 1.68 A·cm^(-2)by adding baffles.The closer the baffles were to upstream,the higher the total oxygen flux,but the lower the flux uniformity the worse the water removal.The oxygen flux of upstream baffles was 8.14%higher than that of downstream baffles,but oxygen flux uniformity decreased by 18.96%at 1.68 A·cm^(-2).The order of water removal and voltage improvement was Case 4>Case 5>Case 3>Case 2>Case 1.Net power of Case 4 was 9.87%higher than that of the smooth channel.To the Case 4,when the cell worked under low back pressure or high humidity,the voltage increments were higher.The potential increment for the back pressure of 0 atm was 0.9%higher than that of 2 atm(1 atm=101.325 kPa).The potential increment for the humidity of 100%was 7.89%higher than that of 50%.

Daily Operation Optimization of a Residential Molten Carbonate Fuel Cell Power System Using Genetic Algorithm

To decrease the cost of electricity generation of a residential molten carbonate fuel cell （MCFC） power system, multi-crossover genetic algorithm （MCGA）, which is based on ＂multi-crossover＂ and ＂usefulness-based selection rule＂, is presented to minimize the daily fuel consumption of an experimental 10kW MCFC power system for residential application. Under the operating conditions obtained by MCGA, the operation constraints are satisfied and fuel consumption is minimized. Simulation and experimental results indicate that MCGA is efficient for the operation optimization of MCFC power systems.

Study and performance test of 10 kW molten carbonate fuel cell power generation system

The use of high-temperature fuel cells as a power technology can improve the efficiency of electricity generation and achieve near-zero emissions of carbon dioxide.This work explores the performance of a 10 kW high-temperature molten carbonate fuel cell.The key materials of a single cell were characterized and analyzed using X-ray diffraction and scanning electron microscopy.The results show that the pore size of the key electrode material is 6.5 lm and the matrix material is a-LiAlO_(2).Experimentally,the open circuit voltage of the single cell was found to be 1.23 V.The current density was greater than 100 mA/cm^(2)at an operating voltage of 0.7 V.The 10 kW fuel cell stack comprised 80 single fuel cells with a total area of 2000 cm^(2)and achieved an open circuit voltage of greater than 85 V.The fuel cell stack power and current density could reach 11.7 kW and 104.5 mA/cm2 at an operating voltage of 56 V.The influence and long-term stable operation of the stack were also analyzed and discussed.The successful operation of a 10 kW high-temperature fuel cell promotes the large-scale use of fuel cells and provides a research basis for future investigations of fuel cell capacity enhancement and distributed generation in China.

Power production enhancement with polyaniline composite anode in benthic microbial fuel cells

In this study,conductive polymer polyaniline(PANI)is employed to modify the anodes of benthic microbial fuel cells(BMFC).Four electrochemical methods are used to synthesize the polyaniline anodes;the results show that the PANI modification,especially the pulse potential method for PANI synthesis could obviously improve the cell energy output and reduce the anode internal resistance.The anode is modified by PANI doped with Fe or Mn to further improve the BMFC performance.A maximum power density of 17.51 mW/m2 is obtained by PANI-Fe anode BMFC,which is 8.1 times higher than that of control.The PANI-Mn anode BMFC also gives a favorable maximum power density(16.78 mW/m2).Fe or Mn modification has better effect in improving the conductivity of polyaniline,thus improving the energy output of BMFCs.This work applying PANI composite anode into BMFC brings new development prospect and could promote the practical application of BMFC.

A 10kW-scale Distributed Power Plant of Natural Gas-Proton Exchange Membrane Fuel Cell

A 10 kW-scale natural gas fueled proton exchange membrane fuel cell(PEMFC) distributed power plant is presented in this paper,which is designed for cogeneration of power and heat. With homemade catalysts for CO removal in a two-stage methanation process and integrated reactor in the fuel processing system,the reformed fuel with CO molar fraction less than 10-5 is obtained for the fuel cell stack. Based on Matlab/Simulink/Stateflow and xPC Target platform,a rapid control prototype(RCP) is developed for real-time condition management,signal tracking and parameter tuning,data storing,and man-machine interaction. In a typical running with 4.3 kW stack power,the hydrogen production efficiency,gross power generation efficiency and heat recovery efficiency approach to 76%,41% and 50%,respectively. The peak stack power reaches 7.3 kW. Though there is still considerable dis-tance to long-term operation at 10 kW-scale net power generation,it is a milestone for the PEMFC-based stationary application in China.

Parameters Influencing Power Generation in Eco-friendly Microbial Fuel Cells

Pulp and papermaking industries generate high volumes of carbohydrate-rich effluents. Microbial fuel cell(MFC) technology is based on organic materials' consumption and efficient power production. Using a classical two-chamber lab-scale MFC design with an external resistance of2000 W, we investigated the effects of anode chamber biofilm adaptation(ACBA) and cathode chamber redox solutions(CCRS) on the operation efficiency of MFC when treating wastewater. In ACBA studies, biofilm growth activation showed an increase in the power density to 20.48, 35.18, and36.98 mW/m^2 when the acetate feeding concentrations were 3, 6, and 12 g/L,respectively. Improvement by biofilm adhesion on granular activated carbon(GAC) was examined by scanning electron microscopy(SEM). The obtained power density increased to 25.47, 33.42, and 40.39 mW/m^2 when the GAC particles concentrations were 0, 50, and 100 g/L, respectively. The generated power densities were 51.26 and 40.39 mW/m^2 as well as the obtained voltages were 0.41 and 0.72 V when the electrode area increased from 16 to 64 cm^2,respectively. Using the MFC optimized parameters, CCRS studies carried out using five different cathodic redox solutions. The results revealed that the use of manganese dioxide dissolved in hydrochloric acid generated the maximum power density of 112.6 mW/m^2, current density of 0.094 A/m^2, and voltage of1.20 V with a successful organic removal efficiency of 86.0% after 264 h of operation.

Power Conversion System Strategies for Fuel Cell Vehicles

Power electronics is an enabling technology for the development of environmental friendly fuel cell vehicles, and to implement the various vehicle electrical architectures to obtain the best performance. In this paper, power conversion strategies for propulsion and auxiliary power unit applications are described. The power electronics strategies for the successful development of the fuel cell vehicles are presented. The fuel cell systems for propulsion and for auxiliary power unit applications are also discussed.

Theoretical On-Board Hydrogen Redox Electric Power Generator for Infinite Cruising Range Fuel Cell Vehicles

The development of hydrogen redox electric power generators for infinite cruising range electric vehicles represents a true technological breakthrough. Such systems consist of a polymer electrolyte membrane hydrogen electrolytic cell equipped with an electrostatic-induction potential-superposed water electrolytic cell that provides a stoichiometric H2-O2 fuel mixture during operation of the vehicle. This generator functions with zero power input, zero matter input and zero emission due to the so-called ＂zero power input＂ electrostatic-to-chemical energy conversion occurring in the electrolytic cell. Here, theoretical simulations were performed to verify the target performance of such generators, assuming a pair of FC （fuel cell） and electrolytic cell stacks, both of which are commercially available.

Regulation of Power Conversion in Fuel Cells

Here we report a regulation about power conversion in fuel cells. This regulation is expressed as that total power produced by fuel cells is always proportional to the square of the potential difference between the \{equilibrium\} potential and work potential. With this regulation we deduced fuel cell performance equation which can describe the potential vs.the current performance curves, namely, polarization curves of fuel cells with three power source parameters: equilibrium potential E_0; internal resistance R; and power conversion coefficient K. The concept of the power conversion coefficient is a new criterion to evaluate and compare the characteristics and capacity of different fuel cells. The calculated values obtained with this equation agree with practical performance of different types of fuel cells.

Application of Solid Oxide Fuel Cell-Auxiliary Power Unit on Different Trucks in Northeast China

A diesel engine of conventional trucks has a low efficiency under the idling condition,leading to a high cost for heating or cooling in the cab during night. The solution to this problem will have great significance on energy conservation and emission reduction. A new auxiliary power unit of solid oxide fuel cell( SOFCAPU) with high efficiency solves this problem perfectly. Heat pump air conditioner is considered as a promising device for the application of SOFC-APU with a high cooling and heating efficiency. To make a quantitative analysis for the application of SOFC-APU,a model is built in Matlab / Simulink. The diesel engine model and SOFC-APU model are fitted based on some experimental data of SOFC-APU and diesel engine during the idling operation. An analysis of the application of SOFC-APU on different trucks in Northeast China is comprehensively made,including efficiency and emission.

Maximum Power Point Tracking With Fractional Order High Pass Filter for Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell (PEMFC) is widely recognized as a potentially renewable and green energy source based on hydrogen. Maximum power point tracking (MPPT) is one of the most important working conditions to be considered. In order to improve the performance such as convergence and robustness under disturbance and uncertainty, a fractional order high pass filter (FOHPF) is applied for the MPPT controller design based on the traditional extremum seeking control (ESC). The controller is designed with integerorder integrator (IO-I) and low pass filter (IO-LPF) together with fractional order high pass filter (FOHPF), by substituting the normal HPF in the original ESC system. With this FOHPF ESC, better convergence and smoother performance are achieved while maintaining the robust specifications. First, tracking stability is discussed under the commensurate-order condition. Then, simulation results are included to validate the proposed new FOHPF ESC scheme under disturbance. Finally, comparison results between FOHPF ESC and the traditional ESC method are also provided. © 2014 Chinese Association of Automation.

A Direct Liquid Fuel Cell with High Power Density Using Reduced Phosphotungstic Acid as Redox Fuel

Direct liquid fuel cells(DLFCs)are proposed to address the problems of high cost and complex storage and transportation of hydrogen in traditional hydrogen-oxygen proton exchange membrane fuel cells.However,present fuels of organic small molecules used in DLFCs are restricted to problems of sluggish electrochemical kinetics and easily poisoning of precious metal catalysts.Herein,we demonstrate reduced phosphotungstic acid as a liquid fuel for DLFCs based on its advantages of high chemical and electrochemical stability,high electrochemical activity on common carbon material electrodes,and low permeability through proton exchange membranes.The application of phosphotungstic acid fuel effectively solves the problems of high cost of anode catalysts and serious fuel permeation loss in traditional DLFCs.A phosphotungstic acid fuel cell achieves a peak power density of466 mW cm^(-2)at a cell voltage of 0.42 V and good stability at current densities in the range from 20 to 200 mA cm^(-2).

Fuel Cells as Energy Systems： Efficiency, Power Limits and Thermodynamic Behavior

Steady-state model of a high-temperature solid oxide fuel cell （SOFC） is considered, which refers to constant chemical potentials of incoming hydrogen fuel and oxidant. Lowering of the cell voltage below its reversible value is attributed to polarizations and imperfect conversions of reactions. An imperfect power formula summarizes the effect of transport laws, irreversible polarizations and efficiency of power yield. Reversible electrochemical theory is extended to the case with dissipative chemical reactions; this case includes systems with incomplete conversions, characterized by ＂reduced affinities＂ and an idle run voltage. Efficiency drop is linked with thermodynamic and electrochemical irreversibilities expressed in terms of polarizations （activation, concentration and ohmic）. Effect of incomplete conversions is modeled by assuming that substrates can be remained after the reaction and that side reactions may occur. Optimum and feasibility conditions are discussed for basic input parameters of the cell. Calculations of maximum power show that the data differ for power generated and consumed and depend on current intensity, number of mass transfer units, polarizations, electrode surface area, average chemical rate, etc.. These data provide bounds for SOFC energy generators, which are more exact and informative than reversible bounds for electrochemical transformation.

Dynamic Performance of Fuel Cell Power Module for Mobility Applications

Fuel cell powered vehicles have been developed as another alternative to internal combustion engine powered vehicles for some applications including passenger cars, buses, trains, motorcycles, forklifts, electric wheelchairs, electric trolleybuses, medical carts, military engines, personal sports craft, mobility devices and other self propelled equipment. Up to now, many researches have focused on the development of the power module in the Fuel cell vehicles (FCVs) and the components of these systems such as membranes, bipolar plates, and electrodes. However, our work in this study focuses on operating the integrated fuel cell power module system efficiently for various operating conditions such as pressure, relative humidity and operating modes. In our validation we have utilized PEMFC single cell, with active area geometry 16 cm2 and of 120 cm2. Some results obtained in our study shown significant performance indicators for PEMFC stack (composed of 2 cells and 4 cells in a series) at different humidification levels.

Current status of national integrated gasification fuel cell projects in China

Coal has been the main energy source in China for a long period.Therefore,the energy industry must improve coal power generation efficiency and achieve near-zero CO_(2) emissions.Integrated gasification fuel cell(IGFC)systems that combine coal gasification and high-temperature fuel cells,such as solid oxide fuel cells or molten carbonate fuel cells(MCFCs),are proving to be promising for efficient and clean power generation,compared with traditional coal-fired power plants.In 2017,with the support of National Key R&D Program of China,a consortium led by the China Energy Group and including 12 institutions was formed to develop the advanced IGFC technology with near-zero CO_(2) emissions.The objectives of this project include understanding the performance of an IGFC power generation system under different operating conditions,designing master system principles for engineering optimization,developing key technologies and intellectual property portfolios,setting up supply chains for key materials and equipment,and operating the first megawatt IGFC demonstration system with near-zero CO_(2) emission,in early 2022.In this paper,the main developments and projections pertaining to the IGFC project are highlighted.

Prospects and challenges of graphene based fuel cells

Novel characteristics of graphene have captured great attention of researchers for energy technology applications.Incorporation of graphene related hybrid and composite materials have demonstrated high performance and durability for fuel cell energy conversion devices.This article overviews graphene based materials for fuel cell technology applications such as electrodes additives,bipolar plates and proton conducting electrolyte membrane.The graphene dispersion over electrodes has revealed enhanced exposure of electrochemically active surface area for improved electro-catalytic activity towards fuel oxidation and oxidant reduction reactions.The issue of device stack durability and degraded performance due to corrosion of bipolar plates is discussed by incorporating graphene based materials.In proton exchange membrane devices,graphene as an electrolyte has shown an excellent performance towards high ionic conductivity and power density.The graphene incorporation in fuel cell devices has exhibited commendable performance and has bright future for commercial applications.

Study on an environmental-friendly and high-efficient fuel cell energy conversion system

The kinds and the distribution of the coal in China are investigated. The results indicated that the 80% coal in China is used by the method of the coal gasification. The possibility of utilization and development of the fuel cell power plant in China is analyzed. A combined cycle generation system is designed. Its net electrical efficiency is about 55%(LHV), which is higher than that of the fire power plant. So it is environmental friendly and high efficient generation mode.

Characterization of Fe/N-doped graphene as air-cathode catalyst in microbial fuel cells

This work proposed a simple and efficient approach for synthesis of durable and efficient non-precious metal oxygen reduction reaction（ORR） electro-catalysts in MFCs. The rod-like carbon nanotubes（CNTs）were formed on the Fe–N/SLG sheets after a carbonization process. The maximum power density of1210 ± 23 m W·mobtained with Fe–N/SLG catalyst in an MFC was 10.7% higher than that of Pt/C catalyst(1080 ± 20 mW ·m) under the same condition. The results of RDE test show that the ORR electron transfer number of Fe–N/SLG was 3.91 ± 0.02, which suggested that ORR catalysis proceeds through a four-electron pathway. The whole time of the synthesis of electro-catalysts is about 10 h, making the research take a solid step in the MFC expansion due to its low-cost, high efficiency and favorable electrochemical performance. Besides, we compared the electrochemical properties of catalysts using SLG, high conductivity graphene（HCG, a kind of multilayer graphene） and high activity graphene（HAG, a kind of GO） under the same conditions, providing a solution for optimal selection of cathode catalyst in MFCs.The morphology, crystalline structure, elemental composition and ORR activity of these three kinds of Fe–N/C catalysts were characterized. Their ORR activities were compared with commercial Pt/C catalyst.It demonstrates that this kind of Fe–N/SLG can be a type of promising highly efficient catalyst and could enhance ORR performance of MFCs.

Comparative Study of Two Carbon Fiber Cathodes and Theoretical Analysis in Microbial Fuel Cells on Ocean Floor

Cathode activity plays an important role in the improvement of the microbial fuel cells on ocean floor （BMFCs）. A comparison study between Rayon-based （CF-R） and PAN-based carbon fiber （CF-P） cathodes is conducted in the paper. The two carbon fibers were heat treated to improve cell performance （CF-R-H ＆ CF-P-H）, and were used to build a new BMFCs structure with a foamy carbon anode. The maximum power density was 112.4mWm-2 for CF-R-H, followed by 66.6mWm-2 for CF-R, 49.7 mWm-2 for CF-P-H and 21.6mWm-2 for CF-P respectively. The higher specific area and deep groove make CF-R have a better power output than with CF-P. Meanwhile, heat treatment of carbon fiber can improve cell power, nearly two-fold higher than heat treatment of plain fiber. This improvement may be due to the quinones group formation to accelerate the reduction of oxygen and electron transfer on the fiber surface in the three phase boundary after heat treatment. Compared to PAN-based carbon fiber, Rayon-based carbon fiber would be preferentially selected as cathode in novel BMFCs design due to its high surface area, low cost and higher power. The comparison research is significant for cathode material selection and cell design.