Abstract: Nanofibers are defined as fibers with diameters less
than 100 nanometers. In this study, behaviours of activated carbon
nanofiber (ACNF), carbon nanofiber (CNF), polyacrylonitrile/ carbon
nanotube (PAN/CNT), polyvinyl alcohol/nanosilver (PVA/Ag) in
proton exchange membrane (PEM) fuel cells are investigated
experimentally. This material was used as gas diffusion layer (GDL)
in PEM fuel cells. In this study, the electrical conductivities of
nanofiber and nanofiber/nanoparticles have been studied to
understand their effects on PEM fuel cell performance. According to
the experimental results, the maximum electrical conductivity
performance of the fuel cell with nanofiber was found to be at
PVA/Ag (at UConn condition). The electrical conductivities of CNF,
ACNF, PAN/CNT are lower for PEM. The resistance of cell with
PVA/Ag is lower than the resistance of cell with PAN/CNT, ACNF,
CNF.
Abstract: In this paper, a prototype PEM fuel cell vehicle
integrated with a 1 kW air-blowing proton exchange membrane fuel
cell (PEMFC) stack as a main power sources has been developed for
a lightweight cruising vehicle. The test vehicle is equipped with a
PEM fuel cell system that provides electric power to a brushed DC
motor. This vehicle was designed to compete with industrial
lightweight vehicle with the target of consuming least amount of
energy and high performance. Individual variations in driving style
have a significant impact on vehicle energy efficiency and it is well
established from the literature. The primary aim of this study was to
assesses the power and fuel consumption of a hydrogen fuel cell
vehicle operating at three difference driving technique (i.e. 25 km/h
constant speed, 22-28 km/h speed range, 20-30 km/h speed range).
The goal is to develop the best driving strategy to maximize
performance and minimize fuel consumption for the vehicle system.
The relationship between power demand and hydrogen consumption
has also been discussed. All the techniques can be evaluated and
compared on broadly similar terms. Automatic intelligent controller
for driving prototype fuel cell vehicle on different obstacle while
maintaining all systems at maximum efficiency was used. The result
showed that 25 km/h constant speed was identified for optimal
driving with less fuel consumption.
Abstract: A comparison of activity and stability of the as-formed
Pt/C, Pt-Co and Pt-Pd/C electrocatalysts, prepared by a combined
approach of impregnation and seeding, was performed. According to
the activity test in a single Proton Exchange Membrane (PEM) fuel
cell, the Oxygen Reduction Reaction (ORR) activity of the Pt-M/C
electrocatalyst was slightly lower than that of Pt/C. The j0.9 V and
E10 mA/cm2 of the as-prepared electrocatalysts increased in the order of
Pt/C > Pt-Co/C > Pt-Pd/C. However, in the medium-to-high current
density region, Pt-Pd/C exhibited the best performance. With regard to
their stability in a 0.5 M H2SO4 electrolyte solution, the
electrochemical surface area decreased as the number of rounds of
repetitive potential cycling increased due to the dissolution of the
metals within the catalyst structure. For long-term measurement, Pt-
Pd/C was the most stable than the other three electrocatalysts.
Abstract: Durability of Membrane Electrode Assembly for
Proton Exchange Membrane Fuel Cells was evaluated in both steady
state and accelerated decay modes. Steady state mode was carried out
at constant current of 800mA/cm2 for 2500 hours using air as cathode
feed and pure hydrogen as anode feed. The degradation of the cell
voltage was 0.015V after such 2500 hrs operation. The degradation
rate was therefore calculated to be 6uV/hr. Continuously Vigorous
fluctuation of the cell voltage, which was switched between OCV and
0.2V, was employed for the accelerated decay mode. No obvious
change in performance of the MEA was observed after 10000 cycles
of such operation.
Abstract: This paper presents a new method to design nonlinear
feedback linearization controller for PEMFCs (Polymer Electrolyte
Membrane Fuel Cells). A nonlinear controller is designed based on
nonlinear model to prolong the stack life of PEMFCs. Since it is
known that large deviations between hydrogen and oxygen partial
pressures can cause severe membrane damage in the fuel cell,
feedback linearization is applied to the PEMFC system so that the
deviation can be kept as small as possible during disturbances or load
variations. To obtain an accurate feedback linearization controller,
tuning the linear parameters are always important. So in proposed
study NSGA (Non-Dominated Sorting Genetic Algorithm)-II method
was used to tune the designed controller in aim to decrease the
controller tracking error. The simulation result showed that the
proposed method tuned the controller efficiently.
Abstract: In order to further understand the behavior of PEM fuel cell and optimize their performance, it is necessary to perform measurements in real time. The internal impedance measurement by electrochemical impedance spectroscopy (EIS) is of great importance. In this work, we present the impedance measurement method of a PEM fuel cell by electrochemical impedance spectroscopy method and the realization steps of electronic load for this measuring technique implementation. The theoretical results are obtained from the simulation of software PSPICE® and experimental tests are carried out using the Ballard Nexa™ PEM fuel cell system.
Abstract: The optimal operation of proton exchange membrane fuel cell (PEMFC) requires good water management which is presented under two forms vapor and liquid. Moreover, fuel cells have to reach higher output require integration of some accessories which need electrical power. In order to analyze fuel cells operation and different species transport phenomena a biphasic mathematical model is presented by governing equations set. The numerical solution of these conservation equations is calculated by Matlab program. A multi-criteria optimization with weighting between two opposite objectives is used to determine the compromise solutions between maximum output and minimal stack size. The obtained results are in good agreement with available literature data.
Abstract: This paper presents a synthetic jet air blower actuated
by PZT for air blowing for air-breathing micro PEM fuel cell. The
several factors to affect the performance of air-breathing PEM fuel cell
such as air flow rate, opening ratio and cathode open type in the
cathode side were studied. Especially, an air flow rate is critical
condition to improve its performance. In this paper, we developed a
synthetic jet air blower to supply a high stoichiometric air flow. The
synthetic jet mechanism is a zero mass flux device that converts
electrical energy into the momentum. The synthetic jet actuation is
usually generated by a traditional PZT actuator, which consists of a
small cylindrical cavity, in/outlet channel and PZT diaphragms. The
flow rate of the fabricated synthetic jet air blower was 400cc/min at
550Hz and its power consumption was very low under 0.3W. The
proposed air-breathing PEM fuel cell which installed synthetic jet air
blower was higher performance and stability during continuous
operation than the air-breathing fuel cell without auxiliary device to
supply the air. The results showed that the maximum power density
was 188mW/cm2 at 400mA/cm2. This maximum power density and
durability were improved more than 40% and 20%, respectively.
Abstract: Fuel cells have become one of the major areas of
research in the academia and the industry. The goal of most fish
farmers is to maximize production and profits while holding labor
and management efforts to the minimum. Risk of fish kills, disease
outbreaks, poor water quality in most pond culture operations,
aeration offers the most immediate and practical solution to water
quality problems encountered at higher stocking and feeding rates.
Many units of aeration system are electrical units so using a
continuous, high reliability, affordable, and environmentally friendly
power sources is necessary. Aeration of water by using PEM fuel cell
power is not only a new application of the renewable energy, but
also, it provides an affordable method to promote biodiversity in
stagnant ponds and lakes. This paper presents a new design and
control of PEM fuel cell powered a diffused air aeration system for a
shrimp farm in Mersa Matruh in Egypt. Also Artificial intelligence
(AI) techniques control is used to control the fuel cell output power
by control input gases flow rate. Moreover the mathematical
modeling and simulation of PEM fuel cell is introduced. A
comparison study is applied between the performance of fuzzy logic
control (FLC) and neural network control (NNC). The results show
the effectiveness of NNC over FLC.
Abstract: The purpose of this paper is applied Taguchi method on the optimization for PEMFC performance, and a representative Computational Fluid Dynamics (CFD) model is selectively performed for statistical analysis. The studied factors in this paper are pressure of fuel cell, operating temperature, the relative humidity of anode and cathode, porosity of gas diffusion electrode (GDE) and conductivity of GDE. The optimal combination for maximum power density is gained by using a three-level statistical method. The results confirmed that the robustness of the optimum design parameters influencing the performance of fuel cell are founded by pressure of fuel cell, 3atm; operating temperature, 353K; the relative humidity of anode, 50%; conductivity of GDE, 1000 S/m, but the relative humidity of cathode and porosity of GDE are pooled as error due to a small sum of squares. The present simulation results give designers the ideas ratify the effectiveness of the proposed robust design methodology for the performance of fuel cell.
Abstract: Non-uniform current distribution in polymer
electrolyte membrane fuel cells results in local over-heating,
accelerated ageing, and lower power output than expected. This
issue is very critical when fuel cell experiences water flooding. In
this work, the performance of a PEM fuel cell is investigated under
cathode flooding conditions. Two-dimensional partially flooded
GDL models based on the conservation laws and electrochemical
relations are proposed to study local current density distributions
along flow fields over a wide range of cell operating conditions.
The model results show a direct association between cathode inlet
humidity increases and that of average current density but the
system becomes more sensitive to flooding. The anode inlet
relative humidity shows a similar effect. Operating the cell at
higher temperatures would lead to higher average current densities
and the chance of system being flooded is reduced. In addition,
higher cathode stoichiometries prevent system flooding but the
average current density remains almost constant. The higher anode
stoichiometry leads to higher average current density and higher
sensitivity to cathode flooding.
Abstract: In this paper a polymer electrolyte membrane (PEM)
fuel cell power system including burner, steam reformer, heat
exchanger and water heater has been considered to meet the
electrical, heating, cooling and domestic hot water loads of
residential building which in Tehran. The system uses natural gas as
fuel and works in CHP mode. Design and operating conditions of a
PEM fuel cell system is considered in this study. The energy
requirements of residential building and the number of fuel cell
stacks to meet them have been estimated. The method involved
exergy analysis and entropy generation thorough the months of the
year. Results show that all the energy needs of the building can be
met with 12 fuel cell stacks at a nominal capacity of 8.5 kW. Exergy
analysis of the CHP system shows that the increase in the ambient air
temperature from 1oC to 40oC, will have an increase of entropy
generation by 5.73%.Maximum entropy generates for 15 hour in 15th
of June and 15th of July is estimated to amount at 12624 (kW/K).
Entropy generation of this system through a year is estimated to
amount to 1004.54 GJ/k.year.
Abstract: The Proton Exchange Membrane Fuel Cell (PEMFC)
control system has an important effect on operation of cell.
Traditional controllers couldn-t lead to acceptable responses because
of time- change, long- hysteresis, uncertainty, strong- coupling and
nonlinear characteristics of PEMFCs, so an intelligent or adaptive
controller is needed. In this paper a neural network predictive
controller have been designed to control the voltage of at the
presence of fluctuations of temperature. The results of
implementation of this designed NN Predictive controller on a
dynamic electrochemical model of a small size 5 KW, PEM fuel cell
have been simulated by MATLAB/SIMULINK.
Abstract: Fuel and oxidant gas delivery plate, or fuel cell
plate, is a key component of a Proton Exchange Membrane (PEM)
fuel cell. To manufacture low-cost and high performance fuel cell
plates, advanced computer modeling and finite element structure
analysis are used as virtual prototyping tools for the optimization
of the plates at the early design stage. The present study examines
thermal stress analysis of the fuel cell plates that are produced
using a patented, low-cost fuel cell plate production technique
based on screen-printing. Design optimization is applied to
minimize the maximum stress within the plate, subject to strain
constraint with both geometry and material parameters as design
variables. The study reveals the characteristics of the printed
plates, and provides guidelines for the structure and material design
of the fuel cell plate.