Fuel Cell Performance Improvements Using Cell-to-Cell Flow Distribution Control

2004 ◽  
Author(s):  
J. Peter Hensel ◽  
Randall S. Gemmen ◽  
Brian J. Hetzer ◽  
Jimmy D. Thornton ◽  
Jeffrey S. Vipperman ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Single Cell ◽  
Proton Exchange Membrane ◽  
Flow Distribution ◽  
Proton Exchange ◽  
Development Effort ◽  
Fuel Cell Stack ◽  
Fuel Cell Performance ◽  
Performance Improvements ◽  
Fuel Flow

Balanced flow distribution to each cell in a fuel cell stack plays a significant role in the stack being able to operate at maximum capability and efficiency. This paper discusses the performance improvements in proton exchange membrane fuel cell stacks that can be obtained by using cell-to-cell flow distribution control. In a specially instrumented four-cell stack that employs needle valves to externally control the air and fuel flows to each cell, fuel to a single cell was reduced. The V-I curves collected under these conditions (unbalanced) are compared to curves collected when the fuel flow to each cell was equal (balanced). Reducing the fuel flow to a single cell by 30% decreased the V-I curve cutoff load by 8.5% — demonstrating the negative effect that unbalanced fuel flows can have on stack performance. Typical fuel cell stacks have no dynamic means to keep flows in the stack balanced between the cells, but this work indicates that flow balancing among cells can extend the V-I curve for a fuel cell to higher current values, allowing fuel cell stacks to operate reliably at higher loading and fuel utilizations. Plans to use novel, custom-built micro-valves to dynamically balance flow to individual cells in a fuel cell stack are being pursued as a result of this work, and the status of this development effort is provided.

scholarly journals Single cell induced starvation in a high temperature proton exchange membrane fuel cell stack

2019 ◽  
Vol 250 ◽  
pp. 1176-1189 ◽  
Author(s):  
Cinthia Alegre ◽  
Antonio Lozano ◽  
Ángel Pérez Manso ◽  
Laura Álvarez-Manuel ◽  
Florencio Fernández Marzo ◽  
...  
Keyword(s):  
High Temperature ◽  
Fuel Cell ◽  
Single Cell ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Fuel Cell Stack ◽  
Exchange Membrane

ac Impedance Study of a Proton Exchange Membrane Fuel Cell Stack Under Various Loading Conditions

2010 ◽  
Vol 7 (3) ◽  
Author(s):  
N. V. Dale ◽  
M. D. Mann ◽  
H. Salehfar ◽  
A. M. Dhirde ◽  
T. Han
Keyword(s):  
Fuel Cell ◽  
Single Cell ◽  
Proton Exchange Membrane ◽  
Low Frequency ◽  
Impedance Analysis ◽  
Pem Fuel Cell ◽  
Ac Impedance ◽  
Proton Exchange ◽  
Fuel Cell Stack ◽  
Exchange Membrane

This paper presents the ac impedance study and analysis of a proton exchange membrane (PEM) fuel cell operated under various loading conditions. Ballard’s 1.2 kW Nexa™ fuel cell used for this study is integrated with a control system. The PEM fuel cell stack was operated using room air and pure hydrogen (99.995%) as input. Impedance data were collected for the fuel cell to study the behavior of the stack and groups of cells under various loads. Single cell impedance analysis was also performed for individual cells placed at different locations in the stack. The ac impedance analysis, also known as electrochemical impedance analysis, showed low frequency inductive effects and mass transport losses due to liquid water accumulation at high current densities. Results show that the stack run time to achieve steady state for impedance measurements is important. Using impedance plots, the average Ohmic resistance for the whole stack was estimated to be 41 mΩ, the same value obtained when summing the resistance value of all individual cells. Impedance analysis for groups of cells at different locations in the stack shows changes in both polarization resistance and capacitive component only in the low frequency region. At high frequencies, single cell inductive and capacitive behavior varied as a function of location in the stack. The effects of artifacts on the high frequency loop and on the high and low frequency intercept loops are also discussed.

Experimental Evaluation of the Dynamic Behavior of an Air-Breathing Fuel Cell Stack

2001 ◽  
Vol 123 (3) ◽  
pp. 225-231 ◽  
Author(s):  
Svein O. Morner ◽  
Sanford A. Klein
Keyword(s):  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Significant Variable ◽  
Transient Effects ◽  
Air Breathing ◽  
Fuel Cell Stack ◽  
Fuel Cell Performance ◽  
Effects Of Temperature ◽  
Exchange Membrane

The performance of an air breathing proton exchange membrane (PEM) fuel cell stack has been experimentally measured to investigate the steady-state and transient effects of temperature, humidity and air flowrate. The results show that hydrogen leaks to the cathode through the membrane causing internal heating of the fuel cell. The leakage rate is found to be linearly dependent on the pressure difference between the hydrogen side and air side which is at atmospheric pressure. Temperature was found to not have a significant effect on the PEM performance, except through its indirect effect on humidity. The humidity of the membrane is found to be the most significant variable in determining the fuel cell performance. The airflow also influences the performance of the fuel cell directly by supplying oxygen and indirectly by influencing the humidity of the membrane. Experiments show that an optimum air flowrate exists that is much larger than required for stoichiometric oxidation of the fuel.

Effect of Clamping Pressure on PEM Fuel Cell Stack Performance

2005 ◽  
Author(s):  
N. Fekrazad ◽  
T. L. Bergman
Keyword(s):  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Thermal Contact ◽  
Compressive Load ◽  
Compressive Force ◽  
Proton Exchange ◽  
Fuel Cell Stack ◽  
Fuel Cell Performance ◽  
Exchange Membrane ◽  
Clamping Pressure

A two-dimensional mathematical model of a Proton Exchange Membrane fuel cell stack is developed. Taking advantage of the geometrical periodicity within the stack, the model is used to predict the detailed thermal, humidity, and electrochemical behavior of the fuel cell. Using recently-reported experimental results, the electrical and thermal contact resistances that develop within the stack, in response to the compressive force used to assemble the stack, are accounted for. The fuel cell performance, reported in terms of its power output and internal temperature distributions, is predicted to be very sensitive to the compressive load applied to the stack.

Sensitivity Analysis of a 2.5kW Proton Exchange Membrane Fuel Cell Stack by Statistical Method

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
N. Rajalakshmi ◽  
G. Velayutham ◽  
K. S. Dhathathreyan
Keyword(s):  
Sensitivity Analysis ◽  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Fractional Factorial ◽  
Factorial Experiments ◽  
Fuel Cell Stack ◽  
Fuel Cell Performance ◽  
Exchange Membrane ◽  
Full Factorial

This paper describes the application of statistical analysis to a 2.5kW proton exchange membrane fuel cell stack operation, by experimental design methodology, whereby robust design conditions were identified for the operation of fuel cell stacks. The function is defined as the relationship between the fuel cell power and the operating pressure and stoichiometry of the reactants. Four types of control factors, namely, the pressures of the fuel and oxidant and the flow rates of the fuel and oxidant, are considered to select the optimized conditions for fuel cell operation. All the four factors have two levels, leading a full factorial design requiring 24 experiments leading to 16 experiments and fractional factorial experiments, 24−1, leading to 8 experiments. The experimental data collected were analyzed by statistical sensitivity analysis by checking the effect of one variable parameter on the other. The mixed interaction between the factors was also considered along with main interaction to explain the model developed using the design of experiments. The robust design condition for maximum fuel cell performance was found to be air flow rate, and the interaction between the air pressure and flow rate compared to all other factors and their interactions. These fractional factorial experiments, presently applied to fuel cell systems, can be extended to other ranges and factors with various levels, with a goal to minimize the variation caused by various factors that influence the fuel cell performance but with less number of trials compared to full factorial experiments.

Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells

2019 ◽  
Author(s):  
Valentina Guccini ◽  
Annika Carlson ◽  
Shun Yu ◽  
Göran Lindbergh ◽  
Rakel Wreland Lindström ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Surface Charge ◽  
Proton Exchange Membrane ◽  
Membrane Surface ◽  
Proton Exchange ◽  
Membrane Thickness ◽  
Fuel Cell Performance ◽  
Cellulose Nanofibres ◽  
Exchange Membrane

The performance of thin carboxylated cellulose nanofiber-based (CNF) membranes as proton exchange membranes in fuel cells has been measured in-situ as a function of CNF surface charge density (600 and 1550 µmol g<sup>-1</sup>), counterion (H<sup>+</sup>or Na<sup>+</sup>), membrane thickness and fuel cell relative humidity (RH 55 to 95 %). The structural evolution of the membranes as a function of RH as measured by Small Angle X-ray scattering shows that water channels are formed only above 75 % RH. The amount of absorbed water was shown to depend on the membrane surface charge and counter ions (Na<sup>+</sup>or H<sup>+</sup>). The high affinity of CNF for water and the high aspect ratio of the nanofibers, together with a well-defined and homogenous membrane structure, ensures a proton conductivity exceeding 1 mS cm<sup>-1</sup>at 30 °C between 65 and 95 % RH. This is two orders of magnitude larger than previously reported values for cellulose materials and only one order of magnitude lower than Nafion 212. Moreover, the CNF membranes are characterized by a lower hydrogen crossover than Nafion, despite being ≈ 30 % thinner. Thanks to their environmental compatibility and promising fuel cell performance the CNF membranes should be considered for new generation proton exchange membrane fuel cells.<br>

Observation of Pressure Drop Behavior in an Operating Fuel Cell Stack

2005 ◽  
Author(s):  
Frano Barbir ◽  
Haluk Gorgun ◽  
Xinting Wang
Keyword(s):  
Fuel Cell ◽  
Pressure Drop ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Cathode Side ◽  
Fuel Cell Stack ◽  
Flow Through ◽  
Drying Conditions ◽  
Exchange Membrane ◽  
The Relationship

Pressure drop on the cathode side of a PEM (Proton Exchange Membrane) fuel cell stack has been studied and used as a diagnostic tool. Since the Reynolds number at the beginning of the flow field channel was <250, the flow through the channel is laminar, and the relationship between the pressure drop and the flow rate is linear. Some departure from linearity was observed when water was either introduced in the stack or produced inside the stack in the electrochemical reaction. By monitoring the pressure drop in conjunction with the cell resistance in an operational fuel cell stack, it was possible to diagnose either flooding or drying conditions inside the stack.

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