System Integration Issues for a Direct Sodium Borohydride Fuel Cell (DNBFC)

2009 ◽  
Author(s):  
Kyu-Jung Kim ◽  
George Miley ◽  
Nie Luo ◽  
Ankeeth Ved
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Sodium Borohydride ◽  
System Integration ◽  
Liquid Fuel ◽  
Solubility Limit ◽  
Ion Conductivity ◽  
Cathode Side ◽  
High Electron ◽  
Fuel Loading

A fuel cell for air independent mobile applications using Direct Sodium Borohydride/Hydrogen Peroxide fuels in a low temperature PEM configuration is under development [1, 2]. As part of the development of this unique all liquid fuel cell, we have been studying methods for system integration, including methods for water management, stacking issues involving fluid conductivity control, and the design of a composite catalysis-diffusion layers. [3, 4] The goal is to find optimal conditions (minimum activation, ohmic and transport losses plus maximum run time per fuel loading) in this unique all liquid fuel cell. In contrast to conventional H2/O2 cells, the high electron and ion conductivity of the aqueous solution based fuels introduces special design considerations. For example, in stack design, the path length of flow channels connecting cells must be lengthened to increase the electric resistance which would otherwise introduce serious electrical shorting. With the catalyst coated throughout the diffusion layer, increasing ion conductivity from reaction sites to the PEM region also becomes a key design consideration, involving the porosity and entanglement of catalyst materials. Water management in this type of cell involves unique issues beyond humidification of the PEM which is automatically wetted by the liquid fuels. Here the issue is recirculation of product water from the cathode side back to the borohydride side to prevent reaction product NaBO2 from exceeding its solubility limit. These system integration issues are studied by a coordinated experimental approach which will be described in the presentation.

Unitized Regenerative Fuel Cell Performance Using Polymer Wicks for Passive Water Management

2013 ◽  
Author(s):  
Sandeep S. Lele ◽  
Michael A. Sizemore ◽  
Sutyen S. Zalawadia ◽  
Aitor P. Zabalegui ◽  
Abdie H. Tabrizi ◽  
...  
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Water Transport ◽  
Current Density ◽  
Pem Fuel Cells ◽  
Cathode Side ◽  
Membrane Electrode ◽  
Flow Channels ◽  
Operating Current ◽  
Regenerative Fuel Cell

Proton Exchange Membrane (PEM) fuel cells rely on effective internal water transport to provide stable performance. Many water management schemes require high heat, high pressure, or high flow rates — effectively introducing parasitic losses and reducing round-trip efficiency. In this work, a radial, non-recirculating, unitized regenerative fuel cell prototype with passive water transport is designed and tested. The cell features a 5 cm2 active area with 1.2 mm wide by 0.6 mm high gas flow channels. Porous polymer wicks are fabricated in the cathode side flow channels and coupled with a bulk water storage structure. The resulting wicks are 0.3 mm wide and 0.6 mm high. Discharge operating voltage measured during current control testing resulted in 1 V at open circuit, 0.8 V at 0.3 A·cm−2, and 0.2 V at 1 A·cm−2. Charge operating current density measured during voltage control testing resulted in 0.1 A·cm−2 at 1.5 V, 0.3 A·cm−2 at 1.6 V, and 0.8 A·cm−2 at 2 V. During the membrane electrode assembly (MEA) conditioning procedure, degradation in operating current density is seen over a 30–100 minute time span.

Three-Dimensional Simulation of Water Droplet Movement in PEM Fuel Cell Flow Channels with Fluid-Mechanics Properties and Different Deformations of GDL

2012 ◽  
Vol 625 ◽  
pp. 53-56 ◽  
Author(s):  
Ning Bao ◽  
Qing Du ◽  
Yan Yin
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Liquid Water ◽  
Water Droplet ◽  
Three Dimensional ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Cathode Side ◽  
Gas Channel ◽  
Flow Channels

Water management plays a significant role in enhancing performance of proton exchange membrane fuel cell (PEMFC). Successful water management requires effective removal of liquid water produced by electrochemical reactions. Therefore, it is a critical challenge to understand liquid water movements in flow channels. In the present study, a three-dimensional unsteady two-phase model for the cathode side of PEMFC consisting of gas channel (GC), gas diffusion layer (GDL) and catalyst layer (CL) is developed using FLUENT software with a volume-of-fluid (VOF) method and user-defined-function (UDF). When fuel cells are assembled, the cross sections of gas channel change, resulting in different water droplet movements. The effects of GDL deformations on water droplet movements are discussed.

A Comparative 1D Analysis of PEM, SO and DB Fuel Cells

2014 ◽  
Author(s):  
Isaac Perez-Raya ◽  
Michael W. Ellis ◽  
Abel Hernandez-Guerrero ◽  
Francisco Elizalde-Blancas ◽  
Carlos U. Gonzalez-Valle ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Sodium Borohydride ◽  
Proton Exchange Membrane ◽  
Numerical Study ◽  
Proton Exchange ◽  
Solid Oxide ◽  
Cathode Side ◽  
Technical Problems ◽  
Exchange Membrane

Although fuel cells represent an attractive alternative for electricity generation, different technical problems, such as the hydrogen storage, have not been solved, as yet. Nowadays direct sodium borohydride fuel cells are considered as a promising technology since NaBH4 (fuel) is a stable, nonflammable and nontoxic liquid solution. In the present study a one-dimensional numerical study of a proton exchange membrane, a solid oxide, and a direct sodium borohydride fuel cell is performed. The objective of this work is to compare qualitatively the fuel cell performance between these technologies. For proton exchange membrane and solid oxide fuel cells there are already established useful models and correlations widely known, and used, to predict the current density and the power generated. Direct Borohydride fuel cells, on the other hand, are still in their early developments; in the present paper DBFCs are analyzed using a novel model. This proposed model for DBFCs includes the prediction of the NaBH4 oxidation in the anode side, the H2O2 reduction in the cathode side and the effect of the solution concentration and temperature on the membrane. It is noteworthy mentioning that this last effect has not been integrated in any of the established models in the current technical literature.

A Critical Review of Water Transport Models in Gas Diffusion Media of PEM Fuel Cell

2008 ◽  
Author(s):  
Jacob LaManna ◽  
Satish G. Kandlikar
Keyword(s):  
Water Management ◽  
Fuel Cell ◽  
Water Transport ◽  
Combustion Engine ◽  
Pem Fuel Cell ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Cathode Side ◽  
Small Scale

Proton Exchange Membrane (PEM) fuel cells are gaining popularity as a replacement to the internal combustion engine in automobiles. This application will demand high levels of performance from the fuel cell making it critical that proper water management is maintained. One of the areas of interest in water management is the transport of water through the Gas Diffusion Medium (GDM) on the cathode side of the cell. Research is currently being conducted to understand how water moves through the porous structure of the GDM. Due to the small scale of the GDM, most work done is analytical modeling. This paper will focus on reviewing current models for water transport within the GDM of a PEM fuel cell to address state of the art and provide recommendations for future work to extend current models.

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.

Miniature Fuel Processors for Portable Fuel Cell Power Supplies

2002 ◽  
Vol 756 ◽  
Author(s):  
Jamie Holladay ◽  
Evan Jones ◽  
Daniel R. Palo ◽  
Max Phelps ◽  
Ya-Huei Chin ◽  
...  
Keyword(s):  
Water Management ◽  
Carbon Monoxide ◽  
Fuel Cell ◽  
Power Loss ◽  
Power Supplies ◽  
The Novel ◽  
Methanol Reforming ◽  
Fuel Cell Stack ◽  
Portable Power ◽  
Novel Catalyst

ABSTRACTMiniature and microscale fuel processors that incorporate novel catalysts and microtechnology-based designs are discussed. The novel catalyst allows for methanol reforming at high gas hourly space velocities of 50,000 hr-1 or higher while maintaining a carbon monoxide levels at 1% or less. The microtechnology-based designs extremely compact and lightweight devices. The miniature fuel processors, with a volume less than 25 cm3, a mass less than 200 grams, and thermal efficiencies of up to 83%, nominally provide 25 to 50 watts equivalent of hydrogen, which is ample for the portable power supplies described here. With reasonable assumptions on fuel cell efficiencies, anode gas and water management, parasitic power loss, the energy density was estimated at 1700 Whr/kg. These processors have been demonstrated with a CO cleanup method and a fuel cell stack. The microscale fuel processors, with a volume of less than 0.25 cm3 and a mass of less than 1 gram, are designed to provide up to 0.3 watt equivalent of power with efficiencies over 20%.

Sign in / Sign up

Export Citation Format

Share Document