Steady and Pulsed Flow Performance Trends of Higher Concentration DMFCs

2006 ◽  
Author(s):  
Larry McCarthy ◽  
Comas Haynes
Keyword(s):  
Energy Density ◽  
Direct Methanol Fuel Cells ◽  
High Energy ◽  
Operating Conditions ◽  
High Energy Density ◽  
Methanol Crossover ◽  
Fuel Delivery ◽  
Fuel Mixtures ◽  
The Impact ◽  
Promising Source

Direct methanol fuel cells (DMFCs) are a promising source of energy due to their potentially high energy density, facilitated fuel delivery and storage, and precluded fuel processing. However, DMFCs have several challenges which need to be resolved before they can replace existing energy sources. Some of these challenges include lower power density, relatively high cost, and uncertain reliability. These issues are all promoted, at least in part, by the methanol crossover phenomenon, wherein membrane permeability allows the undesirable species transport of methanol from the anode to the cathode. This phenomenon also causes the requirement of dilute fuel mixtures, which is undesirable from an energy density viewpoint. Prior research has shown that methanol crossover can be reduced by operating DMFCs in a transient mode [1,2]. Thus, a study has been performed to investigate the impact of hydraulic pulsing (HP) at different operating conditions, such as fuel concentration, current density, and number-of-stoichs (NOS). Furthermore, the cell’s performance is being characterized at different steady flow concentrations to highlight the impact of fuel dilution.

The impact of Hall physics on magnetized high energy density plasma jets

2014 ◽  
Vol 21 (5) ◽  
pp. 056307 ◽  
Author(s):  
P.-A. Gourdain ◽  
C. E. Seyler ◽  
L. Atoyan ◽  
J. B. Greenly ◽  
D. A. Hammer ◽  
...  
Keyword(s):  
Energy Density ◽  
High Energy ◽  
Plasma Jets ◽  
High Energy Density ◽  
The Impact ◽  
Density Plasma

scholarly journals Cation-disordered rocksalt transition metal oxides and oxyfluorides for high energy lithium-ion cathodes

2020 ◽  
Vol 13 (2) ◽  
pp. 345-373 ◽  
Author(s):  
R. J. Clément ◽  
Z. Lun ◽  
G. Ceder
Keyword(s):  
Energy Density ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Short Range ◽  
Short Range Order ◽  
Lithium Ion ◽  
High Energy ◽  
High Energy Density ◽  
Detailed Understanding ◽  
The Impact

Cation-disordered rocksalt oxides and oxyfluorides are promising high energy density lithium-ion cathodes, yet require a detailed understanding of the impact of disorder and short-range order on the structural and electrochemical properties.

Optimizing the Anode Structure of a Passive Tubular-Shaped Direct Methanol Fuel Cell to Operate With High Concentration Methanol

2012 ◽  
Vol 9 (5) ◽  
Author(s):  
Jing Huang ◽  
Travis Ward ◽  
Amir Faghri
Keyword(s):  
Energy Density ◽  
Low Power ◽  
Power Density ◽  
Direct Methanol Fuel Cells ◽  
Fuel Efficiency ◽  
High Energy ◽  
Energy Output ◽  
Methanol Crossover ◽  
High Concentration ◽  
Direct Methanol

In order to take full advantage of the high energy density available in methanol fuel, one must use high concentration methanol in direct methanol fuel cells (DMFCs). However, this causes severe methanol crossover and leads to low power density and fuel efficiency. In this work, a tubular shape is adopted to generate higher volumetric power density; porous polytetrafluoroethylen (PTFE) membranes at the anode are used to control methanol transport with a high concentration fuel. A novel passive tubular-shaped DMFC is improved to achieve stable operation with methanol concentrations up to 20 M. It is observed that a balance between fuel transport resistance, power density, energy density, and fuel efficiency exists. Increased resistance enhances fuel efficiency, hence, energy density, but limits the fuel supply and causes low power density. With the improved anode structure and higher concentration fuel (1 M to 15 M), the energy output of the tubular DMFC increases 591%, from 0.094 Wh to 0.65 Wh with 2 ml fuel. The power densitymaintains the same level as 16 mW/cm2. For different fuel concentrations, there exists an optimum structure to generate the highest power density, which is a result of minimizing the methanol crossover while also providing sufficient fuel. The discharge characteristic at constant voltage and its effect on fuel efficiency are also discussed.

scholarly journals Energy storage: dielectrophores – molecules with non-linear polarizability

2017 ◽  
Vol 17 (4) ◽  
pp. 14-21 ◽  
Author(s):  
L. Mourokh ◽  
P. Lazarev
Keyword(s):  
Energy Storage ◽  
Energy Density ◽  
Selection Process ◽  
High Energy ◽  
Molecular Engineering ◽  
High Energy Density ◽  
High Resistivity ◽  
Energy Storage Devices ◽  
Non Linear ◽  
The Impact

Abstract We examine the feasibility of film capacitors based on dielectrics with high non-linear polarizability as energy storage devices. Capacitors with increased energy density can be built by using composite materials with aromatic molecules (high polarizability) and envelope of alkyl tails (high resistivity). We determine the impact of the second order non-linearity onto energy density and translate high energy density requirements into molecular parameters necessary for high-performance capacitors. The relationship of permittivity and molecular polarizability is obtained by means of the non-linear Clausius–Mossotti equation. In order to demonstrate the the selection process for the molecular composition of dielectrophores, we compare several molecules, using quantum chemistry algorithms (Gaussian09). Starting from Langhals perylene (LP), we proceed with the nitrophenyl-perylene having one NH2 group (donor) and one NO2 group (acceptor). We show that, while their linear polarizabilities are comparable, the hyperpolarizabilities differ by several orders of the magnitudes. Two NH2 and NO2 groups can be attached to the nitro-naphthalene-perylene further increasing of the hyperpolarizability. Even larger polarization can be achieved by additional rylene groups increasing the polarizable electronic mass. We demonstrate that with such molecular engineering, capacitors can have the energy density which is attractive for practical applications.

Eddy current loss and its magnetization effect of electromagnetic buffer under intensive impact load

2020 ◽  
pp. 1-20
Author(s):  
Zixuan Li ◽  
Guolai Yang ◽  
Ning Liu
Keyword(s):  
Energy Density ◽  
Eddy Current ◽  
Impact Load ◽  
Current Model ◽  
High Energy ◽  
Eddy Current Loss ◽  
High Energy Density ◽  
Time Step ◽  
Current Loss ◽  
The Impact

In this paper, a high-energy density electromagnetic buffer (EMB) is studied and analysed for the violent acceleration and high velocity of intensive impact loads. First, the design requirements of the EMB are proposed to select reasonable structure and magnetic circuit parameters. The equivalent current model is used to introduce the primary eddy current affected by demagnetization effect and the induced secondary eddy current. The magnetization process is studied by dividing the conductor tube into the approach end and the departure end. Considering the nonlinear damping and eddy current interaction between primary and secondary, a primary-secondary eddy current loss coupled nonlinear time-step finite element model (FEM) is established to obtain the spatiotemporal distribution characteristics of eddy current. Finally, a test experiment with weak impact, medium impact and intensive impact was carried out. The measured displacement, velocity, damping force, and time nodes responses during buffering are consistent with the established time-step FEM results. The proposed high-energy density EMB can effectively complete the impact buffering process. It is reasonable to obtain the eddy current loss and its magnetization law from the established FEM which is suitable for shock buffering with different impulse strength.

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