Proton Exchange Membrane Fuel Cell Characterizationf or Electric Vehicle Applications
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02-11-2010, 12:39 PM
Proton Exchange Membrane FuelCell Characterizationf or Electric
This paper presents experimental data and an analysis of a proton exchange membrane fuel cell system for electric vehicle applications. The dependence of the fuel cell system’s performance on air stoichiometry, operating temperature, and reactant gas pressure was assessed in terms of the fuel cell’s polarity and power density-efficiency graphs. All the experimen~ were performed by loading the fuel cell with resistive heater coils which could be controlled to provi,de a constant current or constant power load. System parmdtic power requirements and individual cell voltage dia~aS[bution were also determined as a function of the electrical load. It was fotmd that the fuel" cell’s performance improved with increases in temperature, pressure and stoich~ometry within the range in which the fuel cell was operational. Cell voltage imbalances increased with increases in current otaput. The effect of such an imbalance is, however, not detrimental to the fuel cell system, as it is in the case of a battery.
An electr~-hemical fuel ceil is a device that converts chemical energy to direct current electrical energy. By converting an on-board fuel to electricity it could be effetely-ely used to power an electric vehicle. As such, a fuel cell is an energy conversion device like an Latemal combustion engiue. This is in contrast to energy storage systems such as bat*,eries, flywheels and ultra capacitors. Further many of a fuel cells operating characteristics are closer to that of an engine th~n a storage battery. A fuel cell sy~m operation involves startup, fuel and air delivery control as a function of load, and removal of heat mad by prochacts of the reaction. The fuel cell, in other words, is an electrochemical engine. While electrochemistry describes the princspIe of operation of a fuel cell, the engineering challenge of baLancing the many variables over a wide variety of operating conditions remains. The fuel cell system consists ofa complex group of support systems that must operate in balance for efficient performance. Different types of fuel cells are conveniently dassLfied the type of electrolyte they use. Electrolytes that are presently being considered include the proton exchange membrane (a solid polymer material), phosphoric acid (a liquid), alkaline (a liquid), molten cadxmate (a liquid) and solid oxide ceramic). The choice of electrolyte directly affects a fuel cell’s operating characteristics; for example, phosphoric acid is a poor ion conductor at room temperature. As a result the phosphoric acid fuel cell must be heated to 150 to 200°C before it can be used. Today many researchers believe that the proton exchange membrane (PF2eD provides the best characteristics for transportation applications. The data and analysis presented in this paper is for a fuel ceil system manufactured by Ballard Power Systems of Vancouwer, Canada. The fuel ceil system consists of: a 35 cell series connected stack; gas, water and thermal management subsystems; and controls and monitors all assembled in a single enclosure. The area of each cell was 232 can2 and the fuet cell stack itself had a maximumgr oss power output greater than 3000 Watts operating on hydrogen and air. The system was modified by the authors to be able to independently control air stoichiometry, air/hydrogen pressure and stack exit air temperature. Previous papers that have presented experimental data on similar Ballard fuel cells systems are referencesland 2 The paper is organized into sections in the following order; Fuel Cell Operating Principle, Experimental Apparatus, Experimental Results, Results Analysis and Conclusions. The section on fuel cell operating principle is intended to give a brief overview of how a fuel cell works and its operating characteristics. The experimental apparatus section briefly describes the fuel cell system used in the experiments and the associated instrumentation. The experimental results present a series of polarity plots (voltage - current relationship) under a variety of operating conditions. The results analysis section presents the results in terms of power density-efficiency plots implicitly demonstrating theoperating characteristics of the fuel cell ~stem for electric vehicle applications.
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15-03-2012, 03:29 PM
Proton Exchange Membrane Fuel Cell Characterization
for Electric Vehicle Applications
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INTRODUCTION TO FUEL CELLS
Fuel cells have the potential to revolutionize the way we power our nation, offering cleaner, more-efficient alternatives to the combustion of gasoline and other fossil fuels. A fuel cell is a device that uses hydrogen and oxygen to create an electric current.
The amount of power production by a fuel cell depends on several factors, including fuel cell type, cell size, the temperature at which it operates, and the pressure at which the gases are supplied to the cell.
A single fuel cell produces enough electricity for only the smallest application. Therefore, to provide the power needed for most application, individual fuel cells are combined in series into a fuel cell stack. A typical fuel cell stack may of hundred of fuel cells.
A fuel cell is an electrochemical conversion device. It produces electricity from fuel (on the anode side) and an oxidant (on the cathode side), which react in the presence of an electrolyte. The reactants flow into the cell, and the reaction products flow out of it, while the electrolyte remains within it. Fuel cells can operate virtually continuously as long as the necessary flows are maintained.
OBJECTIVES OF OUR PROJECT
Our project and implimentation is entitled design and fabrication of fuel cell for power generation
There are many fuel cells of various ranges depending on the application available in the market. We take alkaline fuel cell for our project and implimentation because of its simple design, low cost and effective power.
Our aim is, to produce electric power from our project and implimentation from this fuel cell.
Following components and materials are used in our project and implimentation.
1) Plastic container
It is the main component used here with its technical name is stack. This stack is the housing for potassium hydroxide and electrodes. The chemical reaction place inside this stack. The external circuits are placed above the stack.
Material used: plastic.
Electrode making process
With the use of PTFE powder, graphite powder and platinum powder, electrodes are to be prepared in powder compaction press machine.
In that single stack we will get 0.7 voltages only. As many as the number of stack that much of voltage can be produced.