12-04-2011, 11:19 AM
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Abstract:
Fuel cell is a device which converts chemical energy into electrical energy just like a battery but it neither requires recharging nor it run down. Fuel cell’s construction is same as that of conventional batteries but working principle is different. Its constriction uses an anode, a cathode and an electrolyte. Hydrogen is the most commonly used fuel in fuel cells. Hydrogen atom is separated into proton and electron at anode, protons are allowed to pass through the electrolyte whereas electrons are left behind and they pass through external circuit. Oxygen is drawn out from atmosphere and it combines with electrons and protons. Forms water as by product.
There are mainly five types of fuel cells Alkali fuel cell, Molten carbonate fuel cell, phosphoric acid fuel cell, PME (Proton exchange membrane) fuel cell, solid oxide fuel cell. Each work on same principle but differ in their actions.
Fuel cells are increasingly used in automobiles. Nowadays they are replacing I.C engines because they are efficient, pollution free, high reliability, noiseless, vibration less, greater flexibility in design of vehicles.
They are also used in hospitals, nursing homes, hotels, office buildings, schools, utility power plants as UPS (uninterrupted power supply) systems as to provide backup power to avoid power crisis.
In telecommunications, with the use of computers, the Internet, and communication networks steadily increasing, Fuel cells offer a reliable source of energy. Fuel cells can replace batteries to provide power for 1kW to 5kW telecom sites without noise or emissions, and are durable, providing power in sites that are either hard to access or are subject to inclement weather. Such systems would be used to provide primary or backup power for telecom switch nodes, cell towers, and other electronic systems that would benefit from on-site, direct DC power supply.
With the increase in the research, more efficient fuel cell will come in future that have power to replace existing sources of energy. They will be commercialized soon.
What is a fuel cell?
A fuel cell is a device that generates electricity by a chemical reaction with water and heat as by-products. Every fuel cell has two electrodes, one positive and one negative, called, respectively, the anode and cathode. The reactions that produce electricity take place at the electrodes.
Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes.
Hydrogen is the basic fuel, but fuel cells also require oxygen. One great appeal of fuel cells is that they generate electricity with very little pollution—much of the hydrogen and oxygen used in generating electricity ultimately combine to form a harmless byproduct, namely water.
How does a fuel cell work?
It operates similarly to a battery, but it does not run down nor does it require recharging. As long as fuel is supplied, a Fuel Cell will produce both energy and heat. The purpose of a fuel cell is to produce an electrical current that can be directed outside the cell to do work, such as powering an electric motor or illuminating a light bulb or a city. Because of the way electricity behaves, this current returns to the fuel cell, completing an electrical circuit. The chemical reactions that produce this current are the key to how a fuel cell works.
There are several kinds of fuel cells, and each operates a bit differently. But in general terms, hydrogen atoms enter a fuel cell at the anode where a chemical reaction strips them of their electrons. The hydrogen atoms are now “ionized,” and carry a positive electrical charge. The negatively charged electrons provide the current through wires to do work. If alternating current (AC) is needed, the DC output of the fuel cell must be routed through a conversion device called an inverter.
Oxygen enters the fuel cell at the cathode and, in some cell types, it there combines with electrons returning from the electrical circuit and hydrogen ions that have traveled through the electrolyte play a key role. It must permit only the appropriate ions to pass between the anode and cathode. If free electrons or other substances could travel through the electrolyte, they would disrupt the chemical reaction.
Whether they combine at anode or cathode, together hydrogen and oxygen form water, which drains from the cell. As long as a fuel cell is supplied with hydrogen and oxygen, it will generate electricity.
Even better, since fuel cells create electricity chemically, rather than by combustion, they are not subject to the thermodynamic laws that limit a conventional power plant. Therefore, fuel cells are more efficient in extracting energy from a fuel. Waste heat from some cells can also be harnessed, boosting system efficiency still further.
Different types of fuel cells:
1. Alkali Fuel Cell:
Technology:
Alkali fuel cells operate on compressed hydrogen and oxygen and generally use a solution of potassium hydroxide in water as their electrolyte. Operating temperatures inside alkali cells are around 150 to 200 degrees C. In these cells, hydroxyl ions (OH-) migrate from the anode to the cathode. At the anode, hydrogen gas reacts with the OH- ions to produce water and release electrons. Electrons generated at the anode supply electrical power to an external circuit then return to the cathode. There the electrons react with oxygen and water to produce more hydroxyl ions that diffuse into the electrolyte.
Alkali fuel cells operate at efficiencies up to 70 percent and, like other fuel cells, create little pollution. Because they produce potable water in addition to electricity, they have been a logical choice for spacecraft. A major drawback, however, is that alkali cells need very pure hydrogen or an unwanted chemical reaction forms a solid carbonate that interferes with chemical reactions inside the cell. Since most methods of generating hydrogen from other fuels produce some carbon dioxide, this need for pure hydrogen has slowed work on alkali fuel cells in recent years. Another drawback has been the need for large amounts of a costly platinum catalyst to speed up the reaction.
Applications:
NASA selected alkali fuel cells for the Space Shuttle fleet, as well as the Apollo program, mainly because of power generating efficiencies that approach 70 percent. Alkali cells also provide drinking water for the astronauts. The cells are expensive -- perhaps too expensive for commercial applications -- but several companies are examining ways to reduce costs and improve the cells' versatility. Most of these alkali fuel cells are being designed for transport applications.
Abstract:
Fuel cell is a device which converts chemical energy into electrical energy just like a battery but it neither requires recharging nor it run down. Fuel cell’s construction is same as that of conventional batteries but working principle is different. Its constriction uses an anode, a cathode and an electrolyte. Hydrogen is the most commonly used fuel in fuel cells. Hydrogen atom is separated into proton and electron at anode, protons are allowed to pass through the electrolyte whereas electrons are left behind and they pass through external circuit. Oxygen is drawn out from atmosphere and it combines with electrons and protons. Forms water as by product.
There are mainly five types of fuel cells Alkali fuel cell, Molten carbonate fuel cell, phosphoric acid fuel cell, PME (Proton exchange membrane) fuel cell, solid oxide fuel cell. Each work on same principle but differ in their actions.
Fuel cells are increasingly used in automobiles. Nowadays they are replacing I.C engines because they are efficient, pollution free, high reliability, noiseless, vibration less, greater flexibility in design of vehicles.
They are also used in hospitals, nursing homes, hotels, office buildings, schools, utility power plants as UPS (uninterrupted power supply) systems as to provide backup power to avoid power crisis.
In telecommunications, with the use of computers, the Internet, and communication networks steadily increasing, Fuel cells offer a reliable source of energy. Fuel cells can replace batteries to provide power for 1kW to 5kW telecom sites without noise or emissions, and are durable, providing power in sites that are either hard to access or are subject to inclement weather. Such systems would be used to provide primary or backup power for telecom switch nodes, cell towers, and other electronic systems that would benefit from on-site, direct DC power supply.
With the increase in the research, more efficient fuel cell will come in future that have power to replace existing sources of energy. They will be commercialized soon.
What is a fuel cell?
A fuel cell is a device that generates electricity by a chemical reaction with water and heat as by-products. Every fuel cell has two electrodes, one positive and one negative, called, respectively, the anode and cathode. The reactions that produce electricity take place at the electrodes.
Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes.
Hydrogen is the basic fuel, but fuel cells also require oxygen. One great appeal of fuel cells is that they generate electricity with very little pollution—much of the hydrogen and oxygen used in generating electricity ultimately combine to form a harmless byproduct, namely water.
How does a fuel cell work?
It operates similarly to a battery, but it does not run down nor does it require recharging. As long as fuel is supplied, a Fuel Cell will produce both energy and heat. The purpose of a fuel cell is to produce an electrical current that can be directed outside the cell to do work, such as powering an electric motor or illuminating a light bulb or a city. Because of the way electricity behaves, this current returns to the fuel cell, completing an electrical circuit. The chemical reactions that produce this current are the key to how a fuel cell works.
There are several kinds of fuel cells, and each operates a bit differently. But in general terms, hydrogen atoms enter a fuel cell at the anode where a chemical reaction strips them of their electrons. The hydrogen atoms are now “ionized,” and carry a positive electrical charge. The negatively charged electrons provide the current through wires to do work. If alternating current (AC) is needed, the DC output of the fuel cell must be routed through a conversion device called an inverter.
Oxygen enters the fuel cell at the cathode and, in some cell types, it there combines with electrons returning from the electrical circuit and hydrogen ions that have traveled through the electrolyte play a key role. It must permit only the appropriate ions to pass between the anode and cathode. If free electrons or other substances could travel through the electrolyte, they would disrupt the chemical reaction.
Whether they combine at anode or cathode, together hydrogen and oxygen form water, which drains from the cell. As long as a fuel cell is supplied with hydrogen and oxygen, it will generate electricity.
Even better, since fuel cells create electricity chemically, rather than by combustion, they are not subject to the thermodynamic laws that limit a conventional power plant. Therefore, fuel cells are more efficient in extracting energy from a fuel. Waste heat from some cells can also be harnessed, boosting system efficiency still further.
Different types of fuel cells:
1. Alkali Fuel Cell:
Technology:
Alkali fuel cells operate on compressed hydrogen and oxygen and generally use a solution of potassium hydroxide in water as their electrolyte. Operating temperatures inside alkali cells are around 150 to 200 degrees C. In these cells, hydroxyl ions (OH-) migrate from the anode to the cathode. At the anode, hydrogen gas reacts with the OH- ions to produce water and release electrons. Electrons generated at the anode supply electrical power to an external circuit then return to the cathode. There the electrons react with oxygen and water to produce more hydroxyl ions that diffuse into the electrolyte.
Alkali fuel cells operate at efficiencies up to 70 percent and, like other fuel cells, create little pollution. Because they produce potable water in addition to electricity, they have been a logical choice for spacecraft. A major drawback, however, is that alkali cells need very pure hydrogen or an unwanted chemical reaction forms a solid carbonate that interferes with chemical reactions inside the cell. Since most methods of generating hydrogen from other fuels produce some carbon dioxide, this need for pure hydrogen has slowed work on alkali fuel cells in recent years. Another drawback has been the need for large amounts of a costly platinum catalyst to speed up the reaction.
Applications:
NASA selected alkali fuel cells for the Space Shuttle fleet, as well as the Apollo program, mainly because of power generating efficiencies that approach 70 percent. Alkali cells also provide drinking water for the astronauts. The cells are expensive -- perhaps too expensive for commercial applications -- but several companies are examining ways to reduce costs and improve the cells' versatility. Most of these alkali fuel cells are being designed for transport applications.
