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FCV (Fuel Cell Technology)

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Fuel Cell is a wonderful device that generates electricity by a chemical reaction. Every of the fuel cell has two electrodes in it; every one of us must have read in our studies about that already. Electrodes are of two kinds, one positive and another one negative and named as anode and cathode respectively.  I understand at young age chemistry is a nightmare for many of us. But we can understand the reactions that produce the electricity take place at the electrode. Again, every fuel cell got an electrolyte that carries electrically charged particles from one electrode to another one and a catalyst which speeds up the reaction process at the electrodes. Hydrogen is considering as one of the basic fuel, but remembers that it also requires oxygen for the process. One of the best thing about this process is it generates electricity with minimum population. Hydrogen and oxygen combines together to generate electricity and form another harmless product named water that comes from silencer.

Fuel Efficiency

Fuel efficiency of vehicle can be defined in different ways. Fuel consumption is one of the way through which we define the fuel efficiency. As much the lower the value of consumption, fuel efficiency will increase. Similarly fuel economy is another way to define fuel efficiency. In that way we see that the distance travel per unit volume of fuel we used. As much higher the distance volume, fuel efficiency will also increase.

 

Fuel Cell

Fuel cells are an important enabling technology for the energy collections of the nation's and have the possible to transform the way we power our nation, offering cleaner, more-efficient alternatives to the combustion of gasoline and other vestige fuels. Fuel cells have the capability to replace the internal-combustion engine in vehicles and produce power in stationary and portable power applications because they are energy-efficient, clean, and fuel-flexible. It is a promising technology to use as a source of heat & electric motors driving vehicles. The best operation of fuel cells is on pure hydrogen. But some fuels like natural gas or gasoline can be change to produce the Hydrogen required for fuel cell. In future it is expected that hydrogen could also join electricity. An energy carrier moves and delivers energy in a useable form to consumers. On the other hand renewable energy sources like sun & wind can not produce energy all the time. There are many types of fuel cells, but they all consist of an anode, a cathode and an electrolyte that allows charges to move between the two sides of the fuel cell. If free electrons or other substances could travel through the electrolyte, they would disrupt the chemical reaction. Due to air pollution, energy dependence, and now climate change have motivated the exploration of cleaner alternative transportation fuels for several decades. In the last several decades, hydrogen fuel cell vehicles (FCVs) have appeared as a zero tailpipe emission alternative to the battery electric vehicle. Fuel cell vehicles (FCVs) have the potential to significantly reduce our dependence on foreign oil and lower harmful emissions that contribute to climate change. FCVs run on hydrogen gas rather than gasoline and emit no harmful tailpipe emissions. Several challenges must be overcome before these vehicles will be competitive with conventional vehicles, but the potential benefits of this technology are substantial.

Hydrogen powered fuel cell could improve energy use and lower carbon production, taking important benefits for consumers, the environment and energy security. But on the other hand on earth hydrogen molecules hardly exist by themselves. They made from other compounds and then delivered efficiently to be used for vehicle fuel cells. Continuing advances in vehicle and fuel technology will be critical to meeting global demand for transportation fuels.

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.

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Different types of fuel cells

Alkali fuel cells operate on compressed hydrogen and oxygen. They generally use a solution of potassium hydroxide (chemically, KOH) in water as their electrolyte. Efficiency is about 70 percent, and operating temperature is 150 to 200 degrees C, (about 300 to 400 degrees F). Cell output ranges from 300 watts (W) to 5 kilowatts (kW). Alkali cells were used in Apollo spacecraft to provide both electricity and drinking water. They require pure hydrogen fuel, however, and their platinum electrode catalysts are expensive. And like any container filled with liquid, they can leak.

Molten Carbonate fuel cells (MCFC) use high-temperature compounds of salt (like sodium or magnesium) carbonates (chemically, CO3) as the electrolyte. Efficiency ranges from 60 to 80 percent, and operating temperature is about 650 degrees C (1,200 degrees F). Units with output up to 2 megawatts (MW) have been constructed, and designs exist for units up to 100 MW. The high temperature limits damage from carbon monoxide "poisoning" of the cell and waste heat can be recycled to make additional electricity. Their nickel electrode-catalysts are inexpensive compared to the platinum used in other cells. But the high temperature also limits the materials and safe uses of MCFCs–they would probably be too hot for home use. Also, carbonate ions from the electrolyte are used up in the reactions, making it necessary to inject carbon dioxide to compensate.

Phosphoric Acid fuel cells (PAFC) use phosphoric acid as the electrolyte. Efficiency ranges from 40 to 80 percent, and operating temperature is between 150 to 200 degrees C (about 300 to 400 degrees F). Existing phosphoric acid cells have outputs up to 200 kW, and 11 MW units have been tested. PAFCs tolerate a carbon monoxide concentration of about 1.5 percent, which broadens the choice of fuels they can use. If gasoline is used, the sulfur must be removed. Platinum electrode-catalysts are needed, and internal parts must be able to withstand the corrosive acid.

Proton Exchange Membrane (PEM) fuel cells work with a polymer electrolyte in the form of a thin, permeable sheet. Efficiency is about 40 to 50 percent, and operating temperature is about 80 degrees C (about 175 degrees F). Cell outputs generally range from 50 to 250 kW. The solid, flexible electrolyte will not leak or crack, and these cells operate at a low enough temperature to make them suitable for homes and cars. But their fuels must be purified, and a platinum catalyst is used on both sides of the membrane, raising costs.

Solid Oxide fuel cells (SOFC) use a hard, ceramic compound of metal (like calcium or zirconium) oxides (chemically, O2) as electrolyte. Efficiency is about 60 percent, and operating temperatures are about 1,000 degrees C (about 1,800 degrees F). Cells output is up to 100 kW. At such high temperatures a reformer is not required to extract hydrogen from the fuel, and waste heat can be recycled to make additional electricity. However, the high temperature limits applications of SOFC units and they tend to be rather large. While solid electrolytes cannot leak, they can crack :)

 

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References

http://www.consumerenergycenter.org/transportation/fuelcell/
http://en.wikipedia.org/wiki/Fuel_cell_vehicle
http://corporate.exxonmobil.com/en/engineering/vehicle-technologies/hydrogen-fuel-cells/overview
http://76.12.4.249/artman2/uploads/1/Martin_et_al_-_Behavioral_.pdf
http://www.businessinsider.com/pro-con-future-of-hydrogen-fuel-cell-electric-vehicles-fcev-2013-4#!HANyx

http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell.htm

http://www.alternative-energy-news.info/technology/fuel-cells/

http://americanhistory.si.edu/fuelcells/basics.htm

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