FUEL CELL AS AN ALTERNATIVE ENERGY SOURCE
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07-01-2011, 11:23 PM
Though any death-knell for the internal combustion engine is decades off, as fossil fuels may last upto 2050 only, we have to consider an alternative for present fuels. The world’s automakers seem to believe that the low emission, high efficiency fuel cell will eventually prove as an alternative, delivering the power and performance that customers expect. Such a high potential candidate needs suitable analysis. This paper is a modest attempt in giving the promising alternative: fuel cell vehicle. Also a brief forecast has been made on the Fuel Cell an Alternative Fuel.
FUEL CELL AS AN ALTERNATIVE ENERGY SOURCE.DOC (Size: 1.15 MB / Downloads: 268)
2. Invention of the little giant
The invention of the fuel cell started in 1839 when the English Physicist William R. Grove, working from the knowledge that running an electric current through water would produce hydrogen and oxygen, showed that combining hydrogen and oxygen could produce electric current and water. Grove’s demonstration opened the way to a new electrical power source, the fuel cell, but little was done with the concept for well over century. It may be recalled that fuel cells were used to provide electrical power to the Apollo Moon capsule and other space crafts, but failed to reach a wider market.
3. Principle of operation
The fuel cell is conceptually simple. It has been known since the beginning of modern chemistry that running an electrical current through water yields hydrogen and oxygen gas according to:
2 H2O on passing current 2 H2 + O2
This reaction is known as “electrolysis”, and as Groove discovered, it can be performed in can be performed in reverse, combining hydrogen and oxygen gas to generate an electrical current, plus water as by-product.
2 H2 + O2 2 H2 + O2
Fuel cells are based on “reverse electrolysis”. They resemble batteries, in that their DC electrical output is due to an electrochemical process.
4. General concept of power generation in a fuel system
However, unlike batteries, fuel cells operate off a continuous stream of air as a source of hydrogen fuel. While straight diatomic hydrogen can be used, in practice this is not a very convenient fuel, and so in general fossil fuels, such as methane, methanol, naphtha, coal gas and other hydrocarbons are broke down to provide hydrogen. In means that fuel cells in principle have much longer service lifetime than batteries.
In general form a fuel cell consists of a porous anode and a porous cathode, with these two electrodes separated by an electrolyte. An oxidant is fed to the cathode to supply hydrogen. The electrolyte supports the transfer of ions between anode and cathode to support the reverse electrolysis reaction.
The anode and cathode may be patterned with channels to allow distribution of oxygen or hydrogen. An individual fuel cell generates from 0.6 to 0.8 volts (DC) and large numbers of such cells have to be stacked in a fuel cell system and connected in series to provide a useful power output. Fuel cells do not “run down” as long as the hydrogen (fuel) and oxygen (air) are supplied. Since there is no combustion, fuel cells are inherently cleaner and more efficient than systems that must burn fuel to release energy.
5. Types of fuel cells
There are two general classes of fuel cells, based on whether the electrolyte is alkaline (basic) or acidic. Resistance in the electrolyte is a source of power loss, but making the electrolyte either very alkaline or very acidic can reduce this problem. There is only one type of alkaline fuel cell, and it is the oldest fuel cell technology. It is still in use in aerospace applications.
There are four types of acidic fuel cells:
• The phosphoric acid fuel cell (PAFC).
• The proton exchange membrane (PEM) fuel cell.
• The molten carbonate fuel cell (MCFC).
• The solid oxide fuel cell (SOFC).
The PAFC and the PEM fuel cells are the best developed acidic fuel cell. The PAFC is in modest use as a fixed AC power source for buildings and in sites, while the PEM is under intense development as a power source for automobiles. The MCFC and SOFC are also under investigation as fixed AC power sources, but their development is not so far advanced as that of the PAFC.
6. Alkaline fuel cells for automobiles
The earliest modern applied fuel cell technology, the alkaline fuel cell, uses strongly alkaline potassium carbonate; the alkaline fuel cell absolutely must have a source of pure hydrogen to operate. The alkaline fuel cells operate at relatively low temperatures, in the range of 800to 950 Celsius. It uses platinum catalyst to utilize the reverse electrolysis reaction rate. The alkaline fuel cell has a number of attractive features. It requires less platinum catalyst than acidic fuel cells, and has a high power to weight ratio. Improvements in the design have resulted in electrolyte’s susceptibility to carbon dioxide poisoning. However, the alkaline fuel cell has to be supplied with pure hydrogen, since any carbon dioxide contaminants will react with potassium hydroxide to form sodium potassium carbonate. It remains useful for aerospace applications, while its lightness is valuable and the requirement for pure hydrogen is not too difficult to meet, but is not generally regarded as useful for terrestrial applications.
7. Components of PEM fuel cells
A PEM fuel cell consists of:
• A source supplying Hydrogen
• An oxidant supplying Oxygen
• An anode and a cathode (a thin and flat cell made up of two electrodes separated by plastic sheet called membrane).The cathode and anode are formed by an electrochemically active catalyst layer, typically platinum.
• An external circuit
• Proton exchange membrane
• Proton exchange material called Nafion®, manufactured by Dupont, is being used as the electrolyte.
• Nafion is made from rolled sheet, solution cast, and sputter-coated fuel cells. Carbon cloth, treated with Teflon® and a platinum-on-carbon catalyst, was rolled onto a porous, tubular, stainless steel or carbon dowel (serving as a current conductor) and bonded into place to provide the inner electrode, called the hydrogen bearing anode, of the fuel cell.
8. Working of a fuel cell
Referring to figure 2 hydrogen from the source is exposed to the anode. The anode then draws the electron from the hydrogen leaving a proton (H¬¬¬¬¬¬¬¬+). On the opposite side of the cell, the cathode absorbs oxygen from air. This produces a potential and causes the electron to move through an external circuit. This creates a current through the circuit which powers the electric motor. As a result,
the oxygen receives two electrons and becomes negatively charged (O¬¬2-). Since, there are negatively charged oxygen ions on one side of the membrane and positively charged protons (H+) on the oilier side, the protons diffuse across the membrane to the cathode. Therefore, the bonding of the oxygen ion and the proton (H+) form water. This device is called a Proton Exchange Membrane fuel cell, or PEM.
The advantage of using a Proton-exchange membrane fuel cell is that they have an operating range of 1 atmosphere to 8 atmospheres of pressure. PEM cells work best at lower temperatures since they cannot tolerant temperature increases. The fuel cells have a high power density and flexible operation. These have lead to its higher efficiency even at partial loads compared with the gasoline engine.
8.1 Characteristics Affecting Cell Efficiency
Reactant pressures, temperature, catalyst loading, and surface area
9.1 Fuel cell powered automobiles
Components of a fuel cell powered auto engine:
• Fuel cell array
• Air delivery system
• Fuel delivery system
• Cooling system
• Electrical system
• Control system Fuel Cell Car (developed by Domino Inc.)
To make a fuel cell system, several single cells must be assembled in series or parallel to form a stack of the desired current, voltage, and power. These stacks are constructed with humidifiers, pumps, and gas filters to form a fuel cell engine. An air compressor is needed to compress the air while the humidifier is used to keep the PEM membrane moist since it conducts the protons in the electrolyte only through an aqueous environment. By keeping the membrane hydrated, this allows the fuel cell to operate properly
9.2 Installing a fuel cell in automobiles
Each fuel cell, measuring about 25 cm by 25 cm and about the thickness of notebook paper, produces slightly less than one volt of electricity. The cells are stacked, side-by-side, up to 200 cells in a series, to achieve the number of volts desired. This fuel cell "stack," anywhere from 60 cm to 90cm, can provide enough energy to drive a car. The electrochemical reactions of a fuel cell begin when hydrogen enters one side of the fuel cell, where it is separated into an electron and a hydrogen ion. In the case of one type of fuel cell, a proton-exchange membrane, the ions move through a membrane to combine with oxygen on the other side, thus making water. Meanwhile, since electrons cannot pass through the membrane, they are forced to take an external route that carries
them through an electric motor. Passing through the motor, the electrons transfer power from die fuel cell to the motor. The motor, in turn drives the wheels of the car. The controlled reaction of hydrogen and oxygen that occurs in a fuel cell is much more efficient than the typical burning (or combustion) process of a standard vehicle engine. As a result, fuel cell vehicles are expected to be two to three times more efficient than conventional cars and light trucks. Furthermore, because the only products are electricity, water, and some heat, the reaction is pollution free.
9.3 Auto fuel cell: Ballard power system ltd
The first "real" demonstration vehicle using modern fuel cell technology was rolled out in 1993 by Ballard Power Systems, a Canadian manufacturer. It's a 900cm bus powered by 20 fuel cell "stacks", an improved version by the same company powered by a single fuel cell stack can be fined in a standard diesel engine compartment Ballard lists its fuel cell efficiencies at 60%(idle) and 0%(full) power.
Fuel Cell Car (developed by SWRI, USA)
9.4 Other fuel cell powered automobiles
Toyota of Japan also has developed fuel cell. The fuel cell plant is estimated to have an energy efficiency of more than 60 percent; two to three times that of gasoline engines. Toyota also unveiled a methanol-fueled fuel cell vehicle. Ford builds a prototype hydrogen fuel cell vehicle, the P2000 project and implimentation. The company is investing in a wide range of technologies that will form a bridge between today's automobiles and tomorrow's fuel cell vehicle.
Fuel Cell Car (developed by Toyota)
10. Advantages of using fuel cells
Usage of fuel cells over other alternatives has many advantages out of which some of them had been listed here.
10.1 Energy Security
Energy dependence is higher today than it was during the "oil shock" of the 1970's, and oil imports are ever increasing. Passenger vehicles alone consume a substantial amount of oil every single day, equivalent to a large portion of our oil imports.
• If just 20 percent of cars used fuel cells, we could cut our oil imports by about 20%.
• If every new vehicle sold in next year was equipped with a 60kw fuel cell, we could double me amount of the country's available electricity supply.
10.2 Environmental and pollution aspects
Fuel cells running on hydrogen derived from a renewable source will be nothing but water vapor. Fuel cells used in transportation can power either buses or automobiles- If a mere 10% of automobiles nation wide were powered by fuel cells, regulated air pollutants would be substantially cut reducing the global warming effects of present fossil based petrol and diesel.
10.3 Fuel flexibility
Technology is under development that will allow fuel cells to be capable of operating on widely available conventional fuels, including diesel fuel and kerosene- Even though fuel cells "like" hydrogen best, fuel flexibility would allow a hydrogen infrastructure (fueling stations, delivery systems) to develop gradually in response to potential demand from fuel cell vehicles, when it makes sense to do so economically. The challenging task of developing an infrastructure without demand would be avoided.
10.4 Other benefits
Fuel cells could create new markets for steel, electronics, electrical and control industries and other equipment suppliers.
• Fuel cell powered automobiles could provide tens of thousands of high quality jobs and reduce trade deficits
• It is estimated that in the developed countries that each 1,000 MW will create 5,000 jobs i.e. 20 percent of cars using fuel cells, about 400,000 Jobs would be created.
• As generators in buildings, utility plants, hospitals and schools, fuel cells operate silently, reducing noise pollution as well as air pollution.
• Their ability to stand alone also makes fuel cells a wise choice for rural power, in places where there are no established power grids and in areas that are inaccessible by power lines.
• As fuel cells contain no moving parts and also no combustion occurs during the process they have less vibration during their operation.
11. Fuel cell powered vehicle Vs other options
11.1 FC Vehicle Vs Gasoline vehicle
Fuel cell cars will differ from traditional gasoline powered cars greatly with respect to emissions; however, fuel cell autos will not diner greatly with regard to their functionality. However, the location of a fuel cell "engine" does differ with respect to that of a typical gas automobile. In fuel cell vehicles, the engine can be mounted almost entirely in the floor, with the hydrogen cylinder being stored in the rear of the vehicle. This allows for plenty of room for passengers and cargo in a fuel cell vehicle.
11.2 FC Vehicle Vs Solar vehicles
Currently, photo voltaic cells are not very efficient. In fact, even state of the art PV cells yield roughly 22% efficiency. The photo voltaic cells on cars typically generate 1,500 to 2,000 watts of electricity. This wattage, unfortunately is only high enough to power a single person, aerodynamic vehicle to a top speed of 57kmph. Furthermore, battery power would have to be utilized during low light situations and this would severely limit the range of the vehicle, since most of the solar batteries last for roughly 320 km at 57mph. Further, solar vehicles are very expensive, with prototypes costing very high (22.5 lakhs to 50 lakhs).It is therefore safe to say that unless the efficiency of photo voltaic cells is greatly improved, and the costs of the vehicles decrease substantially, solar powered cars may not be a viable source of transportation in the near future. This is unfortunate, since solar energy is available to us in limitless quantities and its utilization causes no environmental harm.
12. R & D Work on fuel cells
The Fuel Cell Commercialization Group (FCCG) is an organization with the goal to commercialize carbonate fuel cells for power generation. FCCG members include electric and gas utilities and various other energy users that have identified the opportunity and value of early involvement in the development and commercialization of this type of energy production. The FCCG is working with Energy Research Corporation (ERC) to create a fuel Cell power plant.
12.1 Direct methanol fuel cells
These are a relatively new invention in the world of fuel cells. In this method, the hydrogen is derived directly from the methanol by the anode of the fuel cell. This eliminates the need for the earning of hydrogen fuel, while instead using liquid methanol. An operating
range of roughly 200 Fahrenheit is needed for this process.
12.2 Regenerative fuel cells
These fuel cells utilize water as a fuel. The water is split using solar energy to produce hydrogen and oxygen. These two items are then utilized to create a current, which thereby can be utilized to provide power to an automobile or other object. As by-products, water and heat are generated- This water, however, can be recycled and reused in the fuel cell to generate more electricity. The presence of a cheap fuel source and the reusability of the fuel, makes Regenerative Fuel Cell technology a very heavily researched subject.
13. FACTORS HINDERING THE USE OF FUEL CELL TECHNOLOGY
With the many obvious benefits of fuel cell technology, it is natural to wonder why these vehicles are not present in mainstream society. One primary reason regards safety. As stated previously, hydrogen is used as a fuel source in a fuel cell, and it is a very volatile substance.
One could imagine the catastrophe that could occur if two hydrogen-containing antes collided on a busy road! To prevent this disaster from occurring, researchers are currently developing a manner obtaining hydrogen from water on a small scale. This way, water, not pure hydrogen, would need to be carried as a fuel.
A second major problem with these automobiles is a lack of demand. Despite the current state of our environment, and the implication that continued environmental deterioration poses, there is simply not much of an incentive for people to change their current lifestyles. Possibly, if new environmental legislation was passed or economic benefits were granted for those using "clean" transportation, a market for fuel cell vehicles would develop.
Until recently building a fuel cell sufficiently powerful to power a car was costly .even more than a vehicle powered by electrochemical batteries or a hybrid drives .When the fuel cell technology was first introduced in space by NASA the PEM fuel cell cost around 250 lakhs per kw, but now the cost has come down to 25000 lakhs per kw meaning a fuel cell engine costs around 12.5 lakhs, which is around seven times the price of a typical 1C Engine (about 1.75 lakhs).But the PEM Fuel cell cost can be brought down to around Rs 2500-3000 per kw as the volume of production increases.
Automotive engineering and design will always be about options and evolutions .There have been periods when it seemed that revolution rather than evolution might bring radical changes, but late 1940's project and implimentationions about nuclear-powered care remained comic book fiction.
Even the gas turbine, which certainly brought revolution to the aerospace industry, was after a brief dalliance, dismissed by automotive industry was theoretically viable hopelessly impractical and definitely inappropriate for present day automobiles.
That is the prospect of fuel cell technologies attractive to scientists and engineers, but be assumed that it is not a panacea for the energy and environmental challenges that the automotive industry faces. The future of fuel cell technology is a long way into me future perhaps 10-20 years in terms of really becoming a wholly viable and successive alternative to the Internal -Combustion Engine ,with many more hurdles to overcome. So in the mean time automotive companies must have a portfolio of technologies to make a commercially viable and economical vehicle, fully acceptable to the customers.
• Automotive Engineering International, March 2001 (journal of society of automotive engineering)
• Automotive Engineering International, April 2001 (journal of society of automotive engineering)
• W.R Menetery and J. Chrisney," Energy conversion systems" reference hand book, vol VI—chemical systems
• L.G Austin. "Fuel Cells” scientific American, 2001
• F.T. Bacon,"Thc High Pressure hydrogen-oxygen fuel cell" in Fuel Cells,(New York Reinhold publishing corporation.1960)
• Fuel Cell's 2001's Home page [184.108.40.206]
• Hydrogen fuel Cell Vehicles ['dais -net]
• U.S Fuel Cell Vehicles [eyeforfuelcells.com]
Active In SP
Joined: Jan 2011
29-01-2011, 06:11 PM
I am planning to implement this project and implimentation, need more details and Documents about Fuel Cell. Is it possible to implement this project and implimentation in Bikes. In India any one implemented this already, at least some to get energy from water?