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Here is an essay on ‘Fuel Cell’ for class 6, 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Fuel Cell’ especially written for school and college students.
Essay on Fuel Cell
Essay Contents:
- Essay on the Introduction to Fuel Cell
- Essay on the Design of Fuel Cell
- Essay on the Working of Fuel Cell
- Essay on the Classification of Fuel Cell
- Essay on the Efficiency of Fuel Cell
- Essay on the Applications of Fuel Cell
- Essay on the Economics of Fuel Cell
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Essay # 1. Introduction to Fuel Cell:
A fuel cell is an electrochemical cell that converts a source fuel into an electric current. It generates electricity inside a cell through reactions between a fuel and an oxidant, triggered 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 continuously as long as the necessary reactant and oxidant flows are maintained.
Fuel cells are different from conventional electrochemical cell batteries in that they consume reactant from an external source, which must be replenished a thermodynamically open system. By contrast, batteries store electrical energy chemically and hence represent a thermodynamically closed system.
Many combinations of fuels and oxidants are possible. A hydrogen fuel cell uses hydrogen as its fuel and oxygen (usually from air) as its oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include chlorine and chlorine dioxide.
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Essay # 2. Design of Fuel Cell:
Fuel cells come in many varieties; however, they all work in the same general manner. They are made up of three segments which are sandwiched together- the anode, the electrolyte, and the cathode. Two chemical reactions occur at the interfaces of the three different segments.
The net result of the two reactions is that fuel is consumed, water or carbon dioxide is created, and an electric current is created, which can be used to power electrical devices, normally referred to as the load.
At the anode a catalyst oxidizes the fuel, usually hydrogen, turning the fuel into a positively charged ion and a negatively charged electron. The electrolyte is a substance specifically designed so ions can pass through it, but the electrons cannot.
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The freed electrons travel through a wire creating the electric current. The ions travel through the electrolyte to the cathode. Once reaching the cathode, the ions are reunited with the electrons and the two react with a third chemical, usually oxygen, to create water or carbon dioxide.
The most important design features in a fuel cell are:
i. The electrolyte substance. The electrolyte substance usually defines the type of fuel cell.
ii. The fuel that is used. The most common fuel is hydrogen.
iii. The anode catalyst, which breaks down the fuel into electrons and ions. The anode catalyst is usually made up of very fine platinum powder.
iv. The cathode catalyst, which turns the ions into the waste chemicals like water or carbon dioxide. The cathode catalyst is often made up of nickel.
Essay # 3. Working of Fuel Cell:
Fuel cells are electrochemical devices that directly convert chemical energy to electrical energy. They consist of an electrolyte medium sandwiched between two electrodes (Fig. 1.82). One electrode (called the anode) facilitates electrochemical oxidation of fuel, while the other (called the cathode) promotes electrochemical reduction of oxidant.
Ions generated during oxidation or reduction are transported from one electrode to the other through the ionically conductive but electronically insulating electrolyte.
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The electrolyte also serves as a barrier between the fuel and oxidant. Electrons generated at the anode during oxidation pass through the external circuit (hence generating electricity) on their way to the cathode, where they complete the reduction reaction. The fuel and oxidant do not mix at any point and no actual combustion occurs.
The fuel cell therefore is not limited by the Carnot efficiency and theoretically (although not practically), can yield 100% efficiency. Fuel cells are primarily classified according to the electrolyte material. The choice of electrolyte material also governs the operating temperature of the fuel cell. Lists the various types of fuel cells along with electrolyte used, operating temperature and electrode reactions.
A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load.
Voltage decreases as current increases due to following factors:
i. Activation loss-arised due to kinetics at the electrodes.
ii. Ohmic loss (voltage drop due to resistance of the cell components and interconnects)
iii. Mass transport loss (depletion of reactants at catalyst sites under high loads, causing rapid loss of voltage).
To deliver the desired amount of energy, the fuel cells can be combined in series and parallel circuits, where series yields higher voltage, and parallel allows a higher current to be supplied. Such a design is called a fuel cell stack. The cell surface area can be increased, to allow stronger current from each cell.
Essay # 4. Classification of Fuel Cell:
Fuel cell are classified on the basis of electrolyte and types of electrodes used. Lot of research is going on worldwide in the field of fuel cell. Some of them are in mass production and some of them are in production stage commercially.
The Table below shows the type of few fuel cells:
The working of some of fuel cells is as follows:
1. Proton Exchange Fuel Cells:
In the archetypal hydrogen-oxygen proton exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane, (the electrolyte), separates the anode and cathode sides. This was called a ‘solid polymer electrolyte fuel cell’ (SPEFC) in the early 1970s, before the proton exchange mechanism was well-understood. (Notice that ‘polymer electrolyte membrane’ and ‘proton exchange mechanism’ result in the same acronym).
On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants causing them to become what is commonly referred to as multi-facilitated proton membranes. The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating.
On the cathode catalyst, oxygen molecules react with the electrons (which have travelled through the external circuit) and protons to form water in this example, the only waste product, either liquid or vapour.
In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel, methanol (direct-methanol fuel cells and indirect methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water.
Construction of a High Temperature PEMFC:
Bipolar plate as electrode with in-milled gas channel structure, fabricated from conductive plastics (enhanced with carbon nanotubes for more conductivity); Porous carbon papers; reactive layer, usually on the polymer membrane applied; polymer membrane.
Condensation of water produced by a PEMFC on the air channel wall. The gold wire around the cell ensures the collection of electric current.
The materials used in fuel cells differ by type. In a typical membrane electrode assembly (MEA), the electrode-bipolar plates are usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum, nano iron powders or palladium) for higher efficiency. Carbon paper separates them from the electrolyte. The electrolyte could be ceramic or a membrane.
2. High Temperature Fuel Cells:
a. SOFC (Solid Oxide Fuel Cell):
A solid oxide fuel cell (SOFC) is extremely advantageous “because of a possibility of using a wide variety of fuel”. Unlike most other fuel cells which only use hydrogen, SOFCs can run on hydrogen, butane, methanol, and other petroleum products. The different fuels each have their own chemistry.
For SOFC methanol fuel cells, on the anode side, a catalyst breaks methanol and water down to form carbon dioxide, hydrogen ions, and free electrons. The hydrogen ions meet oxide ions that have been created on the cathode side and passed across the electrolyte to the anode side, where they react to create water. A load connected externally between the anode and cathode completes the electrical circuit.
Below are the chemical equations for the reaction:
Anode Reaction: CH3OH + H2O + 30 → CO2 + 3H2O + 6e+
Cathode Reaction: 3/2 O2 + 6e+ → 30=
Overall Reaction: CH3OH + 3/2 O2 → CO2 + 2H2O + electrical energy
At the anode SOFCs can use nickel or other catalysts to break apart the methanol and create hydrogen ions and Template- CO. A solid called yttria stabilized zirconia (YSZ) is used as the electrolyte. Like all fuel cell electrolytes YSZ is conductive to certain ions, in this case the oxide ion (O=) allowing passage from the cathode to anode, but is non-conductive to electrons. YSZ is a durable solid and is advantageous in large industrial systems.
Although YSZ is a good ion conductor, it only works at very high temperatures. The standard operating temperature is about 950°C. Running the fuel cell at such a high temperature easily breaks down the methane and oxygen into ions. A major disadvantage of the SOFC, as a result of the high heat, is that it ‘places considerable constraints on the materials which can be used for interconnections’.
Another disadvantage of running the cell at such a high temperature is that other unwanted reactions may occur inside the fuel cell. It is common for carbon dust, graphite, to build up on the anode, preventing the fuel from reaching the catalyst. Much research is currently being done to find alternatives to YSZ that will carry ions at a lower temperature.
b. MCFC (Molten Carbonate Fuel Cell):
Molten carbonate fuel cells (MCFCs) operate in a similar manner, except the electrolyte consists of liquid (molten) carbonate, which is a negative ion and an oxidizing agent. Because the electrolyte loses carbonate in the oxidation reaction, the carbonate must be replenished through some means. This is often performed by recirculating the carbon dioxide from the oxidation products into the cathode where it reacts with the incoming air and reforms carbonate.
Unlike proton exchange fuel cells, the catalysts in SOFCs and MCFCs are not poisoned by carbon monoxide, due to much higher operating temperatures. Because the oxidation reaction occurs in the anode, direct utilization of the carbon monoxide is possible.
Also, steam produced by the oxidation reaction can shift carbon monoxide and steam reform hydrocarbon fuels inside the anode. These reactions can use the same catalysts used for the electrochemical reaction, eliminating the need for an external fuel reformer.
MCFC can be used for reducing the CO2 emission from coal fired power plants as well as gas turbine power plants.
Essay # 5. Efficiency of Fuel Cell:
The efficiency of a fuel cell is dependent on the amount of power drawn from it. Drawing more power means drawing more current which increases the losses in the fuel cell. As a general rule, the more power (current) drew, the lower the efficiency.
Most losses manifest themselves as a voltage drop in the cell, so the efficiency of a cell is almost proportional to its voltage. For this reason, it is common to show graphs of voltage versus current (so-called polarization curves) for fuel cells.
A typical cell running at 0.7 V has an efficiency of about 50%, meaning that 50% of the energy content of the hydrogen is converted into electrical energy; the remaining 50% will be converted into heat. (Depending on the fuel cell system design, some fuel might leave the system unreacted, constituting an additional loss.)
Essay # 6. Applications of Fuel Cell:
(i) Power:
Fuel cells are very useful as power sources in remote locations, such as spacecraft, remote weather stations, large parks, rural locations, and in certain military applications. A fuel cell system running on hydrogen can be compact and lightweight, and have no major moving parts. Because fuel cells have no moving parts and do not involve combustion, in ideal conditions they can achieve up to 99.99% reliability. This equates to around one minute of down time in a two year period.
Since electrolyze systems do not store fuel in themselves, but rather rely on external storage units, they can be successfully applied in large-scale energy storage, rural areas being one example. In this application, batteries would have to be largely oversized to meet the storage demand, but fuel cells only need a larger storage unit (typically cheaper than an electrochemical device).
(ii) Cogeneration:
Micro combined heat and power (MicroCHP) systems such as home fuel cells and cogeneration for office buildings and factories are in the mass production phase. The system generates constant electric power (selling excess power back to the grid when it is not consumed), and at the same time produces hot air and water from the waste heat. MicroCHP is usually less than 5 kWe for a home fuel cell or small business.
A lower fuel-to-electricity conversion efficiency is tolerated (typically 15-20%), because most of the energy not converted into electricity is utilized as heat. Some heat is lost with the exhaust gas just as in a normal furnace, so the combined heat and power efficiency is still lower than 100%, typically around 80%. In terms of energy however, the process is inefficient, and one could do better by maximizing the electricity generated and then using the electricity to drive a heat pump.
Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existing CHP products worldwide and can provide combined efficiencies close to 90% (35-50% electric + remainder as thermal) Molten-carbonate fuel cells have also been installed in these applications, and solid-oxide fuel cell prototypes exist.
(iii) Land Vehicles:
There are numerous prototype or production cars and buses based on fuel cell technology being researched or manufactured by motor car manufacturers.
The GM 1966 Electrovan was the automotive industry’s first attempt at an automobile powered by a hydrogen fuel cell. The Electrovan, which weighed more than twice as much as a normal van, could travel up to 70 mph for 30 seconds.
The 2001 Chrysler Natrium used its own on-board hydrogen processor. It produces hydrogen for the fuel cell by reacting sodium borohydride fuel with Borax, both of which Chrysler claimed were naturally occurring in great quantity in the United States.
The hydrogen produces electric power in the fuel cell for near-silent operation and a range of 300 miles without impinging on passenger space. Chrysler also developed vehicles which separated hydrogen from gasoline in the vehicle, the purpose being to reduce emissions without relying on a non-existent hydrogen infrastructure and to avoid large storage tanks.
In 2005 the British firm Intelligent Energy produced the first ever working hydrogen run motorcycle called the ENV (Emission Neutral Vehicle). The motorcycle holds enough fuel to run for four hours, and to travel 100 miles in an urban area, at a top speed of 50 miles per hour. In 2004 Honda developed a fuel-cell motorcycle which utilized the Honda FC Stack.
A few companies are conducting hydrogen fuel cell research and practical fuel cell bus trials. Daimler AG, with thirty-six experimental units powered by Ballard Power Systems fuel cells completing a successful three-year trial, in eleven cities, in January 2007.
There are also fuel cell powered buses currently active or in production, such as a fleet of Thor buses with UTC Power fuel cells in California, operated by Sun-Line Transit Agency. The Fuel Cell Bus Club is a global cooperative effort in trial fuel cell buses.
Apart from land vehicles, fuel cell applications are in developing stages for being used in:
i. Airplanes.
ii. Boats.
iii. Submarines.
(iv) Other Applications:
i. Off-grid power supply.
ii. Distributed generation.
iii. Fork Lifts.
iv. Emergency power systems are a type of fuel cell system, which may include lighting, generators and other apparatus, to provide backup resources in a crisis or when regular systems fail. They find uses in a wide variety of settings from residential homes to hospitals, scientific laboratories, data centers, telecommunication equipment and modern naval ships.
v. An uninterrupted power supply (UPS) provides emergency power and, depending on the topology, provide line regulation as well to connected equipment by supplying power from a separate source when utility power is not available. Unlike a standby generator, it can provide instant protection from a momentary power interruption.
vi. Base load power plants.
vii. Electric and hybrid vehicles.
viii. Notebook computers for applications where AC charging may not be available for weeks at a time.
ix. Portable charging docks for small electronics (e.g., a belt clip that charges your cell phone or PDA).
x. Smartphones with high power consumption due to large displays and additional features like GPS might be equipped with micro fuel cells.
xi. Small heating appliances.
Essay # 7. Economics of Fuel Cell:
Use of hydrogen to fuel vehicles would be a critical feature of a hydrogen economy. A fuel cell and electric motor combination is not directly limited by the Carnot efficiency of an internal combustion engine.
Low temperature fuel cell stacks proton exchange membrane fuel cell (PEMFC), direct methanol fuel cell (DMFC) and phosphoric acid fuel cell (PAFC) use a platinum catalyst. Impurities create catalyst poisoning (reducing activity and efficiency) in these low-temperature fuel cells, thus high hydrogen purity or higher catalyst densities are required.
Although there are sufficient platinum resources for future demand, most predictions of platinum running out and/or platinum prices soaring do not take into account effects of reduction in catalyst loading and recycling.
Recent research at Brookhaven National Laboratory could lead to the replacement of platinum by a gold-palladium coating which may be less susceptible to poisoning and thereby improve fuel cell lifetime considerably. Another method would use iron and sulphur instead of platinum. This is possible through an intermediate conversion by bacteria. This would lower the cost of a fuel cell substantially.