Alternate sources of energy �

Use of alternate energy resources�

• (Energy from any source except fossil fuel which emits green-house gases.)

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Fuel cells�

• A fuel cell is a device that converts the chemical energy from fuel into electricity via a chemical reaction with oxygen or another oxidizing agent.
• A fuel cell can be defined as an electrochemical cell that generates electrical energy from fuel via an electrochemical reaction.
• Every fuel cell has two electrodes called, respectively, a negative electrode (or anode)-The electrode of an electrochemical cell at which oxidation occurs and a positive electrode (or cathode) - The electrode of an electrochemical cell at which reduction occurs.—sandwiched around an electrolyte.
• 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.

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• Fuel cells work like batteries, but they do not run down or need recharging.
• They produce electricity and heat as long as fuel is supplied.
• These cells require a continuous input of fuel and an oxidizing agent (generally oxygen) in order to sustain the reactions that generate the electricity.
• Therefore, these cells can constantly generate electricity until the supply of fuel and oxygen is cut off.

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• Despite being invented in the year 1838, fuel cells began commercial use only a century later when they were used by NASA to power space capsules and satellites.
• Today, these devices are used as the primary or secondary source of power for many facilities including industries, commercial buildings, and residential buildings.

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• A fuel, such as hydrogen, is fed to the anode, and air is fed to the cathode.
• In a hydrogen fuel cell, a catalyst at the anode separates hydrogen molecules into protons and electrons, which take different paths to the cathode.
• The electrons go through an external circuit, creating a flow of electricity.
• The protons migrate through the electrolyte to the cathode, where they unite with oxygen and the electrons to produce water and heat.

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• 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.
• A fuel cell uses the chemical energy of hydrogen or another fuel to cleanly and efficiently produce electricity.
• If hydrogen is the fuel, electricity, water, and heat are the only products.
• Fuel cells are unique in terms of the variety of their potential applications; they can provide power for systems as large as a utility power station and as small as a laptop computer.
• A single fuel cell generates a tiny amount of direct current (DC) electricity. In practice, many fuel cells are usually assembled into a stack. Cell or stack, the principles are the same.

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• Fuel cells can be used in a wide range of applications, including transportation, material handling, stationary, portable, and emergency backup power applications.
• Fuel cells have several benefits over conventional combustion-based technologies currently used in many power plants and passenger vehicles.
• Fuel cells can operate at higher efficiencies than combustion engines, and can convert the chemical energy in the fuel to electrical energy with efficiencies of up to 60%.
• Fuel cells have lower emissions than combustion engines.
• Hydrogen fuel cells emit only water, so there are no carbon dioxide emissions and no air pollutants that create smog and cause health problems at the point of operation.
• Also, fuel cells are quiet during operation as they have fewer moving parts.

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How do fuel cells work?�

• 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.
• Fuel cells are electrochemical devices able to convert chemical energy to electricity through controlled oxidation-reduction (REDOX) processes.
• They behave as open systems which produce electricity as long as they are fed with fuel and oxidant.
• Commonly fuels, hydrogen (H₂) and methanol (CH₃OH) are compounds with small molecules and high density of chemical energy, considered energetic vectors.

• Basically, a fuel cell consists in two electrodes, anode and cathode, separated by an electrolyte.
• The cathode is always the positive electrode and the anode is the negative one as the electrons flow from negative to positive electrode.
• During operation the fuel is continuously fed to the anode while oxidant (oxygen or air) is continuously fed to the cathode.

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• 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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• 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 from the anode.
• In other cell types the oxygen picks up electrons and then travels through the electrolyte to the anode, where it combines with hydrogen ions.
• The electrolyte plays 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, 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.

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• Hydrogen can be produced in many ways:
• reforming of fossil fuels, hydrolysis of hydride type compounds or water electrolysis.
• It can be stored in special tank, under pressure, absorbed in hydride or metal organic framework, included into the structure of organic liquid compounds, or compactly stored in cryogenic form.
• The oxidant is gaseous oxygen extract from air or even purified air.

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Different types of fuel cells.�

• According to the type of electrolyte and fuel which determine the electrodes reactions there are several kinds of fuel cells which differs by the electrolyte and others behaviors.
• Fuel cells are classified primarily by the kind of electrolyte they employ.
• This classification determines the kind of electro-chemical reactions that take place in the cell, the kind of catalysts required, the temperature range in which the cell operates, the fuel required, and other factors.
• These characteristics, in turn, affect the applications for which these cells are most suitable.

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• The choice of which type to use is often based on the targeted application of the fuel cell.
• For example, some types of fuel cells work well for use in stationary power generation plants while others may be useful for powering cars or small portable applications. They are particularly suited for applications in which pollution-free vehicles are needed.
• Selection for a particular application depends on criteria such as cost, efficiency, weight, fuel storage, and so forth.
• The best-known types of fuel cells are alkaline (AFC), molten carbonate (MCFC), phosphoric acid (PAFC), proton exchange membrane (PEMFC), methanol fuel cell, microbial fuel cell and solid oxide (SOFC).
• Each work on the same principle, striping electrons from hydrogen atoms to create electricity.

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Alkaline fuel cell�

• The alkaline fuel cell (AFC), also known as the Bacon fuel cell after its British inventor, Francis Thomas Bacon, is one of the most developed fuel cell technologies.
• Alkaline fuel cells consume hydrogen and pure oxygen, to produce potable water, heat, and electricity.
• They are among the most efficient fuel cells, having the potential to reach 70%.
• As their name suggests, alkaline fuel cells use an alkaline electrolyte, usually KOH.
• They are unique because OH^- ions pass through this electrolyte instead of protons.
• AFC's were first used by NASA in the 1960's for the Apollo missions.

• In an AFC, OH^- ions pass through the electrolyte and water is both produced and used.
• AFCs are known for operating with high efficiency, and at relatively low temperatures. However, the reaction environment must be CO free because this gas will react with the alkaline electrolyte.

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Equipment Design�

• An alkaline fuel cell is a lot like a battery.
• It has two electrodes where the reactions take place and an electrolyte which carries the charged particles from one electrode to the other.
• The anode and cathode are made of lower-cost, nonprecious metals such as nickel/Ag and metal oxides.
• The electrodes are porous as well as catalytic in nature and are separated from each other by a layer of electrolyte.
• It uses an aqueous (water-based) electrolyte solution of potassium hydroxide (KOH) in a porous stabilized matrix.

• The alkaline fuel cell (AFC) is a very efficient fuel cell that requires pure hydrogen fuel and pure oxygen.
• The fuel cell produces power through a redox reaction between hydrogen and oxygen.
• In alkaline fuel cell, the electrolyte used is aqueous potassium hydroxide (KOH).
• The electrolyte acts as a medium for conduction of ions in between the electrodes.
• The electrodes are porous (and catalyzed) graphite electrodes. They are Semi-permeable, Teflon coated carbon material which are heavily catalyzed.

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• In order for a fuel cell to work, it needs hydrogen (H₂) and oxygen (O₂).
• Gaseous hydrogen is generally used as fuel because of its high energy density and easy production (from hydrocarbons using suitable catalysts).
• It can be stored in cylinders for remote terrestrial applications or cryogenically for closed environment applications, such as in space or underwater.
• Similarly the most common oxidant is gaseous oxygen, which is readily and economically available from air for terrestrial applications, and again easily stored in a closed environment.

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• The AFC operates at temperatures of 100°C to 250°C (212°F to 482°F).
• More recent AFCs operate at temperatures of 23°C to 70° C (74°F to 158°F).
• This fuel cell has an operating efficiency of 60% to 70%.
• Cell output ranges from 300 watts (W) to 5 kilowatts (kW).
• Excess heat is removed from the fuel cell as a by-product, and it is hot enough to provide steam to power a steam turbine. The heat can also be used to heat buildings.

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Working �

• The hydrogen enters the fuel cell at the anode.
• A chemical reaction strips the hydrogen molecules of their electrons and the atoms become ionized to form H⁺.
• The electrons travel through wires to provide a current to do work.
• The oxygen enters at the cathode, usually from the air.
• The oxygen picks up the electrons that have completed their circuit.

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• The oxygen then combines with the ionized hydrogen atoms (H⁺) at anode, and water (H₂O) is formed as the waste product which exits the fuel cell.
• The electrolyte plays an essential role as well. It only allows the appropriate ions to pass between the anode and cathode. If other ions were allowed to flow between the anode and cathode, the chemical reactions within the cell would be disrupted.
• In the AFC, hydrogen gas is oxidized to hydrogen ions and combines with the hydroxide ions, which produces water (H₂O) and releases two electrons.
• The electrons flow through the external circuit and return to the cathode, where they reduce oxygen to form more hydroxide ions and water.

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• At anode- catalyst oxidizes the fuel- usually hydrogen- turning the fuel into positively charged ion and negatively charged electron.
• Electrolyte- substance specifically designed so ions can pass through it- electrons cannot.
• Freed electrons travel through wire- creating electric current.
• Oxygen enters through cathode.
• The electrons that flow through an external circuit return to the cathode, reducing oxygen in the reaction producing hydroxide ions.
• These ions travel through the electrolyte to the anode.
• Once reaching anode- ions reunited with hydrogen ions- and create water.
• Electricity and heat are formed as byproducts of this reaction.

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• Alkaline fuel cells operate according to the following reactions:
• At the anode, hydrogen is oxidized according to the reaction producing water and releasing two electrons.

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• The electrons flow through an external circuit and return to the cathode, reducing oxygen in the reaction producing hydroxide ions.

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• The net reaction consumes one oxygen atom and two hydrogen atoms in the production of each water molecule. Electricity and heat are formed as byproducts of this reaction.
• Net reaction (the "redox" reaction): 2H_2​+O₂​=>2H₂​O

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• As the picture below shows, this fuel cell operates on the same principles as the proton exchange membrane fuel cell (PEM). However, here the water is produced at the anode, as opposed to at the cathode as in a PEM.

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• Alkaline Fuel Cell is one of the oldest types of fuel cell.
• Alkaline fuel cells (AFCs) were one of the first fuel cell technologies developed, and they were the first type widely used in the U.S. space program to produce electrical energy and water on-board spacecraft.
• A key challenge for this fuel cell type is that it is susceptible to poisoning by carbon dioxide (CO₂). In fact, even the small amount of CO₂ in the air can dramatically affect cell performance and durability due to carbonate formation.

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• One of the major advantages for an alkaline fuel cell is that non-precious metals can be used as a catalyst.
• However, the catalysts can be easily poisoned by CO₂ (carbon dioxide).
• As such, the hydrogen and oxygen used in an AFC needs to be purified, which is a more costly process.
• A disadvantage is a requirement for pure oxygen and pure hydrogen, and both gases must be supplied continuously.
• The fuel cell is also poisoned easily by carbon dioxide (CO₂), which affects the cell’s lifetime.
• AFCs do not currently have lifetimes beyond about 8,000 operating hours, so they tend to be less cost-effective than other types.

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Advantages�

• Employs a relatively simple design.
• Wide range of operating temperatures and pressures.
• Electrodes, particularly the cathode, do not require precious metals.
• Electrolytes cost far less than other fuel cells.
• They are among the most efficient fuel cells, having the potential to reach 70%.
• No emission of toxic by-products
• Hydrogen-oxygen fuel cell produces potable quality water.
• Low noise and thermal pollution.
• Saves fossil fuel.

Disadvantages�

• Low power density.
• Carbon dioxide degenerates the electrolyte, causing performance to decrease.
• Works best on a pure oxygen supply, as opposed to air.
• The AFC is very susceptible to contamination, so it requires pure hydrogen and oxygen.
• It is also very expensive, so this type of fuel cell is unlikely to be commercialized.

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Phosphoric acid fuel cell (PAFC)

• Phosphoric acid fuel cells (PAFC) are a type of fuel cell that uses liquid phosphoric acid as an electrolyte.
• They were the first fuel cells to be commercialized.
• Developed in the mid-1960s and field-tested since the 1970s, they have improved significantly in stability, performance, and cost.
• Such characteristics have made the PAFC a good candidate for early stationary applications.
• The PAFC is considered the "first generation" of modern fuel cells.
• This type of fuel cell is typically used for stationary power generation, but some PAFCs have been used to power large vehicles such as city buses.

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• In PAFC, the electrolyte is highly concentrated or pure liquid phosphoric acid (H₃PO₄) saturated or contained in a Teflon-bonded, silicon carbide matrix (SiC).
• Like any other fuel cell, the phosphoric acid fuel cell (PAFC) uses oxygen and hydrogen to produce water, electricity, and heat.
• It uses an external reformer to separate hydrogen from a hydrocarbon fuel.
• The electrodes are made of carbon paper coated with a finely dispersed platinum catalyst.
• The PAFC operates at around 150° C to 200° C (300° F to 400° F). This operating temperature is hot enough to provide external heat as well as electricity and improves the conductivity of phosphoric acid.
• If gasoline or diesel is used as a basic fuel, sulfur must be removed from the fuel prior to use or it will damage the electrode catalyst.
• PAFCs are more tolerant of impurities in fossil fuels that have been reformed into hydrogen than are PEMFCs.

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• The electrical efficiency for PAFCs is 40% to 50%, and when the energy produced by the waste heat is considered, the efficiency rises to about 80%.
• Existing phosphoric acid cells have outputs up to 200 kW, and 11 MW units have been tested.
• Today, PAFCs are used in commercial electrical production.

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Equipment Design�

• A phosphoric acid fuel cell is a lot like a battery.
• It has two electrodes where the reactions take place and an electrolyte which carries the charged particles from one electrode to the other.
• The anode and cathode are made of porous carbon electrodes containing a platinum catalyst.
• It uses an phosphoric acid (H₃PO₄) saturated in a silicon carbide matrix (SiC) as an electrolyte.
• The fuel cell produces power through a redox reaction between hydrogen and oxygen.
• In phosphoric acid fuel cell, the electrolyte used is phosphoric acid.
• The electrolyte acts as a medium for conduction of ions in between the electrodes

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• In order for a fuel cell to work, it needs hydrogen (H₂) and oxygen (O₂).
• The hydrogen enters the fuel cell at the anode.
• A chemical reaction strips the hydrogen molecules of their electrons and the atoms become ionized to form H⁺.
• These H⁺ ions travel through the electrolyte towards the cathode.
• The electrons travel through wires to provide a current to do work.

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• The oxygen enters at the cathode, usually from the air.
• The oxygen picks up the electrons that have completed their circuit.
• The oxygen then combines with the ionized hydrogen atoms (H⁺) at cathode, and water (H₂O) is formed as the waste product which exits the fuel cell.
• The electrolyte plays an essential role as well. It only allows the appropriate ions to pass between the anode and cathode. If other ions were allowed to flow between the anode and cathode, the chemical reactions within the cell would be disrupted.

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Working �

• Hydrogen from reformed fuel is fed to the anode of the PAFC, while oxygen or air is fed to the cathode.
• In the electrodes, these two diatomic gases are split into ions by means of a catalyst.
• The phosphoric acid provides the medium to transport protons from the anode to the cathode.
• The protons move through these acidic regions to cross the electrolyte, while the electrons are repulsed and pass as current through a load to get to the cathode.

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• At anode- catalyst oxidizes the fuel- usually hydrogen- turning the fuel into positively charged ion and negatively charged electron.
• Electrolyte- substance specifically designed so ions can pass through it- electrons cannot.
• Freed electrons travel through wire- creating electric current.
• Oxygen enters through cathode.
• The electrons that flow through an external circuit return to the cathode, reducing oxygen in the reaction.
• The hydrogen ions from anode travel through the electrolyte to the cathode.
• Once reaching cathode- hydrogen ions combined with reduced oxygen- and create water.
• Electricity and heat are formed as byproducts of this reaction.

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• Phosphoric acid fuel cells operate according to the following reactions:
• At the anode, hydrogen is oxidized according to the reaction producing hydrogen ions and releasing two electrons.

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• The electrons flow through an external circuit and return to the cathode, reducing oxygen in the reaction producing water.

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• The net reaction consumes one oxygen atom and two hydrogen atoms in the production of each water molecule. Electricity and heat are formed as byproducts of this reaction.
• Net reaction (the "redox" reaction): 2H₂​+O₂​=>2H₂​O

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• As the picture below shows, this fuel cell operates on the same principles as the proton exchange membrane fuel cell (PEM).

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• Usually the hydrogen for the reactions comes from reformed natural gas, and the oxygen comes from an air feed stream.
• Because the PAFC operates at temperatures around 220°C, platinum is still required as a catalyst.
• The PAFC is more resistant, however, to carbon monoxide poisoning than other fuel cells that operate at lower temperatures.
• Phosphoric acid fuel cells are most suitable for combined heat and power systems, known as CHPs, in which heat produced in the system is reused. Some ways that a CHP uses this heat include to heat processes within the system and to heat nearby buildings. The steam produced in this type of system can also be used to drive turbines and therefore produce more electricity. Using a PAFC as a CHP enables the system to reach efficiencies up to 85%.

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• Phosphoric acid is the electrolyte used in an PAFC. As an acid, it requires a very high temperature (150ºC ~ 200ºC) to start the reaction.
• It also uses platinum as a catalyst, similar to PEM fuel cells, which is costly.
• However, PAFC's are more tolerant to impurities because carbon monoxide binds to the platinum catalyst at the anode, decreasing the fuel cell's efficiency,
• and they are very efficient at generating electricity and heat - which makes them ideal for power plants.
• However, they are typically large and heavy which makes them less than ideal for smaller or portable applications.
• PAFCs are typically used in small, stationary, power generation systems, but research is being conducted for application in larger vehicles such as buses.
• PAFCs tolerate a carbon monoxide concentration of about 1.5 percent, which broadens the choice of fuels they can use. Internal parts must be able to withstand the corrosive acid.

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• PAFCs are more than 85% efficient when used for the co-generation of electricity and heat but they are less efficient at generating electricity alone (37%–42%).
• PAFC efficiency is only slightly more than that of combustion-based power plants, which typically operate at around 33% efficiency.
• PAFCs are also less powerful than other fuel cells, given the same weight and volume.
• As a result, these fuel cells are typically large and heavy.
• PAFCs are also expensive.
• They require much higher loadings of expensive platinum catalyst than other types of fuel cells do, which raises the cost.

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Advantages�

• The heat produced in the fuel cell can be used to heat other processes.
• At an operating range of 150 to 200°C, the expelled water can be converted to steam for air and water heating (combined heat and power). This potentially allows efficiency increases of up to 70%.
• The steam produced can be used to drive turbines and produce more electricity in a very efficient manner.
• The design is more tolerant of impurities than earlier fuel cell designs.

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• The PAFC can tolerate a concentration of carbon monoxide (CO) of about 1.5%, which is a larger concentration than can be tolerated by other types of fuel cells.
• Another advantage to the PAFC is that the phosphoric acid electrolyte can operate above the boiling point of water.
• PAFCs are CO₂-tolerant and can tolerate a CO concentration of about 1.5%, which broadens the choice of fuels they can use.
• However, they are much less sensitive to CO than PEMFCs and AFCs.

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Disadvantages�

• External fuel reforming is necessary.
• High capital costs compared to other energy generating systems.
• Bulky
• Requires a platinum catalyst.
• A disadvantage of the PAFC is that, when compared to other fuel cells of similar weight and volume, it produces less power.(low power density).
• Also, PAFCs are expensive because of the platinum catalyst and the need for corrosion-resistant materials (because of the acid).
• At lower temperatures phosphoric acid is a poor ionic conductor, and CO poisoning of the platinum electro-catalyst in the anode becomes severe.

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Methanol fuel cell�

• Methanol fuel cells get their name from the fuel they use, which is methanol that is fed directly to the anode of the membrane electrode assembly.
• Methanol fuel cells use liquid methanol, water, and oxygen to produce water, carbon dioxide, heat, and electricity.
• MFC's are similar to PEMFC's in that protons pass through the electrolyte. These fuel cells run at relatively low temperatures and have low power production.

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• Methanol fuel cells (MFC) are often very similar to proton exchange membrane fuel cells (PEMFC).
• In a MFC, methanol and water are fed into the anode, while oxygen or air is fed into the cathode.
• In the anode, methanol is oxidized using a platinum-ruthenium catalyst.
• Hydrogen is extracted from the methanol, and electrons from the hydrogen are free to flow as current out from the anode, producing current and return back through the cathode.
• Oxygen is supplied through the air and is ionized at the cathode.
• At cathode, oxygen ions combine with hydrogen ions to make water.

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• The operating temperature range of this fuel cell is about 50°C to 120°C (122°F to 248°F).
• At higher temperature and pressure, efficiency of fuel cell increases.
• Typical units have a power rating between 25 W and 5,000 W.

Equipment Design�

• A methanol fuel cell is a lot like a battery.
• It has two electrodes where the reactions take place and an electrolyte which carries the charged particles from one electrode to the other.
• The anode and cathode are made of metals which contain the catalyst like platinum-ruthenium catalyst.
• The electrolyte in a DMFC is often composed of polytetrafluoroethylene (PTFE) with sulfonated side chains.

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• The fuel cell produces power through a redox reaction between methanol and oxygen.
• In methanol fuel cell, the electrolyte used is polytetrafluoroethylene (PTFE) with sulfonated side chains.
• The electrolyte acts as a medium for conduction of ions in between the electrodes

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• In order for a fuel cell to work, it needs methanol (H₂) and oxygen (O₂).
• The methanol enters the fuel cell at the anode.
• A chemical reaction strips the hydrogen molecules of their electrons and the atoms become ionized to form H⁺.
• The electrons travel through wires to provide a current to do work.
• The oxygen enters at the cathode, usually from the air.
• The oxygen picks up the electrons that have completed their circuit.

• The oxygen then combines with the ionized hydrogen atoms (H⁺) at cathode, and water (H₂O) is formed as the waste product which exits the fuel cell.
• The electrolyte plays an essential role as well. It only allows the appropriate ions to pass between the anode and cathode. If other ions were allowed to flow between the anode and cathode, the chemical reactions within the cell would be disrupted.

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Working �

• At anode- catalyst oxidizes the fuel- methanol- turning the fuel into positively charged ion (hydrogen ions) and negatively charged electron.
• Electrolyte- substance specifically designed so ions can pass through it- electrons cannot.
• Freed electrons travel through wire- creating electric current.
• Oxygen enters through cathode.
• The electrons that flow through an external circuit return to the cathode, reducing oxygen in the reaction.
• The hydrogen ions from anode travel through the electrolyte to the cathode.
• Once reaching cathode- hydrogen ions combined with reduced oxygen- and create water. Electricity and heat are formed as byproducts of this reaction.

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• Methanol fuel cells operate according to the following reactions:
• At the anode, methanol is oxidized according to the reaction producing hydrogen ions and releasing electrons.

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• The electrons flow through an external circuit and return to the cathode, reducing oxygen in the reaction producing water.

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• The net reaction consumes one oxygen atom and two hydrogen atoms in the production of each water molecule. Electricity and heat are formed as byproducts of this reaction.
• Net reaction (the "redox" reaction): 
• 2 CH₃OH + 3O₂-------- 4 H₂O + 2CO₂

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• In the cathode, oxygen is split into ions by means of a platinum catalyst and reacts with the protons to produce water.
• Both electrodes consist of a gas diffusion layer covering the catalysts.
• Problems in a DMFC can occur because this catalyst is poisoned by some of the intermediate products formed in methanol oxidation.

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• The electrolyte in a MFC is often composed of polytetrafluoroethylene (PTFE) with sulfonated side chains.
• PTFE is a very stable structure, but it is extremely hydrophobic.
• The sulfonated side chains, on the other hand, are very hydrophilic.
• The electrolyte will therefore be comprised of both hydrophobic and hydrophilic regions.
• The hydrophilic regions hold water and become acidic, allowing the protons to cross from the anode through the electrolyte to the cathode.
• The electrons, on the other hand, pass as current through a load to get to the cathode.
• The carbon dioxide formed from the methanol oxidation reaction is diffused back through the gas diffusion layer of the anode and exits the fuel cell.

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• It is important that the electrolyte stay hydrated to ensure that the protons get passed over to the cathode.
• In order to keep the electrode hydrated (but not overly hydrated to avoid flooding), the relative humidity inside the fuel cell should be maintained at 80-99%.

• Methanol fuel cells may prove most useful in situations that call for low power-density but high energy-density.
• In other words, MFCs are suitable for devices that only require a few watts to function, but are expected to run for days at a time,
• such as cell phones and portable music players. Conversely, automobiles are an unlikely application of this technology because of their high power consumption.

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• Most fuel cells are powered by hydrogen, which can be fed to the fuel cell system directly or can be generated within the fuel cell system by reforming hydrogen-rich fuels such as methanol, ethanol, and hydrocarbon fuels.
• Methanol fuel cells (MFCs), however, are powered by pure methanol, which is usually mixed with water and fed directly to the fuel cell anode.
• Methanol fuel cells do not have many of the fuel storage problems typical of some fuel cell systems because methanol has a higher energy density than hydrogen—though less than gasoline or diesel fuel.
• Methanol is also easier to transport and supply to the public using our current infrastructure because it is a liquid, like gasoline.
• MFCs are often used to provide power for portable fuel cell applications such as cell phones or laptop computers.

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• Methanol Fuel Cells are PEM based fuel cell that use methanol instead of pure hydrogen.
• As such, they share many of the same advantages of a PEM fuel cell, (The advantages of a PEM fuel cell is that they have a high power density and are low in weight.
• They are also able to operate in low temperatures, typically around 80ºC which allows them to start quickly (less warm uptime).)
• with the added benefit that methanol is a much easier and safer fuel for transportation and storage.

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• The disadvantage of methanol is that the reaction is often not as efficient as pure hydrogen because methanol can often move across the membrane without reacting with the catalyst.
• To address these concerns, some fuel cells reform the methanol (RMFC) before it reacts with the catalyst.
• The methanol fuel cell can be used in vehicles because it uses methanol in liquid form to provide the hydrogen source. Lower operating temperatures mean that this fuel cell does not need a large, heavy heat shield.
• A disadvantage is that the efficiency is low, so the MFC is more suited for portable applications, where energy and power density are more important than efficiency.

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• Another disadvantage is that carbon dioxide is a by-product and it is released into the atmosphere, just as it would be from the combustion of methanol.

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• Advantages
• Methanol can be refueled quickly and simply.
• Methanol is stable and easy to handle.
• Methanol is arguably the most efficient carrier of hydrogen.
• The simplicity of methanol storage drastically reduces the weight of the system.
• Ideal for low power-density, but high energy-density applications.
• The lack of an external reformer lowers cost and increases efficiency.

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• Disadvantages
• Fuel can cross electrolyte without reacting, reducing efficiency.
• Low power-density.
• Methanol can corrode various parts of the fuel cell.
• Methanol is toxic and flammable, much like gasoline.
• Some of the intermediate products involved in methanol oxidation can poison the catalyst.
• Fuel cell is costly due to the use of platinum.
• They cannot power large vehicles.

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• Applications
• It is used to power small vehicles, mobile phones, cameras, etc.
• It is used for military applications.
• It is used to power for test and training instrumentation.

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