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HYDROGEN FUEL C ELL 2 0 1 1 -2 0 1 2

Govt. Polytechnic College Perinthalmanna Dept. of Mechanical Engineering 1

Contents

1. Abstract

2. Introduction3. History of Fuel cell

4. Types of Fuel cell Proton exchange membrane Fuel cells

Alkaline fuel cell (AFC)

Direct-methanol fuel cell (DMFC)

Phosphoric acid fuel cell (PAFC)

SOFC(Solid oxide fuel cell)

MCFC( Molten carbonate fuel cell)

5. Polimer exchange membrane fuel cell

6. Woking of hydrogen fuel cell

7. Applications8. Production of Hydrogen

9. Hydrogen storage

10. Hydrogen safety

11. Advantages& disadvatages of Fuel cell

12. Conclusion

13. References





Abstract

A fuel cell is a device that converts the chemical energy from a fuel into electricitythrough a chemical reaction with oxygen or another oxidizing agent.[1] Hydrogen is the mostcommon fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes

used. Fuel cells are different from batteries in that they require a constant source of fuel andoxygen to run, but they can produce electricity continually for as long as these inputs aresupplied.

Hydrogen is the most common fuel, but hydrocarbons such as natural gas andalcohols like methanol are sometimes used. Fuel cells are different from batteries in that theyrequire a constant source of fuel and oxygen to run, but they can produce electricitycontinually for as long as these inputs are supplied.





Introduction

You've probablyheard about fuel cells. In2003, President Bushannounced a program calledthe Hydrogen Fuel

Initiative (HFI) during hisState of the Union Address.This initiative, supported bylegislation in the EnergyPolicy Act of 2005 (EPACT2005) and the AdvancedEnergy Initiative of 2006,

aims to develop hydrogen,fuel cell and infrastructure technologies to make fuel-cell vehicles practical and cost-effectiveby 2020. The United States has dedicated more than one billion dollars to fuel cell researchand development so far.

So what exactly is a fuel cell, anyway? Why are governments, private businesses andacademic institutions collaborating to develop and produce them? Fuel cells generateelectrical power quietly and efficiently, without pollution. Unlike power sources that usefossil fuels, the by-products from an operating fuel cell are heat and water. But how does itdo this?

In this article, we'll take a quick look at each of the existing or emerging fuel-celltechnologies. We'll detail how polymer electrolyte membrane fuel cells (PEMFC) work and examine how fuel cells compare against other forms of power generation. We'll alsoexplore some of the obstacles researchers face to make fuel cells practical and affordable forour use, and we'll discuss the potential applications of fuel cells.

If you want to be technical about it, a fuel cell is an electrochemical energy

conversion device. A fuel cell converts the chemicals hydrogen and oxygen into water, andin the process it produces electricity.

The other electrochemical device that we are all familiar with is the battery. A batteryhas all of its chemicals stored inside, and it converts those chemicals into electricity too. This

means that a battery eventually "goes dead" and you either throw it away or recharge it.

With a fuel cell, chemicals constantly flow into the cell so it never goes dead -- aslong as there is a flow of chemicals into the cell, the electricity flows out of the cell. Mostfuel cells in use today use hydrogen and oxygen as the chemicals.




History of Fuel cell

In 1889, the term “fuel cell” was first coined by

Ludwig Mond and Charles Langer, who attempted to build aworking fuel cell using air and industrial coal gas. Another

source states that it was William White Jaques who firstcoined the term "fuel cell." Jaques was also the firstresearcher to use phosphoric acid in the electrolyte bath.

In the 1920s, fuel cell research in Germany pavedthe way to the development of the carbonate cycle andsolid oxide fuel cells of today.

In 1932, engineer Francis T Bacon began his vitalresearch into fuels cells. Early cell designers used porousplatinum electrodes and sulfuric acid as the electrolyte

bath. Using platinum was expansive and using sulfuric acid

was corrosive. Bacon improved on the expensive platinumcatalysts with a hydrogen and oxygen cell using a less corrosive alkaline electrolyte andinexpensive nickel electrodes.

It took Bacon until 1959 to perfect his design, when he demonstrated a five-kilowatt fuelcell that could power a welding machine. Francis T. Bacon, a direct descendent of the other wellknown Francis Bacon, named his famous fuel cell design the "Bacon Cell."

In October of 1959, Harry Karl Ihrig, an engineer for the Allis - Chalmers Manufacturing

Company, demonstrated a 20-horsepower tractor that was the first vehicle ever powered by a fuelcell.

During the early 1960s, General Electric produced the fuel-cell-based electrical power

system for NASA's Gemini and Apollo space capsules. General Electric used the principles found inthe "Bacon Cell" as the basis of its design. Today, the Space Shuttle's electricity is provided by fuel

cells, and the same fuel cells provide drinking water for the crew.

NASA decided that using nuclear reactors was too high a risk, and using batteries or solar

power was too bulky to use in space vehicles. NASA has funded more than 200 research contractsexploring fuel-cell technology, bringing the technology to a level now viable for the private sector.

The first bus powered by a fuel cell was completed in 1993, and several fuel-cell cars arenow being built in Europe and in the United States. Daimler Benz and Toyota launched prototypefuel-cell powered cars in 1997.

Maybe the answer to "What's so great about fuel cells?" should be the question "What's so

great about pollution, changing the climate or running out of oil, natural gas and coal?" As we

head into the next millennium, it is time to put renewable energy and planet-friendly technology atthe top of our priorities.

Fuel cells have been around for over 150 years and offer a source of energy that is

inexhaustible, environmentally safe and always available. So why aren't they being usedeverywhere already? Until recently, it has been because of the cost. The cells were too expansiveto make. That has now changed.

In the United States, several pieces of legislation have promoted the current explosion in

hydrogen fuel cell development: namely, the congressional Hydrogen Future Act of 1996 and





several state laws promoting zero emission levels for cars. Worldwide, different types of fuel cells

have been developed with extensive public funding. The United States alone has sunk more thanone billion dollars into fuel-cell research in the last thirty years.

In 1998, Iceland announced plans to create a hydrogen economy in cooperation withGerman car maker Daimler Benz and Canadian fuel cell developer Ballard Power Systems. The 10-

year plan would convert all transportation vehicles, including Iceland's fishing fleet, over to fuel-cell-powered vehicles. In March, 1999, Iceland, Shell Oil, Daimler Chrysler, and Norsk Hydroformed a company to further develop Iceland's hydrogen economy.

In February, 1999, Europe's first public commercial hydrogen fuel station for cars andtrucks opened for business in Hamburg, Germany. In April, 1999, Daimler Chrysler unveiled the

liquid hydrogen vehicle NECAR 4. With a top speed of 90 mph and a 280-mile tank capacity, thecar wowed the press. The company plans to have fuel-cell vehicles in limited production by theyear 2004. By that time, Daimler Chrysler will have spent $1.4 billion more on fuel-cell technologydevelopment.

In August, 1999, Singapore physicists announced a new hydrogen storage method of alkalidoped carbon nanotubes that would increase hydrogen storage and safety. A Taiwanese company,San Yang, is developing the first fuel cell powered motorcycle.

Types of fuel cell

The fuel cell will compete with many other energy conversion devices, including thegas turbine in your city's power plant, the gasoline engine in your car and the battery inyour laptop. Combustion engines like the turbine and the gasoline engine burn fuels and usethe pressure created by the expansion of the gases to do mechanical work. Batteries convert

chemical energy back into electrical energy when needed. Fuel cells should do both tasksmore efficiently.

A fuel cell provides a DC (direct current) voltage that can be used to power motors,lights or any number of electrical appliances.

There are several different types of fuel cells, each using a different chemistry. Fuelcells are usually classified by their operating temperature and the type of electrolyte they use.Some types of fuel cells work well for use in stationary power generation plants. Others maybe useful for small portable applications or for powering cars. The main types of fuel cells

include:

Polymer exchange membrane fuel cell (PEMFC)

The Department of Energy (DOE) is focusing on the PEMFC as the most likelycandidate for transportation applications. The PEMFC has a high power density and arelatively low operating temperature (ranging from 60 to 80 degrees Celsius, or 140 to 176degrees Fahrenheit). The low operating temperature means that it doesn't take very long forthe fuel cell to warm up and begin generating electricity. We?ll take a closer look at thePEMFC in the next section.





Solid oxide fuel cell (SOFC)

These fuel cells are best suited for large-scale stationary power generators that could

provide electricity for factories or towns. This type of fuel cell operates at very hightemperatures (between 700 and 1,000 degrees Celsius). This high temperature makesreliability a problem, because parts of the fuel cell can break down after cycling on and off repeatedly. However, solid oxide fuel cells are very stable when in continuous use. In fact,the SOFC has demonstrated the longest operating life of any fuel cell under certain operatingconditions. The high temperature also has an advantage: the steam produced by the fuel cellcan be channeled into turbines to generate more electricity. This process is called co-

generation of heat and power (CHP) and it improves the overall efficiency of the system.

Alkaline fuel cell (AFC)

This is one of the oldest designs for fuel cells; the United States space program has

used them since the 1960s. The AFC is very susceptible to contamination, so it requires purehydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to becommercialized.

Molten-carbonate fuel cell (MCFC)

Like the SOFC, these fuel cells are also best suited for large stationary powergenerators. They operate at 600 degrees Celsius, so they can generate steam that can be usedto generate more power. They have a lower operating temperature than solid oxide fuel cells,which means they don't need such exotic materials. This makes the design a little less

expensive.

Phosphoric-acid fuel cell (PAFC)

The phosphoric-acid fuel cell has potential for use in small stationary power-generation systems. It operates at a higher temperature than polymer exchange membranefuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars.

Direct-methanol fuel cell (DMFC)

Methanol fuel cells are comparable to a PEMFC in regards to operating temperature,but are not as efficient. Also, the DMFC requires a relatively large amount of platinum to actas a catalyst, which makes these fuel cells expensive.





Polymer Exchange Membrane Fuel Cells

The polymer exchange membrane fuel cell (PEMFC) is one of the most promisingfuel cell technologies. This type of fuel cell will probably end up powering cars, buses andmaybe even your house. The PEMFC uses one of the simplest reactions of any fuel cell. First,let's take a look at what's in a PEM fuel cell:

In Figure 1 you can see there are four basic elements of a PEMFC:

The anode, the negative post of the fuel cell, has several jobs. It conducts theelectrons that are freed from the hydrogen molecules so that they can be used in an externalcircuit. It has channels etched into it that disperse the hydrogen gas equally over the surfaceof the catalyst.

The cathode, the positive post of the fuel cell, has channels etched into it that

distribute the oxygen to the surface of the catalyst. It also conducts the electrons back fromthe external circuit to the catalyst, where they can recombine with the hydrogen ions andoxygen to form water.

Theelectrolyte is the protonexchange membrane. Thisspecially treated material,which looks something likeordinary kitchen plasticwrap, only conductspositively charged ions. Themembrane blocks electrons.

For a PEMFC, themembrane must be hydratedin order to function andremain stable.

The catalyst is a special material thatfacilitates the reaction of oxygen and hydrogen. It is usually made of platinum nanoparticles very thinly coated ontocarbon paper or cloth. The catalyst is rough and porous so that the maximum surface area of the platinum can be exposed to the hydrogen or oxygen. The platinum-coated side of thecatalyst faces the PEM.





Working of Hydrogen fuel cell

What do batteries and fuel cells have in common? They are both electrochemicalenergy conversion devices that produce electricity. Also, they both have anodes, cathodes,and an electrolyte.There are also bigdifferences.Batteries produceelectricity untilcompletelydischarged, thenthey have to bereplaced orrecharged. A fuel

cell continues toproduce electricity

as long as it is supplied with fuel and oxygen. In the typical fuel cell used in transportation,that's hydrogen and air. A battery produces essentially no emissions and little heat, while ahydrogen fuel cell emits water and more heat.

While there are several different types of fuel cells, they all work on the same basicprinciple. The proton exchange membrane (PEM) fuel cell will be discussed here. With rareexception, this is the technology being developed for use in cars, trucks, and buses. PEM fuelcells appear to be the most promising for vehicles because the reactions are about thesimplest of any fuel cell design. They also have a high kilowatts-per-cubic-inch powerdensity. Their relatively low operating temperature of 140 to 176 degrees F means they start

to produceelectricity quicklyand don't requireexpensive coolingsystems.

In a PEMfuel cell,

pressurizedhydrogen gas enterson the anode sideand is forcedthrough the catalyst.Here, H2 moleculescome in contactwith catalyst,

splitting it into two H+ ions (protons).and two electrons. The proton exchange membrane andelectrolyte let positively charged proton through and block negatively charged electrons.





Electrons are conducted through the anode and travel through the external circuit asDC (direct current)electric power, whichcan useful forpurposes such aspowering an electricmotor, and then theyreach the cathode.Here they combineon the cathode'scatalyst with theproton comingthrough themembrane and withoxygen gas, or air,forced through thecatalyst, where they

form two oxygenatoms with a strongnegative charge. Thisnegative chargeattracts the two H+ions, which combinewith an oxygen atomand two of theelectrons to form a

water molecule.

The proton exchange membrane is a specially treated material that looks somewhat

like ordinary kitchen plastic wrap. The membrane must be hydrated to transfer protons andremain stable. Thus, fuel cell systems must be designed to operate in sub-zero temperatures,low humidity environments, and high operating temperatures. At about 70 degrees F,hydration is lost without a high-pressure hydration system.

Catalysts play the crucial role of separating hydrogen into ions and protons at theanode and combining them, plus water, at the cathode. Typically these use a platinum groupmetal or alloy with platinum nanoparticles very thinly coated onto carbon paper or cloth. Thecatalyst is rough and porous to expose maximum surface area to the hydrogen or oxygen. Theplatinum-coated side of the catalyst faces the membrane.

Precious metal catalysts plus proton exchange membranes, gas diffusion layers, andbipolar plates make up about 70 percent of a current fuel cell's Because of this, plus the rarityof precious metals and competition from other uses such as catalytic converters, some criticssay platinum is the PEM fuel cell's Achilles heel. Research is under way to solve thispotential impediment. For example, researchers are looking at ways to use less of theprecious metals and to find alternatives. Recycling platinum, especially from catalyticconverters, is already common practice. More abundant gold, reduced to nanometer size,





could be used as a catalyst as well. Enhancing a catalyst with carbon silk can also reduce theamount of precious metals required.cost.

Another problem with PEM fuel cells is that impurities can poison the catalysts,resulting in reduced efficiency and activity so more dense catalysts are required and more

platinum is used. Again, research is underway to solve the problem with various promisingtechniques beingexplored, like usinga gold-palladiumcoating that may beless susceptible topoisoning.

Since asingle fuel cell

produces only about0.7 volts, manyseparate fuel cellsare combined toform a fuel cellstack. They can beconnected in aparallel circuit forhigher current andin series for highervoltage.

Fuel cellsare very efficient. If supplied with pure

hydrogen they can convert 80 percent of the hydrogen's energy content to electric power. If the electricity is used by an electric motor and inverter in a fuel cell vehicle - which are about80 percent efficient - the overall efficiency is 64 percent. This compares to the approximate20 percent energy conversion efficiency of the typical gasoline-fueled vehicle, providing yetanother reason why fuel cell vehicles hold such promise for the future.





Applications

Power

Stationary fuel cells are used for commercial, industrial and residential primary andbackup power generation. Fuel cells are very usefulas power sources in remote locations, such asspacecraft, remote weather stations, large parks,communications centers, rural locations includingresearch stations, and in certain militaryapplications. A fuel cell system running onhydrogen can be compact and lightweight, and haveno major moving parts. Because fuel cells have no moving parts and do not involvecombustion, in ideal conditions they can achieve up to 99.9999% reliability. This equates toless than one minute of downtime in a six year period.

Since fuel cellelectrolyzer systems do not store fuel in themselves, but rather rely onexternal storage units, they can be successfully applied in large-scale energy storage, ruralareas being one example. There are many different types of stationary fuel cells soefficiencies vary, but most are between 40% and 60% energy efficient. However, when thefuel cell’s waste heat is used to heat a building in a cogeneration system this efficiency canincrease to 85%. This is significantly more efficient than traditional coal power plants, whichare only about one third energy efficient. Assuming production at scale, fuel cells could save20-40% on energy costs when used in cogeneration systems. Fuel cells are also much cleanerthan traditional power generation; a fuel cell power plant using natural gas as a hydrogensource would create less than one ounce of pollution (other than CO2) for every 1,000 kW

produced, compared to 25 pounds of pollutants generated by conventional combustionsystems. Fuel Cells also produce 97% less nitrogen oxide emissions then conventional coal-fired power plants.

Coca-Cola, Google, Walmart, Sysco, FedEx, UPS, Ikea, Staples, Whole Foods, GillsOnions, Nestle Waters, Pepperidge Farm, Sierra Nevada Brewery, Super Store Industries,Brigestone-Firestone, Nissan North America, Kimberly-Clark, Michelin and more haveinstalled fuel cells to help meet their power needs. One such pilot program is operating onStuart Island in Washington State. There the Stuart Island Energy Initiativehas built acomplete, closed-loop system: Solar panels power an electrolyzer which makes hydrogen.The hydrogen is stored in a 500 US gallons (1,900 L) at 200 pounds per square inch(1,400 kPa), and runs a ReliOn fuel cell to provide full electric back-up to the off-the-grid

residence. Another closed system loop was unveiled in late 2011 in Hempstead, NY.

Cogeneration

Combined heat and power (CHP) fuel cell systems, including Micro combined heatand power (MicroCHP) systems are used to generate both electricity and heat for homes (seehome fuel cell), office building and factories. 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 ahome fuel cell or small business.

The waste heat from fuel cells can be diverted during the summer directly into theground providing further cooling while the waste heat during winter can be pumped directly

into the building. The University of Minnesota owns the patent rights to this type of system.

Co-generation systems can reach 85% efficiency (40-60% electric + remainder asthermal). Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existing CHPproducts worldwide and can provide combined efficiencies close to 90%. Molten Carbonate(MCFC) and Solid Oxide Fuel Cells (SOFC) are also used for combined heat and powergeneration and have electrical energy effciences around 60%.

Automobiles

Although there are currently no Fuel cell vehicles available for commercial sale, over20 FCEVs prototypes and demonstration cars have been

released since 2009. Demonstration models include theHonda FCX Clarity, Toyota FCHV-adv, and Mercedes-Benz F-Cell. As of June 2011 demonstration FCEVshad driven more than 4,800,000 km (3,000,000 mi),with more than 27,000 refuelings.Demonstration fuelcell vehicles have been produced with "a driving rangeof more than 400 km (250 mi) between refueling".

]

They can be refueled in less than 5 minutes. The U.S.Department of Energy's Fuel Cell Technology Program

claims that, as of 2011, fuel cells achieved 53–59% efficiency at ¼ power and 42–53%vehicle efficiency at full power, and a durability of over 120,000 km (75,000 mi) with lessthan 10% degradation, double that achieved in 2006. In a Well-to-Wheels simulation

analysis, that "did not address the economics and market constraints", General Motors and itspartners estimated that per mile traveled, a fuel cellelectric vehicle running on compressed gaseoushydrogen produced from natural gas could use about40% less energy and emit 45% less greenhouse gassesthan an internal combustion vehicle. A lead engineerfrom the Department of Energy whose team is testingfuel cell cars said in 2011 that the potential appeal isthat "these are full-function vehicles with no limitationson range or refueling rate so they are a directreplacement for any vehicle. For instance, if you drivea full sized SUV and pull a boat up into the mountains,you can do that with this technology and you can't with current battery-only vehicles, whichare more geared toward city driving."

Some experts believe that fuel cell cars will never become economically competitivewith other technologies or that it will take decades for them to become profitable. In July2011, the Chairman and CEO of General Motors, Daniel Akerson, stated that while the costof hydrogen fuel cell cars is decreasing: "The car is still too expensive and probably won't bepractical until the 2020-plus period, I don't know." Analyses cite the lack of an extensive





hydrogen infrastructure in the U.S. as an ongoing challenge to Fuel Cell Electric Vehiclecommercialization. In 2006, a study for the IEEE showed that for hydrogen produced viaelectrolysis of water: "Only about 25% of the power generated from wind, water, or sun isconverted to practical use." The study further noted that "Electricity obtained from hydrogenfuel cells appears to be four times as expensive as electricity drawn from the electricaltransmission grid. ... Because of the high energy losses [hydrogen] cannot compete withelectricity." Furthermore, the study found: "Natural gas reforming is not a sustainablesolution”. The large amount of energy required to isolate hydrogen from natural compounds(water, natural gas, biomass), package the light gas by compression or liquefaction, transferthe energy carrier to the user, plus the energy lost when it is converted to useful electricitywith fuel cells, leaves around 25% for practical use." Despite this, several major carmanufacturers have announced plans to introduce a production model of a fuel cell car in2015. Toyota has stated that it plans to introduce such a vehicle at a price of aroundUS$50,000. In June 2011, Mercedes-Benz announced that they would move the scheduledproduction date of their fuel cell car from 2015 up to 2014, asserting that "The product isready for the market technically. ... The issue is infrastructure."

In 2003 US President George W. Bush proposed the Hydrogen Fuel Initiative (HFI).This aimed at further developing hydrogen fuel cells and infrastructure technologies with thegoal of producing commercial fuel cell vehicles. By 2008, the U.S. had contributed 1 billiondollars to this project. The Obama Administration has sought to reduce funding for thedevelopment of fuel cell vehicles, concluding that other vehicle technologies will lead toquicker reduction in emissions in a shorter time. Steven Chu, the US Secretary of Energy,stated that hydrogen vehicles "will not be practical over the next 10 to 20 years". He toldMIT's Technology Review that he is skeptical about hydrogen's use in transportation becauseof four problems: "the way we get hydrogen primarily is from reforming [natural] gas. ...You're giving away some of the energy content of natural gas. ... [For] transportation, wedon't have a good storage mechanism yet. ... The fuel cells aren't there yet, and thedistribution infrastructure isn't there yet. ... In order to get significant deployment, you need

four significant technological breakthroughs.]Critics disagree. Mary Nichols, Chairwoman of California's Air Resources Board, said: "Secretary Chu has firmly set his mind againsthydrogen as a passenger-car fuel. Frankly, his explanations don’t make sense to me. They arenot based on the facts as we know them."

Forklifts

Fuel cell powered forklifts are one of the largest sectors of fuel cell applications in theindustry.[89] Most fuel cells used for material handling purposes are powered by PEM fuelcells, although some direct methanol fuel forklifts are coming onto the market. Fuel cell fleetsare currently being operated by a large number of companies, including Sysco Foods, FedExFreight, GENCO (at Wegmans, Coca-Cola, Kimberly Clark, Sysco Foods, and Whole

Foods), and H-E-B Grocers.

Fuel cell powered forklifts provide significant benefits over both petroleum andbattery powered forklifts as they produce no local emissions, can work for a full 8 hour shifton a single tank of hydrogen, can be refueled in 3 minutes and have a lifetime of 8–10 years.Fuel cell powered forklifts are often used in refrigerated warehouses as their performance isnot degraded by lower temperatures. Many companies do not use petroleum poweredforklifts, as these vehicles work indoors where emissions must be controlled and instead are





turning towards electric forklifts. Fuel cell forklifts offer green house gas, product lifetime,maintenance cost, refueling and labor cost benefits over battery operated fork lifts.

Airplanes

Boeing researchers and industry partners throughout Europe conducted experimentalflight tests in February 2008 of a manned airplane powered only by a fuel cell andlightweight batteries. The Fuel Cell Demonstrator Airplane, as it was called, used a ProtonExchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power an electricmotor, which was coupled to a conventional propeller. In 2003, the world's first propellerdriven airplane to be powered entirely by a fuel cell was flown. The fuel cell was a uniqueFlatStack TM stack design which allowed the fuel cell to be integrated with the aerodynamicsurfaces of the plane.

There have been several fuel cell powered unmanned aerial vehicles (UAV). AHorizen fuel cell UAV set the record distance flow for a small UAV in 2007. The military isespecially interested in this application because of the low noise, low thermal signature and

ability to attain high altitude. In 2009 the Naval Research Laboratory’s (NRL’s) Ion Tigerutilized a hydrogen-powered fuel cell and flew for 23 hours and 17 minutes. Boeing iscompleting tests on the Phantom Eye, a high-altitude, long endurance (HALE) to be used toconduct research and surveillance flying at 20,000 m (65,000 ft) for up to four days at a time.Fuel cells are also being used to provide auxiliary power in aircraft, replacing fossil fuelgenerators that were previously used to start the engines and power on board electrical needs.Fuel cells can help airplanes reduce CO2 and other pollutant emissions and noise.

Boats

The world's first Fuel Cell Boat HYDRAused an AFC system with 6.5 kW net output.

Iceland has committed to converting its vastfishing fleet to use fuel cells to provide auxiliarypower by 2015 and, eventually, to provide primarypower in its boats. Amsterdam recently introducedits first fuel cell powered boat that ferries peoplearound the city's famous and beautiful canals.

Submarines

The Type 212 submarines of the German and Italian navies use fuel cells to remainsubmerged for weeks without the need to surface.

The latest in fuel cell submarines is the U212A—an ultra-advanced non-nuclear subdeveloped by German naval shipyard Howaldtswerke Deutsche Werft, who claim it to be"the peak of German submarine technology." The system consists of nine PEM (ProtonExchange Membrane) fuel cells, providing between 30 kW and 50 kW each. The ship istotally silent giving it a distinct advantage in the detection of other submarines. Fuel cellsoffer other advantages to submarines in addition to being completely silent; they can bedistributed throughout a ship to improve balance and require far less air to run, allowing ships





to be submerged for longer periods of time. Fuel cells offer a good alternative to nuclearfuels.

Other applications

Providing power for base stations or cell sites

Off-grid power supply Distributed generation Fork Lifts 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 whenregular systems fail. They find uses in a wide variety of settings from residential homes tohospitals, scientific laboratories, data centers, telecommunication equipment and modernnaval ships.

An uninterrupted power supply (UPS) provides emergency power and,depending on the topology, provide line regulation as well to connected equipment bysupplying 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.





Production of Hydrogen

Hydrogen productionis the family of industrial methods for generating hydrogen.Currently the dominant technology for direct production is steam reforming from

hydrocarbons. Many other methods are known including electrolysis and thermolysis. Thefollowing methods are mainly used to produce hydrogen fuel.

1. Steam reforming

Fossil fuels are the dominant source of industrial hydrogen.Hydrogen can begenerated from natural gas with approximately 80% efficiency, or from other hydrocarbonsto a varying degree of efficiency. Specifically, bulk hydrogen is usually produced by thesteam reforming of methane or natural gas At high temperatures (700–1100 °C), steam (H2O)reacts with methane (CH4) to yield syngas.

CH4 + H2O → CO + 3 H2 + 191.7 kJ/mol

In a second stage, further hydrogen is generatedthrough the lower-temperature water gas shift reaction,performed at about 130 °C:

CO + H2O → CO2 + H2 - 40.4 kJ/mol

Essentially, the oxygen (O) atom is stripped from theadditional water (steam) to oxidize CO to CO2. This oxidation also provides energy tomaintain the reaction. Additional heat required to drive the process is generally supplied by

burning some portion of the methane.

CO2 sequestration

Steam reforming generates carbon dioxide (CO2). Since the production isconcentrated in one facility, it is possible to separate the CO2 and dispose of it properly, forexample by injecting it in an oil or gas reservoir (see carbon capture), although this is notcurrently done in most cases. A carbon dioxide injection project has been started by aNorwegian company StatoilHydro in the North Sea, at the Sleipner field. This is disputed inThe Hype about Hydrogen: Fact and Fiction in the Race to Save the Climate, a book byJoseph J. Romm, published in 2004 by Island Press and updated in 2005. Romm says that

directly burning fossil fuels generates less CO2 than hydrogen production.

Integrated steam reforming / co-generation - It is possible to combine steam reformingand co-generation of steam and power into a single plant. This can deliver benefits for an oilrefinery because it is more efficient than separate hydrogen, steam and power plants. AirProducts recently built an integrated steam reforming / co-generation plant in Port Arthur,Texas.





2.Other production methods from fossil fuels

Partial oxidation

The partial oxidation reaction occurs when a substoichiometric fuel-air mixture ispartially combusted in a reformer, creating a hydrogen-rich syngas. A distinction is madebetween thermal partial oxidation (TPOX) and catalytic partial oxidation (CPOX). Thechemical reaction takes the general form:

CnHm + n / 2 O2 → n CO + m / 2 H2

Idealized examples for heating oil and coal, assuming compositions C12H24 andC24H12 respectively, are as follows:

C12H24 + 6 O2 → 12 CO + 12 H2 C24H12 + 12 O2 → 24 CO + 6 H2

Plasma reforming

The Kværner-process or Kvaerner carbon black & hydrogen process (CB&H)[6]

is aplasma reforming method, developed in the 1980s by a Norwegian company of the samename, for the production of hydrogen and carbon black from liquid hydrocarbons (CnHm). Of the available energy of the feed, approximately 48% is contained in the hydrogen, 40% iscontained in activated carbon and 10% in superheated steam. CO2 is not produced in theprocess.A variation of this process is presented in 2009 using plasma arc waste disposaltechnology for the production of hydrogen, heat and carbon from methane and natural gas ina plasma converter

Coal

Coal can be converted into syngas and methane, also known as town gas, via coalgasification. Syngas consists of hydrogen and carbon monoxide. Another method forconversion is low temperature and high temperature coal carbonization.

3.From water

Many technologies have been explored but it should be noted that as of 2007"Thermal, thermochemical, biochemical and photochemical processes have so far not foundindustrial applications." Only high temperature electrolysis of alkaline solutions finds someapplications.





Electrolysis

Approximately 5% of industrial hydrogen is produced by electrolysis. Two types of

cells are popular, solid oxide electrolysis cells (SOEC's) and alkaline electrolysis cells(AEC's) . These cells optimally operate at high concentrations electrolyte (KOH or potassiumcarbonate) and at high temperatures, often near 200 °C. Typical catalysts are yttrium-stabilized zirconium together with nickel.

Thermolysis

Water spontaneously dissociates at around 2500 C, but this thermolysis occurs attemperatures too high for usual process piping and equipment. Catalysts are required toreduce the dissociation temperature.

Photocatalytic water splitting

The conversion of solar energy to hydrogen by means of water splitting process is oneof the most interesting ways to achieve clean and renewable energy systems. However if thisprocess is assisted by photocatalysts suspended directly in water instead of using photovoltaicand an electrolytic system the reaction is in just one step, therefore it can be more efficient.

Sulfur-iodine cycle

The sulfur-iodine cycle (S-I cycle) is a thermochemical process which generateshydrogen from water, but at a much higher efficiency than water splitting. The sulfur andiodine used in the process are recovered and reused, and not consumed by the process. It iswell suited to production of hydrogen by high-temperature nuclear reactors or by

concentrating solar power systems (CSP).

Biohydrogen routes

Although of no industrial significance,[2]

biomass and waste streams can in principlebe converted into biohydrogen with biomass gasification, steam reforming or biologicalconversion like biocatalysed electrolysis or fermentative hydrogen production.

Fermentative hydrogen production

Fermentative hydrogen production is the fermentative conversion of organic substrateto biohydrogen manifested by a diverse group of bacteria using multi enzyme systemsinvolving three steps similar to anaerobic conversion. Dark fermentation reactions do notrequire light energy, so they are capable of constantly producing hydrogen from organiccompounds throughout the day and night. Photofermentation differs from dark fermentationbecause it only proceeds in the presence of light. For example photo-fermentation withRhodobacter sphaeroides SH2C can be employed to convert small molecular fatty acids intohydrogen.





Fermentative hydrogen production can be done using direct biophotolysis by greenalgae, indirect biophotolysis by cyanobacteria, photo-fermentation by anaerobicphotosynthetic bacteria and dark fermentation by anaerobic fermentative bacteria. Forexample studies on hydrogen production using H. salinarium, an anaerobic photosyntheticbacteria, coupled to a hydrogenase donor like E. coli, are reported in literature.

Biohydrogen can be produced in bioreactors that utilize feedstocks, the most commonfeedstock being waste streams. The process involves bacteria feeding on hydrocarbons andexhaling hydrogen and CO2. The CO2 can be sequestered successfully by several methods,leaving hydrogen gas. A prototype hydrogen bioreactor using waste as a feedstock is inoperation at Welch's grape juice factory in North East, Pennsylvania (U.S.).

Enzymatic hydrogen generation

Due to the Thauer limit (four H2 /glucose) for dark fermentation, a non-naturalenzymatic pathway was designed that can generate 12 moles of hydrogen per mole of glucoseunits of polysaccharides and water in 2007.[ The stoichiometric reaction is:

C6H10O5 + 7 H2O → 12 H2 + 6 CO2

The key technology is cell-free synthetic enzymatic pathway biotransformation(SyPaB). A biochemist can understand it as "glucose oxidation by using water as oxidant". Achemist can describe it as "water splitting by energy in carbohydrate". A thermodynamicsscientist can describe it as the first entropy-driving chemical reaction that can producehydrogen by absorbing waste heat. In 2009, cellulosic materials were first used to generatehigh-yield hydrogen. Furthermore, the use of carbohydrate as a high-density hydrogen carrierwas proposed so to solve the largest obstacle to the hydrogen economy and propose theconcept of sugar fuel cell vehicles.

Biocatalysed electrolysis

Besides dark fermentation, electrohydrogenesis (electrolysis using microbes) isanother possibility. Using microbial fuel cells, wastewater or plants can be used to generatepower. Biocatalysed electrolysis should not be confused with biological hydrogen production,as the latter only uses algae and with the latter, the algae itself generates the hydrogeninstantly, where with biocatalysed electrolysis, this happens after running through themicrobial fuel cell and a variety of aquatic plants can be used. These include reed sweetgrass,cordgrass, rice, tomatoes, lupines, algae.

4.Renewable hydrogen

Currently there are several practical ways of producing hydrogen in a renewableindustrial process. One is to use landfill gas to produce hydrogen in a steam reformer, and theother is to use renewable power to produce hydrogen from electrolysis. Hydrogen fuel, whenproduced by renewable sources of energy like wind or solar power, is a renewable fuel.





Hydrogen storage

Hydrogen storage describes the methods for storing H2 for subsequent use. Themethods span many approaches, including high pressures, cryogenics, and chemicalcompounds that reversibly release H2 upon heating. Hydrogen storage is a topical goal in thedevelopment of a hydrogen economy.Most research into hydrogen storage is focused onstoring hydrogen as a lightweight, compact energy carrier for mobile applications.

1.Compressed hydrogen

Compressed hydrogen is the gaseous state of the element hydrogen which is keptunder pressure. Compressed hydrogen in hydrogen tanks at 350 bar (5,000 psi) and 700 bar

(10,000 psi) is used for in hydrogen vehicles. Car manufacturers have been developing thissolution, such as Honda[7] or Nissan.[8]

2.Liquid hydrogen

BMW has been working on liquid tank for cars, producing for example the BMWHydrogen 7

3.Proposals and research

Hydrogen storage technologies can be divided into physical storage, where hydrogenmolecules are stored (including pure hydrogen storage via compression and liquefication),

and chemical storage, where hydrides are stored.

3.1 Chemical storage

Metal hydrides

Metal hydrides, such as MgH2, NaAlH4, LiAlH4, LiH, LaNi5H6, TiFeH2 andpalladium hydride, with varying degrees of efficiency, can be used as a storage medium forhydrogen, often reversibly. Some are easy-to-fuel liquids at ambient temperature andpressure, others are solids which could be turned into pellets. These materials have goodenergy density by volume, although their energy density by weight is often worse than theleading hydrocarbon fuels.

Most metal hydrides bind with hydrogen very strongly. As a result high temperaturesaround 120 °C (248 °F) – 200 °C (392 °F) are required to release their hydrogen content. Thisenergy cost can be reduced by using alloys which consists of a strong hydride former and aweak one such as in LiNH2, NaBH4 and LiBH4. These are able to form weaker bonds,thereby requiring less input to release stored hydrogen. However if the interaction is tooweak, the pressure needed for rehydriding is high, thereby eliminating any energy savings.The target for onboard hydrogen fuel systems is roughly <100 °C for release and <700 bar forrecharge (20-60 kJ/mol H2).





Currently the only hydrides which are capable of achieving the 9 wt. % gravimetricgoal for 2015 (see chart above) are limited to lithium, boron and aluminum basedcompounds; at least one of the first-row elements or Al must be added. Research is beingdone to determine new compounds which can be used to meet these requirements.

Proposed hydrides for use in a hydrogen economy include simple hydrides of magnesium or transition metals and complex metal hydrides, typically containing sodium,lithium, or calcium and aluminium or boron. Hydrides chosen for storage applicationsprovide low reactivity (high safety) and high hydrogen storage densities. Leading candidatesare lithium hydride, sodium borohydride, lithium aluminium hydride and ammonia borane. AFrench company McPhy Energy is developing the first industrial product, based onmagnesium hydrate, already sold to some major clients such as Iwatani and ENEL.

New Scientist stated that Arizona State University is investigating using aborohydride solution to store hydrogen, which is released when the solution flows over acatalyst made of ruthenium.

3.2 Physical storage

Cryo-compressed

Cryo-compressed storage of hydrogen is the only technology that meets 2015 DOEtargets for volumetric and gravimetric efficiency (see "CcH2" on slide 6 in).

Furthermore, another study has shown that cryo-compressed exhibits interesting costadvantages: ownership cost (price per mile) and storage system cost (price per vehicle) areactually the lowest when compared to any other technology.For example, a cryo-compressedhydrogen system would cost $0.12 per mile (including cost of fuel and every associated othercost), while conventional gasoline vehicles cost between $0.05 and $0.07 per mile.

Alike liquid storage, cryo-compressed uses cold hydrogen (20.3 K and slightly above)in order to reach a high energy density. However, the main difference is that, when thehydrogen would warm-up due to heat transfer with the environment ("boil off"), the tank isallowed to go to pressures much higher (up to 350 bars versus a couple of bars for liquidstorage). As a consequence, it takes more time before the hydrogen has to vent, and in mostdriving situations, enough hydrogen is used by the car to keep the pressure well below theventing limit.

Consequently, it has been demonstrated that a high driving range could be achievedwith a cryo-compressed tank : more than 650 miles (1,050 km) were driven with a full tank mounted on an hydrogen-fueled engine of Toyota Prius.

[30]Research is still on its way in

order to study and demonstrate the full potential of the technology.

As of 2010, the BMW Group has started a thorough component and system levelvalidation of cryo-compressed vehicle storage on its way to a commercial product.





Carbon nanotubes

Hydrogen carriers based on nanostructured carbon (suchas carbon buckyballs and nanotubes) have been proposed.Despite initial claims of greater than 50 wt% hydrogen storage, itwas later accepted that a realistic number is less than 1 wt%.

4.Stationary hydrogen storage

Unlike mobile applications, hydrogen density is not ahuge problem for stationary applications. As for mobile

applications, stationary applications can use established technology:

Compressed hydrogen (CGH2) in a hydrogen tank Liquid hydrogen in a (LH2) cryogenic hydrogen tank Slush hydrogen in a cryogenic hydrogen tank

5.Underground hydrogen storage

Underground hydrogen storage is the practice of hydrogen storage in undergroundcaverns, salt domes and depleted oil and gas fields. Large quantities of gaseous hydrogenhave been stored in underground caverns by ICI for many years without any difficulties. Thestorage of large quantities of hydrogen underground can function as grid energy storagewhich is essential for the hydrogen economy.





Hydrogen safety

The Hindenburg Disaster - I s Hydrogen Really Dangerous?

The May 1937 explosion of the German airship Hindenburg has dogged the development of

hydrogen as a fuel since those first terrifying images played out across newspapers and newsreelsthroughout the world. For years, the hydrogen gas that filled the airship and allowed it to float in

the atmosphere was blamed for the raging inferno that consumed the craft in just seconds. Turnsout that’s not the case at all.

So What Really Happened With th e Hindenburg?

Theories abound—everything from sabotage by operatives to a fuel leak and overheatingengines—as to the cause of the initial fire. While speculation about conspiracies will always existon the periphery, the hydrogen gas that provided lift to the craft was not the main contributor tothe fire. Thorough investigation has boiled it down to a fairly well agreed-upon scenario.

The surface skin of the airship was covered with a layer of iron oxide and a coating of reflective aluminum paint. These two chemical compounds are highly flammable and burn at a

very aggressive rate. The skin most likely ignited from an atmospheric discharge (a spark) orperhaps a lightning strike as the airship was docking during the waning phases of an electrical

storm. Reasonable corroboration of this theory was demonstrated in an experiment by retired

NASA engineer Addison Bain in which remnants of the actual surface skin of the ship were setablaze some 60 years after the accident—and they still burned as ferociously as they did thatfateful day.

While the hydrogen gasbags in the ship did eventually succumb to the heat and rupture,the escaping gas caught fire as the surrounding skin burned. But being lighter than the air around

it, the burning gas rose quickly and burned well above the passenger compartment and crew

quarters below, and completely burned itself out within 60 seconds.

As the craft and the hydrogen inside it was consumed by the initial inferno and the skeletalframe of the ship plummeted, the on-board stores of diesel fuel (which powered the maneuveringengines) caught fire and those continued to burn as the wreckage lay on the ground. Had theHindenburg been filled with non-flammable helium instead of hydrogen, the same basic sequencewould still quite likely have ensued. The skin still would have ignited, the lifting gas would haveescaped and the crippled dirigible would have plunged to the ground with the onboard diesel fuel

aflame.

The tragedy of this accident is multifaceted. Not only was there terrible loss of life, but alsothe burgeoning and successful airship industry was dismantled and a stigma was attached tohydrogen—a frankly unjust stigma that lasts to this day.

The Basic Nature and Characteristics of Hydrogen

Hydrogen is non-toxic. It is a naturally occurring, basically benign element found freely in the atmosphere. Bycomparison, petroleum fuels are extremely toxic.

Hydrogen is less flamm able than gasoline . The auto-ignition temperature of hydrogen is 932 degrees Fahrenheit. Compare that to gasoline’sauto-ignition temperature of 536 degrees Fahrenheit (auto-ignition temperature is the minimum





temperature at which a fuel will ignite without a spark or flame). Yes, it’s actually easier for

gasoline to spontaneously combust.

Hydrogen disperses quickly in t he atmosph ere. Because hydrogen is so light (about 15 time lighter than air) it easily dissipates and if a leak orspill does occur, the hydrogen becomes rapidly sparse and difficult to ignite. And even if it doescatch fire, it burns itself out very quickly. By contrast, heavier fuels such as diesel oil and gasoline

do not rapidly dissipate and remain a fire threat for a longer period of time.

Hydrogen stor es safely. The tanks used to store hydrogen, whether in its gaseous or liquid form, undergo demanding

testing procedures. They must endure extreme heat and external pressure forces as well as

collision impacts. Conventional gasoline and diesel fuel tanks are, in most instances, simplestamped steel shells that do not undergo these stringent stress tests.

Hydrogen is clean. The single emission from burned hydrogen is water vapor—that’s it. Compare that to particulate

matter (soot), NOx, CO, CO2 and—among other toxic emissions—from burned petroleum fuels.

I t Really Boils Dow n to Comm on Sense

Think about it. The world that we’ve created for ourselves—with all of our technologicaldevelopments—is fraught with hazards. But it’s also filled with potential—a cornucopia of goodideas that can make our lives better, easier and richer. The caveat here is that it isn’t justautomatic, it requires attention and intelligent use.

We have all learned to handle dangerous but useful tools in our daily lives. We don’t thinktwice about slicing a loaf of bread with a sharp knife, striking a hot match to light a candle or

driving down the road in a car filled with a tank of explosive gasoline. We don’t think about theirdangers because we’ve learned to be smart and judicious in their use.

It is much the same case with hydrogen—new to us as a motor fuel, proper handling andsafety techniques will require a learning curve. Engineers have done their part and developed safe

and effective processes for transporting, storing and dispensing the fuel. It’s up to us as users tobe cognizant of the rules and to follow them.





Fuel cell advantages/disadvantages

Advantages

High efficiency conversion

Fuel cells convert chemical energy directly into electricity without the combustion process. As a result, afuel cell is not governed by thermodynamic laws, such as the Carnot efficiency associated with heat engines,currently used for power generation.

Fuel cells can achieve high efficiencies in energy conversion terms, especially where the waste heatfrom the cell is utilised in cogeneration situation.

High power density

A high power density allows fuel cells to be relatively compact source of electric power, beneficial inapplication with space constraints. In a fuel cell system, the fuel cell itself is nearly dwarfed by other componentsof the system such as the fuel reformer and power inverter

Quiet operation

Fuel cells, due to their nature of operation, are extremely quiet in operation. This allows fuel cells to beused in residential or built-up areas where the noise pollution is undesirable.

Disadvantages

Conceptually, replacing the current oil-based infrastructure with hydrogen would cost

billions, maybe trillions, of dollars. Although abundant in the universe, hydrogen is fairly rare in our atmosphere,

meaning that it has to be extracted (for example through electrolysis, as explained above) andcurrently, the process is cost prohibitive and inefficient

Although abundant in the universe, hydrogen is fairly rare in our atmosphere,meaning that it has to be extracted (for example through electrolysis, as explained above) andcurrently, the process is cost prohibitive and inefficient.

Its production at energy plants creates excessive carbon dioxide. When it burns, a hydrogen flame is virtually invisible; coupled with the gas’s

propensity for escaping, in small amounts, almost any tank, there are concerns about explosions. Onthe plus side, hydrogen is so light it typically is dispersed in the air very quickly.

On-board storage is a major issue; a hydrogen tank would currently be too large for acar.

It is a very flammable gas (think of the Hindenburg), which further adds to the on-

board storage problems.





Conclusion

A fuel cell is a device that converts the chemical energy from a fuel into electricitythrough a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the mostcommon fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimesused. Fuel cells are different from batteries in that they require a constant source of fuel andoxygen to run, but they can produce electricity continually for as long as these inputs aresupplied.

There are many types of fuel cells, but they all consist of an anode (negative side), acathode (positive side) and an electrolyte that allows charges to move between the two sidesof the fuel cell. Electrons are drawn from the anode to the cathode through an external circuit,producing direct current electricity. As the main difference among fuel cell types is theelectrolyte, fuel cells are classified by the type of electrolyte they use. Fuel cells come in avariety of sizes. Individual fuel cells produce very small amounts of electricity, about 0.7

volts, so cells are "stacked", or placed in series or parallel circuits, to increase the voltage andcurrent output to meet an application’s power generation requirements. In addition toelectricity, fuel cells produce water, heat and, depending on the fuel source, very smallamounts of nitrogen dioxide and other emissions. The energy efficiency of a fuel cell isgenerally between 40-60%, or up to 85% efficient if waste heat is captured for use.





References

www.google.com

www.wikipedia.com

http://www.eia.gov/oiaf/servicerpt/hydro/appendixc.html.

http://www1.eere.energy.gov/hydrogenandfuelcells/production/natural_gas.html.

https://www.hfpeurope.org/infotools/energyinfos__e/hydrogen/main03.html

http://www1.eere.energy.gov/hydrogenandfuelcells/production/coal_gasification.

html.

http://www.practicalphysics.org/go/Experiment_677.html.http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=18

66174.

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