Final Hydrogen

7/30/2019 Final Hydrogen

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ON

IN PARTIAL FULFILLMENT OF THE RECORD FOR THEAWARD OF DEGREE

SUBMITTED BY:

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

MODERN ENGINEERING AND MANAGEMENT STUDIES,BALASORE


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I express my sincere thanks to the Head of the

Department, Er. Parthasarathi Giri, Seminar in Charge, Vikas Singh and other faculties for their whole hearted support and valuable guidance,support for literature, critical view and above all the moral support.

I am also indebted to all the teaching and non teaching staff of the department and the college for their co-operation and suggestion, which is the spirit behind this report.

Lastly I would like to thank each and everyoneassociated with me for the seminar. I express my sincere thanks for their goodwill and constructive ideas.


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MODERN ENGINEERING AND

MANAGEMENT STUDIES

KURUDA, BALASORE, ODISHA

DEPARTMENT OF ELECTRONICS AND COMMUNICATION

ENGINEERING

This is to certify that this seminar entitledhas been successfully

presented by , Regd. No:, a student of of our college.

She has exhibited ample innovativeness, high interest andcreativity while preparing the seminar.

This is partial requirement for his B. Tech in Electronics& Communication Engineering.

I wish him all the success in the future endeavors.

SEMINAR IN CHARGE HEAD OF DEPARTMENT

Mr Vikas Singh Mr Parthasarathi Giri


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This paper discusses some crucial energetic, environmental andsustainability issues and the role of hydrogen and fuelcellTechnologies as one of the potential solutions to these issues. Thecommercialization plans in various industrialized countries(USA,Canada, Japan, etc.) For these technologies have started by identifying the most likely early markets for hydrogen as anenergy carrier andfuel cells as power producing devices from micro- to macro-applications, and set realistic near-term andmid-term goals for selectedmarket penetration. The plans outline the major barriers to achieving

those goals andrecommends activities to capitalize on the incentivesand overcome the market barriers. The paper also presentspossiblefuture hydrogen energy-utilization patterns for betterenvironment and sustainable development, and shows how theprinciples of thermodynamics via energy can be beneficially usedto evaluate hydrogen and fuel cell systems and their roleinsustainability. Throughout the paper, current and futureperspectives regarding thermodynamics and sustainabledevelopmentare considered.


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Hydrogen is a versatile energy carrier that can be used to power nearly every end-use energy need. The fuel cell energy conversion devicesthat can efficiently capture and use the power of hydrogen is the key

to making it happen.Stationary fuel cells can be used for backup power, power for remotelocations, distributed power generation, and cogeneration (in whichexcess heat released during electricity generation is used for otherapplications).Fuel cells can power almost any portable application that typically usesbatteries, from hand-held devices to portable generators.Fuel cells can also power our transportation, including personal

vehicles, trucks, buses, and marine vessels, as well as provide auxiliary power to traditional transportation technologies. Hydrogen can play a particularly important role in the future by replacing the importedpetroleum we currently use in our cars and trucks.

Fuel cells directly convert the chemical energy in hydrogen toelectricity, with pure water and potentially useful heat as the only byproducts.Hydrogen-powered fuel cells are not only pollution-free, but also canhave two to three times the efficiency of traditional combustiontechnologies. A conventional combustion -based power plant typically generateselectricity at efficiencies of 33 to 35 percent, while fuel cell systemscan generate electricity at efficiencies up to 60 percent (and evenhigher with cogeneration).

The gasoline engine in a conventional car is less than 20% efficient in converting the chemical energy in gasoline into power that movesthe vehicle, under normal driving conditions.


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Hydrogen fuel cell vehicles, which use electric motors, are muchmore energy efficient and use 40- 60 percent of the fuels energy corresponding to more than a 50% reduction in fuel consumption,compared to a conventional vehicle with a gasoline internalcombustion engine.4In addition, fuel cells operate quietly, have fewer moving parts, andare well suited to a variety of applications.

A single fuel cell consists of an electrolyte sandwiched between twoelectrodes, an anode and a cathode. Bipolar plates on either side of the cell help distribute gases and serve as current collectors. In a Polymer Electrolyte Membrane (PEM) fuel cell, which is widely regarded as the most promising for light-duty transportation, hydrogengas flows through channels to the anode, where a catalyst causes thehydrogen molecules to separate into protons and electrons. Themembrane allows only the protons to pass through it. While theprotons are conducted through the membrane to the other side of thecell, the stream of negatively-charged electrons follows an externalcircuit to the cathode. This flow of electrons is electricity that can beused to do work, such as power a motor.On the other side of the cell, oxygen gas, typically drawn from theoutside air, flows through channels to the cathode. When theelectrons return from doing work, they react with oxygen and the

hydrogen protons (which have moved through the membrane) at thecathode to form water. This union is an exothermic reaction,generating heat that can be used outside the fuel cell.

The power produced by a fuel cell depends on several factors,including the fuel cell type, size, temperature at which it operates, andpressure at which gases are supplied. A single fuel cell producesapproximately 1 volt or less barely enough electricity for even


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the smallest applications. To increase the amount of electricity generated, individual fuel cells are combined in series to form a stack.(The term fuel cell is often used to refer to the entire stack, as wellas to the individual cell.) Depending on the application, a fuel cellstack may contain only a few or as many as hundreds of individualcells layered together. This scalability makes fuel cells ideal for a

wide variety of applications, from laptop computers (50-100 Watts) tohomes (1-5kW), vehicles (50-125 kW), and central power generation(1-200 MW or more).

Fuel cells directly convert the chemical energy in hydrogen to electricity, with pure water andpotentially useful heat as the only byproducts. Hydrogen-powered fuel cells are not only pollution-free, but also can have more than two times the efficiency of traditional combustion technologies.

Overall reaction: 2 H 2(gas) + O 2(gas) 2H 2O + energy

PEM Fuel Cell:Anode reaction: H 2 2H + + 2e - Cathode reaction: O 2 + 2e - + 2H + H2O

Overall reaction: H 2 + 1/2 O 2 H2O


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Benefits of Fuel Cells

Fuel cell vehicles are expected to achieve efficiencies

of 40 to 45 percent. On average, an internal combustion engineconverts about 15 percent of the energy in gasoline to turn a cars wheels. Fuel cell power plants producing electricity andthermal energy are expected to achieve efficiencies of 80percent or more when used as combined heat and powerplants.

The only emission from the tailpipe of a fuel cell vehicle operating on hydrogen is water vapor. Fuel cell vehiclesthat use an on-board fuel reformer will emit two-thirds lesspollution than a gasoline combustion engine. A similarcomparison applies to stationary and portable fuel cellapplications.

Fuel cell systems are highly reliable, which is very desirable for stationary applications that require a high-quality uninterrupted power supply.

Fuel cells can operate on a wide load range andscale from micro production to megawatt production.

The durability of fuel cell systemshas not been established. For transportation applications, fuelcell power systems will be required to achieve the same level of durability and reliability of current automotive engines, i.e.,5,000 hour lifespan (241,000 km equivalent), and the ability tofunction over the full range of vehicle operating conditions(40C to 80C). For stationary applications, more than 40,000


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hours of reliable operation in a temperature at -35C to 40C will be required for market acceptance.

The size and weight of current fuel cell systems

must be further reduced to meet the packaging requirementsfor automobiles. This applies not only to the fuel cell stack, but also to the ancillary components and major subsystems (e.g.,fuel processor, compressor/expander, and sensors) making upthe balance of power system.

Air management forfuel cell systems is a challenge because today's compressortechnologies are not suitable for automotive fuel cellapplications. In addition, thermal and water management forfuel cells are issues because the small difference between theoperating and ambient temperatures necessitates large heat exchangers. Another challenge is to develop a reliable anddurable membrane that operates in low humidity conditions soas to eliminate the need for complicated water management

equipment.

The low operating temperature of PEM fuel cells limits the amount of heat that can be effectively utilized in combined heat and power (CHP)applications.

Technologies need to be developed that will allow higheroperating temperatures and/or more effective heat recovery systems and improved system designs that will enable CHPefficiencies exceeding 80%. Technologies that allow cooling tobe provided from the low heat rejected from stationary fuel cellsystems (such as through regenerating desiccants in a desiccant cooling cycle) also need to be evaluated.


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Energy is a key element of the interactions betweennature and society and is considered a key input for theenvironment and sustainabledevelopment. Environmentaland sustainability issues span a continuously growingrange of pollutants, hazards, and eco-systemdegradationfactors that affect areas ranging from local throughregionalto global. Some of these concerns arise fromobservable, chroniceffects on, for instance, human health,while others stem from actual

or perceived environmentalrisks such as possible accidental releasesof hazardousmaterials. Many environmental issues are caused by orrelated to the production, transformation, and use ofenergy, forexample, acid rain, stratospheric ozonedepletion, and global climatechange. Recently, a variety ofpotential solutions to the current environmental problemsassociated with the harmful pollutant emissions hasevolved. Hydrogen energy systems appear to be the oneofthe most effective solutions and can play a significant roleinproviding better environment and sustainability.In the literature, there have been limited studies onsustainability aspects of hydrogen energy systems(including fuel cell systems)undertaken by severalresearchers. With respective selection of thecriteria comprising performance, environment, market, andsocialindicators the assessment procedure is adapted forthe assessment of the selected options of the hydrogenenergy systems and their

comparison with new andrenewable energy systems.In broadterms, the concept of sustainable development is anattempt to combine growing concerns about a range ofenvironmental issues

with socio-economic issues. Thesustainable development impliessmooth transition to moreeffective technologies from a point view of anenvironmental impact and energy efficiency. New hydrogenpowered fuel celltechnologies in both its high and low-temperaturederivatives are more effective and cleaner


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thanconventional energy technologies, and can be consideredone of the pillars of a future sustainable energy system.The main goal of this paper is to discuss the role ofhydrogen and fuelcell systems for sustainable future, andpresent a case study on the lifecycle assessment of fuelcell vehicles from energy, environment, andsustainability points of views. The role of energy inperformanceassessment and sustainability achievement isalsodiscussed...

Figure: Evolution of global market shares of different finalenergycarriers forthe period 1990-2100. The alcohols category includes methanol andethanol.


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Sustainable development requires a sustainable supplyof clean andaffordable energy resources that do not cause negative societalimpacts. Supplies of suchenergy resources as fossil fuels and uranium

are finite.Energy sources such as sunlight, wind, and falling waterare generally considered renewable and thereforesustainable over the relatively long term. Wastes andbiomass fuels are also usually viewed assustainableenergy sources. Wastes are convertible to usefulenergyforms through such technologies as waste-to-energyincinerationfacilities.Environmental impact is associated with energyresourceutilization.Ideally, a society seeking sustainabledevelopment utilizes only energy resources that release noor minimal emissions to the environment andthus causeno or little environmental impact. However, since allenergy resources may somehow lead to someenvironmental impact,increased efficiency can somewhatalleviate the concerns regarding environmental emissionsand their negative impacts. For the sameservices orproducts, less resource utilization and pollution is

normallyassociated with increased efficiency.Sustainability often leads local and national authoritiesto incorporateenvironmental considerations into energyplanning. The need to satisfy basic human needs andaspirations, combined with increasing worldpopulation,will make the need for successful implementationofsustainable development increasingly apparent. Varioushydrogenenergy-related criteria that are essential toachieving sustainabledevelopment in a society follow:

Information about and public awareness of the benefitsof sustainability investments, Environmental and sustainability education andtraining, Appropriate energy and energy strategies for betterefficiency, Promoting environmentally benign technologies,


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Clean hydrogen production technologies, Development of sustainable hydrogen economyinfrastructure, Commercially viable and reliable hydrogen energysystems,including fuel cells, Availability and utilization of renewable energyresources, Use of cleaner technologies for production,transportation,distribution, storage and use, A reasonable supply of financing and incentives, Academia-industry-government partnership programs, Policy development for sustainable energy programs, Appropriate monitoring and evaluation tools, and Road maps for future implementation.

Environmental concerns are significantly linked tosustainabledevelopment. Activities that continuallydegrade the environment arenot sustainable. For example,the cumulative impact on theenvironment of suchactivities often leads over time to a variety of health,ecological and other problems.Clearly, a strong relation exists between efficiency andenvironmentalimpact since, for the same services orproducts, less resource

utilization and pollution is normallyassociated with increasedefficiency. Note that improvedenergy efficiency leads to reducedenergy losses. Mostefficiency improvements produce direct environmental benefits in two ways: (I)Operating energy inputrequirements are reduced per unit output, andpollutantsgenerated are correspondingly reduced. (ii) Considerationof the entire life cycle for energy resources andtechnologies suggests that improved efficiency reducesenvironmental impact during most stagesof the life cycle.

That is why assessing the future hydrogen technologiessuch as fuelcells over their entire life cycle is essential toobtain correct information on energy consumption andemissions during various lifecycle stages, to determinecompetitive advantages over conventionaltechnologies,and to develop future scenarios for better sustainability.


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In recent years, the increased acknowledgment ofhumankindsinterdependence with the environment hasbeen embraced in theconcept of sustainable development.

With energy constituting a necessity for maintaining andimproving standards of living throughout the world, thewidespread use of fossilfuels may have affected the planetin ways far more significant than first thought. In additionto the manageable impacts of mining and drilling for fossilfuels and discharging wastes from processing andrefiningoperations, the "greenhouse" gases created by burningthesefuels is regarded as a major contributor to a globalwarming threat.Global warming and large-scale climatechange have implications forfood chain disruption,flooding and severe weather events, e.g.,

hurricanes.It is obvious that utilization of hydrogen and fuel celltechnologies canhelp reduce environmental damage and achieve sustainability. Suchtechnologies essentially do notconsume fuel, contribute to global

warming, or generatesubstantial waste as long as hydrogen is producedthroughclean and renewable energy resources. In thisrespect,hydrogen and fuel cell technologies can provide moreefficient,

effective, environmentally benign andsustainable alternatives toconventional energytechnologies, particularly fossil-fuel driven ones.Hydrogen and fuel cell technologies have a crucial roleto play inmeeting future energy needs in both rural andurban areas. Thedevelopment and utilization of suchtechnologies should be given a high priority, especially inthe light of increased awareness of theadverseenvironmental impacts and political consequences offossil-based generation. The need for sustainable energydevelopment isincreasing rapidly in the world.

In fact,widespread use of these technologies is important forachieving sustainability in the energy sectors in bothdeveloping andindustrialized countries. Thesetechnologies are a key component of sustainabledevelopment for four main reasons:


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They have numerous advantages, such as energyefficient andcompatible with renewable energy sourcesand carriers for futureenergy security, economicgrowth and sustainable development. They generally cause much less environmental impactthan otherconventional energy sources andtechnologies. The variety of hydrogenand fuel celltechnologies provides a flexible array of options fortheiruse in various applications. Hydrogen cannot be depleted because the basic sourceis water. If used carefully in appropriate applications, itcan provide a fully reliableand sustainable supply ofenergy almost indefinitely. In contrast, fossilfuel anduranium resources are diminished by extractionandconsumption.

These technologies favor system decentralization andlocal andindividual solutions that are somewhatindependent of the nationalnetwork, thus enhancingthe flexibility of the system and providing economicand environmental benefits to small isolatedpopulations. Inaddition, the small scale of theequipment often reduces the timerequired from initialdesign to operation, providing greater adaptability inresponding to unpredictable growth and/or changes inenergy

demand.It is important to note that if we produce hydrogenthroughconventional technologies using fossil fuels, thiswill not makehydrogen inherently clean in that they maycause some burden on theenvironment in terms ofpollutant emissions, solid wastes, resourceextraction, orother environmental disruptions. Nevertheless, theoveralluse of these technologies almost certainly can provide acleanerand more sustainable energy system than increasedcontrols onconventional energy systems. This is in factclearly shown in the casestudies.

To overcome obstacles in initial implementation,programs should bedesigned to stimulate a hydrogenenergy market so that options can beexploited byindustries as soon as they become cost-effective.


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Financialincentives should be provided to reduce up-frontinvestment commitments and infrastructure costs forproduction, transportation,distribution, storage, and use, and to encourage design innovation, as

well as researchand development activities along withcommercializationpractices.

The interdisciplinary triangle of energy.

Qualitative illustration of the relation between theenvironmentalimpact and sustainability of a process, and its energy

efficiency.


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Fuel cell technology is clean, quiet, and flexible oneand is already beginning to serve humanity in a variety ofuseful ways. Nevertheless,production volume is low andcosts are too high. Public support isneeded to help generate initial demand to break this cycle. Themarket forautomotive power and stationary generationconversionequipment is the largest market for capital equipment inthe

world. Fuel cells and fuel cell powered vehicles will bean economicgrowth leader in the coming decades securinghigh quality employment for many thousands of people.

Four key factors of sustainable development underglobalsustainability.

Fuel cells are considerably efficient power producersand createelectricity in one simple step, with no moving parts and (at least in thecase of PEMFC) at a very low temperature. (Compare this to thecombustion processemployed by traditional power plants: A fuel isburned athigh temperature to create heat, the heat energy isthenconverted to mechanical energy,


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and that mechanical energy is finally converted into electricity.) Sincefuel cells do not combust fossil fuels, they are known as clean powerproducers, they emit none of the acid rain or smog producing pollutants that are the inevitable by-product of burning coal or oil ornatural gas.In principle, a fuel cell operates like a battery. Unlike a battery, it doesnot run down or require recharging, and produces energy in the formof electricity and heat as long as fuel is supplied. The fuel cell convertschemical energy directly into electricity without combustion by combining oxygen from the air with hydrogen gas. It produceselectricity as long as fuel, in the form of hydrogen, issupplied. Theonly by-products are water and heat (Fig. 4).

No pollutants are produced if pure hydrogen is used.However, very low levels of nitrogen oxides are emitted, but usually inthe undetectable range. The carbon dioxide emissions, which comeout from the electrochemical conversion, are relatively low because of high efficiency, and are in concentrated form, facilitating captureHydrogen can be produced from water using renewable solar, wind,hydro or geothermal energy. Hydrogen also can be extracted from

anything that contains hydrocarbons, including gasoline, natural gas,biomass, landfill gas, methanol, ethanol, methane, and coal-based gas.The type of fuel cells is typically distinguished by the electrolyte that isutilized and can be classified into two main categories, based on theiroperating temperatures, such as low temperature fuel cells (e.g., 60-250C) and high temperature fuel cells (e.g., 600-1000C). Low temperature fuel cells have made significant progress in transportationapplications due to their quick start times, compact volume and lower

weight compared to high temperature fuel cells.The common types of low temperature fuel cells are proton exchangemembrane fuel cells, phosphoric acid fuel cells, alkaline fuel cells,unitized regenerative fuel cells, direct methanol fuel cells.The high temperature fuel cells are more efficient than low temperature ones in generating electrical energy. In addition, they provide high temperature waste heat, which is a benefit in stationary


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cogeneration applications, but presents a problem for transportationapplications. Two common ones are molten carbonate fuel cells andsolid oxide electrolyte fuel cells.

Operation of a fuel cell, converting hydrogen andoxygen (from the air) into electricity, water, and heat.

5.1. Hydrogen Production Although hydrogen is the universe's most abundant element, it is

present in the atmosphere only in concentrations of less than one part per million. Most of the Earth's hydrogen is bound up in chemicalcompounds.Hydrogen for large-scale use should therefore be extracted from a source such as water, coal, natural gas, or plant matter. It cannot simply be produced from a mine or a well. Since considerable energy is consumed in the extraction process, hydrogen should properly be

considered an energy carrier rather than an energy source; the energy released when it is finally used is just the energy that was invested in itsoriginal manufacture (minus any losses). Recognizing this fact is of critical importance.

Any analysis of how hydrogen is to be used must also consider how the hydrogen is to be produced. A variety of alternative hydrogenenergy production technologies is available in practice, including:


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: Steam reforming is a chemical process that makeshydrogen from a mixture of water and a hydrocarbon feedstock,usually a fossil fuel. The most common feedstock is natural gas,consisting primarily of methane. When steam and methane arecombined at high pressure and temperature, a chemical reactionconverts them into hydrogen and carbon dioxide. The energy content of the hydrogen produced is actually higher than that of the naturalgas consumed, but considerable energy is required to operate theirformer, so the net conversion efficiency may typically be only about 65-70%. Hydrogen produced bythis technique may cost as little as65/kg. : After steam reforming, the next most common

source of hydrogen at present is the cleanup of industrial off-gases.Numerous industries give off high concentrations of hydrogen in their

waste streams petroleum refineries, blast furnaces, and some chemicalplants, for example. Collecting and purifying these gases is often cost-effective, with costs typically ranging between 80 and 120 /kg. Most off-gas hydrogen is used on-site by the industry that produces it, soalthough off-gas cleanup is an important feature of today's market, it

seems unlikely that it could be expanded enough to meet theincreased demand that would result from widespread use of hydrogenas a fuel. : Electrolysis means passing an electrical current through

water to split individual water molecules into their constituent hydrogen and oxygen.Energy losses during this process are relatively modest:65% energy efficiency is common, and state-of-the-art largeelectrolyzers can be 80 to 85% efficient.Electrolysis has captured considerable attention, even though it accounts for only a small fraction of current hydrogen production,because it is a clean process and water is abundant. At present,

however, the technique is only used at relatively small plants, with a cost of2.40-3.60 $/kg of hydrogen produced. This high cost isexpected to limit electrolysis to niche markets in the near and

midterm.


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In the long term, could electrolysisbecome more competitive? At present, natural gasreforming is more than three times moreenergyefficient than electrolysis if fossil-source electricity isused. : Photo processes use the energy andother specialproperties of light (usually sunlight) toproduce hydrogen from either

water or biomass. Thereare three broad categories of photo process.Photobiological techniques are based on the photosynthesiscycle usedby plants and by some bacteria and algae.The efficiency of photo biological hydrogen productionis only 1 to5%, but researchers hope to increase it to10% or more.Photochemical processes mimic naturalphotosynthesis using syntheticmolecules. Thistechnique is only about 0.1% efficient now, but it

canbe improved. Photo electrochemical techniques uselayers of semiconductor material separated by water.

When exposed to light, the semiconductor layersproduce an electrical voltage that splits the water intohydrogen and oxygen. The best prototypes yetdemonstrated in the laboratory are about 13%efficient,but the maximum theoretical efficiency is believed tobe morethan 35%. It has been estimated that efficiencyin the field of 10 to

15% may be economical, but suchestimates depend strongly onprojections of equipmentcosts.

Note that since all these photo processes use lightas their primary energy source, their efficiencies shouldnot be used directly in cost comparisons with processesthat use hydrocarbon fuels or electricity.Photoprocesses are a major component of current hydrogenresearchprograms.

: This process uses heat tosplit water intohydrogen and oxygen. The conceptuallysimplest version of thistechnique is direct thermalconversion, i.e. heating water to extremetemperatures,perhaps 3400 K. Because of the hightemperaturesrequired, however, direct thermal conversion is

yetimpractical outside the laboratory.


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Chemical reactionscan be employed to reduce the requiredtemperature.Various alternatives have been studied, ofteninvolvingcomplex multistep processes. Hybrid techniquesthatincorporate electrolysis into one or more of the reactionsteps areunder investigation. There has been littlerecent work available onthermo chemical techniques. : This process is the splitting of watermolecules by collisions with high-energy particlesproduced in a nuclear reactor.Since the hydrogen andoxygen atoms thus produced quickly recombine toproduce water again, radiolysis would probably beonlyabout 1% efficient. Most experts agree that radiolysis islesspromising than other techniques.

: In this original and simplest form ofhydrogenenergy production, the solar hydrogenscenario envisions producing electricity from sunlightusing photovoltaic cells, electrolyzing water toproducehydrogen, and substituting this hydrogen for the oil andotherfossil fuels in general use today. The term is nowoften used morebroadly to include electrolysis basedon other renewable sources of electricity, such as wind. This idea has received considerable attention

largely because of the environmental benefits of usinghydrogeninstead of fossil fuels. It also addresses twobarriers to the ultimateachievement of large-scale useof solar energy:

that solar electricity cannot be useddirectly for non-electricapplications, such ascombustion engines, and that electricity is difficult andexpensive to store. Hydrogen may beformed fromthe no catalytic partial oxidation (i.e.,gasification) of hydrocarbonssuch as residual oil. Anyhydrocarbon feedstock that can becompressed orpumped may be used in this technology. However,theoverall efficiency of the process is about 50% and pureoxygen isrequired. Two commercial technologies forthis conversion areavailable: the Texaco gasificationprocess and the Shell gasificationprocess.


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There are also some other hydrogen productiontechnologies, such as: Thermal decomposition of hydrocarbon fuels Thermo catalytic CO2-free production of hydrogenfromhydrocarbon fuels Super adiabatic decomposition of hydrogen sulfide Auto thermal reforming (combining partial oxidationand steamreforming) Sorption Enhanced Reaction Process (SERP) Production of hydrogen from biomass-derived liquids Photo electrochemical hydrogen production Biological H2 from fuel gases and from H2O Two-phase photo biological algal H2-productionsystem

H2 Production from Glucose-6-PhosphateMost of the above listed methods are under heavy investigation forimplementation andcommercialization. The findings show that thereis stillmuch to do for achieving those.

5.2.1. Bulk Storage in Distribution System It is expected that any large-scale hydrogen distributionsystem shouldaddress the problem of bulk storage, to fluctuations in demand.Low-cost and efficient bulkstorage techniques are a major researchgoal. One can storehydrogen as either a gas or a liquid. The most

widelystudied options for storing gaseous hydrogen areundergroundcaverns and depleted underground natural gasformations. Althoughhydrogen is more prone to leak thanmost other gases, leakage isshown not to be a problem forthese techniques. For example, towngas mixturecontaining hydrogen) has been stored successfully inacavern in France, and helium, which is even more leak pronethanhydrogen, has been stored in a depleted naturalgas field near

Amarillo, Texas. The energy consumed inpumping gas in and out of such storage facilities may besignificant, however. Abovegroundstorage tanks at highpressure are another option.


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A certain amount of gaseous storage can be achievedby allowing modest pressure changes in the distributionpipeline system. In thecase of natural gas, this technique isused to help manage transient demand fluctuations, such asthe morning and evening peaks inresidential demand inurban areas. Though the same technique might be usefulfor hydrogen, its potential is limited, particularly if thehydrogen is to be produced from intermittent sources suchas solaror wind.Storage in liquid form uses tanks similar to those usedfor liquidhydrogen distribution. For example, KennedySpace Center uses a 3217 m3 sphere near the launch pad,and can transfer fuel from thistank to the space shuttle atup to 38 m3 per minute. Storage at

liquefier plants is invacuum-insulated spherical tanks that usually holdabout1514 m3. The energy required for liquefaction maynot be a barrier if the hydrogen is to be transported as aliquid anyway, or if theend-use application requires itsfuel to be in liquid form.5.2.2. Hydrogen Storage in End Use The difficulty of onboard storage is the main barrier tofueling

vehicles with hydrogen. Because it is a gas,hydrogen at room

temperature and pressure takes upabout 3,000 times more space thanan energy equivalentamount of gasoline.

This obviously meansthat compression, liquefaction, or some othertechniqueis essential for a practical vehicle. So far,storagerequirements tend to limit range severely. During thepast twodecades, several techniques were examined toovercome this problem.The four main contenders arecompressed gas, cryogenic liquid, metalhydride, andcarbon adsorption. Of these, the first two appearmostpromising for the short-term.Metal hydrides are alsorelatively mature, but require further research

to becompetitive. Carbon adsorption is not yet a maturetechnique, but it appears very promising if the researchgoals may be met. Glass microspheres and onboardpartial oxidation reactors are currently underinvestigation, but as yet are ''insufficientlycharacterized for

evaluation at the systems level." It islikely that different techniques will


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turn out to be mostappropriate for different applications, forexamplebuses are less size-sensitive than cars [20]. Compressed gaseous hydrogen storage is at roomtemperature in a high-strength pressure tank. Includingthe weight of the tank,compressed gas storage holds about 1 to 7% hydrogen by weight,depending on the type of tank used. Lighter, stronger tanks, capableof holding more hydrogen with less weight, are more expensive.Compressing the hydrogen gas at the filling station requires about 20%as much energy as is contained in the fuel. Cryogenic liquid storage is at 20K in a heavilyinsulated tank at ordinary atmospheric pressure. As aliquid, hydrogen contains almost three times moreenergy than an equal weight of gasoline, and takes

uponly about 2.7 times as much space for an equal energycontent.Including the tank and insulation,

thistechnique can hold as much as 16% hydrogen byweight.

Furthermore, liquefaction at the filling stationrequires about 40% as

much energy as is contained inthe fuel. Another disadvantage is theso-called"dormancy problem": despite the insulation, some heatleaksinto the tank, eventually boiling off the hydrogen.A "cryopressure"system stores liquid hydrogen in apressure vessel like that used forcompressed gaseousstorage, allowing containment of the boiled-off gas.This helps with dormancy, but increases weight andsize. Metal hydride systems store hydrogen in the interatomspaces of a granular metal. Various metals can be used.The hydrogen is released by heating. Metal hydridesystems arereliable and compact, but can be heavy and expensive. Varieties now under development can store about 7% hydrogen by weight. Unlikethe compressed gas and cryogenic liquid techniques, metal hydridesrequire little or no "overhead" energy when refueling.They do require energy to release the fuel, however.


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For low-temperature varieties, this energy may be available as wasteheat from the fuel cell or engine. For high-temperature varieties,

which tend to be the less expensive ones, as much as half of the vehicle's energy consumption may go to releasing the fuel from themetal. The carbon adsorption technique stores hydrogen under pressureon the surface of highly porous super activated graphite. Some

varieties are cooled; others are operated at room temperature.Current systems store as much as4% hydrogen by weight. It is hopedto increase this efficiency to about 8%, even for the room temperature

variety. Carbon adsorption is very similar to compressed gas storageexcept that the pressure tank is filled with graphite; the graphite adds

some weight but allows more hydrogen to be stored at the samepressure and tank size.

Glass micro spheres are small, hollow, glass micro balloonswhosediameters vary from about 25 micronsto 500 microns, and whose wallthicknesses are about 1micron. They can be used in large beds to

storehydrogen at high pressures. The micro spheres arefilled withhydrogen gas at temperatures of 200 to400C. The high temperaturemakes the glass wallspermeable, and the gas fills the spheres. Oncethe glassis cooled to room temperature, the hydrogen is trappedinsidethe spheres. The hydrogen can be released asneeded by heating thespheres. The spheres may also becrushed to release hydrogen. Thisoption precludessphere recycling, but is desirable for applications

whereweight is important.Onboard partial oxidation reactor is a concept proposedto help bring about a transition from

conventionalautomobiles to cars powered by hydrogen fuel cells.First, a shift would be made from the internalcombustion engine tothe fuel cell using a conventionalhydrocarbon fuel such as gasoline ordiesel coupled toan onboard partial oxidation process and a watergasshift reaction process. The partial oxidation processyields 30%

hydrogen gas directly and 20% carbonmonoxide.


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Then, the carbon monoxide is chemicallyreacted with steam toproduce additional hydrogen andcarbon dioxide gas, which is readily usable by ahydrogen fuel cell. This fossil-to-hydrogen fuelsystemwould be used as a "bridge" until research yields acommercially ready advanced hydrogen storage systemor a suitable hydrogencarrier. Other techniques are still in the early stages ofdevelopment. Oneuses powdered iron and water. At high temperatures, these react toproduce rust and hydrogen. Other methods are similar to the metalhydride option, but substitute certain liquid hydrocarbons (also knownas "recyclable liquid carriers") or other chemicals for the meta 5.3. Hydrogen Safety

Hydrogen is intrinsically no more dangerous than many other fuels.Its different characteristics require different safety equipment andprocedures, but all fuels have some potential for accidents; if they didnot burn, they would not be much use as a fuel.

Hydrogen is used worldwide in the petroleum and chemical industriesand elsewhere. It was also routinely used in the USA as a fuel (a

component of towngas") before natural gas became widely available.Town gas is still used in some countries. Moreover, hydrogen ranksbetween propane and methane (natural gas) in safety. The physicalproperties of hydrogen make its safety characteristics rather different from those of other fuels. Its low density means that it tends to riseand disperse into the atmosphere in the event of a leak, rather thanremaining in "puddle" near the ground. This increases safety in

wellventilatedapplications. Its low density also means that a hydrogenexplosion releases less energy in a given volume than an explosion of other fuels, and compared to gasoline or natural gas, hydrogenrequires much higher concentrations in the air to produce anexplosion rather than just a flame. Furthermore, hydrogen's low ignition temperature and flammability over a wide range of concentrations make leaks a significant fire hazard, especially inconfined spaces such as a garage.


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Because its clear and odorless, leaking hydrogen is more likely to goundetected than a leak of gasoline or most other fuels.Even the flame of burning hydrogen is invisible.Techniques of leak detection have been and continue to bea researchpriority. A simple approach is to add an odorantlike that added tonatural gas, or possibly a colorant, or both. Any addition may detract somewhat from the environmental cleanliness inherent to purehydrogen, however, and additives would need to be chosen with careto avoid destroying other important features. For example,contaminants may reduce the efficiency and/or lifetime ofa fuel cell.

As with most fuels, the fire and explosion hazards discussed above arethe main safety concerns. In some situations, there may be other

safety issues, such as, in applications that involve hydrogen storageunder highpressure or at extreme low temperatures. Theseproblemscan be minimized with proper equipment design andoperating procedures, however,

and are generally agreed tobe of less concern than hydrogen'sflammability.

5.4. Economics of Hydrogen Hydrogen is currently more expensive than other fueloptions, so it islikely to play a major role in the economyonly in the long term, if technology improvements succeedin bringing down costs. Higherprices for fossil fuelswould not necessarily make hydrogen morecostcompetitivein the short term. Since fossil fuels are currently themain source of heat, feedstock, and electricity for hydrogenproduction plants, rising prices for gas, oil, or coal would also drive upthe price of hydrogen.Since hydrogen is produced in many different ways, from many different sources, most hydrogen-related international commerce islikely to be not of fuel but of technology: plant components,engineering services, construction expertise, and so on. These areascould potentially represent new export markets.


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5.5. Environmental Aspects of Hydrogen Energy The use of hydrogen as a fuel is inherently very clean.

Hydrogen consumed by either combustion or a fuel cell producesonly water as a product. The high temperatures involved incombustion may stimulate some NOxproduction from nitrogen andoxygen in the air, but thisproblem is familiar from other fuels and canbe controlled.Unlike other fuels, hydrogen contains nootherpollutantproducingelements, so it has no potential to produceSO2,CO, CO2, volatile organic chemicals, etc. The environmentalconsequences of hydrogen production should also be considered,

however. As mentioned above, production from fossil fuel feed stocksby steam reforming leads to carbon dioxide emissions greater thanproduction from feedstock by itself. Steam reformers should alsosomehow dispose of feedstock impurities such as sulphur.

Electrolysis is responsible for the emissions of whatever power plants

are used to generate the needed electricity.Production of hydrogen from sustainable harvested biomass, solarenergy, or other renewable sources might considerably reduceproduction emissions, but (as described above) such techniques arebeing fully developed for commercialization. For example, theU.S.Department of Energy (has examined the full-cycleenvironmentaleffects of various scenarios for hydrogen productionand use. It concludes, "Substantial emissions can be generated whenhydrogen is produced from certain energy sources," namely fossilfuels. Thus, the technique of hydrogen production remains crucial.


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. They convert hydrogen and oxygen directly into electricityand water, with no combustion in the process. Theresulting efficiency is between 50and 60%, about double that of aninternal combustion engine.

If hydrogen is the fuel, there are no pollutant emissions from afuel cell itself, only the production of pure water. Incontrast to an internalcombustion engine, a fuel cell produces noemissions of sulphur dioxide, which canlead to acid rain, nor nitrogenoxides which produce smog nor dust particulates.

A fuel cell itself has no moving parts, although a fuel cellsystem may have pumps and fans. As a result, electrical poweris produced relativelysilently. Many hotels and resorts in quiet

locations, for example, could replace dieselengine generators with fuelcells for both main power supply or for backup power inthe event of power outages.

. That is, fuel cells of varying sizes can bestacked together tomeet a required power demand. As mentionedearlier, fuel cell systems can providepower over a large range, from a few watts to megawatts.

They produce no hazardous waste products,and their only by-product is water (or water and carbondioxide in the case ofmethanol cells).

Fuel cells may give us the opportunity to provide the world withsustainable electricalpower.


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At present there are many uncertainties to the success of fuel cells andthe developmentof a hydrogen economy:

This

acceptancedepends largely on price, reliability, longevity of fuel cellsand the accessibility andcost of fuel.Compared to the price of present day alternatives e.g. diesel-engine generators and batteries, fuel cells are comparatively expensive.In order to be competitive, fuel cells need to be mass produced lessexpensive materials developed.

At present there is noinfrastructure in place for either ofthese fuels. As it is we must rely onthe activities of the oil and gas companies tointroduce them. Unlessmotorists are able to obtain fuel conveniently and affordably,a mass

market for motive applications will not develop.

However, if fuel cells proveunsuitable for automobiles, new sources of investment for fuel cells and thehydrogen industry will be needed.

At present stringent environmentallaws and regulations,such as the California Low Emission VehicleProgram have been great encouragements to these fields.Deregulation laws in the utility industry have been alarge impetus forthe development of distributed stationary power generators.Shouldthese laws change it could create adverse effects on furtherdevelopment.


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. Platinum is a scarce naturalresource; the largest supplies to the world platinummarket are from South Africa,Russia and Canada. Shortages of platinum are not anticipated; however changes ingovernment policiescould affect the supply.

The scientific and technical challenges for thehydrogen economy may be given as follows:

Lowering the cost of hydrogen production to a levelcomparable tothe energy cost of petrol. Development of a CO2-free route for the mass production of sustainable hydrogen at a competitive cost.

Development of a safe and efficient nationalinfrastructure forhydrogen delivery and distribution. Development of viable hydrogen storage systems forboth vehicularand stationary applications. Dramatic reduction in costs and significant improvement in thedurability of fuel cell systems.The pathway for the transition from current energyeconomies tohydrogen economy has some scientific, technological, and economicaldrawbacks. The mostsignificant milestones for the hydrogen pathway must bemainly based on the intensification of research and innovationprograms. Figure shows some research anddevelopment priority areas.


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Major R&D activity areas for the pathway to hydrogen economy

Reducing cost and improving durability are the two most significant challenges to fuel cell commercialization. Fuel cell systems must becost-competitive with, and perform as well or better than, traditionalpower technologies over the life of the system.Ongoing research is focused on identifying and developing new materials that will reduce the cost and extend the life of fuel cell stack components including membranes, catalysts, bipolar plates, andmembrane-electrode assemblies. Low cost, high volumemanufacturing processes will also help to make fuel cell systems cost competitive with traditional technologies.

By 2050,theglobalenergydemandcoulddoubleort ripple and oil andgas supplyisunlikelytobeabletomeetthisdemand.


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Hydrogenandfuelcellsareconsideredinmanycountriesasan important alternativeenergyvectorandakeytechnologyforfuturesustainableenergysystemsinthestationarypower,transportation,industrialandresidentialsectors.

However, as withanymajor changesintheenergyindustry,thetransitiontoa hydrogeneconomywillrequires severaldecades. Theintroductionof hydrogenasanenergycarrierhasalsobeenidentifiedasa possible strategy.


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The benefits of hydrogen and fuel cell systems ishighlighted of using the principles of thermodynamics (particularly energy) and life cycleassessment to evaluatetheir key roles in sustainable development. Thefollowingconcluding remarkscan be drawn from this study: Moving towards sustainable development requiresthatenvironmental problems be resolved. These problemscover a continuously growing range of air pollution,water pollution, solid

wastes, pollutants, ecosystemdegradation, and extend over ever-widerareas.

Sustainable development requires a sustainable supply of energy resources that, in the long term, is sustainable available at reasonablecost and can be utilized for all required tasks without causing negativesocietal impacts. Energy resources such as solar, wind, hydro, andbiomass are generally considered renewable and therefore sustainableover the relatively long term. The use of these sources in hydrogenproduction will be a key factor in sustainable development. Assessments of the sustainability of processes and systems, andefforts to improve sustainability, should be based in part uponthermodynamic principles, and especially the insights revealedthrough energy analysis. For societies to attain or try to attain sustainable development, effort should be devoted to developing hydrogen and fuel cell technologies.Renewable energy utilization in hydrogen production can provide a potential solution to current environmental problems.

Advanced hydrogen and fuel cell technologies can provideenvironmentally responsible alternatives to conventional energy systems, as well as more flexibility and decentralization. To realize the energy, energy, economic and environmental benefitsof hydrogen and fuel cell technologies, an integrated set of activitiesshould be conducted including research and development,


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technology assessment, standards development and technology transfer.

These can be aimed at improving efficiency, facilitating thesubstitution of these technologies and other environmentally benignenergy currencies for more harmful ones, and improving theperformance and implementation characteristics of thesetechnologies.

REFERENCES:

EuropeanHydrogenandFuelCellTechnologyPlatform,2005.DeploymentStrategy. /https://www.hfpeurope.org/hfp/keydocsS

A Textbook of Renewable energy systems by B H Khan

www.google.com

www.wikipedia.com
http://www.google.com/http://www.google.com/http://www.wikipedia.com/http://www.wikipedia.com/http://www.wikipedia.com/http://www.google.com/

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