Advance Technique of H2 Production & Storages

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    Advance Technique of H2 Production & Storages

    ABSTRACT

    This paper offers an overview of the technologies for hydrogen production and storages.

    The technologies discussed are reforming of natural gas; gasification of coal and biomass; and

    the splitting of water by water-electrolysis, photo-electrolysis, photo-biological production and

    high- temperature decomposition. For all hydrogen production processes, there is a need for

    significant improvement in plant efficiencies, for reduced capital costs and for better reliability

    and operating flexibility.

    Water electrolysis and natural gas reforming are the technologies of choice in the

    current and near term. They are proven technologies that can be used in the early phases of

    building a hydrogen infrastructure for the transport sector. Small-scale natural gas reformers

    have only limited commercial availability, but several units are being tested in demonstration

    projects. In the medium to long term, centralised fossil fuel-based production of hydrogen, with

    the capture and storage of CO 2, could be the technology of choice. However, the capture and

    storage of CO 2 is not yet technically and commercially proven. Further R&D on the processes

    of absorption and separation are required.

    Other methods for hydrogen production are further away from commercialisation and need

    additional R&D. The production of hydrogen from biomass needs additional focus on the

    preparation and logistics of the feed, and such production will probably only be economical at a

    larger scale. Photo-electrolysis is at an early stage of development, and material costs and

    practical issues have yet to be solved. The photo-biological processes are at a very early stage

    of development with only low conversion efficiencies obtained so far.

    The objective of this paper is to provide a brief overview of the possible hydrogenproduction&storage options available today and in the foreseeable future. Hydrogen storage canbe considered for onboard vehicular, portable, stationary, bulk, and transport applications, butthe main focus of this paper is on vehicular storage, namely fuel cell or ICE/electric hybridvehicles. The technical issues related to this application are weight, volume, discharge rates,heat requirements, and recharging time.

    Another important merit factor is cost. The paper discusses in detail the advantages anddisadvantages of the various hydrogen storage options for vehicular storage identifies the maintechnological gaps, and presents a set of concrete recommendations and priorities for futureresearch development.

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    Index

    Chapter. Topics Page no.

    1). Introduction

    2). Various sources for H2 fuels

    3). Production of Hydrogen

    3.1 Thermo Chemical Process3.2 Electrolytic Process

    3.3 Production from natural gas

    3.4 Autothermal reforming3.5 HYDROGEN FROM SPLITTING OF WATER

    4). Steam Reforming, Autothermal Reforming and Partial

    5) Future Hydrogen Production & Storage Plant

    6). Advance Technique of Production of hydrogen

    6.1 Hybrid Solar System Makes Rooftop Hydrogen

    6.2 Novel Alloy Could Produce Hydrogen Fuel from Sunlight

    7). Introduction is a fuel cell?

    08). HYDROGEN STORAGE TECHNOLOGIES

    09). NEW SCOPE OF HYDROGEN

    10). Application and todays status in market

    Conclusions

    Reference

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    Advance Technique of H2 Production & Storages

    Chapter.1 ENERGY OF FUTURE - HYDROGEN

    Introduction

    With a vision of clean and abundant energy for all, UNIDO-ICHET (United Nations Industrial

    Development Organisation-International Centre for Hydrogen Energy Technologies), Turkey is doing a serious

    effort through Energy Institutes established for this purpose.

    IAHE (International Association for Hydrogen Energy), Florida, USA was founded with the aim ofhelping to convert the world to the Hydrogen economy by informing energy and environmentalscientists, politicians and decision makers alongwith the general public.

    Scientists working in this field strongly feel that Hydrogen Energy System will be a permanent solutionto the projected global crisis in energy supply. This is mainly because all the current fossil fuel resources are intheir mid-depletion region and the pollution levels have already reached unsafe levels.

    As Hydrogen is to be produced from water, it is supposed to be one of the lightest, most efficient, costeffective and cleanest fuel on the planet, if the matured technology is developed. This is realistic since over72% of the globe is covered with water and byproduct again is water. In other words Hydrogen economystarts and ends with water. It can avoid all harmful gases, acid rains, pollutants, ozone depleting chemicals andoil spillages due to conventional fuels. Use of Hydrogen can afford the development of clean and adequateenergy for sustainable development of all.

    Ever growing demand for energy and the rising concern caused by the use of conventional fossil fuels,call for new and clean fuels. Among all kinds of energy sources, hydrogen is the best choice as a clean fuel.The main advantage of hydrogen as energy source lies in the fact that its by product is water, and it can be

    easily regenerated.

    Hydrogen is the simplest element; an atom of hydrogen consists of only one proton and one electron. Itis also the most plentiful element in the universe. Despite its simplicity and abundance, hydrogen doesn't occurnaturally as a gas on the Earthit is always combined with other elements.

    In this presentation we would like to highlight the production, storage, Transportation & application ofhydrogen energy. We have focused on the storage of Hydrogen through carbon nanotubes. In its pureform, hydrogen is colorless and odourless gas. It is an energy carrier, not an energy source.

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    Gas: Natural gas orbio-gas are

    hydrogen sources with

    steam reforming or

    partial oxidation

    Oil: Hydrogen is producedwith

    steam reforming or partial

    oxidation from fossil or

    renewable oils

    Coal: Withgasification

    technology

    hydrogen may

    be produced from

    coal

    Alchoholslike ethanoland methanol

    derived from

    gas or

    biomass - are

    Power: Watrerelectrolysis

    from renewable

    sources

    Wood: Pyrolysistechnology

    for hydrogen from

    biomass

    Algae: Methods for

    utilising the photo-

    synthesis for

    hydrogen

    Various Sources of Hydrogen Gas

    Hydrogen is by far the most plentiful element in the uni- verse, making up 75% of themass of all visible matter in stars and galaxies. hydrogen atoms, the nucleus consists of a single

    proton, although a rare form (or "isotope") of hydrogen con-tains both a proton and a neutron.This form of hydrogen is called deuterium or heavy hydrogen. Other isotopes of hy- drogen alsoexist, such as tritium with two neutrons and one proton, but these isotopes are unstable and decayradioac- tively.

    Chapter 2. Introducton of hydrogen as alternative:

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    Hydrogen (H2) is a colorless, odorless, tasteless, flammable and nontoxic gas at atmospheric

    temperatures and pressures. It is the most abundant element in the universe, but is almost absent from

    the atmosphere as individual molecules in the upper atmosphere can gain high velocities during

    collisions with heavier molecules, and become ejected from the atmosphere. It is still quite abundant on

    Earth, but as part of compounds such as water.

    Hydrogen burns in air with a pale blue, almost invisible flame. Hydrogen is the lightest of all

    gases, approximately one-fifteenth as heavy as air. Hydrogen ignites easily and forms, together with

    oxygen or air, an explosive gas (oxy-hydrogen).

    Hydrogen has the highest combustion energy release per unit of weight of any commonly

    occurring material. This property makes it the fuel of choice for upper stages of multi-stage rockets.

    Hydrogen has the lowest boiling point of any element except helium. When cooled to its boiling

    point, -252.76o C (-422.93o F) hydrogen becomes a transparent, odorless liquid that is only one-

    fourteenth as heavy as water. Liquid hydrogen is not corrosive or particularly reactive. When converted

    from liquid to gas, hydrogen expands approximately 840 times. Its low boiling point and low density

    result in liquid hydrogen spills dispersing rapidly.

    The most common large-scale process for manufacturing hydrogen is steam reforming of

    hydrocarbons, in particular, natural gas (mostly methane). Other methods used for hydrogen production

    methods include generation by partial oxidation of coal or hydrocarbons, electrolysis of water, recovery

    of byproduct hydrogen from electrolytic cells used to produce chlorine and other products, and

    dissociation of ammonia. Hydrogen is recovered for internal use and sale from various refinery and

    chemical streams, typically purge gas, tail gas, fuel gas or other contaminated or low-valued streams.

    Purification methods include pressure swing adsorption (PSA), cryogenic separation and membrane gas

    separation.

    Many hydrogen gas users purchase it as a liquid, which can be vaporized as needed, instead of

    producing it on their own site. Liquefaction of gaseous hydrogen is a multi-stage process using several

    refrigerants and compression/ expansion loops to produce extreme cold. As part of the process, the

    hydrogen passes through "ortho/ para" conversion catalyst beds that convert most of the "ortho"

    hydrogen to the "para" form. These two types of diatomic hydrogen have different energy states. In

    "ortho" hydrogen, which is the most common form at room temperature, the nuclei have "anti-parallel"

    spins. In "para" hydrogen the nuclei have parallel spins. "Ortho" hydrogen is less stable than "para" at

    liquid hydrogen temperatures. It spontaneously changes to the "para" form, releasing energy, which

    vaporizes a portion of the liquid. By using a catalyst such as hydrous ferric oxide to convert most of thehydrogen to the more stable form during the liquefaction process, the liquid hydrogen product can be

    stored without excessive vent loss.

    Some industrial processes with relatively small hydrogen requirements may choose to produce

    some or all of their needs using compact generators. In the past, ammonia dissociation was a common

    technology choice. More recently, improvements in small packaged electrolytic and hydrocarbon

    reforming systems have made these routes to small volume hydrogen production increasingly attractive.

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    In some cases these systems may be the sole source of hydrogen, while in others they may be used to

    supplement and/or back-up other supply sources. Electrolytic production techniques can produce high

    purity hydrogen at elevated pressure, eliminating the need for supplemental compression. They can

    also produce high purity oxygen (at one-half the hydrogen production rate). The latest which will be

    used as fuel. Most hydrogen is bound up in compounds such as water or methane, and energy is

    required to break the hydrogen free from these compounds, then separate, purify, compress and/ or

    liquefy the hydrogen for storage and transportation to usage points. Widespread production,

    distribution and use of hydrogen will require many innovations and investments to be made in efficient

    and environmentally-acceptable production systems, transportation systems, storage systems and

    usage devices.

    Currently, there is a great deal of interest in hydrogen fuel cell technology development and

    investigations into unconventional or specialized hydrogen storage systems. New technologies and

    equipment developed to support these applications will undoubtedly find uses in industry as well.

    Gas Properties

    Molecular Weight

    molecular weight : 2.016 g/mol

    Solid phaseMelting point : -259 CLatent heat of fusion (1,013 bar, at triple point) : 58.158 kJ/kg

    Liquid phaseLiquid density (1.013 bar at boiling point) : 70.973 kg/m

    3

    Liquid/gas equivalent (1.013 bar and 15 C (59 F)) : 844 vol/volBoiling point (1.013 bar) : -252.8 C

    Latent heat of vaporization (1.013 bar at boiling point) : 454.3 kJ/kg

    Critical pointCritical temperature : -240 CCritical pressure : 12.98 barCritical density : 30.09 kg/m

    3

    Triple point

    Triple point temperature : -259.3 CTriple point pressure : 0.072 bar

    Gaseous phaseGas density (1.013 bar at boiling point) : 1.312 kg/m

    3

    Gas density (1.013 bar and 15 C (59 F)) : 0.085 kg/m3

    Compressibility Factor (Z) (1.013 bar and 15 C (59 F)) : 1.001

    specific gravity (air = 1) (1.013 bar and 21 C (70 F)) : 0.0696Specific volume (1.013 bar and 21 C (70 F)) : 11.986 m3/kg

    Heat capacity at constant pressure (Cp) (1 bar and 25 C (77 F)) :0.029 kJ/(mol.K)Heat capacity at constant volume (Cv) (1 bar and 25 C (77 F)) : 0.021kJ/(mol.K)Ratio of specific heats (Gamma:Cp/Cv) (1 bar and 25 C (77 F)) :1.384259

    Viscosity (1.013 bar and 15 C (59 F)) : 0.0000865 Poise

    Thermal conductivity (1.013 bar and 0 C (32 F)) : 168.35 mW/(m.K)

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    Chapter.3. Production of Hydrogen :

    The various technologies that are involved in the production of hydrogen are

    1.Thermo Chemical process.

    2.Electrolytic process.

    3.Photolytic process.

    3.1 Thermo Chemical Process

    1) Steam Methane Reforming: - High temperature steam is used to extract hydrogen from

    any methane source. This is the most common method of producing hydrogen.

    2) Partial Oxidation: - Methods are being is explored in which simultaneously oxygen is

    separated from air and partially oxidizing methane to produce hydrogen.

    3) Splitting water using heat from a solar concentrator.

    4) Burning to generate gas, which is then reformed to produce hydrogen.

    3.2 Electrolytic Process

    Electricity is used to separate water (H2O) into hydrogen and oxygen. Photolytic Process:

    In this, Sunlight is used to split water. Two photolytic processes are being studied.

    1) Photo biological methods: - This involves the exposure of microbes to Sunlight, split

    water to produce Hydrogen.

    2) Photo Electrolysis: - Here, Semiconductors, when exposed to Sunlight & immersed in water,

    generates enough electricity to produce hydrogen by splitting water. Thus Hydrogen can be produced in

    large scale and transported or locally produced depending on the method used. The delivery

    infrastructure for hydrogen will require high-pressure compressors for gaseous hydrogen and

    liquefaction for Cryogenic Hydrogen. These methods have significant capital and operating costs. They

    also have energy inefficiency associated with them.

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    HYDROGEN FROM FOSSIL FUELS

    Hydrogen can be produced from most fossil fuels. The complexity of the processes varies, and in

    hydrogen production from natural gas and coal. Since carbon dioxide is produced as a by-product, the

    CO 2 should be captured to ensure a sustainable (zero-emission) process. The feasibility of the

    processes will vary with respect to a centralised or distributed production plant.

    3.3 Production from natural gas

    Hydrogen can currently be produced from natural gas by means of three different chemical processes:

    1. Steam reforming (steam methane reforming - SMR).

    2. Partial oxidation (POX).

    3. Autothermal reforming (ATR).

    Although several new production concepts have been developed, none of them is close to

    commercialisation.

    3.3.1 Steam reforming

    Steam reforming involves the endothermic conversion of methane and water vapour into hydrogen

    and carbon monoxide . The heat is often supplied from the combustion of some of the methane

    feed-gas. The process typically occurs at temperatures of 700 to 850 C and pressures of 3 to

    25 bar. The product gas contains approximately 12 % CO, which can be further converted to CO2

    and H2

    through the water-gas shift reaction .

    CH 4 + H 2O + heat _CO + 3H2

    CO + H 2O _CO 2 + H 2 + heat

    3.3.2 Partial oxidation

    Partial oxidation of natural gas is the process whereby hydrogen is produced through the partial

    combustion of methane with oxygen gas to yield carbon monoxide and hydrogen . In this

    process, heat is produced in an exothermic reaction, and hence a more compact design is possible

    as there is no need for any external heating of the reactor. The CO produced is further converted

    to H2 as described in equation .

    CH4

    + 12/

    O 2 _CO + 2H 2 + heat

    3.4 Autothermal reforming

    Autothermal reforming is a combination of both steam reforming and partial oxidation .

    The total reaction is exothermic, and so it releases heat. The outlet temperature from the reactor

    is in the range of 950 to 1100 C, and the gas pressure can be as high as 100 bar. Again, the CO

    produced is converted to H 2 through the water-gas shift reaction . The need to purify the output

    gases adds significantly to plant costs and reduces the total efficiency.

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    3.5 Coal :

    Hydrogen can be produced from coal through a variety of gasification processes (e.g. fixed bed,

    fluidised bed or entrained flow). In practice, high-temperature entrained flow processes are favoured

    to maximise carbon conversion to gas, thus avoiding the formation of significant amounts of char,

    tars and phenols. A typical reaction for the process is given in equation , in which carbon isconverted to carbon monoxide and hydrogen.

    C(s) + H 2O + heat _CO + H2

    Since this reaction is endothermic, additional heat is required, as with methane reforming. The CO

    is further converted to CO2

    and H2

    through the water-gas shift reaction, described in equation (2.2).

    Hydrogen production from coal is commercially mature, but it is more complex than the production

    of hydrogen from natural gas. The cost of the resulting hydrogen is also higher. But since coal is

    plentiful in many parts of the world and will probably be used as an energy source regardless, it

    is worthwhile to explore the development of clean technologies for its use.

    3.5.1 Capture and storage of CO2Carbon dioxide is a major exhaust in all production of hydrogen from fossil fuels. The amount of CO 2 will vary

    with respect to the hydrogen content of the feedstock. To obtain a sustainable (zero- emission) production of

    hydrogen, the CO2

    should be captured and stored. This process is known as de-carbonisation. There are

    three different options to capture CO 2 in a combustion process:

    3.5.1.a Post-combustion. The CO 2 can be removed from the exhaust gas of the combustion process inconventional steam turbine or CCGT (combined cycle gas turbine) power plant. This can be done via the"amine" process, for example. The exhaust gas will contain large amounts of nitrogen and some amounts ofnitrogen oxides in addition to water vapour, CO 2 and CO.

    3.5.1.b Pre-combustion. CO 2 is captured when producing hydrogen through any of the processes

    discussed above.

    3.5.1.c Oxyfuel-combustion. The fossil fuel is converted to heat in a combustion process in a conventional

    steam turbine or CCGT power plant. This is done with pure oxygen as an oxidiser. Mostly CO2 and water

    vapour are produced in the exhaust or flue gases, and CO2

    can be easily separated by condensing the water

    vapour.

    In post-combustion and oxyfuel-combustion systems, electricity is produced in near-conventional

    steam and CCGT power plants. The electricity produced could then be used for water electrolysis. If the

    capture and storage of CO 2 is applied to an energy conversion process of relatively low efficiency, and the

    electricity is used to electrolyse water, then the overall efficiency of fuel to hydrogen would not exceed 30%.

    The captured CO 2 can be stored in geological formations like oil and gas fields, as well as in aquifers,4 but the

    feasibility and proof of permanent CO 2 storage are critical to the success of de-carbonisation.The choice of the transportation system for the CO 2 (pipeline, ship or combined) will largely depend

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    on the site chosen for the production plant and the site chosen for storage.

    3.6HYDROGEN FROM SPLITTING OF WATER

    Hydrogen can be produced from the splitting of water through various processes. This paper briefly discusses

    water electrolysis, photo-electrolysis, photo-biological production and high-temperature water decomposition.

    Water electrolysis

    Water electrolysis is the process whereby water is split into hydrogen and oxygen through the

    application of electrical energy, as in equation (3.1). The total energy that is needed for water is increasing

    slightly with temperature, while the required electrical energy decreases. A high-temperature electrolysis

    process might, therefore, be preferable when high-temperature heat is available as waste heat from other

    processes. This is especially important globally, as most of the electricity produced is based on fossil energy

    sources with relatively low efficiencies. Future potential costs for electrolytic hydrogen are presented in Figure

    3, where the possibilities to considerably reduce the production cost are evident.

    H 2O + electricity _H 2 +1

    2/O2

    Future potential costs of electrolytic hydrogen

    0

    1

    2

    3

    4

    Todays small

    plant

    Todays

    large plantFuture

    continuous

    Future

    off-peak

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    Electrolysis

    Alkaline electrolysers use an aqueous KOH solution (caustic) as an electrolyte that usually circulates throughthe electrolytic cells. Alkaline electrolysers are suited for stationary applications and are available at operatingpressures up to 25 bar. Alkaline electrolysis is a mature technology, with a significant operating record inindustrial applications, that allows remote operation.

    The following reactions take place inside the alkaline electrolysis cell:

    Electrolyte: 4H 2O _4H+ + 4OH

    Cathode:4 H 2 + 4e - _2H2

    Anode: 4OH - _O 2 + 2H 2O + 4e

    Sum: 2H 2O _O 2 + 2H2

    Commercial electrolysers usually consist of a number of electrolytic cells arranged in a cell stack.

    Alkaline electrolysers typically contain the main components shown in . The major R&D challenge for the future

    is to design and manufacture electrolyser equipment at lower costs with higher energy efficiency and larger

    turn-down ratios.

    Transfomer/rectifier

    Dioniser/reverse

    osmosis

    Electrolyic

    cell block

    O2/KOH

    Gas

    separator

    H2/KOH

    Gas

    separator

    Deoxidis

    er

    Dryer

    H2

    O2

    KOH

    KOH

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    3.7 Photo-electrolysis (photolysis)

    Photovoltaic (PV) systems coupled to electrolysers are commercially available. The systems offer

    some flexibility, as the output can be electricity from photovoltaic cells or hydrogen from the

    electrolyser. Direct photo-electrolysis represents an advanced alternative to a PV-electrolysis system

    by combining both processes in a single apparatus.. Photo- electrolysis of water is the process whereby

    light is used to split water directly into hydrogen and oxygen. Such systems offer great potential for cost

    reduction of electrolytic hydrogen, compared with conventional two-step technologies.

    Fundamental and applied R&D efforts in relation to materials science and systems engineeringfor photo-electrochemical cells (PEC) are currently being undertaken world wide, with at least 13 OECDcountries maintaining PEC-related R&D projects and/or entire programs. The IEA-HIA co- ordinates andmanagesa significant part of these R&D efforts in a collaborative, task-shared . Four major PEC conceptareas are being studied, comprising two-photon tandem systems, monolithic multi-junction systems, dual-bed redox systems, and one-pot two-step systems. While the first two concepts employ thin-film-on-glassdevices immersed in water, the latter two concepts are based on the application of photosensitive powdercatalysts suspended in water. Various laboratory-scale PEC devices have been developed over the pastcouple of years, thus far demonstrating solar-to- hydrogen conversion efficiencies of up to 16%.

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    The key challenges to advance PEC cell innovation toward the market concern progress inmaterials science and engineering. It is very important to develop photo-electrode materials and theirprocessing technologies with high-efficiency (performance) and corrosion-resistance (longevity)characteristics, paving the path toward smart system integration and engineering. Since no "ideal" photo-electrode .material commercially exists for water splitting, tailored materials have to be engineered.

    Combinatorial chemistry approaches offer fast-tracking experimental options for the necessary materials

    screening, while modelling capabilities of photo-oxidation based on quantum transition theory need to be

    developed. Most important, there is a need for fundamental research on semiconductor doping for band-

    gap shifting and surface chemistry modification, including studies of the associated effects on both surface and

    bulk semi-conducting properties. Corrosion and photo- corrosion resistance present further significant R&D

    challenges to be addressed, with most of the promising materials options at hand. Current-matching between

    anode and cathode, in addition to ohmic resistance minimisation, requires considerable systems design as well

    as sophisticated engineering solutions. Optimisation of fluid dynamics (with its effects on mass and energy

    transfer) and gas collection and handling (with its effects on operational safety) will demand major conceptual

    and application-specific R&D attention.

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    Chapter.4 1 .Steam Reforming , Au tothermal Reforming and Part ial

    Oxidat ion

    In broad terms, steam reforming (SR) is a process of producing hydrogen by combining steam

    and hydrocarbon and reacting in a reformer at temperatures above500 C in the presence of a metal-based

    catalyst. [5] In principle, there are three types of reforming processes:

    Steam Reforming

    Partial Oxidation

    o (Non-Catalytic) Partial Oxidation (POX)

    o Catalytic Partial Oxidation (CPO)

    Autothermal Reforming

    Often times, autothermal reforming is grouped under partial oxidation, because partial oxidation may

    be carried by a combination of non-catalytic oxidation and steam reforming[8]. The advantage ofpartial oxidation and autothermal reforming is that these processes are self-sustaining and do not require

    external provision of heat. However, they are less efficient in producing hydrogen.

    Steam Reforming

    Steam reforming of methane consists of three reversible reactions: the strongly endothermic

    reforming reactions, 2 and 4, and the moderately exothermic water-gas shift

    CH 4 + H 2O ' CO + 3H2

    CO + H 2O ' CO 2 + H2CH + 2H O ' CO + 4H

    [H = +206 kJ mol-1] (2)

    [H = -41 kJ mol-1] (3)-1

    [H = +165 kJ mol ] (4)

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    Steam-methane reforming is still responsible for the bulk of

    hydrogen production in petroleum refineries

    FLOW PROCESS CHART OFH2 Generation from Methanol Reforming

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    Chapter 5-Future Hydrogen Production & Storage Plant

    FLOW SHEET OF HYDROFORM-C

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    "oxygenolysis" for the corresponding "pyrolysis" and "hydrogenolysis" of hydrocarbons.CO 2 is not only

    produced through he shift reaction 3, but also directly through the steam reforming reaction 4. In factreaction 4 results from the combination of reaction 2 and 3. Because of the endothermic behavior of steamreforming, high temperature is favored. In addition, because volume expansion occurs, low pressure isfavored. In contrast, reaction 3 the exothermic reaction is favored by low temperature, while changes in

    pressure have no effect. Reforming reactions 2 and the associated water gas shift reaction 3 are carried outnormally over a supported nickel catalyst at elevated temperatures, typically above 500 C.Reactions 2 and 4 are reversible and normally reach equilibrium over an active

    catalyst, at high temperatures. The overall product gas is a mixture of carbon monoxide,

    carbon dioxide, hydrogen, and unconverted methane and steam. The temperature of the

    reactor, the operating pressure, the composition of the feed gas, and the proportion of steam fed to the

    reactor governs the product from the reformer.

    The amount of carbon monoxide produced through steam reforming of methane is quite high;

    because the water gas shift reaction, shown in equation 3, is thermodynamically favorable at

    higher temperatures. The amount of carbon monoxide inthe final product from the steam reforming of

    methane is determined by the thermodynamics and kinetics of the reaction within the reformer. This

    also determines the downstream processes necessary to reduce CO concentration, which is desired by

    proton-exchange membrane. This is accomplished by a combination of WGS reactions atlower temperatures

    and the preferential oxidation reaction. For solid oxide fuel cell, theCO concentration has to be reduced so

    additional hydrogen may be produced providing high WGS activity at the anode side. [10]

    Steam reforming is the most important route for large scale manufacture of synthesis gas for

    ammonia, methanol, and other petrochemicals and for the manufacture of hydrogen for refineries. In

    general, reforming reactions are catalyzed by group 8-10 metals with nickel as the preferred metal for

    industrial application because of its activity ready availability and low cost. Methane is activated on the nickel

    surface. The resulting CH x species then reacts with OH species adsorbed on the nickel or on the support.[8]

    Steam reforming process is divided into two steps: a section at high temperature

    and pressure (typically 800-1000C and 30-40 bar) in which the reforming and shift

    reaction occurs, followed by an additional two-step shift section at a lower temperature

    (typically at 200-400C) in order to maximize the CO conversion.

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    PLANT OF HYDROFORM-C

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    HYDRO-SWING PLANT FLOW SHEET:

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    Chapter. 6 Advance Tecnique of Production of hydrogen

    Hybrid Solar System Makes Rooftop Hydrogen

    Instead of systems based on standard solar panels, a hybrid option in which sunlight heats a combination

    of water and methanol in a maze of glass tubes on a rooftop. After two catalytic reactions, the system produces

    hydrogen much more efficiently than current technology without significant impurities. The resulting hydrogen can

    be stored and used on demand in fuel cells.For his analysis, compared the hybrid system to three different

    technologies in terms of their exergetic performance. Exergy is a way of describing how much of a given quantity

    of energy can theoretically be converted to useful work."The hybrid system achieved exergetic efficiencies of 28.5

    percent in the summer and 18.5 percent in the winter, compared to 5 to 15 percent for the conventional systems

    in the summer, and 2.5 to 5 percent in the winter," The paper describing the results for analysis was, new system.

    .comparisons took place during the months of July and February in order to measure each system's performance

    during summer and winter months.Like other solar-based systems, the hybrid system begins with the collection of

    sunlight. Then things get different. While the hybrid device might look like a traditional solar collector from the

    distance, it is actually a series of copper tubes coated with a thin layer of aluminum and aluminum oxide and partly

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    filled with catalytic nanoparticles. A combination of water and methanol flows through the tubes, which are sealed

    in a vacuum.

    This set-up allows up to 95 percent of the sunlight to be absorbed with very little being lost as heat to the

    surroundings," Hotz said. "This is crucial because it permits us to achieve temperatures of well over 200 degrees

    Celsius within the tubes. By comparison, a standard solar collector can only heat water between 60 and 70 degreesCelsius."Once the evaporated liquid achieves these higher temperatures, tiny amounts of a catalyst are added, which

    produces hydrogen. This combination of high temperature and added catalysts produces hydrogen very efficiently,

    Hotz said. The resulting hydrogen can then be immediately directed to a fuel cell to provide electricity to a building

    during the day, or compressed and stored in a tank to provide power later.

    The three systems examined in the analysis were the standard photovoltaic cell which converts sunlight directly into

    electricity to then split water electrolytically into hydrogen and oxygen; a photocatalytic system producing hydrogen

    similar, but simpler and not mature yet; and a system in which photovoltaic cells turn sunlight into electricity which

    is then stored in different types of batteries (with lithium ion being the most efficient).

    "We performed a cost analysis and found that the hybrid solar-methanol is the least expensive solution,

    considering the total installation costs of $7,900 if designed to fulfill the requirements in summer, although this is

    still much more expensive than a conventional fossil fuel-fed generator,"

    Costs and efficiencies of systems can vary widely depending on location -- since the roof-mounted collectors that

    could provide all the building's needs in summer might not be enough for winter. A rooftop system large enough to

    supply all of a winter's electrical needs would produce more energy than needed in summer, so the owner could

    decide to shut down portions of the rooftop structure or, if possible, sell excess energy back to the grid.

    The installation costs per year including the fuel costs, and the price per amount of electricity produced,

    however showed that the (hybrid) solar scenarios can compete with the fossil fuel-based system to some degree. 'In

    summer, the first and third scenarios, as well as the hybrid system, are cheaper than a propane- or diesel-combusting

    generator."

    This could be an important consideration, especially if a structure is to be located in a remote area where

    traditional forms of energy would be too difficult or expensive to obtain.

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    6.1 Compressor Used for H2 Storages

    a.Piston-Metal Diaphragm compressor

    Piston-metal diaphragm compressors are stationary high pressure compressors, 4 staged water cooled,

    11~15 kW 30~50Nm3/h 40MPa for dispensation of hydrogen.[1]

    Since compression generates heat, the

    compressed gas is to be cooled between stages making the compression less adiabatic and

    more isothermal. The default assumption on diaphragm hydrogen compressors is an adiabatic efficiencyof 70%.Used in hydrogen stations.

    b. Ionic liquid piston compressor

    A ionic liquid piston compressor, is a hydrogen compressor based on a ionic liquid piston instead of a

    metal piston as in a piston-metaldiaphragm compressor.[3]

    http://en.wikipedia.org/wiki/Pistonhttp://en.wikipedia.org/wiki/Diaphragm_compressorhttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-0http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-0http://en.wikipedia.org/wiki/Adiabatic_processhttp://en.wikipedia.org/wiki/Isothermic_processhttp://en.wikipedia.org/wiki/Adiabatichttp://en.wikipedia.org/wiki/Hydrogen_stationhttp://en.wikipedia.org/wiki/Ionic_liquid_piston_compressorhttp://en.wikipedia.org/wiki/Ionic_liquidhttp://en.wikipedia.org/wiki/Diaphragm_compressorhttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-2http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-2http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-2http://en.wikipedia.org/wiki/Diaphragm_compressorhttp://en.wikipedia.org/wiki/Ionic_liquidhttp://en.wikipedia.org/wiki/Ionic_liquid_piston_compressorhttp://en.wikipedia.org/wiki/Hydrogen_stationhttp://en.wikipedia.org/wiki/Adiabatichttp://en.wikipedia.org/wiki/Isothermic_processhttp://en.wikipedia.org/wiki/Adiabatic_processhttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-0http://en.wikipedia.org/wiki/Diaphragm_compressorhttp://en.wikipedia.org/wiki/Piston
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    c.Guided rotor compressor

    The guided rotor compressor(GRC) is a positive displacement rotary compressorbased upon an

    envoluted trochoid geometry which utilizes a parallel trochoid curve to define its basic compression

    volume. It has a typical 80 to 85% adiabatic efficiency.[6]

    d.Linear compressor

    The single piston linear compressoruses dynamic counterbalancing, where an auxiliary movable mass is

    flexibly attached to a movable piston assembly and to the stationary compressor casing using auxiliary

    mechanical springs with zero vibration export at minimum electrical power and current consumed by the

    motor.[7]

    It is used in cryogenics

    e.Hydride compressor

    In a hydride compressor, thermal and pressure properties of a hydride are used to absorb low pressure

    hydrogen gas at ambient temperatures and then release high pressure hydrogen gas at higher

    temperatures; the bed of hydride is heated with hot water or an electric coil.[8]

    f.Electrochemical hydrogen compressor

    A multi-stage electrochemical hydrogen compressorincorporates a series ofmembrane-electrode-

    assemblies (MEAs), similar to those used in proton exchange membrane fuel cells, this type of

    compressor has no moving parts and is compact. With electrochemical compression of hydrogen a

    pressure of 5000 psi is achieved. Pressure is believed to go beyond 10,000 psi to the structural limits of

    the design.]A patent is pending for an exergy efficiency of 70 to 80% for pressures up to 10,000 psi or

    700 bars.

    http://en.wikipedia.org/wiki/Guided_rotor_compressorhttp://en.wikipedia.org/wiki/Gas_compressorhttp://en.wikipedia.org/wiki/Trochoidhttp://en.wikipedia.org/wiki/Adiabatichttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-5http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-5http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-5http://en.wikipedia.org/wiki/Linear_compressorhttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-6http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-6http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-6http://en.wikipedia.org/wiki/Cryogenichttp://en.wikipedia.org/wiki/Hydride_compressorhttp://en.wikipedia.org/wiki/Hydridehttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-7http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-7http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-7http://en.wikipedia.org/wiki/Electrochemical_hydrogen_compressorhttp://en.wikipedia.org/wiki/Membrane_electrode_assemblyhttp://en.wikipedia.org/wiki/Membrane_electrode_assemblyhttp://en.wikipedia.org/wiki/Proton_exchange_membrane_fuel_cellhttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-8http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-8http://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-8http://en.wikipedia.org/wiki/Exergy_efficiencyhttp://en.wikipedia.org/wiki/Exergy_efficiencyhttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-8http://en.wikipedia.org/wiki/Proton_exchange_membrane_fuel_cellhttp://en.wikipedia.org/wiki/Membrane_electrode_assemblyhttp://en.wikipedia.org/wiki/Membrane_electrode_assemblyhttp://en.wikipedia.org/wiki/Electrochemical_hydrogen_compressorhttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-7http://en.wikipedia.org/wiki/Hydridehttp://en.wikipedia.org/wiki/Hydride_compressorhttp://en.wikipedia.org/wiki/Cryogenichttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-6http://en.wikipedia.org/wiki/Linear_compressorhttp://en.wikipedia.org/wiki/Hydrogen_compressor#cite_note-5http://en.wikipedia.org/wiki/Adiabatichttp://en.wikipedia.org/wiki/Trochoidhttp://en.wikipedia.org/wiki/Gas_compressorhttp://en.wikipedia.org/wiki/Guided_rotor_compressor
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    6.2 Novel Alloy Could Produce Hydrogen Fuel from Sunlight

    Alloy formed by a 2 percent substitution of antimony (Sb) in gallium nitride (GaN) has

    the right electrical properties to enable solar light energy to split water molecules into hydrogen

    and oxygen, a process known as photoelectrochemical (PEC) water splitting. When the alloy is

    immersed in water and exposed to sunlight, the chemical bond between the hydrogen and oxygen

    molecules in water is broken. The hydrogen can then be collected.

    "Previous research on PEC has focused on complex materials," Menon said. "We decided

    to go against the conventional wisdom and start with some easy-to-produce materials, even if

    they lacked the right arrangement of electrons to meet PEC criteria. Our goal was to see if a

    minimal 'tweaking' of the electronic arrangement in these materials would accomplish the

    desired results."

    Gallium nitride is a semiconductor that has been in widespread use to make bright-light

    LEDs since the 1990s. Antimony is a metalloid element that has been in increased demand in

    recent years for applications in microelectronics. The GaN-Sb alloy is the first simple, easy-to-

    produce material to be considered a candidate for PEC water splitting. The alloy functions as a

    catalyst in the PEC reaction, meaning that it is not consumed and may be reused indefinitely.

    University of Louisville and University of Kentucky researchers are currently working toward

    producing the alloy and testing its ability to convert solar energy to hydrogen.

    Hydrogen has long been touted as a likely key component in the transition to cleaner energy

    sources. It can be used in fuel cells to generate electricity, burned to produce heat, and utilized in

    internal-combustion engines to power vehicles. When combusted, hydrogen combines with

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    oxygen to form water vapor as its only waste product. Hydrogen also has wide-ranging

    applications in science and industry.

    Because pure hydrogen gas is not found in free abundance on Earth, it must be manufactured by

    unlocking it from other compounds. Thus, hydrogen is not considered an energy source, but

    rather an "energy carrier." Currently, it takes a large amount of electricity to generate hydrogenby water splitting. As a consequence, most of the hydrogen manufactured today is derived from

    non-renewable sources such as coal and natural gas.

    Sunkara says the GaN-Sb alloy has the potential to convert solar energy into an economical,

    carbon-free source for hydrogen.

    "Hydrogen production now involves a large amount of CO2 emissions," Sunkara said. "Once thisalloy material is widely available, it could conceivably be used to make zero-emissions fuel for

    powering homes and cars and to heat homes."

    .

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    Chapter7

    What is a fuel cell?

    A fuel cell is a device that converts the chemical energy of a fuel (hydrogen, natural gas, methanol,gasoline, etc.) and an oxidant (air or oxygen) into electricity. In principle, a fuel cell operates like a battery. Unlikea battery however, a fuel cell does not run down or require recharging. It will produce electricity and heat as longas fuel and an oxidizer are supplied.

    Both batteries and fuel cells are electrochemical devices. As such, both have a positively charged anode, anegatively charged cathode and an ion-conducting material called an electrolyte. Fuel cells are classified by theirelectrolyte material. Electrochemical devices generate electricity without combustion of the fuel and oxidizer, asopposed to what occurs with traditional methods of electricity generation.

    Fuel cell construction generally consists of a fuel electrode (anode) and an oxidant electrode (cathode) separatedby an ion-conducting membrane. Oxygen passes over one electrode, and hydrogen over the other, generatingelectricity, water and heat. Fuel cells chemically combine the molecules of a fuel and oxidizer without burning orhaving to dispense with the inefficiencies and pollution of traditional combustion.

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    Basic Characteristics

    Some of the general characteristics of fuel cells have been introduced above; however, to understand thedifference between types of fuel cells, several other characteristics must be explained.

    Charge Carrier

    The charge carrieris the ion that passes through the electrolyte, and for several types of fuel cells, the chargecarrier is a hydrogen ion, H+, which is simply a single proton. The charge carrier differs between different types offuel cells.

    Poisoning by Contamination

    Fuel cells can be "poisoned" (experience severe degradation in performance) by different types of molecules.Because of the difference in electrolyte, operating temperature, catalyst and other factors, different molecules canbehave differently in different fuel cells. The major poison for all types of fuel cells is sulfur-containing compoundssuch as hydrogen sulfide (H2S) and carbonyl sulfide (COS). Sulfur compounds are naturally present in all fossilfuels, and small quantities remain after normal processing and must be almost completely removed prior toentering the fuel cell.

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    Fuels

    Hydrogen is the current fuel of choice for all fuel cells. Some gases, such as nitrogen from the air, have only adilution effect on the performance of the fuel cell. Other gases, such as CO and CH4, have different effects on fuelcells, depending on the type of fuel cell. For example, CO is a poison to fuel cells operating at relatively lowtemperatures, such as the Proton Exchange Membrane Fuel Cell (PEMFC). However, CO can be used directly as afuel for the high-temperature fuel cells such as the Solid Oxide Fuel Cell (SOFC). Each fuel cell with its specificelectrolyte and catalysts will accept different gases as fuels and experience poisoning or dilution. Therefore, the gassupply systems must be tailored to a specific type of fuel cell.

    Performance Factors

    The performance of a fuel cell depends on numerous factors. The electrolyte composition, the geometry of the fuelcell (particularly the surface area of the anode and cathode), the operating temperature, gas pressure and manyother factors. For reference material that covers introductory to highly technical information on different types offuel cells, refer to the Fuel Cell Handbook, Fifth Edition, published by the U.S. Department of Energy in October2000.

    Fuel Reformers

    Low-temperature fuel cells ( CO2 + 4 H2

    In the high-temperature fuel cells (MCFC and SOFC), CO in the fuel stream acts as a fuel. However, it is likely thatthe water-gas shift reaction is occurring and the fuel for the actual fuel cell is actually hydrogen.

    CO+ H2O => CO2 + H2

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    Fuel reforming can be done in facilities of different scales. The reforming can be done at a large scale in a centralfacility like a chemical plant. This can result in pure hydrogen, either as a high-pressure gas or as a liquid. Thiswould then be delivered to fuel cell users.

    The fuel reforming can also be performed on an intermediate scale in a location such as a gasoline station.In this example, gasoline or diesel fuels would be refined and delivered to the station with the currentinfrastructure. Onsite equipment would reform the fossil fuel into a mixture composed primarily of hydrogen, but

    could include other molecular components such as CO2 and N2. The purity of this hydrogen will depend on ongoingdevelopments in techniques to cost-effectively separate H2 from other gases. This hydrogen would likely then bedelivered to customers as a high-pressure gas.

    Finally, the fuel reforming process can be performed on a small scale on an as-needed basis immediatelybefore its introduction into the fuel cell. One example would be for a fuel cell-powered vehicle to have a gasolinetank on board that would use the existing infrastructure of gasoline delivery. An on-board fuel processor wouldreform the gasoline into a hydrogen-rich stream that would be fed directly to the fuel cell. At the present time, it isnot practical to perform separation of other products of the reforming process from the hydrogen at this smallscale.

    In the longer term, most, if not all, of the hydrogen used to power fuel cells could be generated fromrenewable resources such as wind or solar energy. The electricity generated at a wind farm could be used to splitwater into hydrogen and oxygen. This electrolysis process would produce pure hydrogen and pure oxygen. Thehydrogen could then be delivered by pipeline to all end-users. Such a shift in source of energy has been described

    as a hydrogen economy. Much has been written about the future potential of this energy use.

    Fuel Cell Functionality

    Fuel cells generate electricity from a simple electrochemical reaction in which an oxidizer, typically oxygen from air,and a fuel, typically hydrogen, combine to form a product, which is water for the typical fuel cell. Oxygen (air)continuously passes over the cathode and hydrogen passes over the anode to generate electricity, by-product heatand water. The fuel cell itself has no moving parts making it a quiet and reliable source of power.

    The electrolyte that separates the anode and cathode is an ion-conducting material. At the anode, hydrogen and itselectrons are separated so that the hydrogen ions (protons) pass through the electrolyte while the electrons passthrough an external electrical circuit as a Direct Current (DC) that can power useful devices. The hydrogen ionscombine with the oxygen at the cathode and are recombined with the electrons to form water. The reactions areshown below.

    Anode Reaction: 2H2 => 4H+ + 4e-

    Cathode Reaction: O2 + 4H+ + 4e- => 2H2O

    Overall Cell Reaction: 2H2 + O2 => 2H2O

    Individual fuel cells can then be combined into a fuel cell "stack." The number of fuel cells in the stack determinesthe total voltage, and the surface area of each cell determines the total current. Multiplying the voltage by thecurrent will yield the total electrical power generated.

    Power (Watts) = Voltage (Volts) X Current (Amps)

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    Fuel Cells vs. Traditional Electricity Methods

    fuel cell car

    In traditional methods of generating electricity, the fuel and air are burned, generating a high-temperature gas. Inthe case of a coal-burning power plant, heat is transferred from this hot gas to high pressure liquid water that isboiled. In the case of a gasoline, diesel or gas turbine engine, the hot gas itself is at high pressure. The high-pressure steam, or hot gas, is expanded in a mechanical device (e.g., cylinder, turbine) and ultimately turns anelectrical generator.

    In a fuel cell, the same basic chemical reactions occur, but generate electricity directly as an electrochemical deviceand therefore, never goes through the step of being a high-temperature gas through normal burning. This directconversion of chemical energy to electrical energy is more efficient and generates much less pollutants than dotraditional methods that rely on combustion.

    Which is Better?

    As mentioned above, the direct conversion of fuel and air to electricity is much more efficient than internalcombustion engines and other methods of generating electricity. Therefore, fuel cells can generate more electricityfrom the same amount of fuel.

    Furthermore, by skipping the combustion process that occurs in traditional power-generating methods, the

    generation of pollutants during the combustion process is avoided. Some of the pollutants that are significantly

    lower for fuel cells are oxides of nitrogen and unburned hydrocarbons, (which together cause ground-level ozone),

    and carbon monoxide (a poisonous gas).

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    chapter 8. 1. HYDROGEN STORAGE TECHNOLOGIES

    Current hydrogen storage systems are inadequate to meet the needs of consumers in a fuel cell vehicle.

    The OTP report continues, Hydrogen's low energy-density makes it difficult to store enough on board a

    vehicle to achieve sufficient vehicle range without the storage container being too large or too heavy."

    Existing and proposed technologies for hydrogen storage include (1) physical storage: pressurizedtanks for gaseous hydrogen and pressurized cryotanks for liquid hydrogen; (2) reversible hydrogen uptake in

    various metal-based compounds including hydrides, nitrides, and imides; (3) chemical storage in irreversible

    hydrogen carriers such as methanol; (4) cryoadsorption with activated carbon as the most common adsorbent;

    and

    (5) advanced carbon materials absorption, including carbon nanotubes, alkali-doped carbon nanotubes, and

    graphite nanofibers. The U.S. Department of Energy report, A National Vision for America's Transition to a

    Hydrogen Economy-To 2030 and Beyond, projects that pressurized tanks will be the predominant hydrogen

    storage technology until about 2015, to be supplanted by hydride storage into the early 2020s, then other solid

    state storage technologies [23]. They see storage technologies maturing sufficiently for

    mass production in the 2020s.

    The Department of Energy timeline for development of storage systems projects that high pressure

    and cryogenic storage will be demonstrated in 2002-3, cost-effective hydride storage systems in 2003-6, and

    carbon-based storage systems in 2006-11 [24].

    Goals for hydrogen storage systems for 2010 that were established in the FreedomCAR

    initiative [2] include

    available capacity of 6 wt% hydrogen

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    specific energy of 2 kWh/kg

    energy density of 1.1 kWh/L

    cost $5/kWh or $1.25/gal (gas equiv.) in CY2001 dollars

    Research into hydrogen storage technologies is still in its infancy, as reflected in the very low level of

    patenting in this area: 14 patents in 2001, and fewer in most previous recent years [25]. Patent data indicatethat the United States is the leader" in this research area, while US-based Energy Conversion Devices and

    Canadian organization Hydro-Quebec and McGill University is where the action appears to be located" [26].

    Likewise, only a few papers on hydrogen storage were presented at the recent (2003) March APS Meeting.

    8.2 Pressurized Tank Storage

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    8.3 Pressurized Tank Storage

    Pressurized tanks of adequate strength, including impact resistance for safety in collisions, have been

    made of carbon-fiber wrapped cylinders. Compressed gas storage in such tanks has been demonstrated at a

    pressure of 34 MPa (5,000 psi) with a mass of 32.5 kg and volume of 186 L, sufficient for a 500-km range.

    Note, however, that this tank volume is about 90% of a 55-gallon drum, rather large for individual

    automobiles. So while the 6 wt% goal can be achieved, tank volume is problematic. Pressures of 70 MPa

    (10,000 psi) have been reached, and in 2002 Germany certified Quantum Technology's 10,000 psi on-board

    storage tank [24]. A footnote in the OTP report cited above [22] says, The Toyota and Honda vehicles

    available for lease in late 2002 use hydrogen stored in high-pressure containers [28]. However, their range will

    be less than optimal because hydrogen's low density does not permit a sufficient amount to be stored (unlike

    CNG [compressed natural gas], which has a higher energy density for the same volume)."

    Low temperature storage of liquid hydrogen does not appear to be suitable for normal vehicle use,

    although research on this possibility is being conducted at a low level by several automobile manufacturers

    [24]. Furthermore, a liquid hydrogen storage system loses up to 1% a day by boiling and up to 30% during

    filling, as well as requiring insulation to keep the hydrogen at 20 K." [29]

    8.4 Hydrogen Uptake in Metal-Based Compounds

    Metal hydridation can be used to store hydrogen above room temperature and below 3 or 4 MPa. However, the

    metals introduce too much additional weight for most vehicle uses. They are also expensive [30].

    Recent work by P. Chen, et al. has shown that lithium nitride can reversibly take up large amounts of hydrogen

    [31]. This material takes up hydrogen rapidly in the temperature range 170-210C, and achieved 9.3 wt%

    uptake when the sample was held at 255C for 30 minutes. Under high vacuum (10 MPa, 10 mbar, or 10

    torr) about two-thirds of the hydrogen was released at temperatures below 200C. The remaining third of the

    hydrogen required temperatures above 320C for release. The hydrogen was taken up as lithium imide (LiNH

    2) and lithium hydride (LiH). These researchers suggest that related metal-N-H systems should be investigated

    to find a hydrogen storage system that works at more practical temperatures and pressures.

    physically adsorbed hydrogen [32]. It does not appear to be suitable for vehicle use

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    8.4 Carbon Nanotube and Related Storage Technologies

    The status of hydrogen storage in advanced carbon materials is still unclear. In this subsection, we

    review briefly the status of carbon nanotube storage, both single-walled and double-walled, and graphite

    nanofiber stack storage. Other carbon-based storage technologies that have been proposed include alkali-doped

    graphite, fullerenes, and activated carbon. High surface area and abundant pore volume in the nanostructured

    materials make these especially attractive as potential absorption storage materials. Some early work gave

    tantalizing results for hydrogen storage in carbon nanotubes. Ogden reported various conflicting, some

    excessively optimistic, results [1]. A query by this subcommittee to Prof. Mildred Dresselhaus of MIT about

    the achievable wt% (6.5 wt% has been suggested) brought this response [33]:

    1. It is hard to say what is a reliable estimate of the hydrogen uptake number because of the differences in

    the reported levels by different groups, presumably doing similar measurements. The reasons for the

    different results between groups are not understood.

    2. The 6.5% value is not yet achievable in my opinion.

    3. The problem seems to be hard to me, arguing from a theoretical standpoint. However I would not

    discount the possibility of a breakthrough that might change the situation dramatically. So far it doesn't

    seem to me that there is yet much available carefully controlled work.

    A 2010 review of carbon nanostructure storage research, sponsored by the German Federal Ministry for

    Education and Research (BMBF), found that follow-up workhas been unable to reproduce any of the high-

    capacity results." [29] They concluded In view of today's knowledge, it is unlikely that carbon

    nanostructures can store the required amount of hydrogen. In any case, this calls into doubt whether carbon

    nanostructures would have any advantage over high-pressure tank storage."

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    ROCKET LAUNCHER

    CONSTRUCTION

    HYDROGEN BUS

    HYDROGEN BUS

    Chapter.9 NEW SCOPE OF HYDROGEN

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    Chapter 10 Application and todays status in market

    SCOPE OF HYDROGEN IN FUTURE

    "Building

    market"

    (2003-2015

    Building infrastructure"

    (2015-2030+)

    1. Decentralised electrolysis,

    small scale SMR, tanked hydrogen

    . As 1 + more carbon based production

    3. As 2 Electrolysis from renewables

    and nuclear becomes important

    Hydrogen economy

    .YEAR 2030

    TIME

    TURN

    OVER

    PROFIT

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    CONCLUSIONS AND RECOMMENDATIONS

    This paper has provided an overview of potential development of hydrogen production from water

    splitting and fossil/hydrocarbon fuels, as well as the remaining R&D gaps that must be overcome.

    For all hydrogen production processes, there is a need for significant improvement in plant efficiencies,

    for reduced capital costs and for better reliability and operating flexibility.

    The commercial cost target for hydrogen production is 0.30 USD/kg H 2, corresponding to an energyprice for gasoline of 2.5 USD/GJ in a competitive market. The hydrogen-producing technologies

    have at best only 2-3 times higher production costs. Distributed hydrogen production based on

    reforming is often competitive with electrolysis, as reforming costs 16-29 USD/GJ and electrolysis

    costs 20-40 USD/GJ, depending on investment and energy costs. In large-scale production plants

    based on natural gas, the production cost is 5-8 USD/GJ. Distributed hydrogen production can becompetitive with centrally produced hydrogen (i.e. large-scale natural gas reforming) depending

    on the transportation distance. For example, transportation of compressed hydrogen gas for

    100 miles will add 15-20 USD/GJ to the cost.

    In the current and near term, water electrolysis and small-scale natural gas reformers aresuitable.

    Water electrolysis is a proven technology that can be used in the early phases of building a hydrogen

    infrastructure for the transport sector. Small-scale natural gas reformers have only limited proven

    and commercial availability, but several units are being tested in demonstration projects.

    In the medium to long term, hydrogen production based on centralised fossil fuel productionwith

    CO 2 capture and storage is feasible. The capture and storage of CO 2 is not yet technically or

    commercially

    proven and requires further R&D on absorption/separation processes and process line-up.

    The other methods for hydrogen production are further away from commercialisation and need

    additional R&D. Production from biomass needs additional focus on the preparation and logistics

    of the feed, and will probably only be economical on a large scale. Photo-electrolysis is at an early

    stage of development, and materials cost and practical issues have to be solved. Photo-biological

    processes are at a very early stage of development and have, so far, obtained only low conversion

    efficiencies. High-temperature processes need further materials development focusing, for example,

    on high-temperature membranes and heat exchangers.

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    Advance Technique of H2 Production & Storages

    SOURCE REFERENCES

    1. Internet ,Books,joural papers

    2. Research paper ofReactor Modeling and Process Analysis for Partial Oxidation of Natural GasBy Bogdan Albrecht

    3. Hydrogenproduction and storages by internation research agency.

    4 A Report Prepared for the Panel on Public Affairs (POPA), American Physical Society

    5. web site ,daily science ,Wikipedia,google, Mahler compay of research and science

    6. New Energy and Fuel News and View forMaking and Saving Money in NewEnergy and Fuel

    R&D Priorities and Gaps