b. b. ale department of mechanical engineering

8/14/2019 B. B. ALE Department of Mechanical Engineering

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HYDROGEN

B. B. ALE

Department of Mechanical Engineering

Pulchowk Campus, Institute of Engineering

Tribhuvan University


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HYDROGEN DATA

Properties Values

Lower heating value 33.33 kWh/kg 120 MJ/kg

Higher heating value 39.41 kWh/kg 141.86 MJ/kg

Density 0.0899 kg/Nm3 70.79 kg/m3 LH2

Boiling point 20.390 K (0.1013 MPa)

Specific heat capacity Cp = 14.199 kJ/kg K Cv = 10.074 kJ/kg K

Explosion limits in air 4.0 75.0% by volume

Detonation limits in air 18.3 59.0% by volume

Diffusion coefficient 0.61 cm2/s (4 times as high as that for CH4)

Energy content(equivalent based onlower heating value)

1 Nm3 H2 = 0.34 l gasoline

1 l LH2 = 0.27 l gasoline

1 kg H2 = 2.75 kg gasoline

Source: http://www.hyweb.de


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SAFETY


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HYDROGEN ECONOMY

Source: www.efcf.com/reports


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Hydrogen is not a natural fuel, but a synthetic energy

carrier. It only carries energy generated by otherprocesses.

For example, hydrogen may be produced from electricity byelectrolysis of water.

However, high-grade electrical energy is also required tocompress or liquefy it, and to transport, transfer and storeit. Moreover, in many cases, hydrogen offers little or noend-use advantage over the source energy.

For example, in all stationary applications, hydrogen wouldcompete with grid electricity, which could be distributeddirectly to the end user with much lower energy losses.


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SAFETY ASPECTS OF HYDROGEN

Hydrogen is

not detonative at open air not decomposing

not auto-igniting

not oxidizing

not toxic not corrosive

not radioactive

not badly smelling

not contagious not endangering water

not damaging the fetus (teratogenic)

not causing cancer (carcinogenic)


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SAFETY ASPECTS OF HYDROGEN

Hydrogen is lighter than air and vanishesrapidly upwards.

Hydrogen has a high diffusion coefficient (fourtimes that of methane) and dilutes rapidly inair.

Hydrogen has significantly narrowerdetonation limits in air than explosion limits when ignited early, it burns before detonationlimits are reached.

Hydrogen burns with an invisible flame withvery little heat radiated from the flame.

Hydrogen is colorless and odorless.


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PROBLEM WITH THE FOSSIL FUEL ECONMY

OurAUTOMOBILES, trains and planes are fueled

almost exclusively by petroleum products like gasolineand diesel. A huge percentage of our power plants useoil, natural gas and coal for their fuel.

Air pollution - When cars burn gasoline, they wouldideally burn it perfectly and create nothing but carbon

dioxide and water in their exhaust. Unfortunately, theinternal combustion engine is not perfect. In the processof burning the gasoline, it also produces:

Carbon monoxide, a poisonous gas

Nitrogen oxides, the main source of urban smog

Unburned hydrocarbons, the main source ofurban ozone

Environmental pollution - The process of transportingand storing oil has a big impact on the environmentwhenever something goes wrong. An oil spill, pipelineexplosion or well fire can create a huge mess.
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PROBLEM WITH THE FOSSIL FUEL ECONMY

Global warming - When you burn a gallon of gas in your car,

you emit about 5 pounds (2.3 kg) of carbon into theatmosphere. If it were solid carbon, it would be extremelynoticeable -- it would be like throwing a 5-pound bag of sugarout the window of your car for every gallon of gas burned. Butbecause the 5 pounds of carbon comes out as an invisiblegas, carbon dioxide, most of us are oblivious to it. The carbondioxide coming out of every car's tailpipe is a greenhousegas that is slowly raising the temperature of the planet. Forexample, if the ice caps melt, sea level will rise significantly,flooding and destroying all coastal cities in existence today.That's a big side effect.

Dependence - The United States, and most other countries,cannot produce enough oil to meet demand, so they import itfrom oil-rich countries. That creates an economicdependence. When Middle East oil producers decide to raisethe price of oil, the rest of the world has little choice but to pay

the higher price.
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ADVANTAGES OF HYDROGEN ECONOMY

The elimination of pollution caused by fossil fuels - Whenhydrogen is used in a fuel cellto create power, it is a

completely clean technology. The only byproduct is water.There are also no environmental dangers like oil spills toworry about with hydrogen.

The elimination of greenhouse gases - If the hydrogencomes from the electrolysis of water, then hydrogen adds no

greenhouse gases to the environment. There is a perfectcycle -- electrolysis produces hydrogen from water, and thehydrogen recombines with oxygen to create water and powerin a fuel cell.

The elimination of economic dependence - The elimination

of oil means no dependence on the Middle East and its oilreserves.

Distributed production - Hydrogen can be producedanywhere that you have electricity and water. People caneven produce it in their homes with relatively simpletechnology.
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TWO POSSIBLE SOURCES FOR THE HYDROGEN

Electrolysis of water- Using electricity, it is easy to splitwater molecules to create pure hydrogen and oxygen.One big advantage of this process is that you can do itanywhere. For example, you could have a box in yourgarage producing hydrogen from tap water, and you

could fuel your car with that hydrogen. Reforming fossil fuels - Oil and natural gas contain

hydrocarbons -- molecules consisting of hydrogen andcarbon. Using a device called a fuel processoror areformer, you can split the hydrogen off the carbon in ahydrocarbon relatively easily and then use the hydrogen.You discard the leftover carbon to the atmosphere ascarbon dioxide.
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RENEWABLE SOURCES OF HYDROGEN

To have a pure hydrogen economy, the hydrogen must bederived from renewable sources rather than fossil fuels so

that we stop releasing carbon into the atmosphere. Several different ways to create electricity that do not use fossil

fuels Nuclear power

Hydroelectric dams

Solar cells

Wind turbines

Geothermal power

Wave and tidal power

Co-generation (For example, a sawmill might burn bark to create power,or a landfill might burn methane that the rotting trash produces.)

But changing the power plants over to nuclear and solar maynot be so easy. Nuclear powerhaspolitical and environmental problems, and solar powercurrentlyhas cost and location problems.
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HYDROGEN PRODUCTION

Steam reforming of natural gas

Coal gasification

Biomass gasification Electrolysis of water

Thermolysis and thermo-chemical cycles


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ELECTROLYSIS CELLThe reactions at the cathode are:

(1) K+ + e => K

a positively charged potas-sium ion isreduced

(2) K + H2O => K+ + H + OH

the ion reacts with water to form ahydrogen atom and a hydroxyl ion

(3) H + H => H2

the highly reactive hydrogen atom thenbonds to the metal of the cathode andcombines with another bound hydrogenatom to form a hydrogen molecule that

leaves the cathode as a gasThe reactions at the anode are:

(1) OH =>OH + e

a negatively charged hy-droxyl ion isoxidized

(2) OH => H2O + O

the ion reacts to form water and an oxygenatom

(3) O + O => O2

the highly reactive oxygen atom then bondsto the metal of the anode and com-bineswith another bound oxygen atom to form anoxygen molecule that leaves the anode asa gas


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STEAM REFORM PROCESS WATER/GAS SHIFT

REACTION PROCESS

Source: www.collegeofthedesert.edu/index.esp


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PARTIAL OXIDATION PROCESS AUTOTHERMAL PROCESS

Source: www.collegeofthedesert.edu/index.esp


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HYDROGEN STORAGE

Compressed hydrogen storage

Hydrogen embrittlement

Liquid hydrogen storage

Hydrogen boil-off and insulation

Hydrogen liquefaction and embrittlement

Hydride storage

Metal hydrides

Chemical hydrides

Doping of hydrides

Carbon nanotubes


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ADIABATIC COMPRESSION WORK VERSUS FINALPRESSURE FOR HYDROGEN AND METHANE

Much more energy per kg is required to compresshydrogen than methane.

Multi-stage compressors with intercoolers operatesomewhere between the two limiting cases of isothermaland adiabatic compression.



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TYPICAL ENERGY REQUIREMENTS FOR THE LIQUEFACTION OF

HYDROGEN VERSUS PLANT CAPACITY.

As expected, more electrical energy is consumed for theliquefaction of hydrogen in small plants than in large facilities. Forexisting plants of 10 and 1,000 kgLH2/h capacity, at least 100 and40 MJ/kgLH2 are required for liquefaction, respectively.



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PHYSICAL METAL HYDRIDES

Hydrogen may be stored physically, e.g. by adsorption in spongymatrices of special alloys as physical metal hydrides. The hydrogen

forms a very close, but not perfect, bond with alloys like LaNi5 or ZrCr2. When a metal hydride storage container is filled with hydrogen, heat is

released and usually lost.

Conversely, when the process is reversed to liberate the storedhydrogen, heat must be added.

Thus the energy needed to package hydrogen in physical metalhydrides may be more or less limited to the energy needed to produceand compress hydrogen to a pressure of 3 MPa [15]. This issignificantly less than for hydrogen stored as compressed gas at 20MPa, and far less than for hydrogen stored at 80 MPa, or as a liquid.

Metal hydrides store only around 55-60 kg of hydrogen per m3,

whereas, ignoring the container, liquid hydrogen has a volumetricdensity of 70 kg/m3. Moreover, metal hydride cartridges are veryheavy. A small metal hydride container holding less than 2 g ofhydrogen weighs 230 g [16].

[15] Product specifications, HERA Hydrogen Storage Systems GmbH, Hfener Strasse 45, DE-90431

Nrnberg / Germany

[16] Lawrence D. Burns et al., Vehicle of Change, Scientific American, p. 47, (October 2002)


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CHEMICAL METAL HYDRIDES

Hydrogen may also be stored chemically in alkali metal hydrides. There are manyoptions in the alkali group like LiH, NaH, KH, CaH2, but complex binary hydridecompounds like LiBH4, NaBH4, KBH4, LiAlH4 or NaAlH4 have also been proposedfor hydrogen storage. None of these compounds can be found in nature. All have tobe synthesized from pure metals and hydrogen.

To produce the hydrides, at least 1.6 time more high grade energy has to beinvested to produce 1 HHV energy unit of hydrogen, giving a stage efficiency of lessthan 1/1.6 = 60 %.


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HYDROGEN TRANSPORTATION Steel bottles and pipelines have been use to transport gaseous

hydrogen for more than half a century with excellent safetyrecords.

Compressed gas H2: Gaseous hydrogen can be transported inpressurised bottles40 (typically at 20 to 30 MPa), in tube-trailers(typically at 20 MPa) and through pipelines. In distribution

pipelines, the pressure is between 0.01 and 2 MPa, while forlong distance transport the pressure can range between 1.1 and30 MPa.

Liquid H2: Liquid hydrogen can only be delivered by truck and

by rail. A truck can carry more hydrogen as a liquid than as acompressed gas because the liquid is denser. Today, LH2 canbe transported in cryo-containers or in trailers in sizes between41 m and 53 m at temperatures of about 20K (i.e. - 253C). A40 m LH2 trailer transports about five times as much hydrogenas a 21 m CGH2 tube trailer.


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HYDROGEN IN TRANSPORTATION

Hydrogen fuel to run IC engine

Hydrogen fuel to run fuel cell

Hydrogen fuel to run hybrid vehicles


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HYDROGEN POWER VEHICLE

Electricity generated fromsolar poweris used to splitwater into hydrogen andoxygen. Oxygen is releasedinto the atmosphere, whilehydrogen is liquefied andstored at a very lowtemperature (-253 C).

During internal combustion,the hydrogen combines withoxygen. The resultingenergy powers the vehicle,while the hydrogen isreturned to the environmentas water. Harmfulemissions are virtuallyeliminated.


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HYDROGEN SYSTEM

It consists of

water purification,

hydrogen production

hydrogen drying and filtration Low pressure storage

Hydrogen compression,

High pressure storage, dispensing, and

venting.


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LIST OF EQUIPMENT FOR HYDROGEN SYSTEM

DI water supplier Hydrogen Electrolyser

Hydrogen dryer and filters

Low pressure storage

High pressure compressor

Hydrogen high-pressure storage

Hydrogen dispensing system

Leak detector, emergency shutdown system Hydrogen venting or draining system

Auxiliary system: control air, chiller, N2, vacuum


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Source: http://avt.inl.gov - INL/CON-06-01109 (weststart_hice_presentation.pdf)


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Source: http://www.ch2bc.org/index2.htm


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Source: Energy, The Master Resource Book, The Basics - page 61


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ACTION PLAN

Infrastructure for hydrogen system

Hydrogen generation & storage system

Hydrogen refueling station

Introduction of hydrogen vehicles Hydrogen buses

Hydrogen cars Hydrogen buses and cars

Hydrogen buses, cars and motorcycle

Hydrogen IC engine or FC

Conversion of gasoline IC engine into hydrogen IC engine FC vehicles


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HYDROGEN STORAGE AND BURNING: EXAMPLE


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LONG TERM VISION IN HYDROGEN FUEL: 5 YEARS

5 years Plan for Hydrogen fuel development andits uses:

Capacity Building in Hydrogen Production byoperating pilot scale Hydrogen fuel production usingElectrolysis.

Technology transfer from developed countries

Research in hydrogen storage: Metal Hydride,

Compressed Cylinders. Application in Cooking and Lighting

Application in Public Vehicles


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FINDINGS

Country has substantial amount of surplushydro electricity, which can be utilized toproduce hydrogen fuel.

Country can significantly benefit by producinghydrogen fuel competitive enough to the currentdiesel fuel in transport in longer term byLowering the off-hour electricity tariff.

Significant reduction in air pollution andGHG emission can be achieved.

Electrolysis technology is its future technologyfor the production of hydrogen fuel.


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FINDINGS

The cost of hydrogen fuel production is largelyaffected by the off peak electricity tariffratherthan its infrastructure cost and a suitable offpeak electricity tariff can lower the hydrogen fuel

price.

In contrast to the centralized infrastructure, thedecentralized system like on site hydrogen

production in small scale such as refuelingstations seems more feasible option since thereis no mass market of hydrogen fuel technology.


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CONCLUSIONS

Hydrogen is an energy carrier (like a

battery) rather than an energy source.

Renewable energy sources should beused to produce hydrogen in order to

reduce emissions.

Think of hydropower to hydrogen to getmaximum environmental benefit. That is,

promote the hydrogen vehicles.

b. b. ale department of mechanical engineering

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