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    Hydrogen fueled vehicle

    Chapter 1


    A hydrogen vehicle is an alternative fuel vehicle that uses hydrogen as its onboard fuel for motive

    power. The term may refer to a personal transportation vehicle, such as an automobile, or any other

    vehicle that uses hydrogen in a similar fashion, such as an aircraft. The power plants of such

    vehicles convert the chemical energy of hydrogen to mechanical energy either by burning

    hydrogen in an internal combustion engine, or by reacting hydrogen with oxygen in a fuel cell to

    run electric motors. Widespread use of key hydrogen for fueling transportation is element of a

    proposed hydrogen economy.

    Hydrogen fuel does not occur naturally on Earth and thus is not an energy source, but is an energy

    carrier. Currently it is most frequently made from methane or other fossil fuels. However, it can be

    produced from a wide range of sources (such as wind, solar, or nuclear) that are intermittent, too

    diffuse or too cumbersome to directly propel vehicles. Integrated wind-to-hydrogen plants, using

    electrolysis of water, are exploring technologies to deliver costs low enough, and quantities great

    enough, to compete with traditional energy sources.

    Many companies are working to develop technologies that might efficiently exploit the potential of

    hydrogen energy for mobile uses. The attraction of using hydrogen as an energy currency is that, if

    hydrogen is prepared without using fossil fuel inputs, vehicle propulsion would not contribute to

    carbon dioxide emissions. The drawbacks of hydrogen use are low energy content per unit volume,

    high tank age weights, the storage, transportation and filling of gaseous or liquid hydrogen in

    vehicles, the large investment in infrastructure that would be required to fuel vehicles, and the

    inefficiency of production processes.

    Dept. of Mechanical Engg. Page 1

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    Chapter 2

    BACKGROUNDHydrogen is widely regarded as a promising transportation fuel because it is clean, abundant, and

    renewable. In a gaseous state, it is colorless, odorless, and non-toxic. When hydrogen is combusted

    with oxygen, it forms water as the by-product. Due to hydrogens high flammability range, it can

    be completely combusted over a wide range of air/fuel ratios. Unlike gasoline, which if combusted

    outside its optimal air/fuel ratio will produce excess carbon monoxide (CO) and hydrocarbons

    (HC), hydrogen does not have a carbon element and therefore will not produce those toxic gases?

    Like gasoline however, when hydrogen is combusted in air (mixture of oxygen and nitrogen) thetemperature of combustion can cause the formation of the nitric oxidizes (NOx). Hydrogen

    however has an advantage over gasoline in this area because it can be combusted using very high

    air/fuel ratios. Using a high air/fuel ratio (i.e. combusting hydrogen with more air than is

    theoretically required) causes the combustion temperature to drop dramatically and thus causes a

    reduction in the formation of NOx. Unfortunately, the use of excess air also lowers the power

    output of the engine.

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    Chapter 3


    Hydrogen is eco-friendly and a clean fuel with products of combustion causing no severe

    environmental degradation. Hydrogen, which is nature's best example of an ideal gas, is very

    difficult to compress. It has high specific energy per unit weight. Its heat of combustion per unit

    weight is about 2.5 times higher than ethanol. Hydrogen also posses higher thermodynamic

    conversion efficiency (30-35 percent) as compared to petrol (20-25 percent). The lower limit of the

    hydrogen air flammability range is higher than that of petrol and LPG. The lower limit of

    detonability of hydrogen is higher than that of methane or petrol. Hydrogen combustion is free

    from harmful emissions that invariably accompany fossil fuels combustion. Hydrogen rapidly

    disperses in air which prevents its concentration from reaching lower limits of flammability and

    detonability in air.

    During combustion process in the heat of hydrogen reaction, part of the atmospheric nitrogen

    combines with oxygen to form oxides of nitrogen. The problem of oxide formation can be

    minimized to some extent by injecting water which vaporizes in the cylinder as the hydrogen

    burns, and lowers temperature to a level which stops oxide formation. Apart from preventing oxide

    formation, water vapor provides weight to the expanding gases in the cylinder and up to a limit

    even improves power output. In earlier prototype designs, water tank was provided where as in

    subsequent designs water is recovered from the water vapours present in the exhaust through a

    suitable arrangement.

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    Chapter 4


    Hydrogen is available in surpluses a byproduct in several industrial processes in petroleum

    refineries or alkali industries. Hydrogen can also be produced using offpeak electricity mainly by

    improving the plant load factor of the power stations in the country. Hydrogen can also be

    produced by biophotolysis which utilizes leaving systems to split water into hydrogen and oxygen

    Hydrogen in small quantities can be produced by partial oxidation of hydrocarbons and electrolysis

    of water. Electrolysis is a very clean and reliable process to produce high purity hydrogen.

    The efficiency of electrolysis (E) is defined by the following equation

    E= Hydrogen produced ( meter cube ) F x100

    Power input by cells (kWhr.)

    Based on experimental studies, value of F can be chosen as 3.3 kWhr. / meter cube.

    Hydrogen can be efficiently produced with photo electrolysis. Hydrogen can also be produced by

    photosynthesis and biochemical reactions activated by sunlight. Hydrogen can be produced with

    the help of photochemical cells which require a liquid electrolyte sandwiched between cathode and



    Hydrogen can be stored in a tank. The tank uses a plastic bladder wrapped with high strength

    composite graphite. The tank has a water volume of 87 liters and is rated up to 3,600 psi. At 3,600

    psi, the tank holds 590 SCF of hydrogen, which is equivalent to 1.4 gallons of gasoline. At 200 HP,

    this tank is emptied in about 5 minutes.

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    Liquid hydrogen containers are available in all sizes ranging from small 100 liters containers to

    large volume containers of 5000 meter cube. Metal hydride storage systems are specially

    appropriate where storage space is limited and pressurized gas storage is very expensive. Metalhydride systems are ideal for mobile storage applications. On account of high operating costs for

    long distances, metal hydride tanks are more appropriate for short-range vehicles. Both metal

    hydride and liquid storage tanks have been demonstrated to be practical for mobile applications.

    For longer distances, say beyond 200 km liquid storage tanks are more appropriate than metal

    hydride systems. Metal hydride tanks are much lighter in weight (8.5 to 11 kg) as compared to

    liquid storage tanks (50 to 150 kg). Quantity of hydrogen stored through metal hydrides is roughly

    3 times more than that stored in liquid or gaseous form for the same weight of the tank.

    The iron and titanium hydride system offers several significant advantages over compressed

    hydrogen gas storage systems, but can not compete with gasoline on an equal energy content basis.

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    Chapter 5


    One of the primary problems encountered in the development of operational hydrogen engines is pr

    mature ignition (pre-ignition). Pre -ignition occurs when the cylinder charge becomes ignited

    before the ignition by the spark plug. If this condition occurs when the intake valve is open, the

    flame can travel back into the induction system. Various fuel injection methods have been

    experimented with over the years. These methods have included carbureted systems, which mix the

    air and fuel at a central point upstream of the intake valves; port injection systems that inject the

    fuel into the air stream near the intake valve; and direct injection systems that inject the fuel

    directly into the combustion chamber.

    For carburetor-type systems, which can have a substantial amount of air and fuel in the manifold,

    pre-ignition can have a devastating effect. Port injection systems, which tend to have less fuel in

    the manifold at any one time, can minimize this effect. Running lean (excess air) and precisely

    timing the injector opening and closing times (tuning the system), can virtually eliminate pre-

    ignition from occurring. Direct injection system can eliminate pre-ignition in the intake manifold;

    however it does not necessarily eliminate it in the combustion chamber. Direct injection systems

    also require higher fuel pressure and tend to be a little more complicated than the other two

    methods. The method that was chosen for this project was the port injection system. The fuel

    injectors used to meter the fuel are solenoid operated pulse-width modulated, sonic flow injectors

    especially designed for gaseous fuels.

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    Figure-1 Cross section of injector

    Each injector body was designed to incorporate a inch tube that transported the hydrogen from

    the injector outlet to within an inch of the intake valve. This was to minimize the amount of

    hydrogen that would be in contact with the air in the runner. That way if pre-ignition was to occur

    damage to the intake system would negligible.

    This new manifold provided short, single runners for each cylinder. For each runner, a 1 inch

    tall injector body was designed and fabricated to house the injectors.

    A distinct advantage of using hydrogen as a fuel, with its wide range of flammability, is the fuel-to-

    air ratio or the quality of the charge mixture can easily be varied to meet different driving

    conditions or loads. This is similar to the strategy used by diesel engines. In contrast, for a gasoline

    engine, the fuel-to-air ratio must be kept more or less constant throughout the driving range. In

    other words, the quantity of the charge is controlled. Using a quality controlled strategy

    enables the engine to operate at a constant wide-open-throttle (WOT) position throughout the

    power band (just add more fuel for more torque).To facilitate the starting of the engine, a choke

    (butterfly valve) was designed and fabricated for each injector body.

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    All eight chokes are linked together and centrally controlled by a hand-operated cable located in

    the cockpit of the vehicle. Once the engine started, the chokes are pulled to the wide-open positionand the quality controlled fuel metering strategy is implemented.

    Since the design of this system allows the flow of hydrogen and air to each cylinder to be

    independent of each other, any occurrence of pre-ignition in one cylinder would not influence

    (ignite) the air/fuel mixture of another. Whereas with systems that manifold all the intake runners

    together, a pre-ignition in one cylinder can light the whole intake manifold on fire. To maximize

    the airflow to engine, each manifold runner, intake port, and injector body and throttle body werematch-ported.

    To supply fuel to each injector, a single fuel rail was designed and fabricated. This fuel rail

    contains a port for each of the fuel injectors.

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    Chapter 6


    The hydrogen ancillary system consists of a high flow capacity pressure regulator, a manual shut-

    off valve, a solenoid operated on/off valve, three pressure gauges and a fuel line. The pressure

    regulator, provided by Control Seal Controls, is used to reduce the pressure of the fuel in the

    storage tank (3600 psi) to a useable fuel rail pressure of 100 psi. Upstream of this valve is a

    manually operated ball valve and pressure gauge. A quarter-turn of this valve will shut off the

    hydrogen in the event of a leak or fire. The pressure gauge reads the pressure of the fuel in the

    storage tank. Downstream of the pressure regulator is a solenoid-operated valve and a secondpressure gauge. The solenoid valve is controlled via a switch mounted in the cockpit of the vehicle.

    This valve is a normally closed valve, meaning in the event of a power failure this valve will

    automatically close. This pressure gauge reads the pressure at the outlet of the pressure regulator.

    The third pressure gauge is located at the engine fuel rail and reads fuel pressure at the engine

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    Chapter 7


    The camshaft that comes with the gasoline engine was designed to produce its maximum power at

    high engine speeds. It was ground to have 48 degrees of valve overlap and 268 degrees of

    duration with a 0.74-inch valve lift at .050-inch tappet lift. This type of grind will typically

    produce excellent airflow (high volumetric efficiency) at high engine speeds, at the expense poor

    air dynamics at the lower engine speeds. For gasoline fueled engines, this typically means low

    efficiencies, poor idle and high emissions. For racing purposes, this compromise for high enginespeeds is worth it.

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    Chapter 8


    If 5-speed manual transmission was installed, this transmission has the following gear ratios:

    1st gear: 3.27:1

    2nd gear: 1.98:1

    3rd gear: 1.34:1

    4th gear: 1:1

    5th gear: 6.8:1

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    Chapter 9


    The engine comes with a Magnetic Breaker less distributor that uses mechanical weights for timing

    advance (maximum of 32 degrees). This system is mechanically linked to the engine through a

    gear on the camshaft. Each time the camshaft completes one revolution the rotor of the distributor

    also makes one revolution. On the same shaft as the rotor are 8 vanes, one for each cylinder.

    Figure-2 View distributor vanes

    Each time one of these vanes pass by the magnetic pick up sensor on the distributor, the coil

    (single) discharges, sending a high voltage signal through the coil wire to the distributor. This

    signal would then be distributed to the proper cylinder via the rotor, rotor cap and spark plug wire.

    This type of ignition system works well for engines that do not have an Engine Control Computer


    Dept. of Mechanical Engg. Page 12

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    Chapter 10


    The theoretical maximum power output from a hydrogen engine depends on the fuel injection

    method used. This is because hydrogen will displace a large portion of the incoming air, and thus

    limiting the amount of air that will enter the combustion chamber. For example, the stoichiometric

    air/fuel ratio for hydrogen 34:1. For this mixture, hydrogen will displace 29% of the combustion

    chamber, leaving only 71% for the air. As a result, the energy content of this mixture will be 15%

    less than it would be if the fuel were gasoline (since gasoline is a liquid, it only occupies a very

    small volume of the combustion chamber, and thus allows more air to enter). Since both thecarbureted and port injection methods mix the fuel and air prior to it entering the combustion

    chamber, these systems limits the maximum power obtainable to 85% of that of gasoline engines

    (rough order of magnitude). For direct injection systems, which mix the fuel with the air after the

    intake valve has closed (and thus the combustion chamber has 100% air), the maximum output of

    the engine can be 15% higher than that for gasoline engines (again, rough order of magnitude).

    Therefore, depending on how the fuel is metered, the maximum output for a hydrogen engine can

    be either 15% higher or 15% less than that of gasoline if a stoichiometric air/fuel ratio is used.

    However, at a stoichiometric air/fuel ratio, the combustion temperature is very high and as a result

    it will form a large amount of nitric oxides (NOx), which is a criteria pollutant. Since one of the

    reasons for using hydrogen is low exhaust emissions, hydrogen engines are not normally designed

    to run at a stoichiometric air/fuel ratio.

    Shown in Figure 12 is a plot of NOx formation versus equivalence ratio phi (equivalence ratio is

    the actual air/fuel ratio divided by the stoichiometric air/fuel ratio. If the value for phi is less than

    one, the mixture has excess air and therefore is lean. If the value for phi is greater than one, the

    mixture has excess fuel and therefore rich).

    From this plot is can be seen that in order to keep the NOx formation low, a phi of 0.45 (A/F of80:1) or less is required (above a phi of .45, NOx emissions increase very quickly as the phi

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    increases). Also shown on this graph is a relationship of power (based on an engine speed of 6,100

    rpm) and torque as phi changes. At a phi equal to 1 (stoichiometric), this engine would

    theoretically produce a maximum power and torque of 510 HP and 440 ft- respectively. However

    at this lb,

    Power output, the engine would be producing a large amount of NOx emissions. From Figure 8 it

    can be seen that the maximum clean power (at 6,100 rpm) and torque (i.e. near zero pollution

    without any exhaust gas after-treatment or pollution control devices) would be about 270 HP and

    230 ft -lb, respectively. This would occur at a .45 phi.

    Figure-3 Compression Vs Air/Fuel mixtures

    Running at a phi of 0.45 also has other benefits besides reducing NOx emissions. The first is its

    effective octane rating is increased (i.e. its ability to operate at higher compression ratio

    increases). As it can be seen in Figure 9, hydrogen can tolerate compressions of 15:1 at a 60% lean

    mixture (.4 phis). Whereas, at a stoichometric or a chemically correct mixture (CCM), it can only

    tolerate compression ratios slightly above 8:1. Limiting the maximum fueling rate to a phi of .45

    (based on low emissions), the engine will have a power vs. engine speed curve similar to the one

    shown in Figure 13.

    Hydrogens simple atomic structure along with its ability to burn under ultra-lean conditions also

    contributes to a ratio of specific heat closer to 1.4.

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    (Ideal gas) . Both the compression ratio and the ratio of specific heat are the two variables in the

    calculation of thermodynamic efficiency (see equation 1).

    Where rv = the compression ratio and ,

    k= the ratio of specific heats

    The higher these values, the higher the thermodynamic efficiency of the engine. The lean air/fuel

    mixtures also lower the chances of pre-ignition occurring.

    Another factor having a significant impact on hydrogen fuel storage is the increase in thermal

    efficiency observed when an engine is converted for operation on hydrogen. This is especially true

    under part-load or stop-start driving conditions.

    The impact of the increase in engine operating efficiency becomes significant when evaluatinghydrogen's potential as a vehicular fuel. The efficiency boost

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    Increases the vehicle's range, relieving the needed BTU (J) capacity of fuel storage. The end result

    is a reduction in the storage container's weight and size, and a significant improvement in the cost

    per mile (kilometer) of the fuel.

    Chapter 11

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    Advancements in engine technology have resulted in the virtual elimination of pollution from

    hydrogen-powered automobiles. Since no carbon is present in a hydrogen fuel system, hydrocarbon

    and carbon monoxide pollution do not exist. However, when the air, consisting of nitrogen and

    oxygen, is heated inside the engine, nitric oxide pollution is formed.

    Using water induction technique, peak combustion temperatures inside the hydrogen engine can be

    maintained at levels below the threshold for nitric oxide formation. This results in a substantial

    decrease in nitric oxide formation, as shown in Figure 16.


    Chapter 12

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    The recent observation of improved engine operating efficiencies, the development of successful

    methods for virtually eliminating nitric oxide formation, and development and refinement of metal

    hydride storage systems, have all enhanced hydrogen's potential as an alternate fuel for vehicular



    Table 1

    (In dollars)


    Cost at pump 100,000

    Penalties Total$/106 BTU mile cost

    *Coal gasoline 3.35 2,150 350 2,500

    *Shale gasoline 2.65 1,750 300 2,050

    *Methanol 3.45 2,450 250 2,700

    *Water hydrogen (liquid) 10.2 7,200 1000 8,200

    Coal hydrogen (liquid) 9.9 6,988 1000 7,988

    *Ammonia 7.65 5,100 1050 6,150

    *Hydrazine 10+ 14,000 850 14,850

    Metal hydride with efficiency correction

    Coal hydrogen (liquid) 5.88 4,150 5001 4,650

    Coal hydrogen (metal hydride) 2.79 21,452 5001 26,453

    1. Penalty is reduced to 1/2 since 1/2 the hydrogen is stored.

    2. A double efficiency penalty is included to compensate for extra weight of hydride storage.

    3. When the advantages of less engine wear and maintenance are factored in hydrogen competes

    better with the other candidates.

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    Dept. of Mechanical Engg. Page 19

    Table 2Variations in hydrogen production costs

    $/106BTU $/106BTU


    gasification8 1.35


    electrolysis8 5


    gasification10 1.5


    decomposition8 2


    gasification13 2.6


    decomposition8 5


    gasification14 1.3 Electrolysis9 2.95


    gasification15 2.5 Electrolysis10 3.5Coal


    (liquid) 5.44


    electrolysis12 4.95


    electrolysis8 3.75



    2 1.9

    Natural gas8 1


    electrolysis13 4.6CTR11



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    Comparison of ideal thermodynamic cycle analysis for

    Hydrogen- and gasoline-fueled engines.


    Hydrogen Gasoline

    Engine1 Engine2

    Intake pressure, psi.

    14 14

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    Compression pressure, (psi) 190 231

    Combustion pressure, (psi) 884 1149

    Blow down pressure, (psi) 60 79

    Intake temperature, (K) 540 600

    Compression temperature, (K) 796 1166

    Combustion temperature, (K) 4120 5791

    Blow down temperature, (K) 2360 3388

    Thermal efficiency

    0.456 0.421

    Work/inlet mixture volume (BTU/ft3) 240.9 340.3

    Work per lb. of air, (BTU) 488 481

    The following can be noted from Table 3:

    1. Peak cycle pressures and temperatures are lower in the hydrogen engine.2. The ideal thermal efficiency of the hydrogen engine is slightly higher than that of the gasoline


    3. The work output per unit of air intake is about the same in either case.

    4. The work output per unit volume of inlet mixture is 27 percent lower for the hydrogen engine.

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    Dept. of Mechanical Engg. Page 22

    Table 4Vehicular Storage Requirements of Fuels Based on 20 gallons of gasoline

    (2.27 x 106 BTU)



    *Gasoline 134 2.76

    *Methanol 285 5.7

    *Ethanol 214 4.78

    *Methane (g)1 500 27.6*Methane (l)2 240 16.1

    *Hydrogen (g)3 2250 66

    *Hydrogen (l)4 353 10.2

    *Hydrogen (MgH2)5 692 10.8

    Corrected for 80% efficiency increase.

    Hydrogen(g)3 -1250 -37

    Hydrogen (l)4 -198 -5.7

    Hydrogen (MgH2)5 -388 -6.1

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    Dept. of Mechanical Engg. Page 23

    Table 5

    Exhaust emissions -Total oxides of nitrogen

    (Otto spark ignition engine)

    *Fed. Req. 3.0 gms/mi.




    *Fed. Req.(a) 0.4 gms/mi.




    2.3 gms/mi.




    *Methanol 0.37 gms/mi.




    *Hydrogen 2.04 gms/mi.




    Hydrogen(d) 0.2 gms/mi.




    Hydrogen(e) 0.02 gms/mi.

    2 gms/106


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    Chapter 13


    1. Preignition

    Preignition is caused by catalytic reactions at the cylinder surface which can be minimised

    by keeping cylinder and piston surface clean.

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    2. Backfiring

    Backfiring can be minimized by avoiding hydrogen and air mixing priors to their entry to

    mixing chamber.


    3. Engine Knock

    Knock in hydrogen engines is caused by the same phenomenon as in case of petroleum fuels It is

    generally seen that knock occurs when hydrogen engine is operated close to the rated capacity.

    Problems of preignition, backfiring and knock can also be overcome by suitable engine


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    4. Water Formation And Engine Corrosion

    Hydrogen engines also cause problems of water formation which apart from engine corrosion alsoform oil-water emulsion which lowers oils ability to lubricate. For overcoming this problem

    special lubricating oils and additives are being developed to check emulsification. A B Welch and J

    S Wallace demonstrated that a hydrogen fueled compression ignition engines can deliver higher

    power outputs than a diesel engine. Further improvements in efficiency can result from some

    modifications in injector geometry and combustion chamber design.

    Chapter 14


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    Eco-friendly and a clean fuel with products of combustion causing no severe

    environmental degradation.

    High specific energy of hydrogen per unit weight.

    In several respects superior to other fuels.

    Easy ignability of hydrogen.

    Wider flammability range.

    It is less hazardous than other fuels.

    Engine can be run on leaner mixtures.

    In certain respects hydrogen is safer than other fuels.

    Many heavy and bulky items.

    Chapter 15


    Easy diffusability and lack of visibility make detectivity of leaking gas difficult.

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    The equipment for storage is costly.

    Production may be polluting and costly.

    Preignition, backfiring and knock may occur.

    Chapter 16


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    There have been noted efforts in India in developing hydrogen as an alternative fuel The US

    National Hydrogen Association is planning transition role of hydrogen as an interim measure

    before it could be finally accepted. The transition strategy is concerned with economics of

    hydrogen production, storage and transport, development of alternative captive fuel market, andselection of eco-friendly production systems and safety guidelines for the use of hydrogen as a

    fuel. California state authorities are reportedly trying to make hydrogen cars environmentally

    acceptable under a very stringent new exhaust emissions legislation which the state proposes to

    enforce strictly from 1997 onwards. It may still take several years of R&D efforts to make

    hydrogen vehicles competitive in performance and cost.


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    Hydrogen is a very clean fuel which hardly leaves any deposits on engine parts. Emissions from

    hydrogen engine are practically non-existent although some problems of nitrous oxide formation

    are encountered. Hydrogen is an ideal fuel for certain types of mobile applications. Hydrogen as a

    vehicular fuel may help to reduce independence on fossil fuels in future.


    [1] "Information from". Retrieved 2011-01-31. See also the cost comparison tables

    here: Buchmann, Isidor. "Batteries against fossil fuel", accessed March 15, 2011. Excerpted from

    Dept. of Mechanical Engg. Page 30
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    Buchman, Isidor.Batteries in a Portable World A Handbook on Rechargeable Batteries for Non-

    Engineers (3rd edition), 2011, Cadex Electronics Inc. ISBN 0-9682118-2-8

    [2] "Efficiency of Hydrogen PEFC, Diesel-SOFC-Hybrid and Battery Electric Vehicles" (PDF). 15

    July 2003. Retrieved January 7, 2009.

    [3] "Honda Civic GX Natural Gas Car Earns Top Spot on ACEEE's "Greenest Vehicles of 2008"

    List for the Fifth Straight Year". 2008-02-19. Retrieved 2011-01-31.

    [4]Stewart, Ben (4 April 2008). "Chevy Volt Plug-in Car Batteries Ready for 2010 - GM Technical

    Center". Popular Mechanics. Retrieved 19 September 2009.

    [5] F. Kreith (2004). "Fallacies of a Hydrogen Economy: A Critical Analysis of Hydrogen

    Production and Utilization". Journal of Energy Resources Technology 126: 249257.

    [6]"Light Weight Hydrogen 'Tank' Could Fuel Hydrogen Economy". 2008-11-

    05. Retrieved 2010-12-12.

    [7] Honda Motor Company (16 June 2008)."Honda Announces First FCX Clarity Customers and

    Worlds First Fuel Cell Vehicle Dealership Network as Clarity Production Begins". Retrieved 1

    June 2009.