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<b>MINISTRY OF EDUCATION AND TRAININGHO CHI MINH CITY UNIVERSITY OF</b>

<b>TECHNOLOGY AND EDUCATION</b>

<b>FACULTY OF INTERNATIONAL EDUCATION</b>

<b>Subject: Alternative Energies for Vehicles</b>

FINAL ASSIGNMENT

<b>HYDROGEN FUEL USED FORAUTOMOTIVE ENGINES</b>

Class id: <b>AEVE320830E_23_2_02FIE</b>

<b>Instructor: Nguyễn Văn TrạngReporter: Group 6</b>

Course: <b>2023 - 2024</b>



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<b>GROUP MEMBERS LIST</b>

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<b>TABLE OF CONTENTS</b>

ABSTRACTFIGURE CATALOGABBREVIATIONCONTENT

Chapter 1 Common theories of hydrogen

1.1. Overview of hydrogen...1

1.1.1. Properties of hydrogen...1

1.1.2. Color code of hydrogen...3

1.1.3. Hydrogen production...6

1.1.4. Method for storing and transporting hydrogen fuel...11

1.2. Overview of hydrogen combustion engine...13

1.2.1. History of hydrogen combustion vehicles...13

1.2.2. Classification of hydrogen combustion engine...15

Chapter 2: Technology of hydrogen fuel engine2.1. Hydrogen fuel in spark ignition engine...19

2.1.1. Manifold induction...19

2.1.2. Port injection...20

2.1.3. Spark ignition direct injection...21

2.2. Hydrogen fuel in compression ignition engine...22

2.2.1. Dual fuel mode operation...22

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2.2.2. Compression ignition direct injection...23

2.3. Advantages and disadvantages of hydrogen fuel...23

2.3.1. Advantages...23

2.3.2. Disadvantages...25

Chapter 3: Applications and challenges of hydrogen combustion engine3.1. Fuel efficiency and emission of hydrogen fuel engine in reality...27

3.1.1. Fuel efficiency of hydrogen fuel engine...27

3.1.2. Emission of hydrogen fuel engine...29

3.2. Economic and safety of hydrogen fuel...30

3.2.1. Economic of hydrogen fuel...30

3.2.2. Safety of hydrogen fuel...33

3.3. Potential and challenges in hydrogen fuel used for vehicles...34

3.3.1. Potential of using hydrogen fuel as a replacement for fossil fuels...34

3.3.2. Barriers and challenges of hydrogen fuel...36INFERENCE

REFERENCE

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The transportation sector is a major contributor to global greenhouse gasemissions, necessitating the development of cleaner, more sustainable energysources. Hydrogen fuel emerges as a viable alternative, with its high specificenergy and the ability to be produced from various renewable sources. Whenused in automotive engines, particularly diesel engines, hydrogen has beenshown to enhance system efficiency, increase output power, and significantlyreduce emissions of greenhouse gases, SO , and NO . However, the integration<small>2x</small>of hydrogen fuel into existing internal combustion engines requires carefulconsideration of combustion characteristics and engine modifications to ensureoptimal performance and safety. This assignment reviews the advantages ofhydrogen fuel, the necessary engine adaptations, and the overall impact onvehicle performance and emissions. The findings indicate that while hydrogen-fueled engines present a clear advantage in terms of emissions reduction,challenges such as cost and space requirements for hydrogen storage remain.Nonetheless, the continued development of hydrogen fuel technology forautomotive engines holds great promise for the sustainable advancement of thetransportation sector.

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<b>FIGURE CATALOG</b>

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a. Physical properties:

Hydrogen has physical properties of a colorless, odorless, tasteless,harmless element. The majority of Earth’s hydrogen is present in molecularforms, including water and organic compounds. The commonly seen isotope ofhydrogen embraces one proton, one electron, and no neutrons in each atom.

Hydrogen fuel has a very low density of 0.0899 g/L at standardtemperature and pressure, which is about 14 times lighter than air. It also has avery low viscosity of 0.0085 cP making it easy to flow. It has a very low boilingpoint of -252.9°C and a very low melting point of -259.1°C. It can be liquefiedunder low temperature and high pressure, but it requires a lot of energy to do so.Liquefied hydrogen has a density of 70.8 g/L at -253°C and 1 atm.

Another physical property for hydrogen to be potential for fuel usage is itsvery high specific heat capacity of 14.3 kJ/kg K. This means it can absorb orrelease a lot of heat without changing its temperature much. It also has a veryhigh latent heat of vaporization of 445 kJ/kg, making its absorption or release ofheat occurs in large amount when it changes from liquid to gas or vice versa.

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b. Chemical properties:

Hydrogen is also a potential source of clean and renewable energybecause of its important chemical properties that affect its use as a fuel. First ofall, it has a high energy content per weight, but a low energy density per volume.This means that hydrogen gas can store a lot of energy in a small mass, but itoccupies a large volume at standard temperature and pressure.

Hydrogen also has the property of being flammable and explosive whenmixed with air or oxygen. Its flammability range is between 4% and 75% byvolume in air which makes it ignite spontaneously when exposed to a spark,heat, or sunlight. Even though the combustion of hydrogen gas with oxygenproduces water and a large amount of heat which can be used to generateelectricity or power vehicles, it also produces nitrogen oxides (NO ) as<small>x</small>pollutants.

Moreover, hydrogen is very reactive and can form compounds withalmost all elements, except some of the noble gases. It can react with metals,nonmetals, and organic compounds, forming hydrides, acids, bases, andhydrocarbons. The property cause hydrogen embrittlement, which is theweakening or cracking of metals due to the absorption of hydrogen atoms. Thehydrogen atoms can diffuse into the metal lattice and create internal stresses ordefects that reduce the strength and ductility of the metal.

Therefore, hydrogen is a great source of fuel both for SI and CI.Specifications of the fuel properties of hydrogen are given in figure 1:

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Figure 1: Fuel properties of hydrogen[1]1.1.2. Color code of hydrogen

To produce hydrogen molecules, energy sources and methods are crucialfactors determining the color of hydrogen. Although hydrogen itself is acolorless gas, there are approximately nine color codes assigned to it, reflectingthe sources or processes used in its production. These colors include green, blue,grey, brown, black, turquoise, violet, purple, red, and white. Green hydrogen isgenerated through water electrolysis using electricity from renewable sources,earning its name due to the absence of CO emissions during production.<small>2</small>Electrolysis, also known as water splitting, requires an energy input. While it is

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an environmentally friendly process, electrolysis is energy-intensive but farmore eco-friendly than grey hydrogen production.

Blue hydrogen originates from fossil fuels, yet CO emissions are<small>2</small>captured and stored underground (carbon sequestration). Many companies arestriving to employ carbon capture, utilization, and storage (CCUS) technology toutilize carbon capture for fuel. Since it emits no CO , blue hydrogen production<small>2</small>is classified as carbon-neutral. The capture and storage of carbon dioxide insteadof releasing it into the atmosphere allow blue hydrogen to become a low-carbonfuel. Two primary production methods are steam methane reforming (SMR) andcoal gasification, both involving carbon capture and storage. Blue hydrogenserves as a cleaner substitute for grey hydrogen, although it is expensive due tocarbon capture technology usage.

Green hydrogen is produced by utilizing electricity from clean energysources. It is considered a low-emission or emission-free fuel because it usesenergy sources such as wind and solar power, thus emitting no greenhouse gasesduring electricity production. Green hydrogen is created when water (H O) is<small>2</small>split into hydrogen (H ) and oxygen (O ). Water splitting, also known as<small>22</small>electrolysis, is an energy-intensive process but significantly moreenvironmentally friendly than grey hydrogen production.

Grey hydrogen is derived from fossil fuels and commonly utilizes steammethane reforming (SMR) with water. In this process, CO is generated and<small>2</small>ultimately released into the air. In short, grey hydrogen is produced from fossilfuels such as natural gas or coal, accounting for about 95% of global hydrogenproduction today. The two primary production methods are steam methanereforming and coal gasification. Both processes release carbon dioxide (CO ). If<small>2</small>CO<small>2</small> is emitted into the atmosphere, the hydrogen produced is called greyhydrogen. Grey hydrogen is not considered a low-carbon fuel.

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Black or brown hydrogen is produced from coal. Black and brown refer tobituminous (black) and sub-bituminous (brown) coal types. Coal gasification isa primary method used to produce hydrogen. However, this process is highlypolluting, with CO and carbon monoxide-CO being generated as by-products<small>2</small>and released into the atmosphere.

Turquoise hydrogen can be extracted by using thermal methanedecomposition through the methane pyrolysis process. Although in theexperimental stage, this process removes carbon in solid form rather than CO<small>2</small>gas. Violet hydrogen is produced using nuclear energy and heat through hightemperature electrolysis combined with water splitting.

Red hydrogen is derived from biomass. Biomass can be converted toproduce hydrogen through gasification. Depending on the type of biomass andthe use of carbon capture technology, red hydrogen may have lower CO<small>2</small>emissions than grey hydrogen. If CO is completely captured and no other<small>2</small>emissions occur, it may be considered green hydrogen.

Pink hydrogen is produced through water electrolysis using electricityfrom nuclear power plants. Red hydrogen is produced through water splitting byusing a catalyst at high temperatures with nuclear power providing the energysource. Pink hydrogen refers to hydrogen produced through electrolysis poweredby nuclear energy. Pink hydrogen is sometimes considered green because it doesnot emit or release CO during operation.<small>2</small>

Yellow hydrogen may indicate hydrogen produced through electrolysisusing solar energy. However, it is also used to indicate that electricity forelectrolysis comes from mixed sources. This combination of sources comesfrom the grid and relies on availability and may include renewable energysources to fossil fuels.

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Figure 2: Colour code of hydrogen1.1.3. Hydrogen production

Hydrogen can be produced from diverse, domestic resources, includingfossil fuels, biomass, and water electrolysis using electricity. The environmentalconsequences and energy efficiency of hydrogen production are contingent onthe specific method employed. Multiple initiatives are currently in progress toreduce the costs associated with producing hydrogen.

a. Natural gas reforming/Gasification

The process involves the reaction of natural gas with steam at hightemperatures (700<small>℃</small> - 1,000<small>℃</small>), resulting in a mixture of hydrogen, carbonmonoxide, and a small amount of carbon dioxide. Carbon monoxide furtherreacts with water to produce additional hydrogen. This method is widelyemployed due to its cost-effectiveness, efficiency, and popularity.

The synthesis gas can also be obtained by subjecting coal or biomass tohigh-temperature reactions with steam and oxygen in a gasification furnace.

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This process, known as gasification, transforms coal or biomass into gascomponents. The resulting synthesis gas contains hydrogen and carbonmonoxide, which can be separated by reacting with steam to obtain hydrogen.The steam-reforming process is characterized by being endothermic, whichmeans that heat must be supplied for the reaction to take place.

Steam-methane reforming gasification:

This well-established production process in which high-temperature(700<small>℃</small> - 1,000<small>℃</small>) is utilized to produce hydrogen from methane sourceslike natural gas. In the steam-methane reforming process, methane reactswith steam at a pressure of 3 -25 bar (1 bar = 14.5 psi), facilitated by acatalyst, resulting in the production of hydrogen, carbon monoxide, and aminor amount of carbon dioxide. The steam-reforming process ischaracterized by being endothermic, which means that heat must besupplied for the reaction to take place.

Afterward, in a process known as “water-gas shift reaction,” carbonmonoxide and steam are chemically reacted with the aid of a catalyst toyield carbon dioxide and a higher amount of hydrogen. In the final stageof the process, referred to as “pressure swing adsorption,” carbon dioxideand various contaminants are eliminated from the gas stream, leavingbehind pure hydrogen. Steam reforming can also be employed to generatehydrogen from alternative fuel sources (such as ethanol, propane, or evengasoline).

Partial oxidation gasification:

In the partial oxidation process, methane and other hydrocarbonspresent in natural gas undergo a reaction with a limited supply of oxygen,typically obtained from air. This limited oxygen quantity is insufficientfor the complete oxidation of hydrocarbons into carbon dioxide and water.

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Consequently, the reaction primarily yields hydrogen, carbon monoxide(and nitrogen when air is used instead of pure oxygen), along with a smallamount of carbon dioxide and other compounds.

Subsequently, in the water-gas shift reaction, carbon monoxidereacts with water to produce carbon dioxide and a larger quantity ofhydrogen. The partial oxidation process is exothermic and generally fasterthan steam reforming, requiring a smaller reaction vessel. Comparatively,the partial oxidation process initially produces a lower amount ofhydrogen per unit of input fuel when compared to steam reforming of thesame type.

Partial oxidation of methane reaction:

<small>2</small>^O<small>2→ CO+2 H2(+ eatℎ)</small>

Water-gas shift reaction:

<small>CO+ H2O →CO2+ H2(+small amount of eatℎ)</small>

b. Electrolysis

Electrolysis is an essential process that uses electricity to split water intohydrogen and oxygen with a device called an electrolyzer. Electrolyzers canrange in size from small-scale devices suitable for decentralized hydrogenproduction to large-scale facilities that can be directly integrated with renewablepower sources.

Similar to fuel cells, an electrolyzer consists of a positive electrode(anode) and a negative electrode (cathode) separated by an electrolyte. Differentelectrolyzers operate in various ways, primarily determined by the specificelectrolyte material used and the type of ions it conducts.

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When the electric current is passed through the water, several chemicalreactions occur at the electrodes. At the cathode (negative electrode), watermolecules (<small>H</small>₂<small>O</small>_{) gain electrons, resulting in the reduction of water and the}

formation of hydrogen gas (<small>H</small>₂_):<small>2 H2O+2 e−</small>

<small>+ H2</small>

At the anode (positive electrode), water molecules lose electrons throughthe process of oxidation, leading to the production of oxygen gas (<small>O</small>₂) andpositively charged hydrogen ions (<small>H+¿¿</small>

<small>2 H</small>₂<small>O →O</small>₂<small>+4 H+¿+4 e−¿</small>

c. Biomass - Derived liquid reforming

Liquid derived from biomass sources, such as ethanol and biofuels, can beconverted to produce hydrogen in a process similar to natural gas reforming.Liquid biomass-derived fuels can be more easily transported than their bulkbiomass counterparts, enabling centralized production or decentralized hydrogenproduction at fueling stations.

The liquid fuel reacts with steam at high temperatures in the presence of acatalyst to create synthesis gas, consisting mainly of hydrogen, carbonmonoxide, and some carbon dioxide. Additional hydrogen and carbon dioxideare generated by reacting carbon monoxide (produced in the first step) withsteam at high temperatures in a "water-gas shift reaction." Finally, hydrogen isseparated and refined.

Steam Reforming Reaction (ethanol):

<small>C2H5OH+H2O</small>(<small>+ eatℎ</small> )<small>→2 CO+4 H2</small>

Water-Gas Shift Reaction:

<small>CO+ H2O →CO2+ H2(+small amount of eatℎ)</small>

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d. Microbial biomass conversion

Biomass can be converted into sugar-rich feedstock, which can befermented to produce hydrogen. Microbial biomass conversion processes exploitthe ability of microorganisms to consume and digest biomass, releasinghydrogen in the process. Depending on the pathway, this research could lead tocommercially viable systems in the medium to long term.

In fermentation-based systems, microorganisms, such as bacteria, breakdown organic matter to produce hydrogen. The organic matter can be refinedsugars, raw biomass sources like corn stalks, or even wastewater. Because theydon't require light, these methods are sometimes referred to as "darkfermentation".

In direct hydrogen fermentation, bacteria naturally produce hydrogen.These bacteria can break down complex molecules through various pathways,and the byproducts of some pathways can be combined by enzymes to producehydrogen. Scientists are researching ways to make hydrogen fermentationsystems faster (improve reaction rates) and more productive, generating morehydrogen from the same amount of organic matter (increase yield).

Microbial electrolysis cells (MECs) are devices that harness the energyand proton produced by bacteria breaking down organic matter, combined with asmall supplemental electric current, to generate hydrogen. This technology isrelatively new, and researchers are working to improve many aspects of thesystem, from finding lower-cost materials to identifying the most effective typesof bacteria to use.

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Figure 3: Schematic diagram of Microbial biomass conversion[2]1.1.4. Method for storing and transporting hydrogen fuel

Hydrogen fuel is a potential alternative to fossil fuels, but it also carriesrisks of combustibility, electric shock, embrittlement…. To apply this superiorenergy source in vehicle, storing and transporting technology is needed to beconsidered precisely.

Main methods for storing hydrogen fuel are:Compressed hydrogen storage:

There is a method of storing hydrogen gas in high-pressure tanks,typically 350–700 bar (5,000–10,000 psi). This method is widely used forhydrogen vehicles, but it requires expensive and heavy tanks and reducesthe cargo space.

Liquid hydrogen storage:

Hydrogen can be stored as a liquid in cryogenic tanks at very lowtemperatures, around -253°C. This way allows for higher density andlonger range than compressed hydrogen. However, it requires a lot ofenergy to maintain the low temperature and causes boil-off losses.

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Metal hydrides storage:

Another way of storing hydrogen is absorbing it into certain metalsor alloys at moderate temperatures and pressures. This method can store alarge amount of hydrogen in a compact and safe way, but it also requireshigh heat to release the hydrogen with a higher cost.

Chemical hydrides storage:

Hydrogen is stored by binding it to chemical compounds that canrelease it upon demand. Although the method can achieve high densitiesand low pressures, it involves complex reactions and catalysts and mayproduce harmful by-products.

Adsorption materials storage:

The adsorption of hydrogen occurs on the surface of porousmaterials such as activated carbon or metal-organic frameworks. Thismethod can store hydrogen at low temperatures and moderate pressures,but it also has a low capacity and a slow kinetics.

Moving on to hydrogen fuel transportation, this is the process ofdelivering hydrogen from the point of production to the fueling station or powergenerator. Hydrogen can be transported in different ways, depending on thedistance, demand, and cost and the main methods are:

Pipeline: Hydrogen can be transported as a pressurized gas throughpipelines, similar to natural gas. This method is suitable for regions withhigh and stable demand, such as industrial clusters or urban areas.Pipelines can offer low-cost and reliable delivery, but they require highinitial investment and maintenance.

Cryogenic liquid tanker: Hydrogen can be transported as a liquid insuper-insulated, cryogenic tanker trucks. This method is suitable for

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longer distances and lower demand, such as remote or rural areas. Liquidhydrogen has a higher energy density than gaseous hydrogen, but itrequires energy-intensive liquefaction and vaporization processes.

Gaseous tube trailer: Hydrogen can be transported as a compressedgas in tube trailers, which are trucks with multiple cylinders. This methodis suitable for shorter distances and smaller demand, such as backup oremergency supply. Gaseous hydrogen has a lower energy density thanliquid hydrogen, but it does not require liquefaction or vaporization.

Chemical carrier: Hydrogen can be transported as a chemicalcompound that can release hydrogen on demand, such as metal hydrides,ammonia, or methanol. This method is suitable for long distances andlarge-scale applications, such as export markets or maritime transport.Chemical carriers can offer high energy density and safety, but theyrequire additional conversion steps and may have environmental impacts.At the point of use, hydrogen fuel needs additional infrastructurecomponents, such as storage tanks, compressors, dispensers, meters, andpurifiers. Therefore, the choice of storing and transporting method with itsinfrastructure depends on various factors, such as the source, quality, quantity,and end use of hydrogen.

1.2. Overview of hydrogen combustion engine1.2.1. History of hydrogen combustion vehicles

The journey of hydrogen as a fuel for internal combustion engines spansover two centuries, marking a fascinating evolution in automotive technology.Back in the early 19th century, visionaries like Franỗois Isaac de Rivaz and Rev.W. Cecil pioneered the concept of hydrogen-powered engines. Rivaz'sinnovative design in 1807 birthed the first hydrogen-oxygen combustion engine,

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propelling a prototype vehicle with a manual control mechanism for fuelinjection and ignition, reminiscent of modern combustion engines.

The momentum continued with Etienne Lenoir's breakthrough in 1860,introducing a practical small horizontal gas engine fueled by hydrogen, derivedfrom water electrolysis. Lenoir's engine, though initially hydrogen-based, lateraccommodated other gases like coal gas, showcasing versatility. Subsequently, ahydrogen-fueled vehicle equipped with Lenoir's engine completed a significanttest drive in 1863, marking a milestone in automotive history.

Despite early promise, hydrogen engines faced formidable challenges,including lower efficiency compared to hydrocarbon engines and storage issues.The dominance of fossil fuels, economically supported by established extractionand refining methods, hindered widespread adoption of hydrogen as anautomotive fuel.

However, the tides shifted during and after World War I and II, ignitingrenewed interest in hydrogen as a viable alternative. Rudolf Erren's pioneeringwork in the 1920s laid crucial groundwork, despite setbacks caused by wartimedestruction. Erren's experimentation with direct hydrogen injection in gasolineand diesel engines set a precedent for future advancements.

Remarkably, even amidst global conflicts, instances like Boris Shelishch'sconversion of trucks to hydrogen in 1941 during the siege of Leningraddemonstrated hydrogen's resilience and efficacy in dire circumstances.

The 1970s witnessed a resurgence of interest in hydrogen engines, fueledby environmental concerns stemming from fossil fuel emissions. Initiatives byresearchers like Roger Billings and institutions in Japan and Germany propelledhydrogen combustion engine development, culminating in the introduction ofthe first Japanese hydrogen vehicle in 1974 and subsequent technologicalrefinements.

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Collaborative efforts between BMW, Mazda, and research institutionsfurther propelled hydrogen engine technology into the 20th century. This era notonly showcased the feasibility of hydrogen in existing engine designs but alsoset the stage for future innovations.

Entering the 21st century, the evolution of hydrogen-powered vehiclesunfolds with a plethora of new models and advancements, driving theboundaries of automotive engineering forward. The trajectory of hydrogen as afuel for internal combustion engines embodies human ingenuity, perseverance,and an unwavering commitment to sustainable transportation solutions.

Figure 4: The history of hydrogen vehicles1.2.2. Classification hydrogen internal combustion engine (HICE)

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