This research projects seeks to investigate the use of hydrogen energy on aircrafts and how it works. In order to attain this aim, the research has focused on various objectives, which encompass the extraction and production of hydrogen energy, the benefits and drawbacks, the characteristics and properties of hydrogen, the storage and transportation, safety and environmental considerations, and the modification of aircrafts. In doing so, the research has assisted in achieving the main aim of the project. As compared to other fossil fuels, hydrogen energy is preferred to power aircrafts due to its various advantages compared to the latter ones. Some companies, including the German Aerospace Center, the Lange Aviation, and the Boeing, use hydrogen energy on aircrafts for unmanned and manned airplanes, and these are some of the examples, which show the use of hydrogen energy for aircrafts. The use of hydrogen energy is deemed to solve various problems of fossil fuels, and, besides, offer a promising energy supply, thus, this provides the independence amongst states.

It is true that fossil fuels including coal, natural gas, and petroleum mostly employed as the energies in the contemporary society are being used up quickly. Besides, the studies have proven that the combustion of these fossil fuels produces such products that are causing the major worldwide problems encompassing the pollution, acid rain, the depletion of ozone layer, and the greenhouse effect. These products are, in their turn, evidenced to pose the vast danger to the whole environment and, in general, for the entire life. According to most scientists and engineers, this global problem can be solved by replacing the subsisting fossil fuel system with a hydrogen energy system; as the latter one is believed to be the clean and efficient fuel. This is evidenced by the fact that combusting hydrogen gas does not result or produce such products as greenhouse gases, the pollution, ingredients of acid rain, and the ozone layer reducing chemicals. Furthermore, hydrogen that is generated from the renewable energy, such as wind and solar, leads to a long-lasting energy system that cannot be modified. The worldwide employment of fossil fuels such as energy is speedily leading to the severe environmental predicaments all over the globe. Such matters as the political, economic and energy crises, in addition to the health of animals, plants and humans are being the essential concerns. As a result, there is an imperative requirement of putting the hydrogen technology into the operation, as this would eradicate most of these predicaments and their impacts.

 

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The desirable and unique features of hydrogen have made it to be recognized as the fuel to be applied as the fuel for engines. Hydrogen is evidenced to be the only fuel generated completely from such renewable resource as water. In general, the practicability of hydrogen as the fuel and specifically for engine applications significantly depends on the efficient, satisfactory and economic solutions of various limiting predicaments. Such limitations that impede the extensive application of hydrogen as the engine fuel are principally linked to various factors including how it is produced, stored, transported, and concerning its purity amongst other factors. Compared to the present and future use of other fuels, these drawbacks of hydrogen can be deemed to be more critical.

Over the past decades, the application of hydrogen as the fuel for engines has been tried on limited circumstances, which offered some unreliable degrees of success. In this case, there is the need to focus on the literature of the same kind to find out how various investigators have put forth regarding the project topic. Besides, there is the need to focus on various factors such as characteristics, properties, extraction, production, storage, transport, safety, and environmental considerations, which are all the important objectives; they will put forth and give a clear understanding on the topic. In general, the project will be concerning the usage of hydrogen as the fuel for aircrafts and how this will work.

• The research has been done; it has found out about the fact that hydrogen could be the best and the only fuel which will be used in future.
• It is widely believed that hydrogen is the best fuel to be used.
• Hydrogen is the lightest element by nature and it contains a large amount of energy in its chemical bond.
• Hydrogen is the natural gas because its efficiency is high, and the production cost is relatively low.
• The pressurized hydrogen gas can be transported via pipelines.
• It has a low density; liquid hydrogen weighs less than petroleum-based fuels.

Hydrogen energy is proposed to be used in order to solve the numerous negative impacts, which are linked with fossil fuels that generally produce and release carbon to the environment (Rigden, 2003). The contemporary interest in the use of hydrogen fuel finds its roots from a technical report of 1970s in the University of Michigan (Jones, 1970). Currently, the transportation (by vehicles, ships, aircrafts, etc.) is principally fueled by petroleum. Apparently, combusting of fossil fuels releases carbon dioxide amongst other pollutants. According to studies, the use of hydrogen energy across the globe is limited due to the limited supply of hydrocarbon resources, whereas the demand for fuels is very high especially in such developing countries as India and China (Hordeski, 2009).

According to the proponents of hydrogen energy, the fuel is environmentally clean, especially when used for the transportation, as it does not release pollutants (Holland and Provenzano, 2008). According to the analysis carried out in the year 2004, the hydrogen supply chain emits a little amount of carbon dioxide as compared to other fossil fuels, and, besides, the use of carbon sequestration and carbon capture techniques during the production of hydrogen would reduce considerably the emission of carbon dioxide (Holland and Provenzano, 2008). Certainly, in terms of weight, the energy density of hydrogen is very low. The maximum efficiency of an internal combustion engine is evidenced to be high (approximately 38 percent); 8 percent higher as compared to the combustion engine fueled by gasoline (Peschka, 1998).

Compared to an internal combustion engine, fuel cells are deemed to be very effective. Nevertheless, fuel cells require the high capital costs, and this is the main impediment towards its development. This implies that technically fuel cells are very efficient compared to the combustion engine, but in economic terms, the latter one is deemed to be effective. Other impediments of hydrogen energy encompass the purity of hydrogen (the requirement is 99.999 percent) and storage problems (Peschka, 1998).

For this reason, this project is significant in analyzing the use of hydrogen energy in aircrafts. By doing so, this will offer the knowledge how to overcome the problem that the hydrogen production depends on the availability of a non-renewable resource. In addition, it will provide the knowledge to the aircraft department; so they can publish the information for designers and engineers.

The purpose of this project is to provide a full Hydrogen Powered Aircraft explanation that includes specific details on the hydrogen fuel, its benefits, drawbacks, and how to overcome the problem that the hydrogen production depends on the availability of a non-renewable resource. What else may this knowledge give to the aircraft department in order for them to publish the information for designers and engineers?

This project will show the research and explain the following objectives:

•          Explaining the use of hydrogen as the fuel for aircrafts and how this may be implemented;

•          Explaining the characteristics of hydrogen;

•          Investigating how to extract hydrogen, and how it will be used;

•          Explaining the production of hydrogen;

•          The research will be done to know the best way of the hydrogen storage;

•          Explaining how to transport hydrogen;

•          Investigating the safety of hydrogen;

•          Researching the environmental considerations linked with the hydrogen production;

•          Modifying aircrafts;

•          The use of hydrogen energy for aircrafts.

•          Will allow aircrafts to be modified;

•          Will improve environmental issues;

•          Will make the fuel weight less;

•          Will have less money spent.

The research will mainly contain the data collected from the secondary sources. This will include peer reviewed journals and textbooks. In addition, it will entail the review of records of the companies that have made the use of hydrogen as a fuel to power engines.

The project has five distinct chapters that seek to explicitly analyze and investigate the use of the hydrogen energy on aircraft. The Chapter one offers the introduction of the project, the background, the project, aims and objectives, the outline of methodology, and the structure of the project. The Chapter Two covers extensively the literature review on various concepts of hydrogen, including its benefits, drawbacks, characteristics and properties, safety, extraction and production, environmental considerations, storage and transport of hydrogen energy. The Chapter three is the Research Methodology, which covers the research strategy, data collection methods, limitations of study, and the chapter summary.

The Chapter four will highlight in details the results and discussions of the research study. The Chapter five will provide the conclusions and recommendations. A reference list/bibliography and appendices used in the study shall follow the last chapter.

Chapter Two

Most scientists believe that the global problems, which have been caused by byproducts of fossil fuels, can be overcome by replacing the subsisting fossil fuel system with a hydrogen energy system, as the latter is believed to be the clean and efficient fuel (Evers, 2010). This is evidenced by the fact that combusting hydrogen gas does not result into or produce such products as greenhouse gases, pollution, ingredients of acid rain, and ozone layer reducing chemicals (Peschka, 1998). Furthermore, hydrogen that is generated from such renewable energy as wind and solar leads to a long-lasting energy system that cannot be modified. The worldwide employment of fossil fuels as energy is speedily leading to severe environmental predicaments all over the globe. Such matters as political, economic and energy crises, in addition to the health of animals, plants and human, are all essential concerns. As a result, there is an imperative requirement of passing to the operation hydrogen technology, as this would eradicate most of these predicaments and their impacts (Evers, 2010). Currently, some companies including the German Aerospace Center, the Lange Aviation, and the Boeing use hydrogen energy for aircrafts for unmanned and manned airplanes, and these are some of the examples, which show the use of hydrogen energy for aircrafts.

According to past researches, hydrogen is not like the other fossil fuels, which are either extracted or mined. The gas is unique as it must be produced (Yürüm, 1995). Apparently, hydrogen is produced from a number of resources, which include such domestic resources as fossil fuels, which encompass the coal, natural gas, biomass, and nuclear as well as some renewable energy technologies; for instance, solar, geothermal, wind and hydroelectric power (Peavey, 2003). Hydrogen is a vital energy carrier due to the fact that it has a great potential for the diversity of supply. It is possible to produce hydrogen at big plants if they are distant from the end use; they should be from 25 to 100 miles from the point starting from the end-use. In addition, it could be produced from small distributed units if they are located closer to the point of the end use, for instance, at some stationary power sites or refueling stations (Yürüm, 1995).

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It is apparent that across the globe researchers have continued to develop a number of technologies aimed at producing hydrogen in the most economical ways from various resources available in the environmentally friendly way (Holland and Provenzano, 2008). A process known as the steam methane reforming may produce hydrogen. This is a method for producing hydrogen from methane into natural gas by using the high temperature steam (Peavey, 2003). Apparently, the steam methane reforming process accounts for around 95% of hydrogen used in the United States presently. In addition, hydrogen can be produced by the process called the partial oxidation. This process produces hydrogen by burning methane into the air. According to experts, these two processes produce the synthesis gas which, during the reaction with water, produces hydrogen (Peavey, 2003).

Another process used to produce hydrogen gas is a renewable electrolysis method. Evidently, this method uses the electric currency to split water into the constituents of hydrogen and oxygen. The required electricity is generated from the use of renewable energy technologies, for instance, geothermal and hydroelectric power, solar and wind. Hydrogen is also produced directly from coal by the process known as gasification (Yürüm, 1995). Gasification is a process where the biomass or coal is converted into gaseous components by applying heat under pressure and in the presence of steam. Evidently, a consequent series of chemical reactions produces the synthesis gas that reacts with steam to produce more hydrogen, later separated and purified (Yürüm, 1995). Producing hydrogen from the burning coal directly has been proven to be more efficient than the actual burning of coal directly to produce electricity; that is then used to produce hydrogen. The studies indicate that experts are in the process of developing the carbon capture as well as the sequestration to ensure that the carbon dioxide produced during the hydrogen production process and is controlled (Holland and Provenzano, 2008). This, in return, will ensure that hydrogen produced from the direct burning of coal is nearly zero greenhouse gas emissions (Holland and Provenzano, 2008).

Alternatively, hydrogen can be produced through the renewable liquid reforming process (Yürüm, 1995). This is a process, whereby the biomass is processed to produce some renewable liquid fuels, for example, bio-oil and ethanol. These liquids can then be mixed with the high temperature steam to produce hydrogen at the point of the end-use (Yürüm, 1995). It is apparent that hydrogen can be produced through the photo biological and photo electrochemical processes (Yürüm, 1995). When microbes, for instance, cyanobacteria and green algae in the presence of sunlight consume water, they produce hydrogen through a metabolic process. Similarly, the photo electrochemical and photo biological processes produce hydrogen from water by using special semiconductors as well as the energy from the sunlight (Yürüm, 1995).

Energy from hydrogen can be extracted through two major ways, which encompass the burning in turbine engines or in internal combustion engines (ICE's); or by using a fuel cell and converting it into electricity.

Mazda, BMW and Daimler-Benz have developed and tested internal combustion engines fueled with hydrogen and revealed that hydrogen can efficiently be employed as an engine fuel. Hydrogen is also useful in powering aircraft gas turbines. This was proven in 1988 when a triple-jet-powered and customized Tupolev-154 airliner flew to Russia using hydrogen. Russia in the cooperation with Daimler-Benz Aerospace Airbus (DASA) developed an aircraft that was powered by liquid hydrogen. Nevertheless, this development had a disadvantage that required the adjustments in components and manufactured parts in order to be capable to handle the Cryogenic liquid hydrogen, which obtains the very low temperatures ranging from 150 degrees by Celsius to 273 degrees by Celsius.

The second method of extracting energy from hydrogen, which involves the use of fuel cells to convert hydrogen into energy, is deemed to be a more efficient method compared to the initial method. According to the research, fuel cell drive models with extremely effective electric drive systems may offer more effective fuel solutions for the engine propulsion compared to internal combustion engines with mechanical transmission systems. Apparently, fuel cells directly change the chemical energy into electricity, thus, losing less energy compared to internal combustion engines. The amount of the electric output produced from fuel cells is evidenced by power electric engines, and, besides, in the contemporary world, individuals are developing and testing the engines with fuel cells.

Presently, individuals are developing various kinds of fuel cells. They encompass the proton-exchange membrane (PEM), which is normally deemed to be the most efficient fuel cell used in automotives, including light trucks. Some of the advantages, which make the proton-exchange membrane to be considered efficient in comparison with other fuel cells, include: the low functioning temperature that allows speedy starts; the power density (the quantity of power it produces for its size and weight) is sufficiently high for the light duty automobiles. In Germany, various experiments have been carried out by the use of the proton-exchange membrane in fuel-cell-powered automobiles. According to the experiment, the fuel cells, together with electric drive vehicles, are capable of moving 18-metric-ton vehicles reliably and efficiently.

Hydrogen fuel is better than burning fossil fuels; for example, coal oil or natural gas in regulating the air conditioning in our buildings or in vehicles as fuel; unlike these fossil fuels, which have a negative effect on the environment as a rise at particular levels and global warming. The only side product of running a hydrogen-powered fuel cell would be oxygen and water, neither of which is harmful to human beings and the environment, in general.

Hydrogen is also used as a form of electricity when combined with oxygen in a fuel cell. The electricity is used in powering vehicles and as a source of heat; and since the only by-products of this is oxygen and water, no other conservatory gases or other particulates are emitted.

Hydrogen is also beneficial since it can also be created locally from several sources. It can be produced centrally and then be circulated to its destination of use. Hydrogen is produced from water, biomass, coal, methane or gasoline, and, therefore, this makes it easier to produce due to numerous sources.

When hydrogen is produced from water, there will be a sustainable supply of power. The production of hydrogen and oxygen from water is done through a process known as electrolysis. The renewable energy is used to power electrolyzers, which, in turn, generate hydrogen from water. The use of the renewable energy contributes to a sustainable method, which is free from those products made of petroleum and do not cause the pollution. The examples of renewable sources include: tidal, hydro, wind, and solar energy. After the production of hydrogen into the electrolyzer, it is used in a fuel cell to manufacture the electrical energy. Out of this, there is the production of heat and water. If energy cells function at elevated temperatures, the system can be arranged as a co-generator, and the dissipated energy is used to heat.

Apart from electrolysis, the manufacture of hydrogen has been consummated by a reaction of dissipated aluminum. The final products being alumina and hydrogen are used again to create aluminum.

Today, the use of hydrogen is being applied in powering the commercial vehicles both by inner ignition engines burning of hydrogen and added fuels combined and exclusively used in fuel cells. Hydrogen is also useful in numerous business applications, like dying of fabrics, the production of fertilizers, making electronics, welding metal and the creation of plastics. When a renewable cost-effective viable manufacturing process of hydrogen is realized, the advantages are extended on many industries. The proving basis for different methods of production can be locally realized to supply these industries with hydrogen.

The sources of the renewable energy are frequently inadequate for the business use because of their irregular availability, for example, the wind might not blow or there might be the inadequate sunshine, therefore, hydrogen can act as a vital link used as a medium of storage in supplying power in these periods. Hydrogen can be utilized as a movable energy source through the compression and then being stored in tiny tanks used like those of propane or gasoline.

As much as hydrogen in the state of fuel is well compared to other fossil fuels, there is a number of issues hanging over this know-how. To start with, hydrogen is more an energy mover related to an energy supplier. While hydrogen constantly exists combined with other elements like water, it must be extracted and, therefore, regarded as a carrier of energy as contrasted to the source, hydrogen is also considered to be expensive when converted into a liquid. Since hydrogen is gas, it is impossible to compress it into liquid without high costs and the input of energy. Hydrogen is the lightest component on the earth, and when it is in the form of gas, it dissipates fast; therefore, it is very difficult to compress this gas. For that, the cost of the hydrogen gas production is rather expensive. Still the units of electrolysis in the HHO generators are used in boosting hydrogen apparatus like in Water4Gas and come at the horsepower expenses. Electricity is needed to produce the HHO gas. It is in this case that the economy of fuel is reduced through the same ways with an attempt to improve it.

Hydrogen as a fuel is also harmful to produce it; other fuels made from fossils may still be needed. In this, other ways of the hydrogen production must make the use of energy to split hydrogen from oxygen; and it may require the fossil fuels like oil or coal. In this, the use of fossil fuels is being evaded with that of coal, a chief component for hydrogen, which contributes to a great extent to the pollution.

By its nature, hydrogen is known to be a very powerful form of fuel, and it is, therefore, also used for making bombs and if not used in the right way it may prove to be hazardous to the environment and the living things, in general. It is exceedingly reactive, flammable and combustible, and an example of how dangerous hydrogen is was evident during Hindenburg disaster where a blimp filled with hydrogen exploded and a lot of people lost their lives.

Therefore, hydrogen should be handled very carefully, and this should be done by storing it at the very low temperatures and elevated pressure. 

Hydrogen is characterized by both chemical and physical properties giving its fuel characteristic feature (Yürüm, 1995). Hydrogen gas is odorless and colorless. It has a molecular weight of around 2.016. According to studies, it is considered to be the lightest element. It has a density that is 14 times less than of air. The density is about 0.08376 kg/m3 at a standard pressure as well as temperature. At the atmospheric pressure and temperatures below 20.k hydrogen is liquid. Compared to all other fuels, hydrogen has the highest energy content per unit mass. Its heating value is 141.9MJ/kg - three times higher as compared to that of gasoline (Yürüm, 1995).

It is apparent that hydrogen has the most different characteristics as compared to other common fuels (Rigden, 2003). As indicated by studies, some of its properties make it less hazardous, whereas other characteristics make it more dangerous theoretically in a number of situations. The unique features of hydrogen make it significantly well suited in the principle to the powered aircraft. Evidently, at a wider range of pressure and temperature, hydrogen is known to have the very high flammable propagation rates in powered aircrafts and in comparison with other fuels. According to studies, the rates remain extremely high including the rates in the very lean mixtures, which are away from the stoichiometric mixture region (Rigden, 2003). The energy release associated with it is very fast, and, as a result, it shortens the combustion duration leading to the production of the high power output as well as increased high rates of pressure due to the spark ignition. The operation on lean mixtures mixed in a spark ignition engine is quite slow as compared to those of other fuels. Evidently, this allows to make the lean mixtures stable as well as to control them in hydrogen powered aircrafts (Peschka, 1998). Scholars have revealed that the operation on lean mixtures in the amalgamation with the fast combustion energy gives out the rates around the top dead centers linked to a very rapid burning of hydrogen and air mixtures, and, as a result, there are the high-output efficiency values. Nevertheless, this kind of lean mixture operations result into the simultaneously lower power output for any given engine size.

Among important features of the hydrogen-powered craft operations are the fact that they are linked to less undesirable exhaust emissions as compared to other fuels (Peschka, 1998). It has been proven that hydrogen fuel emissions contain no unburnt carbon monoxide, hydrocarbons, carbon dioxide smoke, particulates, or oxides of sulfur. The only emissions from the hydrogen fuel are the oxides of nitrogen as well as the water vapor. Besides, hydrogen has a fast burning characteristic (Rigden, 2003). As evidenced by experts, it is due to this characteristic that hydrogen allows a satisfactorily high speed operation for hydrogen powered crafts. As a result, this allows the increased power output with a reduced power penalty for the operation of lean mixtures. In addition, hydrogen has a remarkably low boiling point. This is an element that leads to reduced problems, which are mostly encountered with its operations in the cold season.

Having the spark timing varying in hydrogen powered craft operations ensures that an engine has been effectively improved, and that the possibility of the engine knocking has been avoided. Apparently, the heat transfer feature of hydrogen-powered crafts is different from powered crafts operating on other kinds of fuel. The radioactive component of the heat transfer tends to be small, yet the convective component can be higher, especially for lean mixture operations (Yürüm, 1995). Moreover, the sensitivity element of the oxidation reaction for hydrogen to catalytic actions with a good control can be used to serve as a positive drive to enhance the performance of the powered craft.

Hydrogen is not different than other gases and if not controlled or handled in a right manner, it poses few risks. Usually, the risk of hydrogen is considered relative as compared to other common kinds of fuel, such as gasoline, diesel, and kerosene (Peschka, 1998). Evidently, hydrogen has the smallest molecule in comparison with other kinds of fuel. Due to this element, its tendency to escape through small openings is quite high as compared to other liquid or gaseous fuels. On the basis of hydrogen properties, for instance, viscosity, density, and the diffusion coefficient into the air, in addition, its propensity to leak through holes and joints of low pressure fuel lines may be only from 1.26 to 2.8 times faster than the natural gas leakage through the same hole and not 3.8 times faster as frequently assumed, based solely on diffusion coefficients (Holland and Provenzano, 2008).

For each large leak from a high-pressure storage tank, the rate is limited by the sonic velocity. For this reason, hydrogen will begin with the escape at a high rate as compared to other fuels. If the leak occurs for any given reason, hydrogen disperses much faster than any other fuel. Due to this reason, its hazardous effect is reduced (Peschka, 1998). It is apparent that hydrogen is more buoyant as well as more diffusive in comparison with either gasoline or any other fuel.

According to the research, hydrogen or air mixture can burn in the high volume ratios approximately between 4 % and 75 % of hydrogen in the air (Rigden, 2003). Apparently, the flammability of other gases is quite lower. For instance, the flammability of gasoline is about from 1.2 to 6 percent. Nevertheless, the range has a less practical value. In most leak situations, what determines the ignition capability of the leak is its low flammability limit. The lower flammability limit of hydrogen is four times higher as compared to that of gasoline and approximately 1.9 times higher than that of kerosene.

The studies have revealed that the ignition energy of hydrogen is about 0.02mJ that makes it have the lowest order magnitude as compared to other fuels. The ignition energy is an element of air or fuel ratio. Hydrogen reaches its minimum at around from 25 to 30 per cent content of hydrogen in the air. In addition, hydrogen has the flame velocity, which is approximately 6 times faster as compared to that of gasoline (Rigden, 2003). This, therefore, means that the hydrogen fuel would most likely progress to a detonation in comparison to other fuels. The likelihood of the detonation, however, depends highly on the exact ratio of fuel or air, the temperature, and especially the geometry of the confined space (Holland and Provenzano, 2008). In an open space, the detonation of hydrogen is highly unlikely. The lower detonability fuel or air ratio for hydrogen is between 13 and 18 percent. This about 12 times higher as compared to that of gasoline. The research has indicated that the limit of the lower flammability is 4 percent. This, therefore, means that the explosion is only possible under some unusual scenarios. For instance, hydrogen has, first of all, to accumulate as well as to reach the concentration of 13 percent in a closed space without the ignition. It is only then that the ignition source would be affected.

In the case of explosion, the effect of explosion would not be so high if the one is using the hydrogen fuel. This is because hydrogen has the lowest explosive energy per the unit-stored energy in the fuel. For this reason, therefore, a given volume of hydrogen would have 22 times lower level of the explosive energy than the same volume filled with the gasoline vapor (Holland and Provenzano, 2008).

Nevertheless, the hydrogen flame is almost invisible. Apparently, this is very dangerous as people in the vicinity of the hydrogen fire may not realize when there is the fire (Peschka, 1998). To solve such a problem, it requires the necessary chemicals to be provided with the required luminosity. The low emissivity of hydrogen flames designates that the nearby materials as well as people will be at a lower position to ignite and/or to get harmed by a radiant heat transfer (Rigden, 2003). It is evident that the fumes and soot from the gasoline fire pose a risk to anyone inhaling this smoke, while hydrogen fire produces only the water vapor (Holland and Provenzano, 2008). 

Apparently, the liquid hydrogen offers a different set of safety issues, for instance, the risk of cold burns as well as the increased duration of the leaked cryogenic fuel. According to Holland and Provenzano (2008), a large spill of the liquid hydrogen has the similar characteristics as the spill of gasoline. However, the spill of the liquid hydrogen dissipates faster than the spill of gasoline. Hydrogen may also be hazardous if it is in a vehicle. Apparently, the hazards ought to be considered in such circumstances when the vehicle is not acting or when the car is in its standard operation and in collisions (Peschka, 1998). The potential hazards as a result of hydrogen are happening to the fire. The fire and explosions from hydrogen mostly come due to the poor fuel storage and the mishandled supply line (Hordeski, 2009).

Certainly, hydrogen is the cleanest fuel that is available in the world. Gas turbine engines and hydrogen-fueled internal combustion engines (ICE’s) have small emissions, which result into the air pollution. In addition, the hydrogen-powered-fuel-cell motor vehicles have been evidenced to have no emissions. In contrast, the engines that make use of petroleum fuels usually produce considerable quantities of air contaminants (including carbon monoxide, hydrocarbons, sulfur oxides, nitrogen oxides, among other emissions); air toxins (such human carcinogens, as benzene, acetaldehyde, butadiene, and formaldehyde); and carbon dioxide. These pollutants are evidenced to have the minor and serious health impacts and include headaches and major respiratory diseases, including lung cancer.

Furthermore, burning of hydrogen is proven to lead to small emissions. According to studies, when hydrogen is burned with air in gas turbines or in internal combustion engines under suitable conditions, it produces very low pollutants. On the other hand, the production of carbon monoxide and hydrocarbon usually results merely from the burning of motor oil into internal combustion engines. Moreover, the emissions of nitrogen oxides amplify exponentially depending on the burning temperature. Thus, during the combustion, these emissions can be swayed through the suitable procedure control. The sulfur and particulate emissions are, on the other hand, restricted to small amount of lubricant remnants. In fact, the studies have put forth that the use of hydrogen in fuel aircraft gas turbine engines results to a zero generation of carbon dioxide, at the same time reducing the emissions of nitrogen to eighty percent.

Moreover, when hydrogen is used in some fuel cell momentum systems with the use of low temperatures, it is apparent that the fuel cell totally gets rid of all polluting emissions. In fact, the only byproduct that is obtained from the electricity generation using the atmospheric oxygen and hydrogen is water.

Apparently, compared to other petroleum fuels, hydrogen is evidenced to have a greater energy density. This is evidenced by the fact that per the unit volume hydrogen provides more energy than diesel, gasoline, and kerosene. More to the point, hydrogen is particularly plentiful, and it assists in eliminating the United States’ reliance on the supply sources from foreign countries. According to the research and development projects that have been carried out by various scholars, the use of liquid hydrogen or compressed hydrogen as a fuel for gas turbine engines, internal combustion engines, or fuel cells is currently practical. Nevertheless, the further research is needed to amplify the power production from gas turbine engines and internal combustion engines. In spite of few drawbacks, scholars have put forth that hydrogen has more advantages in comparison with fossils fuels, and, in addition, it reveals more assurance for future.

Developing the cost-efficient, compact, reliable, and safe methods of storing hydrogen is one of main impediments of the extensive usage of hydrogen as the energy source. This is so due to the fact that hydrogen has various features which make it hard to be stored in large amounts without having the considerable space occupied.

The hydrogen storage delineates the techniques of storing hydrogen in order to be used later. These techniques cover various approaches encompassing cryogenics, high pressures, and chemical compounds, which reversibly release hydrogen after heating. In the growth of a hydrogen economy, the storage of the same is a very essential objective.

One of the methods for storing hydrogen is using the squashed gas cylinders. This can only be done at the room temperatures, and they are the same as those employed on vehicles powered by the natural gas. Apparently, gaseous fuels have the moderately small energy per the unit volume; therefore, the platforms that make use of gaseous hydrogen might contain a fairly lessened range as compared to the platforms that make use of liquid fuels, including diesel or gasoline. Besides, hydrogen can be stored in the liquid form. However, hydrogen turns out to be a liquid only when stored at extremely low temperatures; thus, it needs the special tanks to be kept; they ensure that the gas is kept cold, and, moreover, this prevents any losses.

In addition to this, squashed-gas cylinders with 20 megapascals pressure levels and that are created from the stainless steel are highly employed for storing the fuel for on-board automobiles powered by natural gas. High-pressure cylinders, which are created from plastic materials with aluminum or steel liners, are being developed, and they are intended to store hydrogen in its liquid form.

The studies have shown that the storage of liquid hydrogen is better if to compare with the storage of the compressed gas due to the fact that in its liquid state a bigger volume of hydrogen may be kept than hydrogen in the gaseous state. The vehicles are manufactured with fuel tanks that have different capacities. Some automobiles have tanks, which hold up to 100 liters, while others have large tanks, which hold up to 540 liters. The evaporation rates of these tanks are one percent every day. The evaporation rate is the rate at which the liquid hydrogen evaporates into the gaseous hydrogen. There are various challenges, which have been put forth to the storage of hydrogen; however, at the same time, the use of various storage techniques has been applied.

Hydrogen can be transported in various methods. Nevertheless, the method depends on the nature of hydrogen. For instance, both the liquid hydrogen and the gaseous hydrogen may be transported by the use of rails or trucks. Pressurized tanks may be used to transport the liquid hydrogen by rail, truck, ship, or barge. However, the storage tanks should be insulated as this is very essential. The losses that result from the boil-off are very significant due to the fact that hydrogen has an extremely low boiling point. On the other hand, pipelines can be used in the transportation of the pressurized hydrogen. This has been proved in Germany where there are two huge distribution networks for hydrogen with over fifty kilometers of pipelines having pressure of 290 psi, or two MPAs exist. The research indicates that in the past fifty years no accidents have been recorded.

It is of paramount importance to apply a number of changes both to the design and operational features of engines used in hydrogen powered aircrafts to impact on the full potential of hydrogen in aircrafts (Holland and Provenzano, 2008). It is evident that in a hydrogen-powered aircraft, hydrogen is used in either a jet engine or an internal combustion engine as a source of power for the propeller. Apparently, these kinds of engines adapt easily to gaseous fuels, for instance, methane, hydrogen, or propane (Hordeski, 2009). According to the research, slight modifications need to be applied for the right introduction of the appropriate amount of fuel (Yürüm, 1995). Evidently, having the fuel supply system that will be turned in according to the requirements of an engine to work appropriately is necessary for the hydrogen-powered aircraft. When using hydrogen as a source of power, a number of additional issues regarding safety as well as the backfire safe operation in the entire operating region need to be put into consideration. Another issue that the hydrogen powered aircraft needs to address is a storage aspect. Due to the fact that the hydrogen gas has the low volume content, its storage can evidently not compete with that of the liquid gasoline. In comparison with the liquid gasoline, the low energy per unit volume of hydrogen makes it produce the reduced energy in the cylinder. Apparently, an aircraft operating on hydrogen produces the minimal .power as compared to that using gasoline (Yürüm, 1995). To address this problem in the hydrogen aircraft, the incoming air or fuel needs to be compressed before it gets to the cylinder (Hordeski, 2009). As a result, this will ensure that the amount of energy per unit volume of fuel is increased. Moreover, this will also result into an additional weight as well as the complexity, which will be added to hydrogen powered aircrafts.

Besides, it is necessary to ensure the addition of spray nozzles to water so as to provide the backfire free operations. Despite the fact that it is simple in structure, it is fundamentally important to supply the right amount of water according to the load, engine speed and temperature (Holland and Provenzano, 2008). The aircrafts should also have their engines modified to have the high speed, as it has been noted that hydrogen engines are more appropriate if they operate at high speed. This is due to the fact that hydrogen has a high burning rate (Hordeski, 2009).

Airplanes may make use of various energies as the power source. Aircrafts that are powered by hydrogen make use of the same as the power source. The use of hydrogen for airplanes works in various ways. For instance, in an airplane, hydrogen may be combusted in the engine jet or in the internal incineration engine. Besides, hydrogen may be employed in powering a fuel cell in order to produce electricity that is, in turn, used in powering a propeller.

Various companies including the German Aerospace Center, the Lange Aviation, and the Boeing use the hydrogen energy for aircrafts for unmanned and manned airplanes. The Boeing tested the initial manned flight that has been hydrogen powered since 2008. Besides, manned airplanes that are hydrogen powered have also been tested. Nevertheless, according to the Boeing, hydrogen fuel cells are not capable of powering the engines for huge passenger aircrafts; nonetheless, they could be employed as a backup, or the supplementary power units aboard. The Boeing also made the public Phantom Eye UAV as hydrogen powered in 2010. The UAV is power-driven by two Ford inner ignition engines, which have been changed to operate on hydrogen. In addition, the Reaction Engine A2 has been recommended for Europe to employ the thermodynamic characteristics of liquid hydrogen to attain the long distance and extremely high speed airplanes by combusting them into pre-cooled jet engines.

Over the past decades, the application of hydrogen as fuel in engines has been tried on limited circumstances, which offered unreliable degrees of success. In this case, there are valid questions on its efficiency, which forms the aim and objectives of this research that focuses on hydrogen fuel, its benefits, drawbacks, and how to overcome the problem that hydrogen production depends on the availability of a non-renewable resource. This chapter forms the research methodology.

In order to conduct any research, it is imperative to understand the research questions, which form the outline of the research methodology as they influence on the research design, research strategy, data collection methods, and data analysis methods used. The research questions for this study include:

1. What is the use of hydrogen as a fuel for aircraft and how can it be done?

2. What are the characteristics of hydrogen fuel?

3. How is hydrogen extracted and produced and how will it be used?

4. How is hydrogen stored, transported and what are the environmental considerations?

5. How can aircrafts be modified in order to make use of hydrogen as a fuel?

In order to efficiently examine the use of hydrogen energy in aircrafts, a case study of one company that has developed aircrafts that make use of hydrogen as the fuel shall be used. Attaining the research objectives and resolving the research problems is only possible with adopting the right research strategy as mentioned by Lamb et al. (2008). According to Badke (2004), there are two factors, which influence on the selection of a research strategy, which include the research objectives/ aims and the research questions. Although there are varied strategies in the research, the ones used in this study are the quantitative research methodology.

The data will be gathered using secondary sources. The secondary data will be collected from peer-reviewed journals, textbooks and records of established firms that have made use of hydrogen as fuel to power the aircrafts. According to Bennett (2009), secondary data are the ones that have already been collected by other researchers for their own purposes. The data are accessible and available, and, hence, cost effective. The data consume less time, resources and energy to collect as noted by Onkvisit and Shaw (2008). According to Wrenn, Stevens and Loudon (2006), the data may be outdated and fall short while responding to specific questions that need an answer;  they may be substandard and flawed with errors that can negatively influence on the current research. The secondary data, however, will be applied for the study due to the efficient that allows comparisons of various views of different researchers.

A research design is the structure of any scientific work that offers the direction and systematizes the research (Adèr et al., 2008). A design chosen for the particular project usually depends on the research question. The research has revealed that the research designs generally deal with the following: questions to be studied, the relevant data, the type of data to be collected, and the methods of analyzing such data (Adèr et al., 2008). Depending on our research questions, we will employ the quantitative research design in this project.

Hydrogen energy is deemed to be very effective for the use powering engines as compared to other fossil fuels (Peschka, 1998). This has been evidenced from the various analyses carried out which indicate that, unlike other fossil fuels, the combustion of hydrogen does not produce pollutants, greenhouse emissions, which are a major issue in the environment (Rifkin, 2002). The desirable and unique features of hydrogen have made it to be recognized as a fuel applied as the fuel in engines. Hydrogen is evidenced to be the only fuel that is generated wholly from the renewable resource water (Rifkin, 2002). The various factors, which have been focused on in this project, encompass the various characteristics, properties, production and extraction, transportation and storage, and environmental considerations. These factors, which form the aim and objectives of this research, are very vital for understanding how efficient hydrogen energy is for the use towards power aircrafts.

In the contemporary society, the automobile industry has increasingly produced automobiles powered by hydrogen fuel cells. These are exciting promises due to the fact that hydrogen fuel cells have the capability of doubling the efficiency of automobiles, and, at the same time, considerable lessening air pollution (Marshall, 2011). On the other hand, problems linked with fossil fuels have also been provided. Such problems as global warming, pollution, ozone alerts and oil spills are linked with the use of fossil fuels. As a result, these forces are changing the world into a hydrogen economy. According to the research, if these projections are certain, there is a high possibility of moving from the use of fossil fuels to the hydrogen future in the next few decades (Marshall, 2011). Nevertheless, the questions have risen on whether or not the society can be able to shift from a fuel cell economy to a hydrogen fuel economy. Some people deem that the political, technological and economic barriers will act as a hindrance and bound as to the use of fossil fuels over the next centuries.

In the present time, most countries across the world including the United States are greatly depending on fossil fuels. Petroleum products, including diesel and gasoline, fuel the aircrafts, trains, and automobiles nearly entirely, whereas the majority of power plants make use of natural gas, coal and oil as the fuel. Marshall (2011) puts forth that fossil fuels, which are the non-renewable resources, are very likely to be depleted, and this implies that the entire planet would be brought to a standstill. Although fossil fuels play a vital responsibility in our society, it, however, has various drawbacks that are critical to the environment and human life. As a result, hydrogen energy has greatly been preferred due to its various advantages and few drawbacks.  

According to the research, hydrogen energy can be produced using various techniques. The use of carbon sequestration and carbon capture techniques during the production of hydrogen would reduce the emission of carbon dioxide. Hydrogen is produced from a number of resources, which encompass such domestic resources as fossil fuels including coal, natural gas, biomass and nuclear as well as renewable energy technologies, for instance, solar, geothermal, wind and hydroelectric power (Peavey, 2003). In addition, it could be produced from small-distributed units if they are located at or closer to the point of end-use, for instance, at stationary power sites or refueling stations (Yürüm, 1995). Different technologies for producing hydrogen energy are moving ahead to be developed by researchers across the world. A process known as the steam methane reforming may produce hydrogen. This is a method for producing hydrogen from methane into natural gas by using the high temperature steam (Peavey, 2003). Another process used to produce hydrogen gas is a renewable electrolysis method. Evidently, this method uses the electric current to split water into constituents of hydrogen and oxygen. The required electricity is generated from the use of renewable energy technologies, for instance, geothermal, hydroelectric power, solar and wind.

Hydrogen is also produced directly from coal by a process known as gasification (Yürüm, 1995). Alternatively, hydrogen can be produced through the renewable liquid reforming process (Yürüm, 1995). This is a process, whereby biomass is processed to produce renewable liquid fuels, for example, bio-oil and ethanol. These liquids can then be mixed with the high temperature steam to produce hydrogen at or near the point of end-use (Yürüm, 1995). The energy from hydrogen can be extracted through two major ways, which encompass burning in turbine engines or in internal combustion engines (ICE's); or by using a fuel cell to convert it into electricity.

Compared to other fossil fuels, the various characteristics and properties of hydrogen energy have made it very efficient to use in power engines. Hydrogen has a low energy density of about 0.08376 kg/m3. It is apparent that hydrogen has the most different characteristics as compared to other common fuels (Rigden, 2003). As indicated by studies, some of its properties make it less hazardous, whereas others of its characteristics make it more dangerous theoretically in a number of situations. The unique features of hydrogen make it significantly well suited in the principle to powered aircrafts. Evidently, at a wide range of pressure and temperature, hydrogen is known to have very high flame propagation rates in the powered aircrafts, as compared to other fuels. Among the important features of the hydrogen-powered craft operation is the fact that it is linked to less undesirable exhaust emissions as compared to other fuels (Peschka, 1998). Having the spark timing differing in the hydrogen powered craft operation ensures that the engine is effectively improved and that the possibility of the engine knocking is avoided.

Besides, compared to other fossil fuels, hydrogen is preferred to its various advantages. For instance, hydrogen energy is not toxic. Besides, engines that make use of hydrogen energy are believed to last longer in addition to starting faster in any kind of weather. In addition to this, it is true that the production and the use of hydrogen fuel contributes directly to reducing most of the economic, environmental and health predicaments (Yürüm, 1995). Moreover, liquid hydrogen has a very high evaporation rate signifying that no toxic residue or pollution will be left. Among these advantages, having an engine exhaust that is clean, it is deemed as a major advantage of hydrogen gas. In spite of these advantages, hydrogen energy has a number of disadvantages. These encompass the high production and storage costs, combustibility hazard and, besides, it results to the depletion of oxygen from the atmosphere (Tromp et al., 2003). Nevertheless, these are non critical disadvantages as they can be dealt with.

Contemporarily, aviation accounts for more than five percent of the worldwide carbon releases linked to global warming. According to studies, commercial airliners generally produce more than one ton of carbon dioxide for every passenger. However, various companies including the Boeing Company, the flyH2 Aerospace, the German Aerospace Center, and the Lange Aviation amongst others have made use of hydrogen energy to power aircrafts in order to solve this predicament.

Hydrogen has been termed to be the most expensive and the least effective replacement of fossil fuels as other technologies are believed to be cheaper and can be implemented quickly. A wide-ranging research of hydrogen as applied in transportation has revealed that there are the key obstacles on the path to attaining the prospect of hydrogen-powered engines (Nakicenovic, 1998). Various aerospace companies including the Boeing Company and the FlyH2 Company amongst others and researchers have put their efforts in developing hydrogen-powered crafts, which are deemed to be a solution to various problems linked to fossil fuels, in addition to being independent in the energy production.

With the current technology, the production of hydrogen using steam reforming may be attained by the use of the thermal efficiency that is between seventy five to eighty percent (Yürüm, 1995). Nonetheless, the supplementary energy will be necessitated to compress or liquefy the hydrogen, and, besides, transport it using pipelines or trucks. Compared to gasoline, hydrogen energy, due to its low energy density that necessitates more energy input (about 50 megajoules) to be produced and transported (Yürüm, 1995). The studies carried out have revealed that hydrogen fuel cells are very efficient compared to fossil fuels. The maximum efficiency of the internal combustion engine is evidenced to be high (approximately 38 percent); this is 8 percent higher as compared to a combustion engine fueled by gasoline.

The FlyH2 Aerospace, founded in 2007, is located in Cape Town, South Africa. The aerospace has means of promoting and developing hydrogen energy in order to replace fossil fuels, especially in general aviation. The FlyH2 has designed a two-seat airplane that is energized by a system of hydrogen fuel cells and batteries that are of the high energy density (“FlyH2 Aerospace”, 2007). Hydrogen fuel cell has currently progressed to a degree in which the electric air travel is a certainty. Compared to the internal combustion engine (ICE), hydrogen fuel cell systems are deemed to provide a number of advantages. For instance, during a travel, oxygen is bonded with hydrogen to emit electricity and water. The electricity is employed in driving a propeller and an electric motor (“FlyH2 Aerospace”, 2007). Apparently, the only product emitted is small quantities of water vapor. The fact that the drive system has just a single moving part that is the prop-shaft; this has an advantage that it allows the reduced cost of maintenance, longer life for the engine, and high reliability. The electrolysis technique is employed by the company to produce hydrogen on the ground. This is evidenced to keep the production of hydrogen fuel environmentally friendly. The process of hydrogen production is usually powered by wind or solar energy, whichever is available during the generation time.

In 2007, the company developed and tested a fuel cell using local materials. This was aimed at obtaining knowledge that was essential for building a lightweight and compact fuel cell system, which had to be designed into the powerful unmanned aerial vehicle (“FlyH2 Aerospace”, 2007). The main objective of this was to demonstrate the company’s competencies and skills for designing and creating the hydrogen powered airplane.

The Counsel for Scientific and Industrial Research (CSIR) carried out a research in 2007 in order to find the material for fuel cells and techniques for storing gaseous hydrogen. The FlyH2 desired to work hand in hand with the CSIR in order to generate lightweight, powerful and efficient fuel cell systems. Besides, the company is looking forward to work together with the global and local aviation industries in order to further the manufacturing of the hydrogen-powered aircraft (“FlyH2 Aerospace”, 2007).

The fact that the company’s previous designs have been successful has resulted to further development in the area.  The FlyH2 is designing the initial hydrogen powered aviation airplane that will be commercially sold. The model will purely be powered on hydrogen plus atmospheric oxygen. However, the prototype will be helped by batteries, which are high-power and lightweight. During the flight, the batteries will be recharged by hydrogen fuel cells (“FlyH2 Aerospace”, 2007).

The Boeing Company is one of the companies that make use of hydrogen to power their aircrafts. The company has tested both manned and unmanned aircrafts that are hydrogen powered. William established the Boeing Company, headquartered in Chicago, Illinois, in 1916, as an American defense and Aerospace Corporation. In 1997, the Boeing Company merged with McDonnell Douglas, and this signifies how the company has grown over the past years. The company is made up of numerous business units such as the Space and Security, the Boeing Commercial Airplanes, the Boeing Defense, the Boeing Capital, the Operations and Technology, the Engineering and Boeing Shared Service Group. The company is amongst the major international manufacturers of aircrafts by revenue, deliveries and orders. In addition, the Boeing is the third leading defense and aerospace contractor worldwide that stands on the defense-associated revenue. In the United States, by its value, the Boeing is a major exporter, where its supply is a part of the industrial average of Dow Jones.

In 2008, the Boeing Company announced that it had efficiently created a manned aircraft, which uses fuel cells and hydrogen energy. Historically, this is an initial step towards providing an aviation that is clean and energy effective. According to John Tracy, the company’s Chief Technology Officer, “the development of a hydrogen-powered aircraft is viewed as a successful breakthrough, as it promises an environment that is free from carbon pollutants” (“msnbc.com”, 2008). He stated this at the Boeing Company’s Research Center where the hydrogen-powered airplane had been displayed. Due to the increasing fuel prices and the fear of any climate change, the air industry is eager finding the means to incise emissions and energy bills joined towards the global warming (“msnbc.com”, 2008). Hydrogen releases do not pollute, but, on the other hand, this is costly to generate the carrier energy. Tracy further says that the Boeing Company knows that pollution signifies a solemn environmental challenge.

As the company