Jet airplanes currently use a certain type of fuel to generate thrust. For many years, the majority of jet aircraft have used a particular variety of kerosene fuel. It is simply referred to as jet fuel and has a low freezing and boiling point. Within the combustion chambers of their engines, they burn a combination of jet fuel and air. The airplanes are propelled forward as a result of the exhaust gases that emerge from the engines’ backs.
While jet fuel will probably still be used by jet aircraft for many years to come, several aerospace manufacturing firms are looking into hydrogen fuel as a possible substitute. Like jet fuel, hydrogen fuel is still burnt within the combustion chambers of the engines. However, it has a completely different makeup, which makes it a great alternative.
What is hydrogen fuel?
Hydrogen fuel is a type of fuel that, as the name suggests, consists of hydrogen. Hydrogen is the third most abundant element on Earth, behind only oxygen and silicon. It consists of a colorless and odorless gas that some aerospace companies want to use as fuel.
What are the advantages of a hydrogen plane?
Perhaps the biggest advantage is that it is clean. Conventional jet fuel is a type of fossil fuel that, like other fossil fuels, produces emissions when burned. When jet aircraft burn jet fuel, they emit exhaust gases. Hydrogen fuel produces no emissions. Hydrogen is a clean fuel that burns without emissions. The clean-burning properties of hydrogen fuel make it an attractive alternative to traditional jet fuel.
In addition to its clean-burning properties, hydrogen fuel is powerful. It can carry airplanes in the air as jet fuel.
Types of Hydrogen-Fueled Aircraft
Although hydrogen fuel is clean and efficient, many jet aircraft currently do not use it. Most jet aircraft use jet fuel, which is a type of kerosene; currently, they do not use hydrogen fuel.
A number of aerospace companies are working to develop hydrogen planes.
Airbus, for example, has three concepts for hydrogen-powered aircraft. Known as the ZERO project—a reference to zero fuel emissions—it was announced in 2020. If all goes according to plan, Airbus’s hydrogen-powered planes could be operational by 2035.
Boeing is also working on hydrogen-powered planes. In 2008, Boeing demonstrated a hydrogen-powered aircraft known as the Fuel Cell Demonstrator.
Hydrogen is increasingly seen as one of the most promising pollution-free technologies for future aircraft. Despite the fact that the energy density of hydrogen per unit mass is three times that of conventional jet fuel, there are several challenges to overcome before it can be widely adopted.
Why hydrogen fuel?
It has been found that the aviation and space industries emit more than 900 million tons of carbon dioxide (CO2) into the atmosphere every year.
Due to commitments made by more than 30 countries, including the Green Deal of the European Union and several organizations such as the International Civil Aviation Organization (ICAO) and the Air Transport Group (ATAG), the aviation industry is under intense pressure to reduce carbon dioxide emissions between 2005 and 2050, and eventually to zero carbon emissions before 2050.
The energy content of hydrogen is almost three times that of gasoline (specific energy); and due to its natural abundance and the elimination of carbon dioxide emissions, hydrogen fuel is considered a possible alternative to conventional jet fuel in carbon-free production.
To start with, compared with SAFs, utilizing hydrogen decreases GHG emissions.
On account of the power device drive-a nearly “genuine zero” hydrogen arrangement, the vaporous outflows are restricted to water fumes, a side-effect of the energy creation process.
In spite of the fact that water fume is an ozone-depleting agent, its unsafe impacts can be limited through cautious activity.
On account of impetus by means of hydrogen burning—a “zero carbon” arrangement—NOX is created nearby by water fumes. Both have radiative constraining impacts, but the arrangement actually maintains a strategic distance from hurtful fossil fuel byproducts. Second, particularly compared with SAFs, hydrogen is probably going to infiltrate different enterprises, which could accelerate the advancement of energy units and capacity frameworks, advance downstream foundations, and push down creation costs.
This would help the flight business, as the research and development and foundation improvement expenses would be borne somewhat by different enterprises.
Third, compared with batteries, hydrogen has a gravimetric energy density multiple times that of lamp fuel (33 kWh/kg). Heavy capacity tanks negate this advantage, and flying stockpiling frameworks are currently being researched, implying that future put-away hydrogen densities should be 10–21 kWh/kg.
Overall, hydrogen outperforms regular fuel in terms of power density per unit weight. This is profoundly important for flight, a weight-critical application, as it offers the greatest drop weight (MTOW) advantage over any remaining energy stockpiling options.
The primary disadvantage of hydrogen is that, because of its low volumetric thickness, it requires four to multiple times the volume of traditional fuel to convey the equivalent installed energy. Hydrogen actually offers benefits over battery capacity in energy thickness, both in gravimetric (batteries right now offer 0.3 kWh/kg) and volumetric measures.
Fourth, refueling an airplane with hydrogen is probably going to be speedier than re-energizing batteries, enabling quicker completion times.
Similitudes in the refueling system between hydrogen and lamp oil could facilitate the progress between new and old cycles; hydrogen would just require different funneling and possibly various temperatures of liquid.
On the other hand, re-energizing batteries involves something else entirely, requiring super quick charging or fast battery substitution choices and a confined energy circulation foundation.
On the technical side, aeronautical engineers must adopt technologies developed in the automotive and aerospace industries and match the technology with the operation of commercial aircraft, mainly by reducing weight and cost.
- One particular challenge is storing hydrogen on an aircraft. Today, liquid hydrogen storage is one of the most promising options, while hydrogen storage as a compressed gas presents challenges to current aircraft weight and volume requirements.
- In addition, the aviation industry must achieve the same or better safety goals as existing commercial aircraft. Indeed, the design and operation of modern kerosene-powered aircraft now incorporate extensive safety measures.
- This rigorous approach has ensured uniform safety across the industry over the years. Therefore, future hydrogen propulsion systems must achieve similar or better safety levels before hydrogen-powered aircraft can take to the skies. “
- Another major challenge to widespread adoption is the availability and cost of liquid hydrogen at airports. Hydrogen is available in large quantities in oceans, lakes, and the atmosphere, but for industrial use, it must be separated from the oxygen in the water.
Redesign of aircraft and engines To take full advantage of hydrogen, aircraft must undergo significant changes. This can mean redesigning almost every part of the plane, from the propulsion system and fuselage shape to the fuel tank.
Burning hydrogen requires a partial redesign of the aircraft, while fuel cells require a complete redesign. Hydrogen engines are based on modified conventional propulsion systems. Major changes are due to fuel delivery and storage, and the fuselage requires a larger fuel tank due to the reduced bulk density compared to jet fuel.
This requires increasing the size of the fuselage, providing additional drag, or completely redesigning the aircraft structure, such as switching to blended wing fuselages with significant enclosed storage space. In addition to storage considerations, hydrogen fuel cell propulsion requires propulsion systems to be redesigned to integrate distributed electric propulsion, which includes high-voltage/high-power electrical systems.
The form and function of such aircraft require a complete change from today’s tube and wing architecture and reflect the design changes required at the level of production of hybrid or all-electric aircraft.
Storage of Hydrogen Efficient storage solutions are key to unlocking hydrogen’s high gravimetric energy density and must be improved to solve the small-scale energy density problem. Liquid storage is currently the most promising option, offering a high bulk density compared to the gas option. A disadvantage of liquid storage is the requirement for cryogenic cooling (below -253 degrees Celsius). The cooling uses up to 45 percent of the stored energy content, which means that there is a significant energy loss (tank-wing efficiency) between the energy stored and the energy delivered to the thruster. This shows the trade-off that must be made between maintaining high volume density and high efficiency between the tank and the wing.
In addition, the cryogenic requirement requires the addition of cooling systems and significant insulation. This leads to complex and heavy tank structures, thus reducing the effective gravimetric energy density of the fuel. Taking full advantage of hydrogen’s high energy density will require significant advances in the development of lightweight containers and cryogenic cooling systems.
Sustainable Production of Hydrogen Sustainable production of sufficient quantities for the aerospace industry requires a significant increase in the production of “green” hydrogen or the use of carbon capture and storage (CCS) in the production of “blue” hydrogen. Current production is dominated by “grey” hydrogen processes, with 96 percent of hydrogen produced directly from carbon dioxide-releasing processes such as steam methane reforming or coal gasification.
The remaining four percent is produced by electrolysis, which produces “green” hydrogen using only renewable energy sources. Of the 70 million tons of hydrogen produced today, only about a million tons are currently “green.”
Fortunately, there is a clear path to sustainable hydrogen. In this case, it is likely that the energy sector is behind the solution because the transition to the peak of renewable energy can create the need to manage the energy supply and recover excess energy, in which case hydrogen storage is an acceptable solution. This source, combined with the wider adoption of carbon taxed carbon capture and storage, could lead to an increase in sustainable hydrogen production and an associated decrease in price.
Infrastructure The improvement of hydrogen infrastructure must go hand in hand with the technology that makes it possible to use hydrogen in aviation. The two main areas are fuel delivery to airports and airport refueling infrastructure. One way to deliver fuel is through existing gas networks.
A good example of this is the Leeds City Gate study, which shows that existing natural gas networks can be converted to transport hydrogen gas.
This is promising in terms of the key building blocks of hydrogen infrastructure, but requires significant investment from all parties. Long-distance transport of hydrogen must also be considered, especially considering the difference between where hydrogen is produced (overcapacity of renewable energy plants and hydrogen production facilities) and where it is used (airports). Airports may have an additional requirement for on-site liquefaction of hydrogen, provided infrastructure is in place to deliver hydrogen gas. This requires local power generation or a reliable grid connection to avoid network downtime costs.
Costs Hydrogen is more expensive than kerosene on a kWh basis; excluding storage costs, average production costs for “green” hydrogen are $0.14 USD/kWh for “green” hydrogen and 0.05 USD/kWh for “gray” hydrogen.
The latter is equivalent to kerosene, but since “true zero” or “zero carbon” sustainable aviation would require “green” hydrogen, these production methods must come down in price to compete on a cost basis.
Total production costs are based on net-to-wing efficiency. Hydrogen production is often criticized for requiring too many power conversion steps, each of which reduces its overall efficiency (and increases costs). For example, converting electrical energy to hydrogen may seem like an unnecessary step when it is simply converted back to electricity in a fuel cell. In contrast, using a battery to power an airplane seems easier and more efficient. However, if the level of battery improvement is not sufficient for a medium or long flight, hydrogen may remain the only “zero carbon” or “true zero” option.
Furthermore, the question of production efficiency is quickly resolved into a mere question of cost: if burning hydrogen can be cheap, does it matter how many steps it takes?
Again, other sectors can provide a solution. As demand for hydrogen in other transport sectors increases and supply increases in line with renewable energy capacity, costs are likely to decrease. For example, projects are under development in Australia, Saudi Arabia, and North Africa, where “green” hydrogen is expected to cost as little as $0.07/kWh in the future.
Technological improvements in electrolyzes and hydrogen compression methods are also likely to further reduce costs, as improvements in the efficiency of such processes reduce the energy input per hydrogen produced.
An increase in the price of coal could be more important than a decrease in the price of hydrogen. If there is a higher emission fine.
Road towards green hydrogen
Another major challenge to widespread adoption is the availability and cost of liquid hydrogen at airports. Hydrogen is available in large quantities in oceans, lakes, and the atmosphere, but for industrial use, it must be separated from the oxygen in the water.
Today, more than 70 million tons of hydrogen are produced annually, the main source of which is natural gas (or gray hydrogen). The production of hydrogen extracted from fossil fuels is energy-intensive and causes approximately 830 million tons of carbon dioxide emissions per year.
However, electrolyzers running on electricity produced from renewable energy sources offer a low-emission alternative. This process, which leads to “green hydrogen” hydrogen, involves the electrolysis of water to extract the hydrogen.
Less than 0.1% of global hydrogen production is currently considered green hydrogen, but that could change. Between 2014 and 2019, global wind power generation doubled and solar power generation quadrupled.
The International Energy Agency (IEA) predicts that the rapid market growth of renewable energy sources, especially solar and wind, over the next decade will exponentially increase the availability of renewable electricity, lowering its cost and demand for electrolyzers producing green hydrogen is already growing rapidly, with electrolysis capacity expected to reach 40 GW in the EU by 2030.
Increased availability of green hydrogen will thus help reduce its costs by up to 30% by 2030 and 50% by 2050.
This timeline of 2030 is consistent with Airbus’s anticipated implementation of the zero program. In fact, according to Airbus’s director of zero-emission aircraft, Glenn Llewellyn, Airbus aims to use green hydrogen as a fuel for its future zero-emission aircraft.
He believes that as renewable energy costs fall and hydrogen production increases, “green hydrogen” will become more competitive with existing alternatives such as jet fuel and sustainable jet fuel. “To make zero-emission flying a reality, competitive green hydrogen and cross-industry partnerships are essential,” he says.
Making hydrogen available at airports around the world
But for hydrogen to really spread in aviation, it must be available at airports around the world.
And development in this area is in its infancy. One of the biggest challenges is the development of large-scale transport and infrastructure solutions to supply airports with the required amount of hydrogen as jet fuel.
Reuse of existing infrastructure, including the millions of kilometers of pipelines currently used to transport natural gas, could be a cost-effective solution, according to a recent IEA study. Larger quantities of hydrogen could thus be transported from production sites by pipeline, while smaller quantities could be transported by truck. In addition, some airports could develop the necessary infrastructure to support on-site hydrogen production, especially if renewable energy is nearby.
Changing Public Perceptions About Hydrogen
Hydrogen has been used safely for over 40 years in large quantities as an industrial chemical and as a fuel in space exploration. In fact, several million cubic meters of hydrogen are transported and processed every year.
The road to large-scale use of hydrogen in aviation is still long. However, cross-sector international coordination is expected to support the development of the hydrogen economy, an important effort to help meet ambitious global carbon reduction targets over the next two decades.
Hydrogen is prepared to be a critical supporter of diminishing emanations and clamor contamination in different areas of the economy.
End-clients in portability, energy, and industry will focus on hydrogen as a zero-emission energy source, for instance, in energy unit electric powertrains for cars; fixed energy units for conveyed cogeneration of power; and for warming applications and feedstock in modern creation processes.
The life cycle discharge effect of hydrogen use—e.g., the “well-to-wheel” emanations for power devices—relies upon the basic hydrogen creation strategy. Hydrogen is delegated “dark” on the off chance that it is created utilizing petroleum products, causing fossil fuel byproducts; “blue” assuming those discharges are caught or counterbalanced; and “green” assuming it is produced by sustainable power with no fossil fuel byproducts.
“Green” hydrogen can also be used as a spotless energy storage option for excess power from irregular sustainable power ages.
However, the creation limit will be determined by demand, which will most likely be driven by strategies and guidelines that create incentives for areas to decarbonize.
The reception of hydrogen will, consequently, be most inescapable where it addresses an expense-effective pathway contrasted with choices (e.g., zap, biofuels, or carbon catch and capacity) and where the empowering hydrogen supply foundation opens up. Long-range/hard-core ground transportation Hydrogen energy units, in view of Polymer Electrolyte Film (PEM) innovation, are probably going to become the zero-emission powertrain of choice for long-reach and rock-solid transportation applications.
This could incorporate trains on non-energized rail lines, substantial trucks, metropolitan and interurban transport, and certain long-range portions of passenger vehicles, including armadas. In these portions, hydrogen can conquer the reach, charging time, and payload issues faced by battery-electric vehicles. Besides, most use cases work with hostage armadas with a dedicated hydrogen refueling framework.
Many power module modes of transport are in assistance in China and Europe, and more than 16,000 energy-component traveler vehicles are on the road worldwide.
To encourage this adoption, legislators in key industries have set joint targets of sending up to 2.5 million vehicles by 2030. In addition to street and rail versatility, oceanic transportation is a key supporter that will profit from additional development in powertrain innovation (including hydrogen stockpiling) as well as generally lower fuel costs.
The primary show projects with power device ships are now in progress. Industrial hydrogen plays a fundamental part as a feedstock in different assembling and compound handling processes, for instance, smelling salts creation and treatment facility processes. Decarbonizing these cycles would generally require the direct use of “green” hydrogen. For example, steel production requiring direct reduction of iron (DRI) utilizing hydrogen is probably going to undergo such a change, driven by guidelines.
This, therefore, may incite the steel business to drive into hydrogen Research and development for “clean DRI” steel creation. Driven by developing interest from these end-client applications, clean hydrogen creation is getting forward movement. Project declarations for new electrolyzers (electrolytic hydrogen creation plants) have filled in both their number and size. The worldwide electrolyzer limit presently remains at a little more than 100 MW, with many new plants being arranged and a few ideas being developed for the GW scale limit. Generally, the hydrogen economy is rapidly developing as powerful areas focus on hydrogen as a pathway to decarbonization. Aviation and flying could stand to benefit altogether from these advances.