Climate friendly propulsion technologies - Part 2

Decarbonization in Aviation: Industry-Wide Momentum and Innovations

In recent years, "decarbonization" has become an increasingly prominent term, particularly within the aviation industry. The sector's stakeholders are vigorously pursuing initiatives to achieve carbon neutrality, with significant emphasis on developments in Germany and Europe. This push is largely driven by stringent and capital-intensive climate protection regulations, which have accelerated the exploration of alternative propulsion systems for both aircraft and ground support vehicles.

Meeting ambitious climate targets and minimizing the environmental impact of flight operations necessitate the adoption of new propulsion technologies. Among these, hydrogen propulsion stands out as a key innovation, offering significant potential to transform the industry. The following sections delve deeper into the critical role of hydrogen in the future of aviation.

Introduction: Green Propulsion in Aviation

The Path to Sustainable Air Travel

The aviation industry is rapidly exploring sustainable alternatives to traditional jet fuel, focusing on three main technologies: electric propulsion, hydrogen, and Sustainable Aviation Fuel (SAF).

Given the strengths and limitations of the individual technologies, the future of aviation is likely to rely on a combination of these solutions. As Figure 1 shows, electric propulsion will find its place in regional air travel from 2025 onwards including commuter flights such as shuttle flights with eVTOLs (electrically powered vertical take-off and landing vehicles), SAF will be essential for long-haul flights from 2025 and hydrogen may dominate short- and medium-haul flights from 2035. This cross-technology approach is crucial for a sustainable future of aviation.

Diagramme: Sustainable Propulsion Technologies - a Timeline

Fig. 1: Technical development of green propulsion in time (data source: Waypoint2050)

Sustainable Aviation Fuel (SAF)

Sustainable Aviation Fuel (SAF) is already in use and plays a critical role in reducing emissions, especially for long-distance flights. SAF can be used with existing aircraft engines, making it a practical solution as the industry scales up its production. Data from IATA shows that this technology needs to be scaled up further. According to the International Air Transport Association (IATA), only around 0.53 per cent of the industry's global fuel requirements will be covered by SAF in 2024. Delta airlines, for example, has set itself the goal of sourcing 10% of the fuel it needs from SAF by 2030.

Learn more about SAF in this article

Electric Propulsion

It is also important that development in this area is progressing at a rapid pace. This means that battery performance will increase in the future and other areas of application will also become feasible.

Hydrogen

Hydrogen is emerging as a promising option, particularly for short and medium-haul flights. Green hydrogen, produced using renewable energy, is key to minimizing emissions. However, the large storage requirements and the high costs associated with hydrogen systems currently limit its use in long-haul aviation. It should be noted that this technology is still in the experimental phase and that widespread commercial use is not yet in sight.

Building the Hydrogen Infrastructure for Aviation: Challenges, Opportunities, and Risks

Hydrogen Value Chain in Aviation: Infrastructure and Risks

The integration of liquid hydrogen as an energy carrier in aviation necessitates significant infrastructure changes, presenting both opportunities and risks. One of the primary challenges is the need to build or adapt infrastructure to support hydrogen's unique properties.

Pipeline Infrastructure:
Hydrogen can be transported in various ways. Transport by rail is one option but pipeline transport is the most efficient way of transporting hydrogen over longer distances, whereby gaseous hydrogen is transported liquefied, and stored at the airport. Transport with special trucks is an option, but is best suited for short distances, for example at the airport campus.

Storage Facilities:
At the airport, storage facilities similar to current fuel farms will be essential. However, because hydrogen must be stored at cryogenic temperatures, these tanks will need to meet specific and stringent requirements.

On-Site Transport and Distribution:
To deliver hydrogen to aircraft, airports will need specialized fuel trucks and filling stations. These facilities must be designed to handle hydrogen's unique characteristics safely.

On-Campus Production Potential:
As hydrogen demand increases, airports may consider on-site production to reduce dependency on external suppliers and lower costs. However, on-site production requires substantial investments and technological advancements to be feasible and cost-effective at scale.

In summary:

While the hydrogen value chain in aviation holds great promise, it requires careful planning and investment in new infrastructure to mitigate associated risks. Additionally, infrastructure planning for the various propulsion technologies must be included in the next airport master plans.

In order to cover the hydrogen demand, hydrogen production is also possible on the airport campus in the long term. A possible production plant with the associated components is shown in the diagram below. Such a production plant offers the advantage that the airport is autonomous from suppliers and producers, which is associated with cost savings due to a shorter value chain. However, such production on campus is only realistic in the distant future should the demand for hydrogen increase.

Example of a hydrogen production plant on the airport campus © amd.sigma strategic airport development GmbH

Hydrogen Use at Airports: Regulatory Framework

The use of hydrogen in aviation is governed by strict regulations to ensure safety and environmental compliance, focusing on the storage, handling, and distribution of this highly flammable gas. Key regulatory bodies, like the International Civil Aviation Organization (ICAO) and the European Union Aviation Safety Agency (EASA), are central to setting these standards.

EASA is actively developing comprehensive regulations for hydrogen technologies in aviation. This includes collaborating with airports, industry stakeholders, and research institutions to test hydrogen infrastructure, storage, and refueling processes. EASA is also establishing guidelines for the design and construction of hydrogen facilities at airports, alongside training programs for airport personnel.

These efforts are crucial for safely integrating hydrogen as a sustainable aviation fuel, supporting the EU’s goals of reducing carbon emissions and promoting green energy.

The Federal Aviation Administration (FAA) in the United States is also playing a significant role in the integration of hydrogen as a sustainable aviation fuel. Currently, the FAA is working on developing and adapting regulatory frameworks to ensure the safe use of hydrogen technologies at U.S. airports. These efforts include research initiatives and partnerships with aviation companies, airport operators, and technology providers to evaluate the safe application of hydrogen in practical settings.

In addition, the FAA actively participates in international projects and dialogues to promote unified safety standards and ensure that U.S. regulations are compatible with international guidelines. Additionally, the FAA focuses on training airport personnel and establishing safety protocols to regulate the handling and storage of hydrogen at airports. These activities are part of the FAA's broader efforts to reduce carbon emissions in aviation and support the transition to green energy solutions.

It will be essential to define a minimum international standard, enabling international cross-border traffic while allowing for regional particularities.

The Use of Hydrogen at Airports: Where and When?

The adoption of hydrogen in the aviation sector is complex and influenced by various factors. The timeline and location of hydrogen integration into air transport are difficult to predict, but certain trends are emerging.

Factors Driving Hydrogen Adoption

Several key drivers are accelerating the use of hydrogen in aviation:

Government Support and Regulations: Strict climate protection regulations and governmental incentives are pushing the aviation industry towards sustainable solutions, including hydrogen.
Industry Leadership and Research: The presence of leading aviation companies and active participation from research organizations are crucial for advancing hydrogen technology.
Partnerships Across the Value Chain: For the commercial use of hydrogen to be successfully implemented, an optimal cooperation between and among the stakeholder is essential. A comprehensive stakeholder network must be established for this. The passenger should take top priority. An optimal stakeholder network also includes downstream stakeholders such as energy suppliers or research institutions.

Potential Hydrogen Hotspots

Despite high energy costs and the need for an extensive renewable energy infrastructure to produce green hydrogen competitively, Europe is well-positioned to become a leader in the hydrogen aviation sector due to its strong regulatory framework, advanced research, and established industry partnerships.

However, not all regions need to excel in every aspect of the hydrogen value chain.

Specialization in the Value Chain: Some countries may focus on specific segments of the hydrogen value chain. For example, regions with abundant renewable energy resources, like North Africa or the Middle East, could become major producers and exporters of green hydrogen due to their favorable geographical conditions.

In summary, the use of hydrogen at airports is on the rise, driven by government policies, industry collaboration, and regional specialization. While Europe may lead the way, other regions are likely to play pivotal roles in different aspects of the hydrogen economy.

Importers and Exporters of Hydrogen - Global Overview

Fig. 2: Global hydrogen hotspots and distribution corridors

Several southern hemisphere countries, including those in South America, North Africa, the Middle East, and Australia, are positioning themselves as hydrogen exporters, leveraging their potential for low-cost production of blue and green hydrogen.
In contrast, technology-exporting nations like Japan, South Korea, France and the USA are not well-suited to be net hydrogen exporters.
Currently, only China and Australia are expected to achieve self-sufficiency in hydrogen production at a scale sufficient to meet their decarbonization goals.

Conclusion and Outlook

Looking ahead, hydrogen technology is poised to play a crucial role in achieving climate-neutral transportation, but its adoption will vary across different sectors. Two key areas where hydrogen holds promise are ground transportation and aviation, though each faces distinct challenges and timelines.

Hydrogen as a Propulsion Method for Ground Vehicles: Hydrogen-powered ground vehicles, especially in public transport, are nearing mainstream adoption. Cities are already deploying hydrogen buses, which offer a viable solution for reducing urban emissions. Airports are another sector where hydrogen could be applied, but a decision must be made between expanding hydrogen-powered vehicle fleets or continuing to develop electric vehicle (EV) infrastructure. Hydrogen vehicles require new refueling infrastructure, while EVs already benefit from established networks. However, hydrogen-powered vehicles, with quicker refueling times and longer range, may be better suited for heavy-duty use, such as airport ground operations. Both hydrogen and electric vehicles offer climate-neutral solutions when powered by renewable energy.
Hydrogen as a Propulsion Method for Commercial Passenger Flights: The use of hydrogen in aviation is a longer-term goal, with widespread adoption not expected until the 2030s or later. Hydrogen-powered aircraft could significantly reduce the aviation industry’s carbon footprint, but technical challenges are considerable. These include the need for cryogenic storage, redesigning planes to accommodate hydrogen fuel, and developing new fueling systems. While hydrogen shows promise, it will take time for these technologies to mature and become commercially viable.
Economic and Infrastructural Impact: Transitioning to hydrogen requires significant investment in production, storage, and refueling infrastructure. While the current cost of hydrogen, particularly green hydrogen from renewable sources, is higher than traditional fuels, economies of scale and technological advancements will make it more competitive in the future.
Environmental Benefits: Hydrogen offers immense environmental benefits, especially when produced from renewable energy. It can drastically reduce CO2 emissions in sectors like transportation and aviation. However, the development of renewable energy grids is essential to ensure that hydrogen production does not contribute to increased fossil fuel use.
Policy and Regulation: Government policies will be key in accelerating hydrogen adoption. Incentives, carbon pricing, and regulatory frameworks will be needed to support hydrogen production and infrastructure development. Ensuring safe storage, handling, and transportation of hydrogen is also a regulatory priority.
Technological Innovation: Continued advancements in hydrogen technology, such as improving fuel cells and storage methods, will be critical. Collaboration between industries and researchers will be essential for driving down costs and improving efficiency, especially in aviation where challenges are more significant.

Hydrogen technology is advancing rapidly, with ground transportation, particularly public transit and specialized industries, seeing quicker adoption due to simpler infrastructure needs. Aviation, while holding significant long-term potential, faces more complex challenges and a longer timeline. For hydrogen to succeed in both sectors, technological innovation, infrastructure investment, supportive policies, and global collaboration will be essential. In the future, hydrogen could play a transformative role in making transportation climate neutral.