Net zero and geopolitical considerations are driving a rapid evolution in the way that most modes of transport are powered. For the aviation industry, the change could be as important as the arrival of high-energy, refined oil-based aviation jet fuel in the 1950s.
While aircraft tend to dominate aviation discussions, the progression will need to go much further and embrace airports and the airside support vehicles they operate. Airports are also vital components of a nation’s infrastructure and need to be able to accommodate private and public transport as well as delivery vehicles from across the supply chain. Basically, airports need to be able to support new forms of propulsion efficiently, cost effectively and quickly without compromising security or increasing risk.
This article will look at how vehicles could fit into the changing airport energy mix and examine some of the risk management factors that airports will need to consider if they are to integrate hydrogen quickly and painlessly.
Irrespective of the form of transport you are looking at, the benefit of hydrogen is that it potentially offers an energy to weight ratio well beyond the reach of current energy storage systems based on battery technology. Hydrogen also has an advantage over existing battery systems from a space perspective, offering range and power while leaving more space for passengers, equipment or cargo. Unlike batteries, its performance is also not influenced by the weather, a significant consideration for airports in both chillier and warmer climates.
From the specific perspective of an aircraft, the amount of liquid hydrogen needed by volume is still around four times higher than jet fuel[1], so airports will potentially need to store and supply larger amounts of liquid hydrogen as demand rises in the medium-term. It’s worth pointing out that while the volume needed will be higher, hydrogen also offers three times the punch of current jet fuels,[2] so more storage at airports will be necessary, but it won’t need to be quadrupled.
It’s also worth noting that from an airside perspective, an aircraft engine powered by a fuel cell has fewer moving parts than a jet engine, which could in theory deliver a maintenance benefit if the technology evolves in the direction of fuel cells instead of hydrogen combustion.
On the less positive side however, as we discussed in this article, to be practical, hydrogen needs to be stored in its liquid form before going through a vaporization process to be converted back to a gas to power an engine. Various forms of the technology are being tested, and it isn’t currently known if this conversion process will take place on or off the aircraft. If it’s off, the aircraft hydrogen gas will need to be stored in vessels on the aircraft in a similar way to jet fuel, before it makes its way into an engine. To remain in its liquid form, hydrogen needs to be stored at -253°C (-423°F), which requires extra hardware and an enhanced understanding on the part of the staff that are managing it, whether that’s airside or landside. Complicating matters further, liquid hydrogen is also odorless, extremely flammable and burns with a transparent flame.
It could be argued that hydrogen powered vehicles present less risk than battery electric vehicles as hydrogen can be vented safely and diluted to atmosphere in an adverse situation. The battery systems on hydrogen vehicles are around 20% of the energy storage capacity of a battery powered vehicle, meaning that the amount of stored energy is lower, reducing combustion risk and leaving more space for passengers, cargo or equipment within the vehicle, which can be a particularly important consideration for emergency support vehicles.
Without getting too caught up in the science, hydrogen, at this point, comes in the main three forms, gray, blue and green[3], but from the aviation industries’ perspective, the debate around the type of hydrogen is likely to be decided elsewhere. All three have the same physical properties and storage requirements, and, from a risk perspective, they all need to be handled in the same way. There are projects underway to investigate the feasibility of producing hydrogen on site at airports, but the likelihood is that in the initial phases of the switch from fossil fuels to hydrogen, the focus will be on supply rather than production.
The supply and cost of green hydrogen is a challenge, so while some aviation organizations may be incentivised to move towards it, adoption could be relatively slow. In some ways, this could be positive, because there is a risk that demand for hydrogen could run into similar supply chain issues that currently challenge SAF globally: too much demand for feedstock from other industries such as road haulage.[4] WTW’s Energy Market Review recently looked in detail at the risks that hydrogen presents as it moves from highly specialist current uses into more general use, as well as offering examples of investments that are being made in the energy and power sector to accelerate hydrogen innovation and supply.
Many governments are playing an active role in facilitating the development of hydrogen. The U.K.’s Department for Transport, in conjunction with the Connected Places Catapult project, recently published a paper outlining its findings on the infrastructure and process changes that would be required at across the aviation industry to support the introduction of zero-emissions aircraft.[5] It suggested that hydrogen fueled flight was one of the most promising technologies available to help meet net zero objectives, but, in the report’s analysis, the list of infrastructure and process changes is extensive and includes:
According to a separate report by the World Economic Forum, if the aviation industry is going to meet its obligations and start the process of putting in place the infrastructure for hydrogen powered aircraft, it will need to have plans in place by 2025.[6] There are also several aircraft and ground support equipment providers that are looking to start commercial testing or even activity in the next 18 months or so.
While the size of the task of converting to hydrogen could seem daunting, airports have an advantage when it comes to adoption.
Several forms of public transport in a number of countries are now starting the process of experimenting with replacing traditional vehicles with hydrogen fueled equivalents,[7] and some airports are already in the process of putting the hydrogen infrastructure in place.[8] This could then be built out to support airside or landside vehicles as they start to move towards a hydrogen model and then extended further to be available to private vehicles and aircraft if and when appropriate.
The first generation of hydrogen powered aircraft that are in the process of being tested are small, 100-seater regional jets. Most estimates for wide commercial availability of this class of aircraft are currently around 2035[9], well after hydrogen road vehicles are expected to become commonplace.
What this means is that hydrogen adoption projects for airports become a question of scaling up over a decade rather than starting from scratch. It could also give airports a cost and experience advantage as hydrogen moves up the agenda. The implementation will still be expensive and the upskilling process could be extensive, but airport organizations could find themselves, or put themselves, at the center of hydrogen implementation over the next few years.
From a practical perspective, ensuring that the right refueling options are available and in appropriate places for aircraft and the airside vehicles that support them, as well as public transport and private vehicles beyond an airport’s perimeter, will require a detailed understanding of airport operations and how each vehicle is used, as well as the risk requirements of refueling facilities.
Most airports keep vehicle operations under constant analysis to ensure efficiency and reduce risk, but there’s a difference in the way that these vehicles will need to be monitored depending on which type of energy future the industry embraces. With current technology, battery powered electric vehicles can take hours to recharge, creating an accumulation risk, but hydrogen vehicles can be recharged in minutes. Any detailed operational analysis needs to understand and take these kinds of differences into account.
Either way, there will need to be changes in the short-term as airside vehicles currently tend to be parked at locations specific to use. The best way to be ready to implement a hydrogen conversion project is to understand how vehicles are being used today and what the implications could be if a new generation of hydrogen vehicles need to be integrated within existing practices and operations.
The scale of the task, and the costs of converting the aviation industry to new forms of fuel are likely to be significant, but despite the uncertain timescales, the process of implementing hydrogen infrastructure at most airports is likely to be incremental, at least initially.
The infrastructure can be initially tested at regional airports, which also often have the advantage of more available physical space, so that safe zones can be established around hydrogen storage tanks without the immediate need to change existing processes. This won’t be the case for all regional airports, but it does mean there is scope for the process to be rolled out, checked and accelerated gradually as depth of knowledge increases.
Equally, from an airside and landside support vehicle perspective, while there are only a handful of commercial hydrogen vehicles currently available, the number is due to rise, driven potentially by transport sectors such as the haulage of goods where a hydrogen fuel cell is lighter and as a result more practical than a battery based energy storage system.[10] It will be some time before there is a critical mass that leads to wholesale change however, and as a result, the market will dictate the supply and timings.
Ultimately, there are many questions about the specifics and timing of change, but there’s little doubt that change is happening, and the indicators are pointing towards hydrogen playing an important role. Airports would be advised to take this opportunity to ensure they have a granular understanding of vehicle usage and ensure they have developed a potential switchover project implementation process. With that in place, they will be in a position to move quickly when the technology becomes available, and the development and implementation path becomes clearer.
