Is hydrogen the answer for a low-carbon aviation future?

Unlike fossil fuels hydrogen doesn't exist naturally in usable quantities. Globally, the majority of hydrogen is produced from natural gas through a method called steam reforming. This is an energy intensive process that uses steam to separate hydrogen molecules from methane (CH₄). An energy efficient and ‘cleaner’ process is to use surplus renewable electricity at times of low demand to separate water into hydrogen and water by electrolysis. This is known as ‘green hydrogen’. ‘Blue hydrogen’ from natural gas is carbon neutral when combined with carbon capture and storage. The benefit of hydrogen fuel is it eliminates CO₂ emissions when used in propulsion. It can also be used in fuel cells to produce electricity for electric powered aircraft, again eliminating CO₂ emissions.

If hydrogen propulsion is initially more suited to the commuter, regional, short range and electrical aviation markets then regional airports, rather than larger international airports, are best placed to take the lead. Airport operators will need to consider:

• Storage – hydrogen can be transported to the airport, but storage requirements will need to consider cryogenic technologies which keeps hydrogen in a liquid state. This would require additional land use, factoring in the required safety distances due to combustion hazard. Monitoring and leak detection and fire safety systems would also be required.
• Hydrogen production – is it cost effective to produce hydrogen using an onsite solar farm to provide ‘green hydrogen’ or will it be delivered to site by road tanker?
• Safety – handling and safety regulations need to be assessed as there are major differences in the properties of hydrogen and kerosene fuel.
• Refuelling - The introduction of hydrogen fuel aircraft will be phased so airport operations will potentially face a long transitional period with both hydrogen and kerosene refuelling. This raises questions - will safety distances allow refuelling with different fuels on adjacent stands? Do airports need ‘hydrogen only’ stands? Liquid hydrogen refuelling trucks will be different to kerosene trucks so training and safety assurance will be required.
• Refuelling methods – refuelling times will be slower due to the very low density of hydrogen which could affect aircraft turnaround times. Maybe the use of more refuelling hoses could mitigate this, but additional training would be required.
• Airfield hydrant systems – not always used at regional airports and couldn’t be used for two types of fuel i.e. kerosene and hydrogen. Due to the likely phased introduction of hydrogen fuel, the use of tankers would be the primary source of fuel delivery to the aircraft stand.
• Airside vehicles – Perhaps the first step should be to use hydrogen powered vehicles i.e. passenger boarding buses, ground support equipment to understand the safety and operational requirements of using hydrogen?