We all have a role to play in the fight against climate change (see previous post “Airports and the fight against climate change”). There is no doubt that climate action within the aeronautical industry is not only theoretical but has been on the agenda of everyone involved for many years now.
The aviation sector emits more than 900 million tons of carbon dioxide into the atmosphere annually, which is between 2-3% of world emissions. Although industry efforts are reducing emissions by 2% per year, air transport is growing by more than 3.5% per year, on average (with the exception of 2020, due to the pandemic). Therefore, efforts are not yet sufficient.
Hydrogen has always been in the spotlight and is, in practice, one of the alternatives that the aeronautics industry is exploring to reduce CO2 emissions.
In this context, the aeronautics industry is making great strides forward, improving aircraft efficiency, optimising materials, managing processes more effectively and globally reducing emissions as an industry, and in terms of the actual functioning of aircraft.
For more than a decade, an important part of the aerospace industry’s investments has revolved around the search for propulsion systems that increase aircraft efficiency while reducing undesirable emissions into the atmosphere. Decarbonisation is, in practice, an important challenge for aviation, a challenge the sector has tackled decisively.
Green hydrogen as aircraft fuel
Hydrogen has always been in the spotlight and is, in practice, one of the alternatives that the aeronautics industry is exploring to reduce CO2 emissions. The fact that it does not produce harmful emissions makes it a sustainable fuel and the centre of numerous projects for use in aeronautics.
Therefore, the use of liquid hydrogen is seen as a solid alternative to achieve the European Union’s goal of carbon neutrality: balancing CO2 released with that captured naturally by 2050.
The majority of hydrogen in the world today is produced by reforming methane from natural gas, a fossil fuel, which produces carbon dioxide. However, efforts are being made to develop green hydrogen using an electric current as a source of renewable fuel to convert water to oxygen and hydrogen, and reduce emissions during production. If this is possible, then together with the absence of emissions from the actual aircraft, aviation could become a truly ecological form of travel.
In order for Europe to fully realise the environmental benefits of liquid hydrogen as a fuel, the production of clean (or green) hydrogen must be dramatically expanded. Clean hydrogen is produced from water, using an electrical current from a renewable source, rather than from fossil fuels. Today, only a small fraction of the hydrogen used in Europe is clean.
Airbus has taken a great step forward
In recent years, progress has been made in developing the underlying technology for hydrogen aircraft. In 2008, Boeing flew the world’s first hydrogen-powered aircraft from an aerodrome near Madrid, Spain. This was a single-seater vehicle that proved the technology was possible. And, in 2016, the first four-seater hydrogen aircraft, built in Germany by the German Aerospace Centre (DLR), the University of Ulm and a company called H2FLY, took off from Stuttgart airport.
However, the large aeronautics manufacturer Airbus is the first to present commercial aircraft powered entirely by hydrogen: the ZEROe prototypes. The goal is the make the first commercial zero-emissions flight in the world by 2035.
Airbus’ three prototypes are based on hydrogen as the primary energy source for the aircraft engines. In this way, liquid hydrogen would replace kerosene as fuel and only emit water vapor instead of carbon dioxide as a waste product. In other words, the traditional gas turbine engine propulsion method would be replaced by a hybrid-electric propulsion system.
Tests that have already been performed on smaller scales have shown that these can be as fast as conventional aircraft and could carry more than 100 passengers more than 1,000 kilometres.
Industry experts predict that these important breakthroughs are possible within five to ten years. Assuming these technical developments occur, H2 propulsion is more suitable for short and mid-range aircraft. In these cases, fuel cell-powered propulsion emerges as the most economical, climate-friendly and energy-efficient option.
Hydrogen aircraft would be aesthetically similar to traditional aircraft. Smaller aircraft would probably use propellers with hydrogen-powered fuel cells that would provide electric propulsion to turn the propellers. Larger aircraft would burn hydrogen to power jet engines.
Hydrogen aircraft essentially have four main components: a system to safely store liquid hydrogen, fuel cells to convert hydrogen to electricity, a device to control the power of the cells, and an engine to turn the propeller or a turbine. To build complete commercial aircraft, these four areas must be sufficiently developed.
The immediate future
There is still a long way to go until we see hydrogen aircraft flying regularly because important challenges must be overcome first. But if we reach this point, the future of aviation could be much greener than it is today and provide transportation that is in line with a decarbonised world.
Achieving these goals will depend on several factors. First, hydrogen storage technologies must progress to the point that they are able to transport enough liquid hydrogen on aircraft for these trips. New ways to transport hydrogen to airports must be devised so planes can refuel on runways. And aircraft interiors will need to be redesigned to find ways to integrate all the systems and piping necessary to run commercial aircraft on hydrogen.
As a disruptive innovation, this will require significant R&D, investment and additional regulations for hydrogen-powered aircraft. Furthermore, some airport infrastructures will have to be remodelled, including improvements related to the transport and supply of hydrogen.
Another day we will look more closely at how airports are optimising their processes to more effectively manage, and globally reduce, their CO2 emissions.
