Hydrogen is the most abundant element in the universe. When combined with oxygen, hydrogen generates large amounts of energy, which can create heat or electricity with only water as a byproduct.
Hydrogen also has the lowest molecular weight of any known substance, which is why NASA has been harnessing these unique properties of hydrogen to orbit the earth and travel to the moon since 1958. Translating rocket fuel success to earthbound air travel has great potential to mitigate aviation climate impacts but comes with several technical challenges before becoming commercially viable.
“Next to sun and wind, hydrogen is one of the most abundant clean energy sources. Developing technologies that will allow us to reduce the impact on the climate, and provide cheap energy, will be a win win for everyone.” -Jimmy Crosby SVP, Strategic Planning and Operations.
“With more and more companies looking to reduce their carbon footprint, the benefit of hydrogen fuel cells is becoming more prevalent. Even when operating with hydrogen produced using natural gas, total emissions from production to end user can be reduced by over 30%. The technology for fuel cell electric vehicles has existed for years, why stop there?” -Nicole Pellegrin, Process Engineer II
“Hydrogen is one of the key areas DK Innovation is focusing on. We are mapping hydrogen innovation and partnering with companies like Utility Global to inform DelekUS on future development options.” -Sarit Soccary Ben Yochanan EVP, Chief Strategy & Innovation Officer and Strategic Development
Hydrogen as an alternative fuel
Under ambient conditions, traditional fossil fuels like gasoline and jet fuel exist as liquids and are transported using pipelines, railcars, trucks, and tankers. Hydrogen, however, is a gas and challenging to both liquefy and keep liquid, and in order to do so requires significant energy itself.
This means that specialized infrastructure will be required to make hydrogen a ubiquitous fuel. In addition, once liquefied, hydrogen carries less energy per unit volume compared to liquid fuels, which leads to onboard storage challenges. For example, an average Boeing 737 aircraft carries around 5100 liters of fuel, containing 688,000 megajoules of energy.
To provide the same amount of energy with liquid hydrogen would require more than 4 times the volume. However, because of its low weight, this increased volume of hydrogen would be more than 11 times lighter, which does have benefits for air travel. This fundamental volumetric storage issue is one of the major challenges in making hydrogen a transportation fuel, and development of novel materials and processes to address this have been the focus of organization like the Department of Energy for many years.
What’s The First Goal?
As always, safety is the top priority. To maintain personnel and mechanical safety, storage for the hydrogen must be developed. Additionally, processes to utilize the stored energy, like fuel cells, need further development to make reliable hydrogen-powered flight a reality.
According to the International Energy Association (IEA), aviation accounted for more than 2% of global energy-related CO2 emissions in 2021. Additionally, aviation emissions are growing more quickly than road, rail, or shipping, thus making the need for sustainable aviation fuels ever increasing. Due to the pervasive nature of airborne travel, multiple solutions will be needed. In addition to hydrogen, sustainable aviation fuels (SAF) from renewable feedstocks like used cooking oil, cover crops, ethanol, or waste, are highly favored to be part of the solution. Electrification also holds potential for short distance flights, though weight restrictions from heavy battery components may be a limiting factor.
Adaptability and fit for purpose will be the name of the game in future carbon conscious air travel. Technological improvements in the aviation space are requisites as we continue to strive towards a more sustainable future.